Crystal structures, Hirshfeld surface analysis and PIXEL calculations of four (E)-1-(2-hydroxyphenyl)-3-phenylprop-2-en-1-one derivatives, containing methoxy substituents. The importance of π interactions

Abstract

A detailed structural analysis has been carried out on four chalcone (E)-1-(2-hydroxyphenyl)-3-phenylprop-2-en-1-one derivatives, having a varying number of methoxy substituents, namely (E)-3-(3,4-dimethoxyphenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one, (1), (E)-3-(4-methoxyphenyl)-1-(2-hydroxy-4-methoxyphenyl)prop-2-en-1-one, 2, (E)-3-(2,5-dimethoxyphenyl)-1-(2-hydroxy-4-methoxyphenyl)prop-2-en-1-one, 3, and (E)-3-(2,5-dimethoxyphenyl)-1-(2-hydroxy-3,4-dimethoxyphenyl)prop-2-en-1-one, 4. Crystal structures were determined at 100 K by single crystal X-ray diffraction. Compound 2 displayed an unexpectedly large interplanar angle of 25 and 28,o between the phenyl groups in the two independent molecules, due to the formation of a dimeric substructure requiring a pronounced phenyl group rotation to minimise steric hindrance. Such a substructure was absent in 1, 3 and 4. In all cases the 2-hydroxyl substituent forms intramolecular hydrogen bonds with its neighbouring carbonyl group. Different combinations of C–H⋯O, C–H···π and/or π ···π interactions are displayed by 1, 3 and 4, with also CO··· π intermolecular interactions present in 2. The relative contributions of various intermolecular contacts in these structures were investigated using Hirshfeld surfave analysis and the associated two dimensional fringerprint plots. Important molecule pairs were identified in the crystal structures using the PIXEL method. The PIXEL lattice energy calculations revealed that in all cases the dispersion contribution was the major contributor to the packing stabilization, followed by the Coulombic contribution.A search of structures of alkoxy derivatives of (E)-1-(2-hydroxyphenyl)-3-phenylprop-2-en-1-one derivatives in the CCDC data base has also been carried out.