Metal (cadmium and manganese)-mediated assemblies of two acetohydrazide zinc porphyrins for use in supramolecular solar cells

In this work, a metal-mediated assembling strategy has been used to construct four assemblies (ZnPx-M-A) with two acetohydrazide zinc porphyrins bearing two different donor groups (ZnPx, benzimidazyl unit for ZnP1, phenol group for ZnP2) appended (E)-4-[(pyridin-4-ylmethylene)amino] benzoic acid ligands (A), in which the metal ions (M, M = Cd²⁺ and Mn ²⁺) are used to bridge the ZnPx and A units, resulting in a ZnPx-M-A organized mode. Further, these assemblies were immobilized on the semiconducting TiO₂ electrode surfaces by the carboxylic groups of A units, and their photovoltaic performances were performed under irradiance of 100 mW cm^-2 AM 1.5G sunlight. The assembled structures were characterized by transmission electron microscopy (TEM), computational calculations and energy-dispersive X-ray spectroscopy (EDX). Photoelectrochemical studies reveal a significantly improved photovoltaic performance for ZnP2-Mn-A compared to other assemblies, which are also reflected by their corresponding UV-Vis absorption, fluorescence spectra and HOMO-LUMO energy gaps.