Experimental and theoretical investigation of molecular structure and conformation of the 4-isopropylthioxanthone

In this study, the molecular structure and conformational analyses of the 4-isopropylthioxanthone (4-ITX) are reported according to experimental and theoretical results. The compound crystallizes in the centrosymmetric P1¯ space group with only one molecule in the asymmetric unit, presenting the most stable conformation, in which the three fused-rings adopt a planar geometry, and the isopropyl group assumes a torsional angle with less sterical hindrance. The structural and conformational analyses were performed using theoretical calculations such as Hartree–Fock (HF), DFT method in combination with 6-311G(d,p) and 6-31++G(d,p) and the results were compared with infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The supramolecular assembly of 4-ITX is kept by non-classical C–H⋯O hydrogen bonds and weak interactions such as π–π stacking. 4-ITX was also studied by 1H and 13C NMR spectroscopy. UV–Vis absorption spectroscopic properties of the 4-ITX showed the long-wavelength maximum shifts towards high energy when the solvent polarity increases.

► 4-Isopropylthioxanthone presents interesting behavior in solution and solid state.
► The structural and IR analysis match well with the theoretical and experimental data.
► Weak interactions contribute to stabilize the molecular conformations and assembly.
► Intermolecular H-bond contributes to increase the carbonyl bond length.
► Increasing the solvent polarity the energy of the UV–Vis bands is increased.