Publications

Thiocoumarin-based Au(I) Complexes and Au(0) Systems
over TiO2 as Hybrid Photocatalysts for Hydrogen Generation under UV–Vis Light

A. Agrelo-Lestón, J. Llorca, E. Martínez, I. Angurell, L. Rodríguez, L. Soler

Advanced Science (2024) 2404969

Abstract:
This work focuses on the photocatalytic production of hydrogen from the photodehydrogenation of ethanol using several gold(I) complexes and gold(0) systems over titanium dioxide (P90 TiO2) as hybrid photocatalysts. The photocatalytic systems are composed of at least one coumarin-based ligand, which can enhance the photocatalytic activity by its photon-absorbing capacity due to its chromophore properties. The photocatalytic behavior for hydrogen generation of the studied samples is compared under UV–vis light setting the total gold-based co-catalyst loading at 1 wt% onto the TiO2 photocatalysts and when the gold content is maintained at 0.25 wt%. The incorporation of gold co-catalysts results in an enhancement of hydrogen production up to 2.7 times compared to a conventional Au/TiO2 reference sample. The results show an increase in the total hydrogen production under UV–vis light due to the combined presence of coumarin chromophore, gold-based co-catalysts, and gold plasmonic nanoparticles. A deep characterization of the samples from each group is performed by UV–vis spectroscopy, XPS, HRTEM, and HAADF-STEM, observing the presence of plasmonic gold nanoparticles for sample “AuL1NPs” and the reduction of the gold present in sample “AuL1a,” which explains the highest observed hydrogen production rates of this study.

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Exploring aurophilic interactions in P,C–Au(I)–Y complexes: Pathways to supramolecular aggregation

A. Frontera and L. Rodríguez

Advances in Inorganic Chemistry (2024) 84, 55

Abstract:
In this chapter we provide an extensive overview of Au’s inclination to form supramolecular assemblies through the establishment of Au···Au contacts, mainly in the solid state. We have focused on P–Au–Y and C–Au–Y configurations (where Y is O, N, S, P, or a halogen atom) based on the expertize of our research groups. We first assess the natural tendency of linear Au(I) complexes to aggregate, supported by statistical evidence. The following sections are dedicated to analyzing the supramolecular structures resulting from P–Au–Y and C–Au–Y configurations, breaking down the analysis according to the specific Y atom. It should be noted that our approach is targeted, selecting instances that either highlight exceptional supramolecular structures or provide valuable insights through comparisons among different substituents or ligands. We have contemplated extending our findings to those reported in the literature by experts in the field. This would allow us to present a more comprehensive and expansive overview of our research.

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Unraveling the Formation of Ternary AgCuSe Crystalline Nanophases and Their Potential as Antibacterial Agents

M. Lin, B. Vargas, L. Yedra, H. van Gog, M.A. van Huis, R.G. Mendes, J. Llorca, M. Estruch-Blasco, M. Pernia Leal, E. Pajuelo, S. Estradé, F. Peiró, L. Rodríguez, A. Figuerola

Chemistry of Materials (2024) 36, 10154

Abstract:
AgCuSe nanoparticles could contribute to the growth ofstrongly light-absorbing thin films and solids with fast ion mobility, amongother potential properties. Nevertheless, few methods have been developedso far for the synthesis of AgCuSe nanoparticles, and those reported delivernanostructures with relatively large sizes and broad size and shapedistributions. In this work, a colloidal cation exchange method is establishedfor the easy synthesis of AgCuSe NPs with ca. 8 nm diameters and narrowsize dispersion. Notably, in this lower size range the conucleation andgrowth of two stoichiometric ternary compounds are generally observed,namely the well-known eucairite AgCuSe compound and the novel fischesserite-like Ag3CuSe2 phase, the latter being less thermodynamicallystable as predicted computationally and assessed experimentally. Anoptimal range of Cu/Ag precursor molar ratio has been identified toensure the growth of ternary nanoparticles and, more specifically, that of the metastable Ag3CuSe2 nanophase isolated for the firstoccasion. The attained size range for the material paves the way for utilizing AgCuSe nanoparticles in new ways within the field ofbiomedicine: the results obtained here confirm the antibacterial activity of the new AgxCuySez nanoparticles against Gram-positivebacteria, with significantly low values of the minimal inhibitory concentration.

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Gold(I) complexes as powerful photosensitizers – a visionary frontier perspective

A. Pinto and L. Rodríguez

Dalton Transactions (2024) 53, 13716

Abstract:
Singlet oxygen production and its reactivity have significant implications in fields ranging from polymer science to photodynamic therapy. Extensive research has focused on the development of organic-based materials and heavy metal complexes, including Ru(II), Rh(III), Ir(III) and Pt(II). However, metal complexes containing Au(I) have been scarcely explored and warrant further investigation. This review provides a
comprehensive analysis of reported compounds, classified based on the ligands coordinated to the gold(I) centre. Additionally, future directions in photosensitizer development and singlet oxygen applications are discussed.

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Exploring the effect of the axial ligands on the anticancer activity of [C,N,N’] Pt(IV ) cyclometallated compounds

A. Lázaro, R. Bosque, S. Marín, R. Pérez-León, J. Badia, L. Baldomà, L. Rodríguez, M. Crespo and M. Cascante

Dalton Transactions (2024) 53, 13030

Abstract:
The synthesis of three novel [C,N,N’] Pt( IV) cyclometallated compounds containing hydroxo, dichloroacetato or trifluoroacetato axial ligands is reported. Compound [PtCl(OH) 2{(CH3 )2 N(CH2 )2 NvCH(4-FC6 H3 )}] (3) was prepared by the oxidative addition of hydrogen peroxide to [C,N,N’] Pt( II) cyclometallated compound [PtCl{(CH3) 2N(CH2 )2 NvCH(4-FC6 H3)}] (1) and further the reaction of compound 3 with dichloroacetate or trifluoroacetate anhydrides led to the formation of the corresponding compounds [PtCl(CHCl2COO)2{(CH3)2N(CH2)2 NvCH(4-FC6H3)}] (4) and [PtCl(CF3COO)2{(CH3)2N(CH2)2NvCH(4-FC6H3)}] (5). The properties of the new compounds along with those of the compound [PtCl3 {(CH3)2N(CH2)2NvCH(4-FC6H3)}] (2), including stability in aqueous media, reduction potential using cyclic voltammetry, cytotoxic activity against the HCT116 CRC cell line, DNA interaction, topoisomerase I and cathepsin inhibition, and computational studies involving reduction of the Pt(IV) compounds and molecular docking studies, are presented. Interestingly, the antiproliferative activity of these compounds against the HCT116 CRC cell line, which is in all cases higher than that of cisplatin, follows the same trend as the reduction potentials so that the most easily reduced compound 2 is the most potent. In contrast, according to the electrophoretic mobility and molecular docking studies, the efficacy of these compounds in binding to DNA is not related to their cytotoxicity. The most active compound 2 does not modify the DNA electrophoretic mobility while the less potent compound 3 is the most efficient in binding to DNA. Although compounds 2 and 3 have only a slight effect on cell cycle distribution and apoptosis induction, generation of ROS to a higher extent for the most easily reduced compound 2 was observed.

