Crystal structures, Hirshfeld surface analysis and PIXEL calculations of two chalcone derivatives, containing isopropoxy substituents: Importance of dispersion energy

Abstract

The crystal structures, Hirshfeld surface analysis and PIXEL calculations are reported for (E)-3-(4-methoxyphenyl)-1-(2-hydroxy-5-isoproproxyphenyl)prop-2-en-1-one, 1, and (E)-3-(3-methoxy-4-isopropoxyphenyl)-1-(2-hydroxy-4,6-diisoproproxyphenyl)prop-2-en-1-one, 2. Different sets of C—H···O, C—H···π, off-set, face-to-face π ···π and/or C=O··· π intermolecular interactions are displayed by each compound. Due to the bulk of the isoproproxy unit and the consequent steric hindrance in forming aggregates in the solid state, compounds 1 and 2 exhibit larger interplanar angles than do corresponding chalcones with methoxy units. The total stabilization energies of the crystal packing, Etot distributed as Coulombic (Ecoul), polarization (Epol), dispersion (Edisp), and repulsion (Erep) have been computed by PIXEL. For compound 1, six motifs (molecule pairs) and for compound 2, with two independent molecules in the asymmetric unit, thirteen motifs are identified by the PIXEL calculations to have energies, -Etot, above the cut-off value of 10 kJ.mol−1. For each of these motifs, the largest contributor to the Etot value is the Edisp term, irrespective of the type(s) of interaction(s) connecting the two molecules, if any, in the motifs.