Density functional study of technetium and rhenium compounds

Density functional calculations employing the B3LYP method and the LANL2DZ basis set have been performed on several Re dioxo complexes of simple polyamines. An extended test of the ability of the methodology to offer a good description of these complexes was performed, calculating the MO2+, MO? and MO4- metal oxides (both for Tc and Re) and the complex [MO2(NH3)(4)](+). It is shown that the results agree well with the experimental information available. The effect of the ligands is to stabilize the linear geometry of the dioxo metal core, much higher in energy than the bent geometry for the isolated species. The ligand-stabilized core exhibits a ringlet electronic state, while the triplet is more stable for the isolated core. The consequence of these facts is that the metal-oxygen distance in the complexes is larger than that in any of the metal oxides. The calculated structures of the Re and Te complexes with the amines exhibit a reasonable, although not perfect, agreement with the experimental data available. The B3LYP/LANL2DZ method seems able to describe with semiquantitative precision, the structure of Re and Tc complexes of the type, studied. (C) 2002 Elsevier Science B.V. All rights reserved.