Structure elucidation of lanthanide complexes by theoretical tools: Novel pyrazole–pyridine Tb(III) tripod

The structure of Tb3+ complexes derived from pyrazole-pyridine tripod was investigated using the semiempirical Sparkle model. Four most probable structures were predicted and their excited electronic states were calculated using the intermediate neglect of the differential overlap/spectroscopic (INDO/S) method. The singlet-excited state frequencies and oscillator strengths were used to predict the absorption spectra which were compared to the experimental one. The results suggest that the terbium tripod complex presents the Tb[podand] · 4H2O structure where the podand ligand was coordinated to Tb3+ ion by six oxygen atoms from the carboxylate groups. This finding agrees with the feeble luminescence experimentally measured for this chelate.