VIBRATIONALLY COUPLED DIOXYGEN IN DIOXYGEN ADDUCTS OF COBALT PORPHYRIN COMPLEXES WITH PYRIDINE - MODE-SPECIFIC VARIATIONS IN COUPLING STRENGTHS

Resonance Raman spectra of O-16(2) and O-18(2) adducts of cobalt tetra phenylporphine complexes with pyridine and several deuteriated analogu es are presented. It is shown that the bound O-2 has a marked tendency to vibrationally couple with internal modes of the trans-axial pyridi ne. Moreover, it is shown that the inherent coupling strength varies d epending upon the specific modes which are in a position to couple wit h the v(O-O) mode. That is, throughout the series of complexes, specif ic modes associated with the given deuteriated pyridine couple to diff erent extents. This variation of coupling strength presumably reflects differences in the precise mode formulations for the various ligands. In order to document the vibrational frequencies of the coordinated p yridine isotopomers, the spectra of the corresponding bispyridine ferr ous tetraphenylporphine complexes were also acquired and are presented .