Metal-Nitroxyl Interactions. 48. EPR Spectra of Spin-Labeled Pyridines Coordinated to Chromium (III) Tetraphenylporphyrin Chloride (S = 3/2) and Comparison of the Electron-Electron Exchange Interaction with Analogous Complexes with Metal S = 1/2

Kundalika M. More, Sandra S. Eaton, Gareth R. Eaton, Kalman Hideg

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Abstract

EPR spectra were obtained for 13 spin-labeled pyridines coordinated to chromium(III) tetraphenylporphyrin chloride. In fluid solution weak electron-electron exchange interaction caused broadening of the nitroxyl signal and stronger interaction caused resolved splitting. Resolved spin-spin splitting was observed in frozen solution. Values of the exchange coupling constant, J, between ±0.005 and ±0.27 cm-1 were obtained by computer simulation of the frozen-solution spectra. The stronger exchange interaction for 4-substituted pyridines than for analogous 3-substituted pyridines is consistent with πdelocalization of the unpaired spin density from the metal into the pyridine ring, π delocalization was also dominant in the vanadyl trifluoroacetylacetonate complexes of these spin-labeled pyridines. The values of J for the Cr(III) (S = 3/2) complexes were 1/2to 2/3 of the values observed for the vanadyl (S = 1/2) complexes of the same spin-labeled pyridines.

Original languageEnglish
Pages (from-to)3865-3869
Number of pages5
JournalInorganic Chemistry
Volume25
Issue number22
DOIs
Publication statusPublished - Oct 1986

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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