Single crystal ESR and ENDOR of bis-(salicylaldoximato) Cu(II): Bis-(Salicylaldoximato)Ni(II): Copper, nitrogen and proton hyperfine data and structure of the internal H-bond
1978; Elsevier BV; Volume: 32; Issue: 1 Linguagem: Inglês
10.1016/0301-0104(78)85217-3
ISSN1873-4421
AutoresA. Schweiger, Hs. H. Günthard,
Tópico(s)Magnetism in coordination complexes
ResumoAn investigation of the ESR and ENDOR spectra of the complex Cusal2 substituted into single crystals of Nisal2 is reported. An analysis of the spectra is presented yielding g tensor, the hyperfine interaction tensors of 63Cu, 14N and four protons and the quadrupole tensor of 14N, as well as the orientation of the principal axes systems of these quantities. Interpretation of the hyperfine pattern of the set of two perfectly equivalent 14N nuclei is shown to require a detailed analysis of the second order perturbation terms expressed in the coupled spin basis. For certain orientations of the crystal the 14N hyperfine pattern shows up to sixteen lines. Analysis of this phenomenon is achieved by exact diagonalization of the energy matrix and is traced back to noncrossing of energy levels. From the magnetic data bonding parameters of Cusal2 in an extended Maki—McGarvey picture and spin densities on Cu and 14N are derived. Cusal2 features an intramolecular hydrogen bridge of type OH…O. Based on some assumptions concerning spin densities, the experimentally determined magnetic constants and a seven-center dipole—dipole interaction model, the structure of the H-bond is inferred to be bent and nonsymmetric, with the angle ∠ OH…O lying in the range 130–143°.
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