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

We report the synthesis of an unprecedent mono-gold(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 at 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

Study of the effect of the chromophore and nuclearity on the aggregation and potential biological activity of gold(I) alkynyl complexes

The synthesis and characterization of four organometallic gold(I) complexes containing different water soluble phosphanes (TPPTS, PTA and DAPTA) and chromophoric units (4-pyridylethynyl and propargyloxycoumarin) is here reported. The analysis of their absorption and emission spectra led us to attribute their luminescent behavior to the chromophoric organic ligands. Moreover, the presence of the gold(I) metal atom has been observed to be the responsible of an efficient intersystem crossing process responsible for the observed phosphorescence emission. Broad emission bands are observed in most cases due to the formation of organized aggregates in solution in agreement with microscopic characterization. Biological activity of the complexes showed very low effects against tumor cell growth but an inhibitory potency against thioredoxin reductase (TrxR). The missing/low cytotoxic effects could be related to a low bioavailability as determined by atomic absorption spectroscopy. Graphical abstract The synthesis, characterization, aggregation and emissive properties of four organometallic gold(I) complexes containing different water soluble phosphanes and chromophoric units is here reported. Biological activity of the complexes showed very low effects against tumor cell growth but an inhibitory potency against thioredoxin reductase (TrxR

A coumarin based gold(I)-alkynyl complex: a new Q1 class of supramolecular hydrogelators

A phosphine-gold(I)-alkynyl-coumarin complex, [Au{7-(prop-2-ine-1-yloxy)-1-benzopyran-2-one}-(DAPTA)] (1), was synthesized and the formation of long luminescent fibers in solution was characterized via fluorescence microscopy and dynamic light scattering. The fibers presented strong blue and green luminescence, suggesting that the gold(I) in the complex increased intersystem crossing due to the heavy atom effect, resulting in a significant increase in triplet emission. The X-ray structure of the fibers indicates that both aurophilic, π-π interactions and hydrogen bonding contribute to their formation in aqueous solvents

Tuning supramolecular aurophilic structures: the effect of counterion, positive charge and solvent

The synthesis of the cationic gold(I) complexes [Au(C≡CC5H4N)(CH3-PTA)]X (X = I, 1; X = OTf, 4), [Au(C≡CC5H4N-CH3)(PTA)]X (X = I, 2; X = OTf = 5; PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane) and [Au(C≡CC5H4N-CH3)(DAPTA)]X (X = I, 3; X = OTf = 6, DAPTA = 3,7-diacetyl-1,3,7-triaza-5- phosphabicyclo[3.3.1]nonane) gives cationic complexes showing unexpected supramolecular assemblies in water going from rod-like structures (1) to vesicles (2 and 3) and square-like structures (5 and 6). These morphologies are completely different from the fibers previously obtained with their parent neutral complexes [Au(C≡C5H4N)(PTA)] and [Au(C≡C5H4N)(DAPTA)]. Nevertheless, the introduction of triflate as counterion in 1 (complex 4) gives rise to the formation of highly soluble complex in water which does not display any significant aggregation in solution. These results reveal the importance of the introduction of a positive charge on the global supramolecular assemblies and how the counterion can modify also the resulting package. Interestingly, we have also proved that the aggregation of complexes 2, 3, 5 and 6 is also affected by the solvent with direct influence on their absorption and emission properties and the global morphology of the aggregates

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

Different gold microstructures have been synthesized by using supramolecular gold(I) organometallic compounds as templates and Ag nanoparticles as reducing agent. 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 square-based prisms gold microstructures, depending on the shape of the supramolecular gold(I) precursor assembly. In addition to temperature and reaction time, the solvent has a strong influence on the formation and morphology of the gold structures. Well-defined star-like morphologies have been obtained in chloroform

Estructuras supramoleculares de oro(I) con propiedades luminiscentes. Estudios de agregación y aplicaciones

