Abstract: The Cu-terpyridine complex was studied through quantum chemical calculations using B3LYP method with 6311+G(d,p) basis sets in the GAUSSIAN 2003 program package. Copper atoms and ions can bond to terpy in a mono-, bi- or tridentate mode.  The geometry optimizations were carried out for the mono-, bi-, and tridentate structures of the Cu-terpy complex.  The geometry optimizations yielded five local minimum energy structures: a tridentate (T), a bidentate (B), and three monodentate isomers (M_I, M_II and M_III). The lowest energy structure was the T isomer and the second lowest energy structure corresponds to the B isomer and was located ~ 6000 cm^-1 higher in electronic energy than the T isomer.  The M_I, M_II and M_III isomers were separated by about 1000 cm^-1, with the most stable M conformer being about 2000 cm^-1 higher in electronic energy than the B form. Due to the different numbers of Cu-N σ-bonds in the monodentate, bidentate, and tridentate forms, the predicated BDEs were in the order of

for both the neutral and ionic isomers of Cu-terpy complex. 

Keywords: Copper, terpyridine, computational calculations, metal-ligand bonding.