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A novel family of square-planar Pd(II) complexes based on isoquinoline-functionalised pyrazolate ligands [Pd(pzR(n,n)iq)2] (R(n,n) = C6H3(OCnH2n+1)2, n = 4, 6, 8, 10, 12, 14, 16, 18) has been synthesised and characterised. The new complexes show mesomorphic properties and exhibit columnar mesophases that are highly-stable in exceptionally wide temperature ranges of up to 345 °C. The formation of nanochannels in the fluid liquid crystal phases generates continuous pathways for one-dimensional proton conduction on the basis of C–H⋯N proton transfer. The complex with an intermediate chain length (n = 12) shows the highest proton conductivity of 1.34 × 10−4 S m−1 at 269 °C in the hexagonal columnar mesophase, and an activation energy of 0.84 eV. The influence of both the terminal alkyl chain length and the mesophase columnar organisation on the proton conduction mechanism is demonstrated. The series of Pd(II) complexes investigated in this work constitutes one of the first examples of proton-conducting metallomesogens with potential applications in PEM fuel cells., Ministerio de Economía y Competitividad, Programa de Financiación de Universidad Complutense de Madrid-Santander Universidades (Spain), Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

The introduction of structural asymmetry in metallomesogens is an established strategy to improve their mesomorphic behaviour in terms of lower melting temperatures and higher stability ranges of the mesophase, which is particularly important for metallomesogens that have potential application as electrolytes that require wide operational temperature ranges. Here in this work, a novel series of unsymmetrical bis(isoquinolinylpyrazolate)palladium(ii) compounds bearing four alkyl side-chains with different lengths are described. Rectangular and hexagonal columnar mesophases were formed with low melting temperatures of 42-45 degrees C in most cases, whereas the clearing temperatures reached values up to 412 degrees C. The charge transport properties have been studied by complex impedance spectroscopy, showing that the mesophase favours proton conduction in the absence of water or humidity. The exceptional thermal stability of these species makes them promising candidates to act as a platform for ionic conduction via the nanochannels originated in the columnar mesophases. The results presented confirm that introducing structural asymmetry in the Pd(ii) metallomesogens studied is a valid strategy to enhance the liquid crystalline properties, which opens new ways to develop water-free electrolytes based on unsymmetrical bis(isoquinolinylpyrazolate) Pd(ii) compounds for potential applications such as proton exchange membranes (PEMs)., Ministerio de Economía y Competitividad (España), Instituto de Salud Carlos III, Comunidad de Madrid, Universidad Complutense de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

The use of liquid crystals for the fabrication of displays incorporated in technological devices (TVs, calculators, screens of eBook’s, tablets, watches) demonstrates the relevance that these materials have had in our way of living. However, society evolves, and improved devices are looked for as we create a more efficient and safe technology. In this context, metallomesogens can behave as multifunctional materials because they can combine the fluidic state of the mesophases with properties such as photo and electroluminescence, which offers new exciting possibilities in the field of optoelectronics, energy, environment, and even biomedicine. Herein, it has been established the role of the molecular geometry induced by the metal center in metallomesogens to achieve the self-assembly required in the liquid-crystalline mesophase. Likewise, the effect of the coordination environment in metallomesogens has been further analyzed because of its importance to induce mesomorphism. The structural analysis has been combined with an in-depth discussion of the properties of these materials, including their current and potential future applications. This review will provide a solid background to stimulate the development of novel and attractive metallomesogens that allow designing improved optoelectronic and microelectronic components. Additionally, nanoscience and nanotechnology could be used as a tool to approach the design of nanosystems based on luminescent metallomesogens for use in bioimaging or drug delivery., Associate Laboratory for Green Chemistry—LAQV, FCT/MCTES (Portugal), Projects UIDB/50006/2020, PROTEOMASS Scientific Society (Portugal), Proteomass 2020 funds, Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

