Bromine-79 NQR for uncoordinated Br– ions in trans-[CoBr2(en)2][H5O2]Br2

Abstract

AbstractA single 79Br NQR line showing a frequency of 19.594 MHz at room temperature has been observed in the crystals of trans-[CoBr2(en)2] [ H5O2 ] Br2 and assigned to the Br - ions which are not coordinated to the central Co(III) atom. The electric field gradient (EFG) at the Br - nuclei arises from O-H • • • Br - hydrogen bond formation between the Br - ions and the terminal O - H hydrogen atoms in [ H5O2 ] + ions. The induced EFG is greater for the present bromine complex than that for the isostructural chlorine complex. A point charge model calculation explains well the relative magnitude of the EFG in the two crystals by introducing Sternheimer's antishielding factors for the halogen ions.