CONSTRUCTION OF PORPHYRIN-CONTAINING ROTAXANES FOR LONG-RANGE PHOTOINDUCED CHARGE SEPARATION

In order to investigate long-range photoinduced charge separation and to mimic the array of tetrapyrrolic chromophores in bacterial photosyn thetic centres, several multicomponent systems bearing porphyrins have been designed. In a zinc(II)-gold(III) porphyrin dimer, bridged by a 2,9-diphenyl-1,10-phenanthroline (dpp) spacer, photoinduced electron t ransfer occurs from the zinc porphyrin excited state to the gold porph yrin cation in 55 ps. Threading the bis-porphyrin dimer into a dpp con taining macrocycle by means of Cu(I) leads to a [2]-rotaxane complex i n which the same electron transfer process was accelerated to 2 ps. Mo re complex systems such as [3]- and [5]-rotaxanes bearing porphyrins a s stoppers are promising for increasing the distance between the porph yrins and therefore extending the lifetime of the charge separated sta te.