Influence of the d orbital occupation on the structures and sequential binding energies of pyridine to the late first-row divalent transition metal cations: a DFT study.
The ground-state structures and sequential binding energies of the late first-row divalent transition metal cations to pyridine (Pyr) are determined using density functional theory (DFT) methods. Five late first-row transition metal cations in their +2 oxidation states are examined including: Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+). Calculations at B3LYP, BHandHLYP, and M06 levels of theory using 6-31G* and 6-311+G(2d,2p) basis sets are employed to determine the structures and theoretical estimates for the sequential binding energies of the M(2+)(Pyr)x complexes, where x = 1-6, respectively. Structures of the Ca(2+)(Pyr)x complexes are compared to those for the M(2+)(Pyr)x complexes of Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+) to further assess the effects of the d-orbital occupation on the preferred binding geometries. The B3LYP, BHandHLYP, and M06 levels of theory yield very similar geometries for the analogous M(2+)(Pyr)x complexes. The overall trends in the sequential BDEs for all five metal cations at all three levels of theory examined are highly parallel, and are determined by a balance of the effects of the valence electronic configuration and hybridization of the metal cation, but are also influenced by repulsive ligand-ligand interactions. Present results for the M(2+)(Pyr)x complexes are compared to the analogous complexes of the late first-row monovalent transition metal cations, Co(+), Ni(+), Cu(+), and Zn(+) previously investigated to assess the effect of the charge/oxidation state on the structures and sequential binding energies. Trends in the sequential binding energies of the M(2+)(Pyr)x complexes are also compared to the analogous M(2+)(water)x, M(2+)(imidazole)x, M(2+)(2,2'-bipyridine)x, and M(2+)(1,10-phenanthroline)x complexes.
Department of Chemistry, Wayne State University , Detroit, Michigan 48202, United States.
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