Comprehensive analysis of C–H⋯π(alkyne) interactions in the crystal packing of diastereomers of 1,2-di(7′-methoxynaphth-1′-yl)-3,6-di(4′′-n-propylphenylethynyl)benzene

Abstract

An exceptional example of multiple C–H⋯π(alkyne) contacts has been discovered in the crystal packing of the syn-diastereomeric conformer of 1,2-di(7′-methoxynaphth-1′-yl)-3,6-di(4′′-n-propylphenylethynyl)benzene (syn-1). In contrast, the chiral crystal of anti-1, derived from a racemic mixture via spontaneous resolution, predominantly features conventional C–H⋯π(arene) contacts. The comprehensive analysis of the C–H⋯π contacts in the crystal packing of 1 was conducted using Hirshfeld surface, van der Waals crust, and quantum theory of atoms-in-molecules (QTAIM) methods. The electron density at the bond critical points (σ_BCP) along the bond path in the C–H⋯π contacts exhibits a moderate correlation with the dimensionless penetration index (p_CH). This finding unveils the essentially identical characteristics of the C–H⋯π interactions, irrespective of the sp- and sp²-carbons. The C–H⋯π(alkyne) contacts are almost statistically populated within the range of pure van der Waals interactions, whereas the C–H⋯π(arene) contact exhibits a slight deviation from the criteria. The crystal structure of syn-1 exemplifies an exceptional formation of multiple C–H⋯π(alkyne) contacts, contrasting with the generally rare occurrence of C–H⋯π(alkyne) interactions.