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Slow magnetic relaxation and luminescence properties in β-diketonate lanthanide(iii) complexes. Preparation of Eu(III) and Yb(III) OLED devices

A. Tubau, L. Rodríguez, P. Pander, L. Weatherill, F. B. Dias, M. Font-Bardía and R. Vicente

Journal of Materials Chemistry C (2024) 12, 8127

Abstract:
The reaction of [Ln(btfa)3(H2O)2] (btfa− = 4,4,4-trifluoro-1-phenyl-1,3-butanedionate) with 4,4′-dinonyl-2,2′-bipyridyl (4,4′-dinonylbipy) in ethanol allows isolation of mononuclear complexes [Ln(btfa)3(4,4′-dinonylbipy)] Ln = Sm (1-Sm), Eu (2-Eu), Tb (3-Tb), Dy (4-Dy), Er (5-Er) and Yb (6-Yb). The solid state luminescence emission in the visible region for 1-Sm, 2-Eu, 3-Tb and 4-Dy and in the NIR region for 1-Sm,5-Er and 6-Yb shows efficient energy transfer from the 4,4,4-trifluoro-1-phenyl-1,3-butanedionate ligands to the central Ln3+ ion for all the compounds. Finally, complexes 2-Eu and 6-Yb were successfully used as emitters in multilayer vacuum-deposited OLEDs. The electroluminescence quantum efficiency (EQE) of the corresponding devices reached 2.1% and ∼0.1–0.2% for 2-Eu (λEL = 614 nm) and 6-Yb (λEL = 977 nm), respectively. Maximum radiant emittance recorded for the Ln-associated emission achieved 135 μW cm−2 for 2-Eu and 121 μW cm−2 for 6-Yb. These values for efficiency and radiant emittance are unusually high for such type of emitters. Moreover, magnetic studies were performed on all compounds. Alternating current (AC) dynamic measurements indicated Single Molecular Magnet (SMM) behaviour for 4-Dy and field-induced slow relaxation of the magnetization for complexes 3-Tb, 5-Er and 6-Yb. The anisotropy energy barriers and pre-exponential factors are 91.1 cm−1, τ0 = 7.2 × 10−9 s (under zero magnetic field) and ΔE = 109.3 cm−1, τ0 = 9.3 × 10−10 s under 0.1 T magnetic field for 4-Dy and ΔE = 24.6 cm−1, τ0 = 8.7 × 10−8 s (under 0.07 T) for 5-Er. Besides, we observe that for compounds 3-Tb and 6-Yb the relaxation of the magnetization does not occur through the Orbach process.

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Investigating the Impact of Packing and Environmental Factors on the Luminescence of Pt(N^N^N) Chromophores

G. Romo-Islas, S. Burguera, A. Frontera, L. Rodríguez

Inorganic Chemistry (2024) 63, 2821

Abstract:
Four Pt(II)(N^N^N) compounds featuring DMSO coordination at the fourth position were synthesized. Ligands varied in terms of pyridyl central ring (hydrogen/chlorine substituent) and lateral rings (triazoles with CF3 substitution or tetrazoles). Coordination to pyridine yielded tetra-nitrogen coordinated Pt(II) complexes or Pt-functionalized polymers using commercial 4-pyridyl polyvinyl (PV) or dimethylaminopyridine (DMAP). Luminescence behaviours exhibited remarkable environmental dependence. While some of the molecular compounds (tetrazole derivatives) in solid state displayed quenched luminescence, all the polymers exhibited 3MMLCT emission around 600 nm. Conversely, monomer emission was evident on polymethylmethacrylate (PMMA) or polystyrene (PS) matrices. DFT calculations were used to analyze the aggregation of the complexes both at the molecular level and coordinated to the PV polymer and their influence on the HOMO-LUMO gaps.

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Effect of substituents on the 1O2 production and biological activity of (N^N^N)Pt(py) complexess

G. Romo-Islas, M. Gil-Moles, A. Saxena, A. Frontera, M.C. Gimeno, Laura Rodríguez

Dalton Transactions (2024) 53, 2475

Abstract:
Twelve (N^N^N)Platinum pyridyl complexes, (N^N^N)Pt(pyF), were synthesised and investigated for their singlet oxygen generation and potential biological activities. They exhibited 1IL and 1MLCT absorption transitions at approximately 325 and 360 nm, identified through TD-DFT calculations. Luminescence was observed only in the L1-derived compounds in solution, with a dual emission with main contribution of phosphorescence in deaerated conditions. Room temperature phosphorescence was detected in all solid-state cases. Electron-withdrawing substituents at specific positions (R1 and X) and the number of fluorine atoms in R2 were found to enhance the photosensitizing capabilities of these compounds.
Biological assessments, including cytotoxicity and photocytotoxicity, were conducted to evaluate their potential as chemotherapeutic agents and photosensitizers. Complexes with chloro substitution in the N^N^N tridentate ligand of the central pyridine ring exhibited promising chemotherapeutic properties. Ancillary pyridine ring substitution became significant under irradiation conditions, with fluoromethylated substituents enhancing cytotoxicity. Complex 2-CF3 was the most efficient singlet oxygen producer and a highly effective photosensitizer. CHF2-substituted complexes also showed improved photosensitizing activity. DNA binding studies indicated moderate interactions with DNA, offering insights into potential biological applications.

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Molecularly imprinted polypyrrole -based electrochemical melamine sensors

E. Brazys, V. Ratautaite, B. Brasiunas, A. Ramanaviciene, L. Rodríguez, A. Pinto, D. Milea, Prentice, A Ramanavicius

Microchemical Journal (2024) 199, 109890

Abstract:
This study describes the development of a molecularly imprinted polymer (MIP) polypyrrole-based (Ppy-based) electrochemical melamine sensor. Two different modifications of polymeric layers in the design of MIP-based melamine sensor systems were assessed. The addition of gold nanoparticles (AuNPs) or gold(I) complexes in the polymerization solution containing pyrrole was studied. The characteristics of all polypyrrole layers were evaluated indirectly using a [Fe(CN)6]3–/[Fe(CN)6]4– as a redox probe by application of differential pulse voltammetry (DPV). The most optimal results were obtained when the MIP polymerization was prepared from a solution containing 50 mM pyrrole, 5 mM melamine, and 0.05 nM 3.5 nm diameter AuNPs. Under these conditions, the observed response of MIP to melamine was 6.61 times greater than that of non-imprinted polymer (NIP). To further characterize the detection of melamine, overoxidized forms of both MIP and NIP were employed. The utilization of MIP resulted in a linear correlation within the concentration range from 50 nM to 5 µM melamine, with an estimated limit of detection (LOD) of 0.83 nM melamine.

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Visible light harvesting alkyne hydrosilylation mediated by pincer platinum complexes

Laura Ibáñez-Ibáñez, Ariadna Lázaro, Carmen Mejuto, Margarita Crespo, Cristian Vicent, Laura Rodríguez, Jose A. Mata

Journal of Catalysis (2023), 428, 115155

Abstract:
In this manuscript we assess the catalytic properties of pincer platinum complexes in alkyne hydrosilylation either under photo or thermal conditions. The visible light-induced hydrosilylation proved to be more efficient. It can be performed at room temperature and required lower catalyst loadings than that operating under thermal conditions. The platinum complexes play a dual role in photohydrosilylation as serve as a photosensitizer and a catalyst enabling species in bond breaking/forming transformations. In addition, alkyne hydrosilylation is achieved with moderate regio- and stereoselectivity but is enhanced under photocatalytic conditions and in the case of terminal alkynes we have observed the formation of β(Z) products not observable under thermal conditions. Such differences in selectivity constitute an example of stereodivergent catalysis dictated under photochemical or thermal conditions. The selectivity differences are ascribed to a distinctive reaction mechanism for the light- vs thermally-induced process that involve radical or organometallic intermediates, respectively.

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Syntheses, Characterization, and DNA Binding Studies of a Series of Copper(II), Nickel(II), Platinum(II) and Zinc(II) Complexes Derived from Schiff Base Ligands

Valentina Iannace, Dr. Ferran Sabaté, Molly Bartlett, Dr. Jessica Berrones Reyes, Dr. Ariadna Lázaro, Alessia Fantoni, Prof. Ramon Vilar, Prof. Laura Rodríguez, Prof. Antonella Dalla Cort

Eur. J. Inorg.Chem. (2023), 26, e20230014

Abstract:
Three series of metal salophen complexes derived from Zn2+, Cu2+, Pt2+ and Ni2+ have been synthesized and their interaction with quadruplex DNA has been evaluated. The compounds differ on the number of ethyl piperidine substituents. They have been characterized by 1H NMR, IR and UV-visible spectroscopies and by HR-mass spectrometry. Their luminescent properties have been also evaluated and we can observe that, as expected, Zn2+ and Pt2+ complexes are those displaying more interesting luminescence with an emission band red-shifted with respect to the corresponding uncoordinated ligand. DNA interactions with G4 and duplex DNA were evaluated by FRET melting assays (for the Zn2+, Cu2+ and Ni2+ complexes) and by emission titrations (for one Pt2+ complex) which indicated that the disubstituted compounds 2-Ni and 2-Pt are the only ones that display good affinity for G4 DNA structures.

