Conformational Stabilities, EPR, IR and VCD Studies of Tris(ethylenediamine)nickel(II) Chloride

Conformational stabilities of the transition metal complex of the [Ni(en)3]Cl2 was studied using Density Functional Theory (DFT). The deformational potential energy profiles (PEPS), pathways between the different isomeric conformational energies were calculated using B3LYP/6-31G. Relative conformational energies of the �"(λλλ), �"(λλ�×), �"(λ�×�×) and �"(�×�×�×) were 0.04, 0.36, 0.17, 0.0 kcal mol-1, respectively, which were small compared to the barrier heights for the reversible phase transitions 51.12, 50.48, 49.64 kcal mol-1, respectively. The frequency assignment was carried out by fitting Fourier transform infrared (FTIR) spectra and using Gaussian and GaussView computer programs. The theoretical vibrational circular dichroism (VCD) absorption spectra are presented for all conformations in the range of 400-3500 cm-1. Calculated electron paramagnetic resonance (EPR) g-tensor parameters of the [Ni(en)3]Cl2, gx = 2.69, gy = gz = 2.71, are well compared to the corresponding experimental values and indicate a spherical electronic structure for the Ni atom in this compound.