Single-crystal ENDOR-TRIPLE resonance studies on copper(II) complexes with unsaturated dichalcogeno ligands

Abstract

The signs of the isotropic hyperfine couplings of the chelate ring 13C nuclei in bis(diethyl-dithiocarbamato)Cu(II)/Ni(II), bis(diethyl-dithiocarbamato)Cu(II)/Zn(II), bis(diethyl-diselenocarbamato)Cu(II)/Zn(II) Cu/Zn(et2dsc)2, tetra-n-butylammonium-(maleonitrile-dithiolato)(diethyl-dithiocarbamato)Cu(II)/Ni(II) (n-Bu4N)[Cu/Ni(mnt)(et2dtc)] and of the 31P nucleus in tetra-n-butylammonium-(maleonitrile-dithiolato)(diethyl-dithiophosphato)Cu(II)/Ni(II) are measured by electron nuclear-nuclear triple resonance (TRIPLE) experiments and found to be negative. The 13C ENDOR spectra of Cu/Zn(et2dsc)2 and (n-Bu4N)[Cu/Ni(mnt)(et2dtc)] are analysed. The negative signs found for the 13C and 31P coupling constants are proof for a spin-polarization mechanism that is responsible for the spintransfer to these ‘next-neighbour’ atoms.