Single-crystal EPR and 15N powder ENDOR studies of [(C4H9)4N][TcVINBr4/TcVOBr4]

K. Köhler, R. Kirmse, R. Böttcher, U. Abram

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Single-crystal EPR and 15N powder ENDOR studies of tetra-n-butylammoniumtetrabromonitrido-technetate(VI), (Bu4N)[TcNBr4], diamagnetically diluted by the isostructural oxotechnetate(V) complex are reported. The EPR spectra are typical of an ion with 4d1 configuration and confirm an "in-plane" π-type molecular orbital of the unpaired electron (C4v, symmetry). At low temperatures very complex 99Tc and 79,81Br hyperfine patterns are observed in the single-crystal EPR spectra. The 15N hyperfine tensor has been derived from powder ENDOR measurements. Hyperfine and ligand hyperfine data are analyzed to evaluate the electron spin delocalization and compared to those obtained from molecular orbital calculations (EHMO and NDDO). The nitrogen coupling is mainly determined by spin polarization. The fraction of the unpaired electron that is delocalized over ligand orbitals is larger in the bromo than in the corresponding chloro complex [TcNCl4]-.

Original languageEnglish
Pages (from-to)281-287
Number of pages7
JournalChemical Physics
Issue number2
StatePublished - 1 Mar 1992
Externally publishedYes


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