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Supramolecular luminescent Pt(ii) tweezers: aggregation studies and 1O2 production

Guillermo Romo-Islas, Rosa M. Gomila, Antonio Frontera, Laura Rodríguez

Inorganic Chemistry Frontiers (2023) 10, 6204

Abstract:
Four series of Pt(II) tweezer compounds have been designed and synthesized in order to explore their ability to form supramolecular assemblies with luminescence ability. The compounds present the general chemical structure (diphos)Pt(N^N^N), where diphos is a diphosphane that differs in the flexibility and chain length (diphos = bis(diphenylphosphanyl)methane, dppm; 1,2-bis(diphenylphosphanyl)ethane, dppe and 1,2-bis(diphenylphosphanyl)benzene, dppbz) and confers the tweezer structure to the complexes. The four series are defined as a function of the substituents of the N^N^N ligands with different electronic properties (hydrogen vs. chloride) and bulkiness (p-tolyl vs. CF3). We can identify the presence of intra- and intermolecular Pt⋯Pt, Pt⋯π and π⋯π interactions based on the spectroscopic absorption and emission profiles and supported by DFT calculations giving rise to aggregates with different stabilities. The aggregation process has been carefully analyzed both in solution and in the solid state. The resulting emission properties are affected by aggregation, exemplified by the phosphorescence emission enhancement in the absence of the chloride substituent.

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Heterometallic Au(I)−Cu(I) Clusters: Luminescence Studies and 1O2 Production

G. Romo-Islas, J.S. Ward, K. Rissanen, L. Rodríguez

Inorganic Chemistry (2023) 62, 8101

Abstract:
Two different organometallic gold(I) compounds containing naphthalene and phenanthrene as fluorophores and 2-pyridyldiphenylphosphane as the ancillary ligand were synthesized (compounds 1, with naphthalene and 2, with phenanthrene). They were reacted with three different copper(I) salts with different counterions (PF6-, OTf- and BF4-; OTf = triflate) to obtain six Au(I)/Cu(I) heterometallic clusters (compounds 1a-c for naphthalene derivatives and 2a-c for phenanthrene derivatives). The heterometallic compounds present NIR pure room temperature phosphorescence both in solution, the solid state, and air-equilibrated samples, as a difference with the dual emission recorded for the gold(I) precursors 1 and 2. The presence of Au(I)-Cu(I) metallophilic contacts have been identified using single crystal X-ray diffraction structure resolution of two of the compounds which play a direct role in the resulting NIR emission. Polystyrene (PS) and poly(methyl methacrylate) (PMMA) polymeric matrixes were doped with our luminescent compounds and the resulting changes in their emissive properties were analyzed and compared with those previously recorded in the solution, and the solid state. All complexes were tested to analyze their ability to produce 1O2 and present very good values of ΦΔ up to 50%.

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Ligand and Gold(I) Fluorescein−AIEgens as Photosensitizers in Solution and Doped Polymers

A. Pinto, A. Llanos, R.M. Gomila, A. Frontera, L. Rodríguez

Inorganic Chemistry (2023) 62, 7131

Abstract:
The synthesis of fluorescein propargyl diether (L) and two different dinuclear gold(I) derivatives containing a watersoluble phosphane [1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]-decane (PTA) for complex 1 and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA) for complex 2] has been successfully performed. All compounds display intrinsic emission from fluorescein, being less intense for gold(I) complexes due to the heavy-atom effect. All compounds aggregate in acetonitrile/water mixtures with the formation of larger aggregates for those samples containing more water content, as evidenced by dynamic light scattering and small-angle X-ray scattering experiments, in agreement with the absorption and emission data. The emission of the samples increases when they are used to obtain luminescent materials with four different organic matrices [poly(methyl methacrylate, polystyrene (PS), cellulose, and Zeonex]. The compounds display very high values of singlet oxygen (1O2) production in dichloromethane. Singlet oxygen production was also evaluated in the doped matrices, being the highest in PS and with an exciting increase on PS microspheres. Density functional theory (BP86-D3) and GFN2-xTB calculations were used to model the assembly of L and complexes 1 and 2 with the different organic matrices and rationalize the experimental findings based on the geometries, molecular electrostatic potential surfaces, and complementarity and HOMO−LUMO gaps.

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Ligand and Gold(I) Mono- and Dinuclear Gold(I) Coumarin Complexes: Luminescence Studies and Singlet Oxygen Production

C. Sobrerroca, I. Angurell, A. de Aquino, G. Romo, C. Jubert, L. Rodríguez

ChemPlusChem (2023), 88, e202300020

Abstract:
The 4-(thiolmethyl)-7-(diethylamino)-2H-chromen-2-one ligand has been synthesized and used as chromophore in several mono- and dinuclear gold(I) compounds that contain a phosphane at the second coordination position. Four final products were able to obtain in pure form containing one coumarin and one phosphane ligand in the case of PTA (1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane) and PPh3 (triphenylphosphine); one coumarin and two gold(I)-phosphane groups in the case of phosphane=DAPTA (3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) and two coumarin and two gold(I) atoms in the case of phosphane=DPEphos (bis[(2-diphenylphosphino)phenyl]ether), when it was used a diphosphane. Other diphosphane ligands used were not able to give the desired products in pure form. The luminescent properties of the compounds are governed by the fluorescence of the coumarin moiety in all compounds both for measurements carried out in solution and also immobilized in PMMA organic matrix. Phosphorescence emission can be detected in all cases at 77 K both for the uncoordinated coumarin ligand and the gold(I) derivatives, being more favoured in the presence of the gold(I) heavy atom. The compounds have been used as photosensitizers to generate 1O2 with moderate quantum yields values.

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Toward Near-Infrared Emission in Pt(II)-Cyclometallated Compounds: From Excimers’ Formation to Aggregation-Induced Emission

A. Lázaro, R. Bosque, J.S. Ward, K. Rissanen, M. Crespo, L. Rodríguez

Inorganic Chemistry (2023), 62, 2000

Abstract:
Two series of Pt(II)-cyclometallated compounds containing N^C^N tridentate and alkynyl-chromophore ligands have been synthesized and structurally characterized. The N^C^N ligands differ on the presence of R1 = H or F in the central aromatic ring, while six different chromophores have been introduced to the alkynyl moiety. Single-crystal X-ray structures for some of the compounds reveal the presence of weak intermolecular contacts responsible for the formation of some dimers or aggregates. The photophysical characterization shows the presence of two emission bands in solution assigned to the 3π−π* transition from the N^C^N ligands mixed with 3MLCT/3ILCT transitions (higher energy band) in deaerated samples. The formation of excimers has also been identified as a broad band at longer wavelengths [near-infrared (NIR) emission] that becomes the main emission band for compounds containing phenanthrene as the chromophore. NIR emission behavior has also been explored using acetonitrile/water mixtures, and the presence of aggregates that emit at ca. 650 nm has also been detected.

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Supercritical CO2 Synthesis of Porous Metalloporphyrin Frameworks: Application in Photodynamic Therapy

M. Kubovics, O. Careta, O. Vallcorba, G. Romo-Islas, L. Rodríguez, J.A. Ayllón, C. Domingo, C. Nogués, A.M. López-Periago

Chemistry of Materials (2023), 35, 1080

Abstract:
A series of porous metalloporphyrin frameworks prepared from the 5,10,15,20-tetra(4-pyridyl)porphyrin (H2TPyP) linker and four metal complexes, M(hfac)2 M = Cu(II), Zn(II), Co(II), and Ni(II) (hfac: 1,1,1,5,5,5-hexafluoroacetylacetonate), were obtained using supercritical CO2 (scCO2) as a solvent. All the materials, named generically as [M-TPyP]n, formed porous metal−organic frameworks (MOFs), with surface areas of ∼450 m2 g−1. All MOFs were formed through the coordination of the metal to the exocyclic pyridine moieties in the porphyrin linker. For Cu(II), Zn(II), and Co(II), incomplete metal coordination of the inner pyrrole ring throughout the structure was observed, giving place to MOFs with substitutional defects and leading to a certain level of disorder and limited crystallinity. These samples, prepared using scCO2, were precipitated as nano- to micrometric powders. Separately, a layering technique from a mixture of organic solvents was used to crystallize high-quality crystals of the Co(II) based MOF, obtained with the formula [{Co(hfac)2}2H2TPyP]n. The crystal structure of this MOF was elucidated by single-crystal synchrotron X-ray diffraction. The Zn(II)-based MOF was selected as a potential photodynamic therapy drug in the SKBR-3 tumoral cell line showing outstanding performance. This MOF resulted to be nontoxic, but after 15 min of irradiation at 630 nm, using either 1 or 5 μM concentration of the product, almost 70% of tumor cells died after 72 h.

