Discotic liquid crystals of transition metal complexes, 54: Rapid microwave-assisted synthesis and homeotropic alignment of phthalocyanine-based liquid crystals

Abstract

ABSTRACT:The most difficult problem on syntheses of the phthalocyanine-based liquid crystals is the long reaction time. In order to shorten the reaction time, we have developed novel Methods A, B and D, for the syntheses of phthalocyanine-based liquid crystals by using microwave heating and/or adding a phase transfer catalysis of Aliquat 336. A series of phthalocyanine derivatives C n PcZn(1) (n = 10, 12, 14, 16 and 18: a, b, c and e) could be successfully synthesized in a dramatically short reaction time of 30-60 min using Methods A and B by microwave heating. On the other hand, anothor series of the derivatives C n (OH)PcZn (2a-2e) could not be synthesized by microwave heating. Therefore, all these derivatives were synthesized using conventional Method C by oil bath heating, but the reaction took a very long time (22.5-88 h). To shorten the reaction time, we have developed Method D by oil bath heating with adding a phase transfer catalyst of Aliquat 336. In this method, we successfully shortened the reaction time from 88 h to 3 h for the synthesis of the derivative 2a. Thus, the reaction time for oil bath heating can be also greatly shortened by adding the phase transfer catalyst of Aliquat 336. Furthermore, we have established from POM, DSC and temperature-dependent X-ray diffraction measurements that the derivative C 10 PcZn (1a) shows a very rare pseudohexagonal columnar (Col hr ) phase, and that the derivatives C n PcZn (1b-1e) and C n (OH)PcZn (2b-2e) exhibit spontaneous perfect homeotropic alignment in a large area between two glass plates in their Col tet phases.

Alternative Technologies That Facilitate Access to Discrete Metal Complexes

“…330 Addition of a second bipyridyl unit provided the basic chromophoric framework 590 with the potential for modulating luminescent properties (Scheme 179, reaction In order to optimize the synthesis of phthalocyanine-based zinc-containing liquid crystals, for which the main drawback is the rather long reaction time (from 22 to 88 h), Akabane et al have developed a microwave procedure, using ethylene glycol as the solvent, enabling the reaction time to be reduced to less than 1 h (Scheme 180). 331 Five complexes 593 were synthesized in good yield (58−83%) and characterized.…”