Synthesis, Electronic and Photophysical Characterization of π-Conjugated meso-Ferrocenyl-porphyrin Fluorescent Redox Switches

Abstract

A series of meso-ferrocenyl-porphyrin dyads linked by four different π-conjugated bridging units (directly bound, vinyl, ethynyl, and phenyl) have been synthesized to investigate the influence of the conjugated linker on both the electronic and photochemical properties of the porphyrin chromophore. The basic structure consists of 5-(Fc)-15-(4-methylbenzoate)-10,20-diphenylporphyrin zinc(II), where Fc = ferrocene, vinylferrocene, ethynylferrocene, or phenylferrocene. Upon introduction of the various electron-donating ferrocenyl moieties at the meso-position of the porphyrin ring, Soret and Q-band electronic transitions of the resultant dyads are red-shifted compared with those of the nonferrocenyl reference porphyrin system 15-(4-methylbenzoate)-10,20-diphenylporphyrin zinc(II). The electronic properties of these systems have been investigated by electrochemical (cyclic voltammetry) and computational (DFT/TDDFT) methods, while UV/vis absorption and fluorescence emission spectroscopic analysis is also prese...