Carbon chemical shifts and proton spin relaxation in Halogenobis(N,N-diethyldithiocarbamato) iron(III) complexes

Abstract

Carbon chemical shifts and proton longitudinal and transverse relaxation times have been measured for a series of halogenobis( N,N- diethyldithiocarbamato)iron(111) complexes (Cl, Br, I) and the results interpreted in terms of current relaxation theory. For the chloro complex the zero field splitting parameters are sufficiently small to yield electronic relaxation times longer than the overall molecular correlation time and good agreement is obtained between the experimental and theoretical nuclear relaxation times. The agreement is poor for the Br and I derivatives. Although the electronic relaxation is a complex process it is shown that one electronic relaxation time may dominate the nuclear relaxation process. 13C and lH contact shifts are in good agreement with the proposal that it is the n electronic framework of the ligand that is responsible for transmission of unpaired spin density.