Synthesis and spectroscopic properties of 1,2-diiminetricarbonylrhenium(I)chloride complexes with aliphatic diimines (or 1,4-diaza-1,3-butadienes) asligands

Re(1,2-diimine)(CO)(3)Cl complexes with the aliphatic bidentate ligands dii minosuccino-dinitrile (DISN), benzilbisanile (BEAN), bisacetylbisanile (BAB A), and benzildiimine (BEDIM) are reported. The compounds show Re(I) to pi* (diimine) metal-to-ligand charge transfer ((MLCT) absorptions in the visibl e spectral region. The energy of these MLCT-transitions decreases in the se ries BABA > BEDIM > BEAN > DISN, depending on the pi* acceptor properties o f the coordinated diimine ligands. The maxima of these CT bands undergo a s olvent-dependent shift (negative solvatochromism), which indicates a partia l charge redistribution in the excited state. The compounds are not photolu minescent at room temperature and 77 K.