Complexation of hafnium with two ligands viz. diethylene triamine pentaacetic acid (DTPA) and its dimethyl ester derivative (DMDTPA) has been studied by using time differential perturbed angular correlation (TDPAC) technique. Nuclear quadrupole coupling constant (ν_Q), asymmetry of the EFG (η) and the frequency distribution (δ) for these complexes have been obtained. Square antiprism structures have been suggested for these complexes using these parameters. A systematic trend of the ν_Q has been observed in these and other hafnium complexes with similar ligands and has been explained in terms of the electronegativity of the donor atoms in the ligands.