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ESR.‐Spektren von CuN 4 ‐Chromophoren: Komplexe des zweiwertigen Kupfers mit Pyridin und Pyridinderivaten
Author(s) -
Schneider W.,
Zelewsky A. V.
Publication year - 1965
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19650480713
Subject(s) - chemistry , delocalized electron , excited state , crystallography , chromophore , hyperfine structure , pyridine , antibonding molecular orbital , ground state , magnetic circular dichroism , molecular orbital , spectral line , photochemistry , atomic orbital , atomic physics , electron , molecule , quantum mechanics , physics , organic chemistry , medicinal chemistry
The ESR. spectra of four copper complexes, containing pyridine, 4‐picoline, 4‐dimethylaminopyridine, and 4‐cyanopyridine as ligands, have been measured in the solid state. Single crystals of the corresponding Pt II oder Cd II compounds were used as host lattices and magnetic diluents. The spectra of the CuN 4 chromophores, showing resolved hyperfine structure due to copper and nitrogen nuclear magnetic momenta, could be analysed within a Spin‐Hamiltonian corresponding to effective symmetry D 4 h . They have been interpreted by means of molecular orbital theory, and the delocalization parameters have been deduced on the assumption of near degeneracy of the excited levels within the widths of the observed visible absorption band. It is shown that the delocalization parameters apparently do not display any influence of the widely different substituents in the 4 position of the ligands. The parameter describing the π‐antibonding character of the excited state, E g , differs from the expected value. This is probably due to some fundamental deficiency in the MO scheme so far generally applied to chromophores CuO 4 , CuO 2 N 2 and CuN 4 .