Dyes based on the azo‐1H‐pyrrole moiety – synthesis, spectroscopic and electrochemical properties, and adsorption on TiO2

Abstract

A series of novel azo dyes based on the azo‐1H‐pyrrole moiety were synthesised. The dyes were characterised in terms of their spectroscopic, electrochemical, and physicochemical properties. In these dyes, the electron‐rich 1H‐pyrrole moiety was assembled as π‐bridges in donor–acceptor π‐conjugated dye, and aminophenylimine fragments and the carboxyl group were used as donor and anchoring acceptor groups respectively. The dyes had adequate HOMO and LUMO levels that matched the conduction band of TiO2 and the redox potential of the electrolyte. The adsorption of these azo compounds with carboxyl group(s) on TiO2 was investigated. Experimental data showed that the introduction of two carboxyl groups could greatly enhance the adsorption efficiency of the studied dyes on TiO2. The sorption kinetics was measured for selected dyes derived from 5‐aminoisophthalic acid. Results indicate that a pseudo‐second‐order equation can better describe the adsorption kinetics of these dyes on TiO2.