474645-03-9Relevant academic research and scientific papers
Participation of Co-ligands in electronic transitions of platinum(II) diazabutadiene complexes
Klein, Axel,Van Slageren, Joris,Zalis, Stanislav
, p. 5216 - 5225 (2008/10/08)
The low-lying electronic transitions and photochemical reactions of a series of [(iPr-DAB)Pt(R)2] (where the coligand R = CH3, CD3, adme, neop, neoSi, C≡CiBu, C≡CPh, Ph, Mes) compounds were studied using both experimental (electronic absorption and resonance Raman spectroscopy) and theoretical (density functional theory, DFT) techniques. The high-lying filled orbitals were revealed to have a significant co-ligand contribution in the case of alkyl complexes, while this contribution is predominant for the complexes with unsaturated co-ligands. Because the electronic transition removes electron density from the σ(Pt-C) bond in the former complexes, it is best described as a metal-to-ligand charge transfer transition (MLCT) with partial sigma-bond-to-ligand charge transfer (SBLCT) character. Because the σ(Pt-C) orbital is not involved in the HOMOs of the latter complexes, the low-lying transitions were characterized as mixed MLCT/L'LCT, where L'LCT stands for ligand-to-ligand charge transfer from the π system of the unsaturated co-ligand to the τ*(iPr-DAB) orbital. The alkyl complexes are photoreactive on visible light irradiation with Pt-C bond homolysis as the primary step. The efficiency of the photoreaction increases with increasing σ donor strength of the alkyl ligand. The absolute quantum yield is quite low. The other complexes are virtually photostable, except when irradiated at relatively high energies.
