Heavy atom effect in diamagnetic metal acetylacetonates

Abstract
Spectral data are presented for acetylacetonate complexes of eighteen diamagnetic closed shell metal ions. The nature of the metal ion has relatively little effect on the absorption and phosphorescence energies, but has a very marked effect on the phosphorescence lifetime, τ, in solid ethanol glasses at 77 K. The possibility that the observed variations in τ are the result of an intramolecular heavy atom effect is examined. Comparison of τ with ligand 1H n.m.r. resonances indicate that a significant degree of heavy atom induced spin–orbit coupling occurs only with the Th4+, Lu3+, La3+ and In3+ complexes. In the other cases it is suggested that the principal factor in determining τ may be the energy difference between the Tπ,π* and Tn,π* states and a specific model is proposed.

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