Experimental and theoretical studies of vibrational spectrum and molecular structure and related properties of pyridoxine (vitamin B6)

• Pyridoxine (vitamin B6) plays important roles in enzymatic reactions.
• The molecular structure and vibrational study for pyridoxine have been studied theoretically for the first time.
• Vitamin B6 has 8 conformers each having C1 point group symmetry.

Vibrational spectrum of pyridoxine has been investigated using experimental IR and Raman spectroscopic and density functional theory (DFT) methods. Vibrational assignments of the observed IR and Raman bands have been proposed in light of the results obtained from computations. In order to assign the observed IR and Raman frequencies the potential energy distributions (PEDs) have also been computed. Optimized geometrical parameters suggest that if the OH groups of the two methyl groups are replaced by H atoms the resulting molecule has Cs point group symmetry. To investigate molecular stability and bond strength we have used natural bond orbital analysis (NBO). Charge transfer occurs in the molecule have been shown by the calculated highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) energies. The mapping of electron density iso-surface with electrostatic potential (ESP), has been carried out to get the information about the size, shape, charge density distribution and site of chemical reactivity of the molecule.

The experimental IR and Raman spectra of vitamin B6 are reproduced here. All the observed bands have been assigned in light of the computed spectra and PEDs.Figure optionsDownload as PowerPoint slide