The molecular geometries, electronic structures, infrared spectra and thermochemical properties of cobalt and nickel tris(carbohydrazide) nitrates ([Co(CHZ)₃](NO₃)₂ and [Ni(CHZ)₃](NO₃)₂) as well as copper bis(carbohydrazide) nitrate ([Cu(CHZ)₂(NO₃)₂]) were investigated by using the density functional theory. The obtained results show that these three complexes have a six-coordinated octahedron feature, and the nitrate ions are also coordinated with the copper cation. Detailed natural bond orbital (NBO) analyses indicate that the donor-acceptor interactions between the ligands and metal cations result in decreasing of occupancies of amino N—H bond orbitals, and subsequently, cause the stretching vibrations of amino groups to shift to lower wave number, which is in accord with the experimental result. The NBO analyses also show that all of the metal cations are almost in ＋1 oxidation state, and the M—N coordination bonds are covalent, but the Cu—O coordination bonds are predominantly ionic in nature. The calculated heats of reaction reveal that the synthesis reactions for the studied compounds are exothermic. Moreover, the computed heats of formation predict that the stabilities of the title compounds decrease in the order: [Ni(CHZ)₃](NO₃)₂＞[Co(CHZ)₃](NO₃)₂＞[Cu(CHZ)₂(NO₃)₂], which is in good agreement with the available experimental thermal stabilities.

Key words: carbohydrazide, coordination compound, density functional theory, electronic structure, thermochemical property