[spa] Hace unos años, en el grupo de investigación donde se ha realizado esta Tesis Doctoral, se estudió un sistema de oro(I)-alquinilo con una fosfina soluble en agua, que dio lugar a la formación de un hidrogel. Este ejemplo es de destacar, ya que fue el primer trabajo acerca de la formación de un hidrogel con una estructura química tan simple. Las interacciones aurofílicas y otras interacciones débiles estaban involucradas en el proceso de gelificación. Este resultado es el punto de partida de este Tesis Doctoral. El trabajo realizado en esta Tesis Doctoral se ha centrado en la síntesis de diferentes tipos de complejos de oro(I) que contienen la fórmula general [Au(C≡C- org)(PR3)] (org = piridina, cumarina, tetrapirrol) (PR3 = PTA, DAPTA, TPPTS) (fosfinas solubles en agua). Se han introducido cambios en la unidad cromófora (cumarina, tetrapirrol, bipiridina o terpiridina en lugar de la piridina) y se ha estudiado cuidadosamente la formación de complejos iónicos en lugar de neutros con el objetivo de analizar cómo estas modificaciones pueden afectar a los conjuntos supramoleculares resultantes y en sus propiedades luminiscentes. Por otra parte, en los últimos años, se han empleado varias técnicas y métodos para atribuir la presencia de aurofilicidad intra- e intermolecular en solución, en nuestro caso, los experimentos de RMN de 1H llevados a cabo con los complejos que forman hidrogeles a diferentes concentraciones y temperaturas nos han proporcionado información sobre los parámetros termodinámicos implicados en la formación de agregados. Así se ha podido analizar con más detalle cuáles son las fuerzas particulares responsables de la formación de estos hidrogeles organometálicos. También, la técnica SAXS nos ha permitido analizar con más detalle el proceso de agregación que tiene lugar con los complejos derivados de la bipiridina. Más recientemente, el interés en este tipo de compuestos desde el punto de vista biológico está aumentando y los resultados parecen bastante prometedores. De hecho, los informes iniciales recientes sobre la bioactividad de los complejos de oro(I)-alquinilo indican que este tipo de complejos organometálicos ofrecen oportunidades para el desarrollo de nuevos fármacos quimioterapéuticos contra el cáncer y las enfermedades infecciosas. Además, en general, las fuerzas intermoleculares débiles están involucradas en los procesos de reconocimiento molecular, y para ello hemos querido explorar cómo los conjuntos supramoleculares pueden ser modificados en presencia de aniones (principalmente haluros). Los objetivos particulares de esta Tesis Doctoral se relacionan a continuación, juntamente con el capítulo en el que se describen. En el Capítulo 2 se ha sintetizado un nuevo compuesto de oro(I) derivado de la 4- etinilpiridina con una pequeña variación (introducción de grupos acetilo) con respecto al complejo precursor que forma el hidrogel, para ver si tiene un claro efecto sobre las propiedades estructurales y luminiscentes resultantes. También, se han realizado tratamientos térmicos sobre la estructura supramolecular formada para observar la formación de nanopartículas metálicas de oro. En el Capítulo 3, se han estudiado los procesos de agregación que tienen lugar en los complejos de oro(I)-alquinilo derivados de la 4-etinilpiridina mediante diferentes técnicas espectroscópicas, tales como absorción UV-vis, RMN (a diferentes temperaturas y concentraciones) y DLS, para estimar la constante de equilibrio del proceso de agregación y la presencia de interacciones aurofílicas. Se han realizado cálculos computacionales para saber de la existencia de contactos Au-Au. En el Capítulo 4, se han sintetizado complejos catiónicos de oro(I) derivados de la 4-etinilpiridina para observar si forman ensamblajes supramoleculares diferentes respecto a los complejos precursores neutros. También, se ha estudiado cómo el contraión puede modificar la morfología supramolecular resultante. Además, se ha realizado un estudio de cómo se ve afectada la agregación de estos complejos con carga positiva por el disolvente con influencia directa sobre sus propiedades de absorción y emisión, y la morfología global de los agregados. En el Capítulo 5, se