Quantitative Evaluation of C–H···O and C–H···π Intermolecular Interactions in Ethyl-3-benzyl-1-methyl-2-oxoindoline-3-carboxylate and 3-Methyl-but-2-en-1-yl-1,3-dimethyl-2-oxoindoline-3-carboxylate: Insights from PIXEL and Hirshfeld Analysis

Abstract

The X-ray crystallographic structures of two biologically active molecules, namely (±)-ethyl-3-benzyl-1-methyl-2-oxoindoline-3-carboxylate (I) and (±)-3-methyl-but-2-en-1-yl-1,3-dimethyl-2-oxoindoline-3-carboxylate (II) have been investigated based on the molecular conformation and supramolecular packing of the molecules in the solid state. These two structures assemble via C–H···O=C and C–H···π intermolecular interactions which contribute towards the stability of the crystal packing. In order to gain quantitative insights into the nature of non-covalent interaction between different molecules the interaction energy of the molecular pairs obtained after analysis of the crystal structures for both the molecules has been performed by using the PIXEL approach along with high level DFT+Disp calculations. Hirshfeld surface analysis and the associated fingerprint plots provide rapid quantitative insight into the intermolecular interactions in molecular solids. This article provides support to the fact that every molecule can be explored in detail for an understanding of its solid state structure via experimental and computational tools in crystal engineering. This manuscript outlines the significance (nature and energetic) of weak intermolecular interactions in ethyl-3-benzyl-1-methyl-2-oxoindoline-3-carboxylate and 3-methyl-but-2-en-1-yl-1,3-dimethyl-2-oxoindoline-3-carboxylate in the solid state (using PIXEL) and comparison with that in the gas phase (using TURBOMOLE) and their partitioning into coulombic, polarization, dispersive and repulsive components. Furthermore, Hirshfeld surface analysis has also been used to probe such intermolecular interactions.