Intramolecular hydrogen bonds of gossypol imine derivatives

Evaluation of intramolecular hydrogen bond energies of twenty gossypol imine derivatives was carried out using H-1 NMR spectroscopy and quantum chemistry methods. Gossypol imine derivatives contain various intramolecular hydrogen bonds: O-H center dot center dot center dot O, N-H center dot center dot center dot O, O-H center dot center dot center dot N, C-H center dot center dot center dot O and O-H center dot center dot center dot r hydrogen bonding of these compounds. It was found that the position of the O-H group proton signals in the H-1 NMR spectra made it possible to provide an initial estimation of the hydrogen bond energies and the degree of proton involvement in non-covalent interactions. Using geometric characteristics, hydrogen bond length, distance between electronegative atoms involved in the hydrogen bonding, and hydrogen bond angle, made it possible to compare the energies of all intramolecular hydrogen bonds of the studied gossypol imine derivatives in the gas phase. It was shown that the strengths of the intramolecular hydrogen bonds C(6)O-H center dot center dot center dot OC(7) are different for compounds in dienamine and diimine tautomeric forms, which may be a key factor affecting the tautomeric equilibrium of this class of compounds.

Automated summary

The intramolecular hydrogen bond energies of twenty gossypol imine derivatives were evaluated using H-1 NMR spectroscopy and quantum chemistry methods. These derivatives exhibit various types of intramolecular hydrogen bonds. The position of the O-H group proton signals in the H-1 NMR spectra provided an initial estimation of hydrogen bond energies and proton involvement in non-covalent interactions. Geometric characteristics, such as hydrogen bond length and angle, allowed for comparison of the energies of all intramolecular hydrogen bonds. The strength of the C(6)O-H center dot center dot center dot OC(7) intramolecular hydrogen bond differed between dienamine and diimine tautomeric forms.