Temperature dependent study of the single crystal electronic spectrum of octahedral Ni²⁺ ion subjected to distortions in weak fields

Electronic spectra of two high spin d 8 nickel complexes, Ni(en)3Cl2.2H2O and Ni(OAc)2.4H2O, are reported. Polarized spectra were measured at 298 K. Temperature dependent spectra were measured using unpolarized light down to 20 K. The spectra at 20 K are well resolved revealing the features of spin-forbidden transitions and vibrational fine structure on some of the bands. Some of the spectra are deconvoluted to separate out the overlapping bands. The assignments are made using D 3 symmetry for Ni(en)3Cl2.2H2O complex while D 4 symmetry is used for Ni(OAc)2.4H2O. The energies of the spectroscopic states are calculated and compared with the observed transition energies. The distortion parameters are determined. © 1992 the Indian Academy of Sciences.