DISK-LIKE LIQUID-CRYSTALS OF TRANSITION-METAL COMPLEXES - PART 21 - CRITICAL MOLECULAR-STRUCTURE CHANGE FROM COLUMNAR TO LAMELLAR LIQUID-CRYSTAL IN BIS(DIPHENYLGLYOXIMATO)NICKEL(II)-BASED COMPLEXES

The critical molecular structure change from columnar to lamellar meso phases in bis (diphenylglyoximato)nickel (II)-based complexes has been investigated. When the number of the long chains surrounding the core complex part was reduced from eight to four, the mesophase changes it s structure from columnar Col(hd) to novel disk-like lamellar D-L.rec( P2(1)2(1)). When the length of the four chains at the F-positions was fixed and the remaining four chains at m-positions were gradually made shorter, each of the complexes shows a columnar Col(ho) mesophase. Su rprisingly, even when the substituents at m-positions are methoxy or m ethyl groups, a columnar Col(ho) mesophase is still observed. When the substituents at m-positions were OH groups, another novel disk-like l amellar D-L.rec(P2(1)1) mesophase is observed. Hence, it can be shown that the critical molecular structure change from the columnar to lame llar mesophase occurs between methoxy and hydroxy groups at the m-poos tion. In both of the two novel D-L.rec mesophases in the present study , the core complex parts are parallel to the layers and the long chain s are normal to both the layers and the core complex planes. Such a un ique mesophase structure has not been previously observed. The synthes is of these complexes and the temperature-dependent X-ray structural a nalyses of the unique mesophases are reported.