Experimental and computational insights into the nature of weak intermolecular interactions in trifluoromethyl-substituted isomeric crystalline N-methyl-N-phenylbenzamides. (9th September 2015)

• Record Type: Journal Article
• Authors: Panini, Piyush; Chopra, Deepak
• Is Part Of: New journal of chemistry. Volume 39:Number 11(2015:Nov.)
• Page Start: 8720
• Page End: 8738
• Publication Date: 2015-09-09
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c5nj01670c
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : The nature and role of weak interactions, involving fluorine in crystalline N -methyl- N -phenylbenzamides, have been studied in the absence of strong H-bonds. Abstract : The knowledge about the prevalence of weak interactions in terms of the nature and energetics associated with their formation is of significance in organic solids. In the present study, we have systematically explored the existence of different types of intermolecular interactions in ten out of the fifteen newly synthesized trifluoromethyl derivatives of isomeric N -methyl- N -phenylbenzamides. Detailed analyses of all the crystalline solids were performed with quantitative inputs from interaction energy calculations using the PIXEL method. These studies revealed that in the absence of a strong hydrogen bond, the crystal packing is mainly stabilized by a cooperative interplay of weak C–H⋯OC, C–H⋯π, and C(sp 2 )/(sp 3 )–H⋯F–C(sp 3 ) hydrogen bonds along with other related interactions, namely, π⋯π and C(sp 3 )–F⋯F–C(sp 3 ). It is of interest to observe the presence of short and directional weak C–H⋯OC hydrogen bonds in the packing, having a substantial electrostatic (coulombic + polarization) contribution towards the total stabilization energy. The C(sp 3 )–F group was recognized in the formation of different molecular motifs in the crystal packing as utilizing different intermolecular interactions. The contribution from electrostatics among the different weak hydrogen bonds was observed in the decreasing order: C–H⋯OC > C–H⋯F–C(sp 3 ) > C–H⋯π. Furthermore, there was an increase in the electrostatic component with a concomitant decrease in the dispersion component for the shorter and directional hydrogen bonds.