Theoretical and Experimental Studies on Electronic Structure, Cocrystallization, and Intramolecular Proton Transfer of Two Tautomers: (E)-2 and (Z)-6 Methylene}-3 4-Dienone

Abstract

In this work, the structure of (E)-2-{[2-(hydroxymethyl) phenylimino]methyl}-5-methoxyphenol was characterized by X-ray single crystal diffraction technique, infrared spectroscopy, and quantum chemical computational methods as both experimental and theoretically. The compound crystallizes in the triclinic space group P1 with a = 9.4601 (5) Å, b = 11.7273 (7) Å, c = 12.4400 (8) Å, α = 88.179 (5)°, β = 71.442 (4)°, γ = 84.977 (5)°, and Z = 4. X-Ray study shows that both enol-imine and keto-amine tautomeric forms coexist in the asymmetric unit as two independent molecules. The molecular geometry was also optimized at the B3LYP/6-311G(d,p) level by using density functional theory started from the crystallographically achieved parameters of molecule. From the optimized geometry of the molecule, molecular electrostatic potential was evaluated, frontier molecular orbitals and natural bond orbital analysis were performed, and vibrational frequencies were computed theoretically. The polarizable continuum model calculations starting from the optimized geometry were also carried out in both gaseous and solution phase to investigate the energetic behavior and dipole moment of the title compound with the same level of theory. © 2010 Wiley Periodicals, Inc.