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Luminescent chiral furanol-nanographenes via straightforward Ni-catalyzed Csp2-F
functionalization: mechanistic insights into the Scholl reaction

Judith Sala, Lorena Capdevila, Cristina Berga, Araceli de Aquino, Laura Rodríguez, Sílvia Simon and Xavi Ribas

Chem. Eur. J. (2023) e202303200

Abstract:
Here we report the stepwise synthesis of new nanographenes (NGs) and polycyclic aromatic hydrocarbons (PAHs) obtained via Scholl ring fusion applied at aromatic homologation compounds, which are obtained through one-step Ni-catalysed Csp2−F functionalization. The latter are rapidly accessed valid precursors for the Scholl reaction, and screening of experimental conditions allowed us to describe for the first time furanol-bearing PAHs. Mechanistic insights are obtained by DFT to rationalize the formation of the furanol PAHs under moderately acidic conditions. All PAHs and NGs synthesized show moderate/weak fluorescent properties, and all PAHs crystallized show some degree of curvature and are obtained as racemic mixtures. Enantiomeric separation by chiral HPLC of one furanol-bearing PAH allowed the study of their chiroptical CD properties.”

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Intra- vs Intermolecular Aurophilic Contacts in Dinuclear Gold(I) Compounds: Impact on the Population of the Triplet Excited State

A. de Aquino, J.S. Ward, K. Rissanen, G. Aullon, J.C. Lima, L. Rodriguez

Inorganic Chemistry (2022), 61, 20931

Abstract:
Two series of dinuclear gold(I) complexes that contain two Au−chromophore units (chromophore = dibenzofurane or dimethylfluorene) connected through a diphosphane bridge that differs in the flexibility and length (diphosphane = dppb for 1,4-bis(diphenylphosphino)butane, DPEphos for bis[(2-diphenylphosphino)phenyl]ether, xanthphos for 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene, and BiPheP for 2,2′-bis(diphenylphosphino)-1,1′-biphenyl)have been synthesized and structurally characterized. Their photophysical properties have been carefully investigated, paying attention to the role of the presence, or absence, of aurophilic contacts and their nature (intra- or intermolecular character). This analysis was permitted due to the X-ray crystallographic determination of all of the structures of the compounds discussed herein. The quantum yields of the triplet population, ϕT, have been calculated by nanosecond-laser flash photolysis measurements, and we could determine the main role of the character of the aurophilic contacts in the resulting ϕT, being especially favored in the presence of intermolecular contacts. Time dependent density functional theory (TD-DFT) calculations support the absorption and emission assignments and the shorter distance between S1 and the closest triplet excited state energy in the case of the compounds with a higher triplet-state population.

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Supramolecular gold(I) vesicles: an in-depth study of their aggregation process

A. Pinto, J. Sonet, R.M. Gomila, A. Frontera, J.C. Lima, L. Rodríguez

Inorganic Chemistry Frontiers (2022), 9, 6047

Abstract:
The synthesis of two gold(I) complexes containing a pyridyl ligand with a polyethyleneglycol pendant arm at one position and a chromophore (aniline or coumarin) at the second coordination position is herein reported. These compounds have been observed to aggregate in acetonitrile/water mixtures and the results have been compared with two other gold(I) compounds previously synthesized by our group that contain a water soluble phosphane instead of the pyridyl ligand. We observed that the coumarin derivative is much more stable while the aniline analogue decomposes in the presence of small amounts of water. The aggregation of this coumarin gold(I) compound has been deeply studied by DLS, SAXS, optical microscopy and electron microscopy (SEM and cryo-TEM). The calculation of the crystal packing parameter confirms a vesicle-type assembly. In order to obtain more detailed information about the composition of vesicles, the number of molecules involved in the self-assembly process has been determined (Nagg = 82). DFT calculations support these data, determining a size of around 90 Å for the vesicles, which may form coacervates to yield the larger structures observed under a microscope.

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Development of gold(I) phosphorescent tweezers for sensing applications

A. de Aquino, F.J. Caparrós, G. Aullón, K.-N. Truong, K. Rissanen, J.C. Lima, L. Rodríguez

Dalton Transactions (2022), 51, 16282

Abstract:
The 4-(thiolmethyl)-7-(diethylamino)-2H-chromen-2-one ligand has been synthesized and used as chromophore in several mono- and dinuclear gold(I) compounds that contain a phosphane at the second coordination position. Four final products were able to obtain in pure form containing one coumarin and one phosphane ligand in the case of PTA (1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane) and PPh3 (triphenylphosphine); one coumarin and two gold(I)-phosphane groups in the case of phosphane=DAPTA (3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) and two coumarin and two gold(I) atoms in the case of phosphane=DPEphos (bis[(2-diphenylphosphino)phenyl]ether), when it was used a diphosphane. Other diphosphane ligands used were not able to give the desired products in pure form. The luminescent properties of the compounds are governed by the fluorescence of the coumarin moiety in all compounds both for measurements carried out in solution and also immobilized in PMMA organic matrix. Phosphorescence emission can be detected in all cases at 77 K both for the uncoordinated coumarin ligand and the gold(I) derivatives, being more favoured in the presence of the gold(I) heavy atom. The compounds have been used as photosensitizers to generate 1O2 with moderate quantum yields values.

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Highly emissive supramolecular gold(I)–BTD materials

A. Pinto, M. Echeverri, B. Gómez-Lor, L. Rodríguez

Dalton Transactions (2022), 51, 8340

Abstract:
Herein we report the synthesis of three light emitting rod-shaped gold(I) complexes by combining ethynyl-functionalized 2,1,3-benzothiadiazole (BTD), with different N-heterocyclic (imidazole, benzimidazole and phenantroimidazole) carbene gold(I) complexes. As could be determined by single crystal structure determination, the size of the N-heterocyclic carbene affects the relative disposition of the two ligands in the linear gold complexes (nearly perpendicular in the benzimidazole vs. planar in the phenantroimidazole derivative) which translates to different types of interactions between neighbouring units. In fact, the planar conformation in the more π-extended phenantroimidazole carbene allows Au(I) atoms to get sufficiently closer favouring aurophilic interactions. This compound is obtained as two different colour emitting solids which is ascribed to changes in packing modes probably leading to differences in the strength of aurophilic interactions. Interestingly, while the emission in the solid state is almost quenched, the incorporation of the compounds in polymer matrixes enhances the emissive properties of the compounds reaching near unity quantum yields.

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How to achieve near unity fluorescence quantum yields on gold(I) benzothiadiazole-based derivatives

A. Pinto, M. Echeverri, B. Gómez-Lor, L. Rodríguez

Dyes and Pigments (2022), 202, 110308

Abstract:
The synthesis of three new gold(I) benzothiadiazole derivatives has been carried out by the reaction of 4-ethynyl- 7-(4-nonylphenyl)benzo[c] [1,2,5]thiadiazole (L) with three different gold(I)-PR3 (PR3 = triethylphosphane (2), triphenylphosphane (3) and tri-1-naphthylphosphane (4)) sources and their light emitting properties thoroughly investigated. The new compounds display denoted luminescence properties with fluorescence quantum yields above 80% in all cases except for the complex containing the bulkiest PNaph3 phosphane. The resulting emission is mainly dominated by the organic 2,1,3-benzothiadiazole moiety (BTD) and can be modulated following different strategies. On one hand, the emission wavelength of these compounds in solution can be ca. 60 nm shifted varying the polarity of the solvents. Interestingly, quantum yields and lifetimes can be strongly increased by changing the environment conditions, from water:acetonitrile solutions to dispersion of the compounds within organic matrixes. In this way, we have been able to obtain near unity fluorescence quantum yields, with the highest values recorded for gold(I) BTD compounds. The effect of the solvents on the emission changes has been rationalized with the help of the Lippert-Mataga equation and the multiparametric Kamlet-Taft method to analyse the excited state polarity.

