Molecular engineering for optical properties of 5-substituted-1,10-phenanthroline-based Ru(II) complexes.

A series of homo- and heteroleptic Ru(II) complexes [Ru(phen)3−n(phen-X)n](PF6)2 (n = 0–3, X = CN, epoxy, H, NH2) were prepared and characterized. The influence of electron-withdrawing or electron-releasing substituents of the 1,10-phenanthroline ligands on the photo-physical properties was evaluated. It reveals fundamental interests in the fine tuning of redox potentials and photo-physical characteristics, depending both on the nature of the substitution of the ligand, and on the symmetry of the related homo- or heteroleptic complex. These complexes exhibit linear absorption and two-photon absorption (2PA) cross-sections over a broad range of wavelength (700–900 nm) due to absorption in the intra-ligand charge transfer (ILCT) and the metal-to-ligand charge transfer (MLCT) bands. These 2PA properties were more particularly investigated in the 700–1000 spectral range for a family of complexes bearing electro-donating ligands (phen-NH2).