Positron annihilation studies on coordination compounds. 1. Investigation of positron lifetime and angular correlation of annihilation γ photons on the mixed complexes of bis(dimethylglyoximato)cobalt(III) with unidentate ligands

K. Burger, B. Lévay, A. Vértes, C. Vârhelyl

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Abstract

Positron annihilation investigation of bis(dimethylglyoximato)cobalt(III) mixed complexes formed with unidentate ligands, compared with ESCA results on the same complexes, suggested that the cobalt(III) central atom and the nitrogen donor atom of the parent complex have a negligible effect on the change of the positron lifetime. Mainly electrons of halide, pseudohalide, and S-bonded sulfite ion, each coordinated along the Z axis of the mixed complex, affect the annihilation rate of positrons. The positron lifetime decreasing effect of the unidentate ligands water, ammonia, nitrite, and organic bases was found to be negligible. It has been demonstrated that the positron lifetime decreases parallel to the increasing negative character of the halides I-, Br-, and Cl- and to the increasing π-acceptor ability of S- and Se-bound pseudohalides SCN, SeCN. Halides bound in the outer coordination sphere have the effect of decreasing the positron lifetime lower than those in the inner sphere. The positron lifetime of mixed complexes containing one halide ion is longer than those containing two halides. Considering angular correlation data it seems that the localization of positrons on halide ligands decreases (the curves become narrower) in the order Cl-, Br-, I-. From this respect pseudohalide ligands lie between Cl- and Br- in accordance with their optical electronegativity values. These results suggest the possible role of positron-halide and positron-pseudohalide bound states in the positron annihilation process.

Original languageEnglish
Pages (from-to)1424-1427
Number of pages4
JournalJournal of physical chemistry
Volume81
Issue number14
Publication statusPublished - Jan 1 1977

ASJC Scopus subject areas

  • Engineering(all)
  • Physical and Theoretical Chemistry

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