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Gold(I) complexes bearing a PNP-type pincer ligand: photophysical properties and catalytic investigations

M. Casciotti, G. Romo-Islas, M. Álvarez, F. Molina, J.M. Muñoz-Molina, T.R. Belderrain, L. Rodríguez

Dalton Transactions (2022), 51, 17162

Abstract:
The synthesis and characterization of two dinuclear and five tetranuclear gold(I) complexes bearing the 2,6-bis(diphenylphosphinomethyl)pyridine diphosphane ligand (DPPMPY) are herein reported. The reaction between the dinuclear complexes, DPPMPY(AuCl)2 (1) or DPPMPY(AuBr)2 (2), with 1 or 2 equivalents of Ag salts yielded five tetranuclear gold(I) complexes, DPPMPY2Au4X2 (3–7), differing in the terminal ancillary ligands (X = Cl, Br, acetonitrile) and the counter ions (SbF6− or BF4−). The structures of complexes 1, 2, 3, and 5 were confirmed by single-crystal X-ray diffraction studies. The Au⋯Au distances found in complexes 3 and 5 are in the range of aurophilic interactions and the arrangement of the Au atoms varies from a linear arrangement in complex 3 to a zigzag arrangement in complex 5. The photophysical characterization of the compounds was performed both in solution and in the solid state. Very high emission quantum yields were observed for the acetonitrile complexes 4 and 6 in the solid state. The use of this family of gold(I) complexes as catalysts for lactone synthesis via oxidative heteroarylation of alkenes was investigated and yields up to ca. 65% were obtained. Dicationic halide complexes 3 and 5 showed a slight enhancement of the yield of the catalytic reaction, indicating that there is no influence of the counter ion employed on the reaction outcome. Luminescence techniques have been also used to follow the progress of the catalytic reaction.

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Aggregation of gold(I) complexes: phosphorescence vs. singlet oxygen production

A. Pinto, J.S. Ward, K. Rissanen, M. Smith, L. Rodríguez

Dalton Transactions (2022), 51, 8795

Abstract:
Herein we report on the synthesis of six new phosphane-gold(I)-4-ethynylaniline complexes (neutral and cationic), with a tris-naphthalene substituted tertiary phosphane bearing a secondary amine as a linker and containing different halogen groups (Cl and Br) in the naphthyl group. We have demonstrated in this work how the careful control of the intermolecular aggregation process can modulate the competition between phosphorescence emission and energy transfer from the triplet state of the gold(I) complexes to produce singlet oxygen.

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Amino acids with tetrazine ethers as dual fluorescent and bioorthogonal probes for peptide modification

E. Ros, M. Bellido, J.A. Matarin, A. Gallen, M. Martinez, L. Rodriguez, X. Verdaguer, L. Ribas de Pouplana, A. Riera

Organic and Biomolecular Chemistry (2022), 12, 14321

Abstract:
A set of 3-bromo-1,2,4,5-tetrazines with three distinct substitutions have been used as reagents for late-stage functionalization of small molecules through nucleophilic aromatic substitution. Spectroscopic studies of the products obtained proved that tetrazine ethers are intrinsically fluorescent. This fluorescence is lost upon inverse Electron-Demand Diels–Alder (iEDDA) cycloaddition with strained alkenes. Tetrazine-phenol ethers are rather interesting because they can undergo rapid iEDDA reactions with a second order rate constant (k2) compatible with bioorthogonal ligations. As a showcase, L-tyrosine was derivatized with 3-bromo-6-methyl-1,2,4,5-tetrazine and coupled to the peptide drug octreotide. This peptide was detected in cellular flow cytometry, and its fluorescence turned off through a bioorthogonal iEDDA cycloaddition with a strained alkene, showing for the first time the detection and reactivity of intrinsically fluorescent tetrazines in a biologically relevant context. The synthesis and characterization of fluorescent tetrazine ethers with bioorthogonal applicability pave the way for the generation of useful compounds for both detection and bioconjugation in vivo.

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Aggregation-Induced Emission with Alkynylcoumarin Dinuclear Gold(I) Complexes: Photophysical, Dynamic Light Scattering, and Time-Dependent Density Functional Theory Studies

C. Cunha, A. Pinto, A. Galvão, L. Rodríguez, J.S. Seixas de Melo

Inorganic Chemistry (2022), 61, 696

Abstract:
Aggregation-induced emission (AIE) has gained a remarkable amount of interest in the past 20 years, but the majority of the studies are based on organic structures. Herein, three dinuclear gold(I) complexes, with the general formula [PPh2XPPh2-Au2- Coum2], where the Au(I) atom is linked to three different diphosphanes [PPh2XPPh2; DPPM for X = CH2 (1.1), DPPP for X = (CH2)3 (1.2), and DPPA for X = CC (1.3)] and the propynyloxycoumarin precursor (1, 4-methyl-substituted coumarin), have been synthesized. The compounds present AIE characteristics, AIEgens, with high luminescence quantum yields in the solid state when they are compared to dilute solutions. Photophysical studies (steady-state and time-resolved fluorescence) were obtained, with AIE being observed with the three gold(I) complexes in acetonitrile/water mixtures. This was further corroborated with dynamic light scattering measurements. Time-dependent density functional theory (TDDFT) electronic calculations show that the compounds have different syn and anti conformations (relative to the coumarin core) with 1.1 syn and 1.2 and 1.3 both anti. From time-resolved fluorescence experiments, the augment in the contribution of the longer decay component is found to be associated with the emission of the aggregate (AIE effect) and its nature (involving a dimer) rationalized from TDDFT electronic calculations.

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Chalcone-based fluorescent chemosensors as new tools for detecting Cu2+ ions

L.J. Gomes, T. Moreira, L. Rodríguez, A.J. Moro

Dyes and Pigments (2022), 197, 109845

Abstract:
The design and full characterization of new fluorescent chemosensors for Cu2+ is herein presented. The structure of the sensors is based on a chalcone backbone as the chromophoric unit, with di-(2-picolyl)amine (DPA) as a receptor moiety. Two systems, bearing one or two chalcone-DPA units, were synthesized and fully characterized. UV–Vis titrations with several metal ions were performed and both chemosensors exhibited a strong hypsochromic shift in the absorption spectra upon Cu2+ addition, indicating a higher selectivity for this metal over other divalent cations. Additionally, fluorescent spectra recorded in the same conditions revealed a stronger quenching effect in the presence of Cu2+, even in the presence of other metal cations, with association constants above 106 M􀀀 1 and detection limits below the micromolar level for both chemosensors. Paper test-strips with one of the chemosensors were prepared to attest its possible application for detecting copper in aqueous samples.

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Aggregation versus Biological Activity in Gold(I) Complexes. An Unexplored Concept

A. Pinto, C. Roma-Rodrigues, J.S. Ward, R. Puttreddy, K. Rissanen, P.V. Baptista, A.R. Fernandes, J.C. Lima, L. Rodríguez

Inorganic Chemistry (2021), 60, 18753

Abstract:
The aggregation process of a series of mono- and dinuclear gold(I) complexes containing a 4-ethynylaniline ligand and a phosphane at the second coordination position (PR3-Au-C CC6H4-NH2, complexes 1−5, and (diphos)(Au-CCC6H4-NH2)2, complexes 6−8), whose biological activity was previously studied by us, has been carefully analyzed through absorption, emission, and NMR spectroscopy, together with dynamic light scattering and small-angle X-ray scattering. These experiments allow us to retrieve information about how the compounds enter the cells. It was observed that all compounds present aggregation in fresh solutions, before biological treatment, and thus they must be entering the cells as aggregates. Inductively coupled plasma atomic emission spectrometry measurements showed that mononuclear complexes are mainly found in the cytosolic fraction; the dinuclear complexes are mainly found in a subsequent fraction composed of nuclei and cytoskeleton. Additionally, dinuclear complex 8 affects the actin aggregation to a larger extent, suggesting a cooperative effect of dinuclear compounds.

