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

An exceptional example of multiple C-H & ctdot;pi(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 & ctdot;pi(arene) contacts. The comprehensive analysis of the C-H & ctdot;pi 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 (sigma(BCP)) along the bond path in the C-H & ctdot;pi contacts exhibits a moderate correlation with the dimensionless penetration index (p(CH)). This finding unveils the essentially identical characteristics of the C-H & ctdot;pi interactions, irrespective of the sp- and sp(2)-carbons. The C-H & ctdot;pi(alkyne) contacts are almost statistically populated within the range of pure van der Waals interactions, whereas the C-H & ctdot;pi(arene) contact exhibits a slight deviation from the criteria. The crystal structure of syn-1 exemplifies an exceptional formation of multiple C-H & ctdot;pi(alkyne) contacts, contrasting with the generally rare occurrence of C-H & ctdot;pi(alkyne) interactions.