Importance of intermolecular –CC–H⋯X–C (X = F, O, N) and –Y–H⋯F–C (Y = O, N) hydrogen bonds in crystal structures

Abstract

Weak hydrogen bonds involving organic fluorine have been well demonstrated through structural, computational, and experimental charge density analyses in our previous studies. As the acetylenic hydrogen (pK_a > 25) is more acidic than aromatic hydrogen (pK_a > 30), it is expected to act as a better hydrogen bond donor than aromatic hydrogen. In this study, we intend to explore the potential of weak hydrogen bonds involving –CC–H group as donors. A detailed study on the –CC–H⋯X–C (X = F, O, N) and –Y–H⋯F–C (Y = O, N) hydrogen bonds in small organic molecules has been conducted using Cambridge structure database analysis, estimation of the stabilization energy using Gaussian 16, and topological properties of these interactions using Bader's Atoms in Molecule (AIM) theory using AIM 2000. Our study provides novel insights into the role of the –CC–H group as a donor to form weak hydrogen bonds involving electronegative elements as an acceptor in crystal engineering.