Sign of the Nuclear Quadrupole Coupling Constants in Some Ionic Ferrous Compounds

Nuclear quadrupole coupling constants have previously been determined for a large number of iron-containing compounds by using the Mössbauer effect. In general, the sign of the coupling constant has not been determined although this parameter can have interesting structural implications. We have used the magnetic perturbation technique to determine the sign of the nuclear quadrupole coupling constants in FeSO4, FeSO4·7H2O, FeCO3, FeCl2·4H2O, and FeSiF6·6H2O. A recent proposal that a correlation exists between the isomer shift and quadrupole coupling in ionic ferrous compounds and that this correlation can be used to infer the sign of the latter is found to be incorrect.