han sintetizado cuatro complejos organometálicos de oro(I) que contienen diferentes fosfinas solubles en agua y unidades cromóforas (4- etinilpiridina y propargiloxicumarina) con propiedades luminiscentes. Se han estudiado sus propiedades luminiscentes mediante absorción UV-vis y emisión, así como sus propiedades estructurales mediantes microscopía óptica y electrónica. También, se ha analizado su actividad biológica contra el crecimiento de células tumorales así como sus actividades inhibidoras contra la enzima tiorredoxina reductasa. En el Capítulo 6, se han sintetizado nuevos sistemas organometálicos de oro(I) derivados del [4]calixpirrol con fosfinas solubles en agua, para observar si forman estructuras supramoleculares en agua. Se han estudiado las interacciones intermoleculares con el fin de comprender el empaquetamiento supramolecular resultante. Se han realizado estudios de los procesos de reconocimiento molecular para la detección de haluros y comparado con los resultados previamente estudiados con el ligando libre. En el Capítulo 7, se han sintetizado cuatro complejos de oro(I) derivados de la bipiridina y de la terpiridina con fosfinas solubles en agua. Se han estudiado sus propiedades luminiscentes y estructurales. También, se ha realizado un estudio detallado del proceso de agregación y desagregación en agua y DMSO mediante las técnicas espectroscópicas de RMN, de absorción UV-vis y de emisión, así como la técnica SAXS. En el Capítulo 8, se han sintetizado diferentes nanoestructuras de Au aprovechando las distintas estructuras supramoleculares que forman ciertos complejos de oro(I), mediante la reducción del oro con la presencia de nanopartículas de plata. En el Capítulo 9, se han diseñado y sintetizado nuevos sistemas fotocatalíticos de oro(I) con TiO2 como soporte para la obtención de energía (H2).[eng] A few years ago, in the research group where this Doctoral Thesis was carried out, a gold (I) -alkynyl system was studied with a water-soluble phosphine, which gave rise to the formation of a hydrogel. This example is noteworthy, since it was the first work on the formation of a hydrogel with such a simple chemical structure. Aurophilic interactions and other weak interactions were involved in the gelation process. This result is the starting point of this Doctoral Thesis. The work done in this Doctoral Thesis has focused on the synthesis of different types of gold (I) complexes containing the general formula [Au (C≡C-org) (PR3)] (org = pyridine, coumarin, tetrapyrrole) (PR3 = PTA, DAPTA, TPPTS) (water soluble phosphines). Changes have been made in the chromophoric unit (coumarin, tetrapyrrole, bipyridine or terpyridine instead of pyridine) and the formation of ionic complexes rather than neutral ones has been carefully studied in order to analyze how these modifications can affect supramolecular assemblies And their luminescent properties. On the other hand, in the last years, several techniques and methods have been used to attribute the presence of intra- and intermolecular aurophilicity in solution, in our case, the 1H NMR experiments carried out with the complexes that form hydrogels to different Concentrations and temperatures have provided us with information about the thermodynamic parameters involved in the formation of aggregates. Thus it has been possible to analyze in more detail what are the particular forces responsible for the formation of these organometallic hydrogels. Also, the SAXS technique has allowed us to analyze in more detail the aggregation process that takes place with complexes derived from bipyridine. More recently, the interest in this type of compounds from the biological point of view is increasing and the results seem quite promising. In fact, recent initial reports on the bioactivity of gold (I) -alkynyl complexes indicate that these organometallic complexes offer opportunities for the development of new chemotherapeutic drugs against cancer and infectious diseases. In addition, in general, weak intermolecular forces are involved in molecular recognition processes, and for this we wanted to explore how supramolecular assemblies can be modified in the presence of anions (mainly halides)