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Improving the emission quantum yield in dinuclear Eu(III) and Tb(III) complexes with 2-fluorobenzoate

A. Tubau, L. Rodríguez, A. Lázaro, R. Vicente, M. Font-Bardía

New J. Chemistry (2021), 45, 22208

Abstract:
The reaction of Ln(NO3)2 6H2O salts (Ln = Eu and Tb) with an excess of 2-fluorobenzoic acid (H-2FBz) in an ethanol/water mixture allows the isolation of dinuclear compounds with the formula [Ln2(m2-2FBz)4(2FBz)2(H-2FBz)2(H2O)2] (Ln = Eu (1) and Tb (2), 2FBz = 2-fluorobenzoate). A solid-state photoluminescence study of complexes 1 and 2 shows the 4f–4f lanthanide transitions in the visible range with improved emission quantum yields. 1 and 2 are water soluble and photoluminescence studies have also been performed in water and D2O solutions, showing that the emission due to the 4f–4f electronic transitions is still present. The magnetic behaviors of 1 and 2 are also reported.

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Comprehensive Investigation of the Photophysical Properties of Alkynylcoumarin Gold(I) Complexes Concept

A. Pinto, C. Cunha, G. Aullón, J.C. Lima, L. Rodríguez, J.S. Seixas de Melo

J. Phys. Chem. B (2021), 125, 11751

Abstract:
Six gold(I) complexes (R3P-Au-Coum) containing threedifferent alkynylcoumarin chromophores (Coum) with different electron-donating and electron-withdrawing characteristics and two different water-soluble phosphanes (PR3 = PTA (a) and DAPTA (b)) have been synthesized (1a,b, unsubstituted coumarin; 2a,b, 4-methyl substituted coumarin; 3a,b, 3-chloro and 4-methyl substituted coumarin). A comprehensive study of the photophysical properties of the R3P-Au-Coum, together with their propynyloxycoumarin precursors 1−3, was performed in solution at room and low temperatures. Spectral and photophysical characteristics of the R3P-Au-Coum essentially depend on the electronic characteristics of the propynyloxycoumarin ligand. The presence of the Au(I) atom was found to be responsible for an increase of the intersystem crossing, with triplet state quantum yield values, ϕT, ranging from ∼0.05 to 0.35 and high coumarin phosphorescence quantum yield values for derivatives 1 and 2; fluorescence dominates the deactivation in derivatives 3. Efficient singlet oxygen photosensitization was observed for the new compounds 3a,b. From TDDFT calculations, the relevant HOMO and LUMO of the compounds, i.e., those involved in the transitions, are dominated by the frontier orbitals associated with the coumarin core. The Au(I)-phosphane structure introduces a new transition assigned to an intraligand transition involving the phosphane ligand, and π(CC) system, to the p orbitals of phosphorus and gold atoms.

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Effect of Gold(I) on the Room-Temperature Phosphorescence of Ethynylphenanthrene

A. de Aquino, F.J. Caparrós, G. Aullón, J.S. Ward, K. Rissanen, Y. Jung, H. Choi, J.C. Lima, L. Rodríguez

Chemistry. A European Journal (2021), 27, 1810

Abstract:
The synthesis of two series of gold(I) complexes with the general formulae PR3-Au-C/C-phenanthrene (PR3= PPh3 (1a/2a), PMe3 (1b/2b), PNaph3 (1c/2c)) or (diphos)(Au-C/C-phenanthrene)2 (diphos=1,1-bis(diphenylphosphino)-methane, dppm (1d/2d), 1,4-bis(diphenylphosphino)butane, dppb (1e/2e)) has been realized. The two series differ in the position of the alkynyl substituent on the phenanthrene chromophore, being at the 9-position (9-ethynylphenanthrene) for the L1 series and at the 2-position (2-ethynylphenanthrene) for the L2 series. The compounds have been fully characterized by 1H, 31P NMR, and IR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction resolution in the case of compounds 1a, 1e, 2a, and 2c. The emissive properties of the uncoordinated ligands and corresponding complexes have been studied in solution and within organic matrixes of different polarity (polymethylmethacrylate and Zeonex). Room-temperature phosphorescence (RTP) is observed for all gold(I) complexes whereas only fluorescence can be detected for the pure organic chromophore. In particular, the L2 series presents better luminescent properties regarding the intensity of emission, quantum yields, and RTP effect. Additionally, although the inclusion of all the compounds in organic matrixes induces an enhancement of the observed RTP owing to the decrease in non-radiative deactivation, only the L2 series completely suppresses the fluorescence, giving rise to pure phosphorescent materials. recorded in solution.

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Using Room Temperature Phosphorescence of Gold(I) Complexes for PAHs Sensing

M. Rosental, R.N. Coldman, A.J. Moro, I. Angurell, R.M Gomila, A. Frontera, J.C. Lima, L. Rodríguez

Molecules (2021), 26, 2444

Abstract:
The synthesis of two new phosphane-gold(I)–napthalimide complexes has been performed and characterized. The compounds present luminescent properties with denoted room temperature phosphorescence (RTP) induced by the proximity of the gold(I) heavy atom that favors intersystem crossing and triplet state population. The emissive properties of the compounds together with the planarity of their chromophore were used to investigate their potential as hosts in the molecular recognition of different polycyclic aromatic hydrocarbons (PAHs). Naphthalene, anthracene, phenanthrene, and pyrene were chosen to evaluate how the size and electronic properties can affect the host:guest interactions. Stronger affinity has been detected through emission titrations
for the PAHs with extended aromaticity (anthracene and pyrene) and the results have been supported by DFT calculation studies.

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Gold(I)-doped films: new routes for efficient room temperature phosphorescent materials

A. de Aquino, F.J. Caparrós, K.-N. Truong, K. Rissanen, M. Ferrer, Y. Jung, H. Choi, J.C. Lima, L. Rodríguez

Dalton Transactions (2021), 50, 3806

Abstract:
The synthesis of four novel gold(I)-phosphane complexes coordinated to 9-phenanthrene chromophore has been carried out through the reaction of 9-phenanthreneboronic acid and the corresponding AuClPR3 (PR3 = PPh3 for triphenylphosphane (1a); 1,4-bis(diphenylphosphanyl)butane or dppb (2b); is(diphenylphosphanyl)acetylene or dppa (2c); (AuCl)2(diphos) (diphos = bis(diphenylphosphanyl)methane or dppm (3)) sources. The X-ray crystal structures of compounds 1a and 2b show the existence of MOFlike intermolecular assemblies that contain empty inner cavities in the absence of aurophilic contacts. In
contrast, the formation of a tetranuclear complex with intramolecular aurophilic interactions was evidenced for 3. Photophysical characterization indicates dual emission in all gold(I) complexes when oxygen is removed from the sample, while only fluorescence emission is recorded for the uncoordinated ligand. The introduction of the compounds within PMMA and Zeonex was assayed, and luminescent films containing gold(I) complexes where phosphorescence is the sole pathway for emission are obtained, instead of the dual emission (with significant fluorescence contribution) recorded in solution.

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Base-assisted synthesis of 4-pyridinate gold(I) metallaligands: a study of their use in self-assembly reactions

M. Ferrer, A. Gutiérrez, M. Martínez, C. Da Silva, A.V.G. Netto, L. Rodríguez, G. Romo-Islas, F. Pan, K. Rissanen

Dalton Transactions (2021), 50, 3806

Abstract:
The synthesis of di- and tritopic gold(I) metallaligands of the type [(Au4-py)2(μ2-diphosphane)] (diphosphane = bis(diphenylphosphanyl)isopropane or dppip (1), 1,2-bis(diphenylphosphanyl)ethane or dppe (2),
1,3-bis(diphenylphosphanyl)propane or dppp (3) and 1,4-bis(diphenylphosphanyl)butane or dppb (4)) and [(Au4-py)3(μ3-triphosphane)] (triphosphane = 1,1,1-tris(diphenylphosphanylmethyl)ethane or triphos (5)
and 1,3,5-tris(diphenylphosphanyl)benzene or triphosph (6)) from [(AuCl)2(μ2-diphosphane)] or [(AuCl)3(μ3-triphosphane)] and 4-pyridylboronic acid in the presence of Cs2CO3 has been conducted.
Interestingly, when [(AuCl)2(μ2-dppm)] (dppm = bis(diphenylphosphanyl)methane) was used as a starting material, the cyclic tetranuclear gold(I) compound [(Au4-py)2(CH)2{μ2-Au(PPh2)2}2] (I) was obtained instead.
All the products have been characterized by IR and multinuclear NMR spectroscopy, mass spectrometry and elemental analysis and in the case of 1, 3, 5 and I by X-ray crystallography, which showed the presence of aurophilic interactions in all of them. The obtained metallaligands have been used as building blocks in self-assembly reactions with cis-blocked palladium or platinum acceptor moieties producing [2 + 2] metallamacrocycles
or trigonal bipyramidal (TBP) [2 + 3] metallacages in good yields. The photophysical properties of both the metallaligands and the corresponding assemblies have been investigated.

