LAUSR

Abstract Coordination properties and biological activity of the compounds depend significantly on their capability of taking the conformation, most appropriate for complex formation or binding to the target biomolecule. The hydrazones formed by B6 vitamers, pyridoxal, and pyridoxal 5’-phosphate are known for their metal chelating ability closely related to their beneficial and adverse effects on living cells. The conformational behavior of two hydrazones derived from pyridoxal 5’-phosphate and 2-,3-pyridinecarbohydrazide is studied utilizing quantum chemistry and NMR techniques. Four possible rotations resulting in different rotamers are analyzed: phosphate group, pyridoxal 5’-phosphate rotation, carbonyl group, and 2- or 3-pyridinyl rotation. Ground states energies, rotation barriers, as well as the structural peculiarities of different species were estimated on the B3LYP/6-311G++(d,p) level of the density functional theory, while the proportion of different rotamer groups was evaluated from the experimental 1D NOESY measurements.