Rhodium(I) macrocyclic and cage-like structures containing diphosphine bridging ligands

Three series of rhodium organometallic complexes, mono- (1c, 2c, 5c, 6c), di- (1a-6a) and tetranuclear (1b, 5b, 6b), containing six different diphosphines (1,1'- bis(diphenylphosphino)methane or dppm (1), 1,2-bis(diphenylphosphino)ethane or dppe (2), 1,4-bis(diphenylphosphino)butane or dppb (3), bis(diphenylphosphino)acetylene or dppa (4), 1,2-bis(diphenylphosphino)benzene or dppbz (5) and 4,5-bis(diphenylphosphino)-9,9'-dimethylxanthene or xantphos (6) were successfully synthesised. These Rh(I) complexes were characterised by conventional techniques. The influence of the flexibility/rigidity of these P-donor ligands was carefully analysed, including their effect on both synthesis and catalysis. The luminescent properties of the dinuclear and tetranuclear complexes were investigated and only those containing dppa, dppbz and xantphos displayed luminescence. Structures of dinuclear complexes were modelled by using DFT methods in order to elucidate the most possible conformation. The different types of complexes were applied in the catalytic hydrogenation of (E)-4- phenylbut-3-en-2-one, showing high activity and similar catalytic behaviour. No cooperative effect could be inferred

Exploiting metallophilicity for the assembly of inorganic nanocrystals and conjugated organic molecules

The accurate engineering of interfaces between inorganic nanocrystals and semiconducting organic molecules is currently viewed as key for further developments in critical fields such as photovoltaics and photocatalysis. In this work, a new and unconventional source of interface interaction based on metal–metal bonds is presented. With this aim, an AuI organometallic gelator was exploited for the formation of hydrogel-like nanocomposites containing inorganic nanoparticles and conjugated organic molecules. Noteworthy, the establishment of metallophilic interactions at the interface between the two moieties greatly enhances interparticle coupling in the composites. Thus, we believe that this new hybrid system might represent a promising alternative in several fields, such as in the fabrication of improved light-harvesting devices.Peer Reviewe

Modulation of supramolecular gold(I) aggregates by anion's interaction

The gold complexes [Au(4-pyridylethynyl)(PTA)] and [Au(4-pyridylethynyl)(DAPTA)] (PTA = 1,3,5-triaza-7-phosphaadamantane; DAPTA = 3,7-diacetyl-1,3,7-triaza-5- phosphabicyclo[3.3.1]nonane) were used as host in molecular recognition processes of sodium hexametaphosphate (HMP) and a single stranded 24-long oligonucleotide. Experiments were performed by absorption titrations and looking at the resulting host:guest adducts by polarized optical, fluorescence and scanning electron microscopy. The resulting information indicates that different type of interactions are present with the two different guest molecules. In the case of HMP, the compounds aggregate giving rise to larger structures, favoring exciton splitting coupling and the formation of head to tail interactions. In the case of oligonucleotide studies, the formation of smaller supramolecular structures is observed, with less contribution of aurophilic contacts and organized in a parallel way (head to head interactions organized by the presence of the oligonucleotide)

Study of the effect of the chromophore and nuclearity on the aggregation and potential biological activity of gold(I) alkynyl complexes

The synthesis and characterization of four organometallic gold(I) complexes containing different water soluble phosphanes (TPPTS, PTA and DAPTA) and chromophoric units (4-pyridylethynyl and propargyloxycoumarin) is here reported. The analysis of their absorption and emission spectra led us to attribute their luminescent behavior to the chromophoric organic ligands. Moreover, the presence of the gold(I) metal atom has been observed to be the responsible of an efficient intersystem crossing process responsible for the observed phosphorescence emission. Broad emission bands are observed in most cases due to the formation of organized aggregates in solution in agreement with microscopic characterization. Biological activity of the complexes showed very low effects against tumor cell growth but an inhibitory potency against thioredoxin reductase (TrxR). The missing/low cytotoxic effects could be related to a low bioavailability as determined by atomic absorption spectroscopy. Graphical abstract The synthesis, characterization, aggregation and emissive properties of four organometallic gold(I) complexes containing different water soluble phosphanes and chromophoric units is here reported. Biological activity of the complexes showed very low effects against tumor cell growth but an inhibitory potency against thioredoxin reductase (TrxR