Rapid synthesis of phthalocyanine-based discotic liquid crystals by using a novel hand-made microwave-heating apparatus

Abstract

Phthalocyanine ( Pc )-based discotic liquid crystals could be prepared very rapidly by using our developed novel microwave-heating apparatus. It took only 10-20 min to synthesize these Pc metal complexes and metal-free Pc derivatives in an organic solvent (glycerin) by microwave irradiation, whereas it took 24-48 h to synthesize them by the conventional oil bath method. To our knowledge, it is the first example of metal-free Pc derivatives synthesized by microwave methods in an organic solvent. In the vast examples of Pc syntheses by conventional oil bath methods, the Pc metal complexes can be obtained in higher yields by “Template Effect” of the metal than the corresponding metal-free Pc derivatives. Therefore, we expected that the present Pc metal complexes ( C n S )8 PcCu (2) could be also prepared by microwave methods in higher yields than the metal-free Pc derivatives ( C n S )8 PcH 2 (1). Contrary to our expectation, the yields of the metal complexes ( C n S )8 PcCu (2) were lower than those of the metal-free derivatives ( C n S )8 PcH 2 (1). It is very interesting that this result by the microwave method is quite opposite to the results by conventional oil bath method. Hence, in this work we have focused our interest on the “Template Effect” in the syntheses of Pc derivatives by the microwave method in order to investigate the relationship between microwave heating and template effect. It is the first attempt in Pc syntheses by the microwave method.