Far-red absorbing azodipyrrin dyes — Synthesis, X-ray crystallographic, and spectral characterization of 1,9-diazodipyrrins and their metal complexes

Abstract

A series of novel 1,9-diazodipyrrins (4) were readily synthesized by reacting aryldiazonium salts with 5-aryldipyrromethanes under both acidic and basic conditions. The zinc complex of 1,9-diphenylazodipyrrin (5aZn) was confirmed by X-ray crystallographic analysis, and 1,9-diazodipyrrins and their zinc and nickel complexes (5M) were characterized by 1H and 13C NMR, IR, UV–vis, and MS. All of the metal complexes absorb almost all colours of the rainbow; the absorption maximums are >650 nm and the half-band widths are over 100 nm. The fluorescence of the zinc complexes of 1,9-diphenylazodipyrrin (5aZn) and 1,9-di(2-iodophenylazo)dipyrrin (5cZn) were also explored.