Structural and spectroscopic study and intermolecular chalcogen bonding interactions in 1,3-dicarbonyl compounds

Abstract

Two new 1,3-dicarbonyl compounds bearing an o-hydroxyphenyl moiety (for short, I and II) were synthesized and subjected to structural, experimental and theoretical studies. Vibrational spectroscopy (IR and Raman) and X-ray diffraction were used for solid phase studies, while NMR and electron spectroscopy allowed analysis in solution. The crystal structures of I and II, determined by X-ray diffraction methods, are closely related to each other (rms deviation of homologous atoms from their best fit is 0.147 Å). The observed planarity of β-hydroxyphenylcarbonyl enols fragment in the compounds is enforced by both extended π-bonding and intramolecular OH⋯O bonds. Molecules in I are arranged in the lattice as center-symmetric dimers held by relatively weak intermolecular OH⋯O bonds. Hirshfeld surface (HS) analysis, atoms in molecules (QTAIM), and natural bonding orbitals (NBO) approaches were employed to study theoretically selected dimers constructed from X-ray data. The results were combined with experimental ones to obtain deep insight into the strength and type of intermolecular interactions. A chalcogen bond interaction was detected in I. Although the O⋯O interaction is unusual, it participates in the attractive forces that stabilize the crystal lattice. The title compounds are present in the solid state only as the keto–enol tautomer, while in solution the diketo tautomer is also detected at concentrations of 5%. In vitro studies showed that I have better antimicrobial properties than II, mainly against the S. aureus strain.