Polynuclear Silver(I) Triazole Complexes: Ion Conduction and Nanowire Formation in the Mesophase

Advanced Functional Luminescent Metallomesogens: The Key Role of the Metal Center

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.

Cyclotriphosphazenes as Scaffolds for the Synthesis of Metallomesogens

(Amino)cyclotriphosphazenes have been used as new scaffolds for the synthesis of silver(I) metallomesogens. Two cyclotriphosphazenes, [N₃P₃(NHCy)₆] (phos-1) and nongem-trans-[N₃P₃(NHCy)₃(NMe₂)₃] (phos-2), were reacted with the silver complex having a pro-mesogenic ligand, [Ag(OTf)L] (L = CNC₆H₄{OC(O)C₆H₂(3,4,5-(OC₁₀H₂₁)₃)}-4; OTf = OSO₂CF₃), in different molar ratios, 1:1, 1:2, or 1:3, to give two series of cationic metallophosphazenes, [N₃P₃(NHCy)₆{AgL}_n](TfO)_n (phos-1.n) and nongem-trans-[N₃P₃(NHCy)₃(NMe₂)₃{AgL}_n](TfO)_n (phos-2.n) with n = 1, 2, or 3. The chemical structure of these compounds, deduced from spectroscopic techniques, was in accordance with coordination of the silver fragments "AgL" to nitrogen atoms of the phosphazene ring, whereby their number n depends on the molar ratio used. Despite the presence of the bulky substituents on the core N atoms, cyclotriphosphazenes coordinated to three "AgL" units exhibited mesomorphism at room temperature. The mesophase was characterized as columnar hexagonal according to the optical microscopy and X-ray diffraction studies. A model based on an intermolecular association in pairs of the metallocyclotriphosphazenes having three AgL units has been proposed in order to explain the mesomorphic columnar arrangement in these materials. Starting silver complex, [Ag(OTf)L], also exhibited a columnar hexagonal mesophase at room temperature.

Anion-controlled supramolecular crystal structures and ionic liquids from fatty acid-substituted ethyl-nicotinate ionic compounds

A series of bio-inspired fatty acid-substituted ethyl-nicotinate ionic compounds with a flexible ester group were prepared, and two crystals and four ionic liquids were obtained.