Opto-magnetic studies of metal-ligand interactions in transition metal complexes having closed shell configurations

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Spectroscopic and magnetic properties have been investigated for complexes of d^<10> closed shell metal ions, and the results of significance are summarized as follows.(1) Mixed ligand complexes of the type Zn(X-PhS)_2(phen)The triplet sublevels associated with the lowest ligand charge transfer (LLCT) triplet excited state have been investigated for a series of the complexes of the type Zn(X-PhS)_2(phen), where X is a substituent on the benzenthiol ligand and phen is 1,10-phenanthroline. The zero field splitting parameters D* are significantly larger than the values calculated quantum mechanically based on a model of pure charge transfer state. This discrepany suggests that the phen localized pipi* states mixes with the LLCT state. The degree of mixing is obtained based on this mixing mechanism from the results of both the lifetime and the zero field splitting. The mixing coefficients determined show a good and expected correlation with the electron donating ability of the substituent X on benzenethiol. Thus, the participation of LLCT to phen localized pipi* state is well substantiated.(2) Complexes of the type MX_2(phen)Fluorescence and the triplet sublevel properties have been investigated for a series of complexes of the type MX_2(phen), where M is Zn(II) or Cs(II) and X is C1, Br, or I. The fluorescence lifetime, zero field splittings,and the radiative rate constants for sublevels are all interpreted satisfactorily by a theoretical model in which the phen localized pipi* state mixes with charge transfer state arising from the electron promotion from p orbital of halogen to pi* orbital phen.