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A new perfluoromethyl aminoenone derivative and the role of the hydrogen bonding in the intra- and intermolecular interactions

Abstract:

The structure of a new perfluoromethyl derivative, (Z)-4,4,4-trifluoro-1-(2-hydroxyphenyl)-3-(methylamino)-2-buten-1-one (1), was investigated in both crystalline state and solution since the prototropy enable the existence of three tautomeric species in equilibrium. The preference in the configurational E/Z arrangement is strongly dependent on the intramolecular hydrogen bond interactions. The vibrational and electronic spectra of 1 were discussed and assigned by using DFT calculations. The crystal, solved by single-crystal X-ray diffraction, shows the prevalence of the tautomer aminoenone over the imino-enol and imino-ketone forms. Therefore, an almost planar molecular conformation is observed due to the formation of two intramolecular amino and phenolic hydrogen bonds to the same carbonyl oxygen acceptor atom that stabilize the Z configuration. The molecular packing is held by the O–H⋯O(keto) and N–H⋯O hydrogen bonds, F⋯F, C–H⋯π and π-stacking interactions that contribute to the crystal stabilization. The intra and intermolecular contacts were also characterized by Natural Bond Orbital (NBO) analysis and Atoms in Molecules (AIM) approach. Hirshfeld surfaces and their associated fingerprint plots were generated for 1 and for a related structure, to visualize different intermolecular interactions and their relative contributions to the total surface.