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Tripodal gold(I) polypyridyl complexes and their Cu+ and Zn2+ heterometallic derivatives. Effects on luminescence

A. Pinto, G. Spigolon, R. Gavara, C. Zonta, G. Licini, L. Rodríguez

Dalton Transactions (2020), 49, 14613

Abstract:
Three gold(I) tripodal complexes containing the tris(2-pyridylmethyl)amine (TPA) ligand coordinated to Au–PR3 moieties (PR3 = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane, PTA (1), 3,7-diacetyl-
1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane, DAPTA (2) and triphenylphosphane (3)) were prepared together with a cage-like structure containing triphosphane 1,1,1-tris(diphenylphosphinomethyl)ethane (4). The luminescence of these complexes has been studied and they show a red shift upon the formation of heterometallic complexes by reaction with Zn(NO3)2, CuCl and [Cu(CH3CN)4]BF4.
The different coordination motifs of the Zn2+ and Cu+ heterometallic species and the resulting changes in the recorded absorption, emission and NMR spectra were analysed and supported by TD-DFT calculations.

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Room-Temperature Phosphorescence and Efficient Singlet Oxygen Production by Cyclometalated Pt(II) Complexes with Aromatic

A. Lázaro, C. Cunha, R. Bosque, J. Pina, J.S. Ward, K.-N. Truong, K. Rissanen, J.C. Lima, M. Crespo, J.S. Seixas de Melo, L. Rodríguez

Inorganic Chemistry (2020), 59, 8220

Abstract:
The synthesis of five novel cyclometalated platinum(II) compounds containing five different alkynyl-chromophores was achieved by the reaction of the previously synthesized Pt−Cl cyclometalated compound (1) with the corresponding RCCH by a Sonogashira reaction. It was observed that the spectral and photophysical characteristics of the cyclometalated platinum(II) complexes (Pt−Ar) are essentially associated with the platinum-cyclometalated unit. Room-temperature emission of the Pt−Ar complexes was attributed to phosphorescence in agreement with DFT calculations. Broad nanosecond (ns)-transient absorption spectra were observed with decays approximately identical to those obtained from the emission of the triplet state. From the femtosecond-transient absorption (fs-TA) data, two main excitedstate decay components were identified: one in the order of a few picoseconds was assigned to fast intersystem crossing to populate the triplet excited-state and the second (hundreds of ns) was associated with the decay of the transient triplet state. In general, efficient singlet oxygen photosensitization quantum yields were observed from the triplet state of these complexes.

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Facile morphology control of gold(0) structures from aurophilic assemblies

E. Aguiló, M. Dalmases, M. Lin, J.C. Lima, R. Gavara, A. Figuerola, J. Llorca, L. Rodríguez

Dalton Transactions (2020), 49, 4200

Abstract:
Different gold microstructures have been synthesized by using and Ag nanoparticles as reducing agents. The use of fibers resulting from supramolecular assemblies of neutral gold(I) compounds gives rise to the formation of microrods. The use of supramolecular assemblies from ionic molecules results in spherical or squarebased prism gold microstructures, depending on the shape of the supramolecular gold(I) precursor assembly. In addition to temperature and reaction time, solvents exert a strong influence on the formation and morphology of gold structures, as borne out by the example that well-defined star-like morphologies have been obtained in chloroform.

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Luminescent Tetranuclear Gold(I) Dibenzo[g,p]chrysene Derivatives: Effect of the Environment on Photophysical Properties

F.J. Caparrós, M. Outis, Y. Jung, H. Choi, J.C. Lima, L. Rodríguez

Molecules (2020), 25, 949

Abstract:
A new 2,7,10,15-tetraethynyldibenzo[g,p]chrysene ligand (1) and two tetranuclear gold(I) derivatives containing PPh3 (3) and PMe3 (4) phosphines were synthesized and characterized by 1H and 31P NMR, IR spectroscopy, and high-resolution mass spectrometry. The compounds were studied in order to analyze the effect of the introduction of gold(I) on the supramolecular aggregation and photophysical properties. Absorption and emission spectra displayed broad bands due to the establishment of pi···pi interactions as an indication of intermolecular contacts and the formation of aggregates. A decrease of the recorded quantum yield (QY) of the gold(I) derivatives was observed compared to the uncomplexed ligand. The introduction of the complexes into poly methyl methacrylate (PMMA) and Zeonex 480R matrixes was analyzed, and an increase of the measured QY of 4 in Zeonex was observed. No phosphorescent emission was detected.

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Luminescent phosphine gold(I) alkynyl complexes. Highlights from 2010 to 2018

M. Pujadas, L. Rodríguez

Coordination Chemistry Reviews (2020), 408, 213179

Abstract:
An overview of the homometallic phosphine-Au(I)alkynyl complexes reported in the literature from 2010 to 2018 have been collected and reported in this review article. They have been classified for better understanding, between mononuclear and polynuclear compounds. Their luminescent properties have been discussed along the text and the specific absorption and emission data collected in Annex I. This type of compounds are being used for a wide range of applications in fields such as biomedicine, chemosensors or luminescent materials among others and their interest is increasing in the last years. Some particular examples have been also selected herein.

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Influence of the Attachment of a Gold(I) Phosphine Moiety at the Upper Rim of a Calix[4]pyrrole on the Binding of Tetraalkylammonium Chloride Salts

Q. Sun, G. Aragay, A. Pinto, E. Aguiló, L. Rodríguez, P. Ballester

Chemistry – A European Journal (2020), 26, 3348

Abstract:
We report the synthesis of an unprecedented monogold(I) phosphine complex based on a “two wall” aryl-ethynyl extended calix[4]pyrrole. We describe and compare the binding properties of the parent 10α,20α-bis-aryl-ethynyl calix[4]pyrrole ligand and the prepared organometallic compound as receptors for tetraalkylammonium chloride salts in dichloromethane and acetone solutions. We describe the results of 1H NMR, UV-vis titrations and isothermal titration calorimetry (ITC) experiments in DCM and acetone solution, aiming to thermodynamically characterize the formed complexes. The obtained results indicate a noticeable decrease in the binding affinity of the chloride for the mono-gold(I) receptor 1 compared to the parent ligand 2. The increase in the negative value of the electrostatic surface potential at the center of the aromatic ring of the gold(I) meso-aryl-ethynyl substituent serves to explain the observed results and the presence in solution of the chloride complex of 1 as a mixture of two conformers.

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Luminescent PtII and PtIV Platinacycles with Anticancer Activity Against Multiplatinum-Resistant Metastatic CRC and CRPC Cell Models

A. Lázaro, C. Balcells, J. Quirante, J. Badia, L. Baldomá, J.S. Ward, K. Rissanen, M. Font-Bardia, L. Rodríguez, M. Crespo, M. Cascante

Chemistry – A European Journal (2020), 26, 1947

Abstract:
Platinum-based chemotherapy persists to be the only effective therapeutic option against a wide variety of tumours. Nevertheless, the acquisition of platinum resistance is utterly common, ultimately cornering conventional platinum drugs to only palliative in many patients. Thus, encountering alternatives that are both effective and non-cross-resistant is urgent. In this work, we report the synthesis, reduction studies and luminescent properties of a series of cyclometallated (C,N,N’) PtIV compounds derived from amine-imine ligands, and their remarkable efficacy at the high nanomolar range and complete lack of cross-resistance, as an intrinsic property of the platinacycle, against multiplatinum-resistant colorectal cancer (CRC) and castration-resistant prostate cancer (CRPC) metastatic cell lines generated for this work. We have also determined that the compounds are effective and selective for a broader cancer panel, including breast and lung cancer. Additionally, selected compounds have been further evaluated, finding a shift in their antiproliferative mechanism towards more cytotoxic and less cytostatic than cisplatin against cancer cells, being also able to oxidize cysteine residues and inhibit topoisomerase II, thereby holding great promise as future improved alternatives to conventional platinum drugs.

