TAUTOMERISM OF SUBSTITUTED SALICYLALDEHYDE AND 2-DIPHENYLPHOSPHINEBENZALDEHYDE 1'-PHTHALAZINYLHYDRAZONES: X-RAY CRYSTALLOGRAPHY AND QUANTUM CHEMICAL MODELING
S. I. Levchenkov1, L. D. Popov2, I. N. Shcherbakov2, G. G. Aleksandrov3, A. A. Zubenko4, V. A. Kogan2
1Southern Scientific Center, Russian Academy of Sciences, Rostov-on-Don
2Chemistry Department, Southern Federal University, Rostov-on-Don
3N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow
4North-Caucasian Zonal Research Veterinary Institute, Novocherkassk, Russia
Keywords: hydrazones, tautomerism, X-ray crystallography, hydrogen bond, density functional theory
Abstract
1'-Phthalazinylhydrazones of salicylaldehyde, its substituted derivatives, and 2-diphenylphosphinebenzaldehyde are synthesized and studied. A description is given of the structures salicylaldehyde 1'-phthalazinylhydrazone (1а) and 2-diphenylphosphinebenzaldehyde 1'-phthalazinylhydrazone (2), which exist in the crystal in the hydrazonophthalazone tautomeric form. Molecules of hydrazone 1а form in the crystal infinite stacks of hydrogen bonded dimers with intermolecular π-stacking interactions. A quantum chemical calculation is made of the geometry and total energy of the possible tautomers in vacuum and in aqueous and chloroform solutions. The hydrazonophthalazone tautomers are shown to be the most stable in all cases. The X-ray crystallography results are compared with the calculated data.
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