First-principles study of the hexahalogenotechnetate(IV) ions [X = Cl, Br]

We report all-electron scalar relativistic calculations of the structural and electronic properties of the octahedral hexahalogenotechnetate(IV) ions TcX 6 2 - [X = Cl, Br] using spin-polarized density functional theory. The calculated bond distances are in good agreement with X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) data available for salts of hexachloride and hexabromide technetate ions. Molecular-orbital analysis shows the importance of the hybridization between Tc 4 d orbitals and p orbitals of the ligands. Normal modes of vibration of the hexachloride and hexabromide complexes of Tc and Re have also been computed and assessed by comparison with spectral data for salt crystals of technetate/rhenate complex ions.