On the electronic structure of [Pt(4,4′-X2-bipy)Cl2]0/-/2-: An electrochemical and spectroscopic (UV/Vis, EPR, ENDOR) study

E. J L McInnes, Robert D. Farley, Christopher C. Rowlands, Alan J. Welch, Lorenzo Rovatti, Lesley J. Yellowlees

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Abstract

A series of complexes of general formula [Pt(4,4'-X2-bipy)Cl2] (bipy = 2,2'-bipyridine; X = NH2, OEt, Me, H, Ph, Cl or CO2Me) has been prepared and their redox chemistry and UV/Vis spectroscopy examined. The half-wave potential of the first reduction process from cyclic voltammetry varies linearly with the Hammett parameter of X, and also with the MLCT maximum from UV/Vis spectroscopy. The first reduction processes of the complexes with X = OEt, Me, H, Ph, Cl or CO2Me are reversible and these complexes undergo a second quasi-reversible or irreversible reduction at potentials 580-760 mV more negative. The reduced, 17 e- species are characterised by EPR spectroscopy and the total platinum contribution (5d and 6p) to the SOMOs is calculated to be only ca. 7-12%. The bulk of the unpaired electron density is carried in the bipy ligand p* system and orientation-selective 1H ENDOR spectra of [Pt(4,4'-X2-bipy)Cl2]- (X = H or CO2Me) show that C5 and C5' carry the greatest spin density among the four ring C(H) positions. The second reduction product of [Pt(4,4'-(CO2Me)2-bipy)Cl2] is EPR silent indicating spin-pairing of the two reduction electrons in the same orbital in this particular complex. © The Royal Society of Chemistry 1999.

Original languageEnglish
Pages (from-to)4203-4208
Number of pages6
JournalJournal of the Chemical Society, Dalton Transactions
Issue number23
Publication statusPublished - 7 Dec 1999

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