DISCOTIC METALLOMESOGENS - MESOPHASE CROSSOVER OF COLUMNAR RECTANGULAR TO HEXAGONAL ARRANGEMENTS IN BIS(HYDRAZINATO)NICKEL(II) COMPLEXES

Three series of zylidene)-N'-(3',4',5'-trialkoxylbenzoyl)hydrazine and their nickel(II) complexes, bis ialkoxybenzylidene)-N'-(3',4',5'-tria lkoxybenzoyl) hydrazinato]nickel(II), were prepared and characterized. The mesomorphic properties of these disc-like compounds were also stu died in terms of liquid crystallinity. The orange nickel(II) complexes with ten soft alkoxy side chains exhibited columnar disordered mesoph ases, which were characterized based on DSC analysis and optical polar ized microscopy. Nickel complexes with shorter side chains (n = 5-8) d isplayed a monotropic columnar rectangular disordered (Col(rd)) phase; however, complexes with longer side chains showed monotropic (n = 10) and enantiotropic (n = 12, 14) columnar hexagonal disordered (Col(hd) ) phases. Similar nickel complexes (n = 14) with eight side chains exh ibited a columnar hexagonal phase, whereas complexes (n = 14) with six side chains formed crystalline phases. The structures of these column ar disordered phases were confirmed by X-ray powder diffraction. XRD d ata indicated that mesophase crossover from columnar rectangular (Col( r)) to hexagonal arrangements (Col(h)) was observed with increasing si de chain lengths.