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Aggregation induced emission of a new naphthyridine-ethynyl–gold(I) complex as a potential tool for sensing guanosine nucleotides in aqueous media

A.J. Moro, J. Avó, M. Malfois, F. Zaccaria, C. Fonseca Guerra, F.J. Caparrós, L. Rodríguez, J.C. Lima

Dalton Transactions (2020), 49, 171

Abstract:
A new organometallic alkynyl–gold(I) complex capable of exhibiting aggregation induced emission was designed and synthesized. The linear complex structure possesses a central Au(I) atom, bearing two axial ligands: (1) 1,3,5-triaza-7-phosphaadamantane and (2) 2-acetamido-7-ethynyl-1,8-naphthyridine. While the former accounts for its partial solubility in an aqueous environment, the latter acts as a receptor unit for binding guanosine nucleotides and derivatives via multiple hydrogen bonding interactions. At high concentrations, aggregation of the complex was observed by the formation of new absorption (λmax ∼ 400 nm) and emission bands (550–700 nm). Formation of aggregates of ca. 60 nm diameter was confirmed by Small Angle X-ray Scattering (SAXS). Disruption of the aggregates in the presence of guanosine derivatives resulted in a ratiometric signal with apparent association constants in the order of 105 M−1 and high sensitivity (around 63% signal change) which are, to the best of our knowledge, in line with the highest values recorded for nucleotide sensors based on hydrogen bonding and capable of working in water. Computational studies indicate the presence of additional hydrogen bonding interactions that account for the strong binding of the Au(I) complex to phosphorylated guanosine nucleotides.

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Highlights on Gold TADF Complexes

J.C. Lima, L. Rodríguez

Inorganics (2019), 7, 124

Abstract:
Thermally activated delayed fluorescence (TADF) and TADF-organic light-emitting diodes (OLEDs) systems are being given increasing attention in research nowadays. Much more work has been done for organic-based materials in this field, but the use of TADF organometallic systems has also emerged in recent years. In particular, TADF-based gold compounds have not been particularly well-explored, with a higher number of examples of Au(I)-molecules and fewer for the higher oxidation state Au(III) derivatives. Nevertheless, the novelty and observed results deserve attention. A careful analysis has been performed in this review by classifying the reported compounds into two different groups regarding the oxidation state of the metal, and within each group, the ancillary ligands. Specific examples to illustrate their potential applications are included.

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Supramolecular tripodal Au(I) assemblies in water. Interactions with a pyrene fluorescent probe

A. Pinto, G. Hernández, R. Gavara, E. Aguiló, A.J. Moro, G. Aullón, M. Malfois, J.C. Lima, L. Rodríguez

New J. Chem. (2019), 43, 8279

Abstract:
The synthesis of three gold(I) tripodal complexes derived from tripropargylamine and containing thewater soluble phosphines PTA (1,3,5-triaza-7-phosphaadamantane), DAPTA (3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) and TPPTS (triphenylphosfine-3,30,300-trisulfonic acid trisodium salt) is described here. The three complexes are observed to give rise to the formation of supramolecular aggregates in water and very long fibers. This property has been analyzed by means of 1H-NMR spectroscopy at different concentrations and SAXS. The results point out the important role of the phosphine moieties as the main enthalpic or entropic contribution in the resulting Gibbs energy of aggregate formation. The tripodal structure of the three complexes together with the presence of gold(I) atoms makes them ideal candidates to interact with hydrophobic molecules also in water. For this, the interaction with pyrene in this solvent has been evaluated with successful results in all three complexes. The highest association constant corresponds to 2 as the host. DFT studies indicate the location of pyrene in the tripodal cavity as the most stable conformation. The interaction with pyrene has been additionally studied within cholate hydrogel matrixes pointing out the stability of the resulting host:guest adducts in different media.

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Supramolecular assemblies and photophysical properties of ionic homo- and heteronuclear metallophilic complexes

N. Svahn, I. Sanz, K. Rissanen, L. Rodríguez

J. Organomet. Chem. (2019), 897, 170

Abstract:
The synthesis of two dinuclear ionic complexes with chemical formula [Au(PR3)2][Au(C≡CC5H4N-4)2]that contain the water soluble phosphines, PR3, PTA (1, 3,5-triaza-7-phosphaadamantane, 1) and DAPTA (3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane, 2) is herein described. The differences on their intermolecular reorganization have been analyzed and compared with the previously reported for the neutral complexes [Au(PR3)(C≡CC5H4N-4)]. It has been evidenced that the reorganization of the ligands giving rise to the dinuclear ionic complexes produces a complete change in the properties giving rise to Au/Au intermolecular assemblies. These aurophilic contacts are the responsible for the resulting luminescence which is not displayed for the parent compounds [Au(PR3)2]Cl and [PPh4][Au(C≡CC5H4N-4)2]. Compounds 1 and 2 were made react with three different silver salts (nitrate, triflate and hexafluorophosphate) giving rise to 1:1 heterometallic assemblies with some changes both on the wavelength and emission intensity.

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Luminescence studies of new [C,N,N’] cyclometallated platinum(II) and platinum(IV) compounds

A. Lázaro, O. Serra, L. Rodríguez, M. Crespo, M. Font-Bardia

New J. Chem. (2019), 43, 1247.

Abstract:
The synthesis of six novel cyclometallated platinum(IV) compounds (3a-3c and 4a-4c) derived from ligand (4-FC6H4)CHQN(CH2)3N(CH3)2 (L) was achieved by intermolecular oxidative addition of halogens to cyclometallated platinum(II) compounds [Pt(CH3){(CH3)2N(CH2)3NQCH(4-FC6H3)}] (1) and [PtX{(CH3)2N(CH2)3NQCH(4-FC6H3)}] (2a, XQCl; 2b, XQBr; 2c, XQI). While compound 2b could be obtained from 2a through Cl for Br substitution reaction, 2c was best obtained through cyclometallation of ligand L with [PtI2(dmso)2]. The X-ray molecular structures of [C,N,N0] platinum(II) (2b) and platinum(IV) (3b and 4b) cyclometallated compounds and of the [N,N0] platinum(II) compound Ib, all of them containing bromido ligands, are reported. The absorption and emission spectra were also studied in dichloromethane solution at room temperature. All compounds, except 3c and 4c arising from oxidative addition of iodine, display a broad emission band in the 340–360 nm range, attributed to platinum disturbed intraligand (IL) transitions, when excited at the highest energy band, and higher emission intensities were observed, in general, for cyclometallated platinum(IV) compounds.

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Preparation and Antitumoral Activity of Au-Based Inorganic-Organometallic Nanocomposites

M. Dalmases, A. Pinto, P. Lippmann, Ingo Ott, L. Rodríguez, A. Figuerola

Frontiers in Chemistry (2019), 7, 60

Abstract:
The synergy between gelator molecules and nanostructured materials is currently a novel matter of study. The possibility to carefully design the skeleton of the molecular entity as well as the nanostructure’s morphological and chemical features offers the possibility to prepare a huge variety of nanocomposites with properties potentially different than just the sum of those of the individual building blocks. Here we describe the synthesis and characterization of nanocomposites made by the unconventional combination of phosphine-Au(I)-alkynyl-based organometallic gelating molecules and plasmonic Au nanoparticles. Our results indicate that the interaction between the two moieties leads to a significant degree of aggregation in both hydrophilic and hydrophobic media, either when using DAPTA or PTA-based organometallic molecules, with the formation of a sponge-like hybrid powder upon solvent evaporation. The biological activity of the nanocomposites was assessed, suggesting the existence of a synergetic effect evidenced by the higher cytotoxicity of the hybrid systems with respect to that of any of their isolated counterparts. These results represent a preliminary proof-of-concept for the exploitation of these novel nanocomposites in the bioEmedical field.

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