Single and double quantum transitions in the multi-frequency continuous wave electron paramagnetic resonance (cwEPR) of three six co-ordinate nickel(II) complexes: [Ni(EtL)2(Me5dien)] and [Ni(5-methylpyrazole)6]X2, X = (ClO4)− or (BF4)−. The single crystal X-ray structure at room temperature of [Ni(