Está depositada la versión postprint del artículo, Several series of dihalide Pd(ii) compounds bearing pyridyl or isoquinolinylpyrazole ligands have been strategically designed and synthesised to exhibit columnar mesomorphism in wide stability ranges. The coordination of the pyrazoles to the fragments PdX2 (X = Cl, Br, I) generates half-disc molecules that are capable of self-assembling into discotic dimers via intermolecular interactions. This disc-like shape is required for the supramolecular organisation of the lamellar columnar mesophases, which are formed at temperatures below 100 degrees C in most cases. It was found that these metallomesogens behave as 2D proton conducting materials under anhydrous conditions. The high fluidity properties of the mesophase facilitate proton conduction as a result of the spontaneous dissociation of the acidic pyrazole proton at the melting temperature. For the first time, lamellar columnar mesophases are demonstrated to serve as a 2D platform to induce water-free proton conductivity in dihalide Pd(ii) metallomesogens., Ministerio de Economía y Competitividad (España), Universidad Complutense de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

The luminescence properties of Pt(II) compounds can be modulated by controlling the assembly of their molecules both in the solution and in the solid state. This fact constitutes a powerful tool for developing materials with stimuli-responsive luminescence properties. Herein, we describe the self-assembly behaviour of several series of Pt(II) metallomesogens in two different media upon controlled conditions. On the one hand, we explore the ability of several metal cations to induce the formation of Pt⋯Pt aggregates in solution, with the main goal of enhancing the phosphorescent emission of these compounds. On the other hand, since these compounds exhibit liquid crystalline mesophases and the temperature can control the aggregation, we have fabricated Pt(II) compound-doped polymer films and silicone membranes that show stimuli-responsive luminescent properties. In both cases, the interactions between the Pt(II) compounds and the metal cations, or the polymer matrices, play a key role in the aggregation-induced emission enhancement (AIEE) behaviour of the dyes. The effects of the alkyl chain length, the molecular asymmetry, and the nature of the ligands in the establishment of these interactions are also evaluated., Ministerio de Economía y Competitividad, MINECO/FEDER (Spain), project CTQ2015-63858-P, PROTEOMASS Scientific Society (Portugal), Associate Laboratory for Green Chemistry-LAQV/REQUIMTE, FCT/MEC (Portugal), project UID/QUI/50006/2013, Universidad Complutense de Madrid-Santander Universidades (Spain), Fundación Alfonso Martín Escudero (Spain), Ministerio de Economía y Competitividad (Spain) and European Social Fund - BES-2014-070964, Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

Luminescent hollow micro- and nanocrystals have been successfully obtained taking advantage of the self-assembly behavior and the aggregation-induced emission enhancement properties of several bispyrazolate Pt(II) metallomesogens decorated with four terminal alkyl chains. Oil-in-water droplets have been used to confine the Pt(II) compounds and drive them to be self-assembled via intermolecular Pt···Pt interactions into spherical aggregates of about 200 or 50 nm. Evaporation of the oil phase generates highly-stable aqueous dispersions of nanocrystals that emit a bright orange light as a result of the existence of 3MMLCT excited states. Different methods and conditions have been tested for studying the effect of several parameters such as the temperature and the stirring speed in the final particle size and in the polydispersity index. Moreover, the micro- and nanocrystals are able to entrap hydrophobic drugs between the alkyl chains of the compounds, forming stable dispersions of drug-loaded capsules in water. The droplet method is applied in the area of metallomesogens for the first time to synthesize self-assembled Pt(II) nanocapsules, which opens a new field of study that could allow the use of these liquid crystal materials in biomedical applications., Associate Laboratory for Green Chemistry-LAQV, FCT/MCTES (Portugal), project UIDB/50006/2020), PROTEOMASS Scientific Society (Portugal), Fundación Alfonso Martín Escudero (España), Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

