Structurally-modified subphthalocyanines: Molecular design towards realization of expected properties from the electronic structure and structural features of subphthalocyanine

This feature article summarizes recent contributions of the authors in the synthesis of structurally-modified subphthalocyanines. The structural modification covers (1) modification of the conjugated system of subphthalocyanines to create novel conjugated systems comprising three pyrroles or pyrrole-like subunits, (2) core-modification by expansion of the inner pyrrolic five-membered ring to larger six- and seven-membered ring units, and (3) exterior-modification by annulation of functional units to subphthalocyanines. These modifications in the structure of subphthalocyanines have been performed with the aim of demonstrating unique properties originating from the bowl-shaped C _3v-symmetric structure as well as the electronic structure delineated by the 14À-electron conjugated system on the curved molecular surface. The possible structural modifications surveyed in this feature article and their concomitant properties will provide important future guidelines to the design of subphthalocyanine-based functional molecules, considering the fact that subphthalocyanines have recently been attracting considerable attention as potential candidates in the field of optoelectronics and molecular electronics.