Synthesis, electronic characterization and significant second-order non-linear optical responses of meso-tetraphenylporphyrins and their ZnII complexes carrying a push or pull group in the β pyrrolic position

This work describes the synthesis and characterisation by electronic absorption spectroscopy, cyclic voltammetry and by a solvatochromic investigation of meso-tetraphenylporphyrins and their Zn(II) complexes substituted at the β pyrrolic position by a pseudo-linear, π-delocalised organic linker carrying either an electron-withdrawing (pull) or electron-donating (push) group. The second-order NLO response of these push-pull porphyrinic chromophores has been investigated by the EFISH technique working with a non-resonant incident wavelength of 1.907 μm. The porphyrin ring substituted at the β pyrrolic position by an electron-acceptor π-system behaves as a significant donor group, comparable to a ferrocenyl group or to a phthalocyanine. Unexpectedly, the porphyrin ring substituted at the β pyrrolic position with an electron-donor π-system shows a larger and significant second- order NLO response.