Chromophoric dipyrrin complexes capable of binding to TiO2: synthesis, structure and spectroscopy.

The synthesis, characterisation, and TiO2 binding studies of a series of chromophoric complexes of 5-(4-carboxyphenyl)-4,6-dipyrrin (L(b)) are presented. The synthesis of [Ru(bipy)(L(b))2] (bipy = 2,2-bipyridine), [Rh(L(b))3], and [Pd(L(b))2] was achieved by initial coordination of 5-(4-methoxycarbonylphenyl)-4,6-dipyrrin (L(a)) followed by hydrolysis of the ester group. The carboxyl groups that are located on the peripheries of these complexes are able to engage in intermolecular hydrogen bonding interactions in the solid state, as revealed by X-ray crystallography.