Pursuits for Metallomesogenic Materials Showing Spin-crossover Behavior

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The following synthetic approaches have been made in search for mesomorphic materials showing spin-crossover behavior at ambient temperatures.1. Modifications of Prototype Solid Complexes Exhibiting the Target PropertyIron(II)-aminotriazole coordination polymers exhibiting room temperature spin-crossover with hysteresis was selected as a prototype and various modifications were introduced such as substituting 4-amino group on the ligand with 4-alkoxybenzylideneamino group. All of the samples obtained so far have proven to contain at most trinuclear species and not mesomorphic either.2. Elaboration of the Designs for Metal Complexes and Ligands(a) 6-Coordinate tris-chelate complexes was then selected in the hope of obtaining somehow low-spin materials. A Ru(II) complex soluble in ambient temperature nematics has been obtained using an alkylated, mesogenic ligand. Polypyridyl ligands have also been prepared newly for stronger ligand fields and multinucleating functions.(b) [M(salen)] is among the family of mononuclear complexes of multidentate Schiff base chelates, which has produced a number of spin-crossover complexes in tha past, and in this study has been derivatized into polycatenar mesogens (M=Ni, Cu, and VO) by grafting 4 to 6 alkyl chains. Columnar mesophases have been observed in most cases.3. Attempts to Induce Lyotropic MesophasesAttempts were made to bring the above ionic coordination compounds into lyotropic mesophases with water or alcohols. Success has been made with a polyether-grafted extended aromatic compound, which has a common amphiphilic character (but with inverted center-periphery constitution), and the chromonic mesophase has been observed in water.