Mapping the unpaired electron density in [Pt(bipy)L2]- (bipy = 2,2′-bipyridine; L = Cl-, CN-, 13CN-): A combined EPR-ENDOR-theoretical study

E. J L McInnes, Robert D. Farley, Stuart A. Macgregor, Kenneth J. Taylor, Lesley J. Yellowlees, Christopher C. Rowlands

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Abstract

The X-band EPR and electron-nuclear double resonance (ENDOR) spectra of the formally d9, 17-electron radical anions [Pt(bipy)L2]- (bipy = 2,2'-bipyridine; L = Cl-, CN-, 13CN-) are reported. The 195Pt (I = 1/2, 34%) anisotropic hyperfine matrices are analysed in terms of both 5d and 6p contributions to the singly occupied molecular orbitals (SOMOs). For L = Cl- there is 5.0% 5dyz and 7.6% 6pz character, for L = CN- there is <1% 5dyz and 13.1% 6pz. The bulk of the unpaired electron density is delocalised about the bipy p* system and ENDOR spectra reveal the superhyperfine couplings to the 1H, 14N and 13C (L = 13CN-) nuclei. The unpaired electron densities in the 14N 2pz orbitals contributing to the p* systems are calculated to be 12% and 4% for L = Cl- and CN-, respectively. The cyanide p-orbitals make little contribution to the SOMO for [Pt(bipy)(CN)2]-. There is a good agreement with density functional theory (DFT) MO calculations on the radical anions. DFT calculations also show the atomic orbital compositions of the lowest unoccupied (LU) MO of [Pt(bipy)L2]- and the SOMO of [Pt(bipy)L2]- to be virtually identical.

Original languageEnglish
Pages (from-to)2985-2991
Number of pages7
JournalJournal of the Chemical Society, Faraday Transactions
Volume94
Issue number19
Publication statusPublished - 1998

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