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

Abstract

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.

Pyridine: A Useful Ligand in Transition Metal Complexes

“…Thus theoretical approach adopted to study pyridine binding to metals using pyridine ligands to a group of first transition metals ions in their +2 oxidation states. DFT calculation employed by Rodgers [95]…”

S2N2– A 6π‐Electron Ligand with Tunable σ‐ and π‐ Donor‐Acceptor Property

“…This interaction contributes only 8.2 % of the total orbital interaction energy. Hence, S 2 N 2 in 1Mo can act as a strong σ‐donor and weak π‐acceptor ligand, which is similar to N‐heterocyclic aromatics like pyridines . Furthermore, it can also act as σ‐acceptor at the S‐atom by the charge transfer of N lone pair to S 2 N 2 σ*‐MO.…”

“…N‐donor aromatic hydrocarbons, such as pyridine and its structural analogs represent a class of extremely valued ligands and ubiquitously have played important roles in the development of coordination chemistry . Interestingly, the heteroatom substitution in the aromatic hydrocarbons introduces Lewis basicity due to σ‐lone pair of nitrogen and Lewis acidity due to C−N π*‐orbitals . Moreover, the interactions of these classes of compounds with the transition metal fragments could be widely varied from the formation of σ‐type or π‐type complexes.…”

Cyclic Aromatic 6π-Electron S2N2 ‒ A Ligand with Tunable σ- and π- Donor-Acceptor Property

“…N-donor aromatic hydrocarbons, such as pyridine and its structural analogs represent a class of extremely valued ligands and ubiquitously have played important roles in the development of coordination chemistry. [1][2][3][4][5][6] Interestingly, the heteroatom substitution in the aromatic hydrocarbons introduces Lewis basicity due to σlone pair of nitrogen and Lewis acidity due to C-N π*-orbitals. [6][7][8][9] Moreover, the interactions of these classes of compounds with the transition metal fragments could be widely varied from the formation of σ-type or πtype complexes.…”

“…[1][2][3][4][5][6] Interestingly, the heteroatom substitution in the aromatic hydrocarbons introduces Lewis basicity due to σlone pair of nitrogen and Lewis acidity due to C-N π*-orbitals. [6][7][8][9] Moreover, the interactions of these classes of compounds with the transition metal fragments could be widely varied from the formation of σ-type or πtype complexes. Accordingly, a wide variety of N-based aromatic hydrocarbon ligands has been designed and synthesized in order to generate organometallic compounds with diverse structures, shapes, nuclearity and dimensionality.…”