The introduction of structural asymmetry in metallomesogens is an established strategy to improve their mesomorphic behaviour in terms of lower melting temperatures and higher stability ranges of the mesophase, which is particularly important for metallomesogens that have potential application as electrolytes that require wide operational temperature ranges. Here in this work, a novel series of unsymmetrical bis(isoquinolinylpyrazolate)palladium(ii) compounds bearing four alkyl side-chains with different lengths are described. Rectangular and hexagonal columnar mesophases were formed with low melting temperatures of 42-45 degrees C in most cases, whereas the clearing temperatures reached values up to 412 degrees C. The charge transport properties have been studied by complex impedance spectroscopy, showing that the mesophase favours proton conduction in the absence of water or humidity. The exceptional thermal stability of these species makes them promising candidates to act as a platform for ionic conduction via the nanochannels originated in the columnar mesophases. The results presented confirm that introducing structural asymmetry in the Pd(ii) metallomesogens studied is a valid strategy to enhance the liquid crystalline properties, which opens new ways to develop water-free electrolytes based on unsymmetrical bis(isoquinolinylpyrazolate) Pd(ii) compounds for potential applications such as proton exchange membranes (PEMs)., Ministerio de Economía y Competitividad (España), Instituto de Salud Carlos III, Comunidad de Madrid, Universidad Complutense de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

The use of liquid crystals for the fabrication of displays incorporated in technological devices (TVs, calculators, screens of eBook’s, tablets, watches) demonstrates the relevance that these materials have had in our way of living. However, society evolves, and improved devices are looked for as we create a more efficient and safe technology. In this context, metallomesogens can behave as multifunctional materials because they can combine the fluidic state of the mesophases with properties such as photo and electroluminescence, which offers new exciting possibilities in the field of optoelectronics, energy, environment, and even biomedicine. Herein, it has been established the role of the molecular geometry induced by the metal center in metallomesogens to achieve the self-assembly required in the liquid-crystalline mesophase. Likewise, the effect of the coordination environment in metallomesogens has been further analyzed because of its importance to induce mesomorphism. The structural analysis has been combined with an in-depth discussion of the properties of these materials, including their current and potential future applications. This review will provide a solid background to stimulate the development of novel and attractive metallomesogens that allow designing improved optoelectronic and microelectronic components. Additionally, nanoscience and nanotechnology could be used as a tool to approach the design of nanosystems based on luminescent metallomesogens for use in bioimaging or drug delivery., Portuguese Foundation for Science and Technologies, Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

Luminescent hollow micro- and nanocrystals have been successfully obtained taking advantage of the self-assembly behavior and the aggregation-induced emission enhancement properties of several bispyrazolate Pt(II) metallomesogens decorated with four terminal alkyl chains. Oil-in-water droplets have been used to confine the Pt(II) compounds and drive them to be self-assembled via intermolecular Pt···Pt interactions into spherical aggregates of about 200 or 50 nm. Evaporation of the oil phase generates highly-stable aqueous dispersions of nanocrystals that emit a bright orange light as a result of the existence of 3MMLCT excited states. Different methods and conditions have been tested for studying the effect of several parameters such as the temperature and the stirring speed in the final particle size and in the polydispersity index. Moreover, the micro- and nanocrystals are able to entrap hydrophobic drugs between the alkyl chains of the compounds, forming stable dispersions of drug-loaded capsules in water. The droplet method is applied in the area of metallomesogens for the first time to synthesize self-assembled Pt(II) nanocapsules, which opens a new field of study that could allow the use of these liquid crystal materials in biomedical applications., Associate Laboratory for Green Chemistry (Portugal), PROTEOMASS Scientific Society (Portugal), Fundación Alfonso Martín Escudero (España), Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

The luminescence properties of Pt(II) compounds can be modulated by controlling the assembly of their molecules both in the solution and in the solid state. This fact constitutes a powerful tool for developing materials with stimuli-responsive luminescence properties. Herein, we describe the self-assembly behaviour of several series of Pt(II) metallomesogens in two different media upon controlled conditions. On the one hand, we explore the ability of several metal cations to induce the formation of Pt⋯Pt aggregates in solution, with the main goal of enhancing the phosphorescent emission of these compounds. On the other hand, since these compounds exhibit liquid crystalline mesophases and the temperature can control the aggregation, we have fabricated Pt(II) compound-doped polymer films and silicone membranes that show stimuli-responsive luminescent properties. In both cases, the interactions between the Pt(II) compounds and the metal cations, or the polymer matrices, play a key role in the aggregation-induced emission enhancement (AIEE) behaviour of the dyes. The effects of the alkyl chain length, the molecular asymmetry, and the nature of the ligands in the establishment of these interactions are also evaluated., Ministerio de Economía y Competitividad (España), PROTEOMASS Scientific Society (Portugal), Associate Laboratory for Green Chemistry (Portugal), Universidad Complutense de Madrid, Fundación Alfonso Martín Escudero (Spain), European Commission, Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

