Synthesis, structure, and spectroscopic properties of chiral oxorhenium(V) complexes incorporating polydentate ligands derived from L-amino acids: A density functional theory/time-dependent density functional theory investigation

The oxorhenium(V) complexes [(ReO)-O-V(L-A)Cl-2] bearing the (N-2-pyridylmethyl) of L-valine (HLA1), L-leucine (HLA2), and L-phenylalanine (HLA3) and [(ReO)-O-V(L-B)Cl] containing the {(N-2pyridylmethyl)-(N-(5-nitro-2-hydroxybenzyl)} of L-valine (H2LB1), L-leucine (H2LB2), and L-phenylalanine (H2LB3) are presented in this article. The complexes are isolated in enantiomeric pure form examined from X-ray structure determination. The complexes are characterized by spectroscopic and electrochemical methods. The molecular structures observed in the solid state are grossly preserved in solution (H-1, C-13, and circular dichroism spectra). Gas-phase geometry optimization and the electronic structures of [(ReO)-O-V(L-A(1))Cl-2], [(ReO)-O-V(L-A(2))Cl-2], and [(ReO)-O-V(L-B(2))Cl] have been investigated with the framework of density functional theory. The absorption and circular dichroism spectra of the complexes were also calculated applying time-dependent density functional theory (TDDFT) using the conductor-like polarizable continuum solvent model to understand the origin of the electronic excitations. The chemical shift (H-1 and C-13) as well as H-1-H-1 spin-spin coupling constant were also computed by the gauge-independent atomic orbital method, and the computed values are consistent with the experimental data.