PES as functions of the trans-angle (θ) and the dihedral angle (ε) for optimized bond length is calculated. It is found that the most unstrained stable conformation of the CuCl2− 4 is D2d at θ = 129.45◦ and ε = 90.0◦. Calculated EPR g values change smoothly and in a logarithmic manner in the experimental range. The g33 value varies from 2.1287 (D4h) to 2.2836 (Td), and g11 = g22 from 2.035 to 2.1001. The Cu hyperfine values of the D4h are A11 = −196.455 and A22 = A33 = −17.533. At the most stable D2d conformation, the values are A11 = −177.606 and A22 = A33 = 2.6266, all in the 10−4 cm−1 unit. The variation of EPR g values with molecular charge in the range of −2.0 to −2.8 were studied, and it was found that by increasing molecular charge, both components of g values are increased. For the D2d conformation with molecular charge of −2.6, g⊥ = 2.085 (expt. = 2.094) and g = 2.243 (expt. = 2.238). For the D4h conformation, calculated g values with increasing molecular charge improved, but g⊥ values deviated increasingly from experimental values. Frequencies are also calculated in the range of D2d to D4h.

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