Está depositada la versión postprint del artículo, Several series of dihalide Pd(ii) compounds bearing pyridyl or isoquinolinylpyrazole ligands have been strategically designed and synthesised to exhibit columnar mesomorphism in wide stability ranges. The coordination of the pyrazoles to the fragments PdX2 (X = Cl, Br, I) generates half-disc molecules that are capable of self-assembling into discotic dimers via intermolecular interactions. This disc-like shape is required for the supramolecular organisation of the lamellar columnar mesophases, which are formed at temperatures below 100 degrees C in most cases. It was found that these metallomesogens behave as 2D proton conducting materials under anhydrous conditions. The high fluidity properties of the mesophase facilitate proton conduction as a result of the spontaneous dissociation of the acidic pyrazole proton at the melting temperature. For the first time, lamellar columnar mesophases are demonstrated to serve as a 2D platform to induce water-free proton conductivity in dihalide Pd(ii) metallomesogens., Ministerio de Economía y Competitividad (España), Universidad Complutense de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

A novel family of square-planar Pd(II) complexes based on isoquinoline-functionalised pyrazolate ligands [Pd(pzR(n,n)iq)2] (R(n,n) = C6H3(OCnH2n+1)2, n = 4, 6, 8, 10, 12, 14, 16, 18) has been synthesised and characterised. The new complexes show mesomorphic properties and exhibit columnar mesophases that are highly-stable in exceptionally wide temperature ranges of up to 345 °C. The formation of nanochannels in the fluid liquid crystal phases generates continuous pathways for one-dimensional proton conduction on the basis of C–H⋯N proton transfer. The complex with an intermediate chain length (n = 12) shows the highest proton conductivity of 1.34 × 10−4 S m−1 at 269 °C in the hexagonal columnar mesophase, and an activation energy of 0.84 eV. The influence of both the terminal alkyl chain length and the mesophase columnar organisation on the proton conduction mechanism is demonstrated. The series of Pd(II) complexes investigated in this work constitutes one of the first examples of proton-conducting metallomesogens with potential applications in PEM fuel cells., Ministerio de Economía y Competitividad (España), Universidad Complutense de Madrid, Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

Ministerio de Economía y Competitividad, (España), Universidad Complutense de Madrid, Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

New dicatenar isoquinoline-functionalized pyrazoles, [HpzR(n,n)iq] (R(n,n)=C6H3(OCnH2n+1)2; n=4, 6, 8, 10, 12, 14, 16, 18), have been strategically designed and synthesized to induce mesomorphic and luminescence properties into the corresponding bis(isoquinolinylpyrazolate)platinum(II) complexes [Pt(pzR(n,n)iq)2]. Thermal studies reveal that all platinum(II) compounds exhibit columnar mesophases over an exceptionally wide temperature range, above 300 °C in most cases. The photophysical behavior was also investigated in solution and in the solid state. As a consequence of the formation of Pt⋅⋅⋅Pt interactions, the weak greenish emission of the platinum derivatives turns bright orange in the mesophase. Additionally, the complexes are sensitive to a great variety of external inputs, such as temperature, mechanical grinding, pressure, solvents, and vapors. On this basis, they are used as dopant agents of a polyvinylpyrrolidone or poly(methyl methacrylate) polymer matrix to achieve stimuli-responsive thin films., Ministerio de Economía y Competitividad (España), Universidad Complutense de Madrid, European Commission, Portuguese Foundation for Science and Technology, Scientific Society PROTEOMASS (Portugal), Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub