Heteroleptic Ru(II) complexes containing aroyl hydrazone and 2,2′-bipyridyl: Synthesis, X-ray crystal structures, electrochemical and DFT studies

Four heteroleptic Ru(II) complexes [Ru(bpy)2(L)]X (L = bidentate N, O− donor hydrazone ligands, X = ClO4 or PF6) have been synthesized and characterized. Single crystal X-ray structures of two of the complexes are also reported. The complexes show strong absorptions in the 400–600 nm region of the visible radiation, with very similar room temperature emission spectra to that of reference [Ru(bpy)3]X2 but with the lowest energy MLCT (metal to ligand charge transfer) band bathochromically shifted by about 50 nm. Results obtained from both electrochemical experiments and DFT calculations show remarkable differences in the HOMO–LUMO properties of the hydrazone complexes compared to [Ru(bpy)3]X2. TDDFT calculations have been used to understand the nature of the electronic transitions.

Graphical abstractRu(II) complexes, which are strongly absorbing in the visible region of the electromagnetic radiation, were synthesized and characterized. In these complexes the lowest energy MLCT band is bathochromically shifted with respect to reference complex [Ru(bpy)3]2+. The HOMO–LUMO properties of the complexes are suitable for their possible applications in DSSC.Figure optionsDownload full-size imageDownload as PowerPoint slide