Heterocyclic N-oxide ch⋯o hydrogen bonding (part 3). crystal packing of 2,2′-bipyridine-1,1′-dioxide and pyridine N-oxide

Abstract

Short intermolecular CH⋯O contacts of 2.212(2) and 2.325(2) Å are found in the crystal structure of 2,2′-bipyridine-1,1′-dioxide (BPDO) and are assigned as CH⋯O hydrogen bonds based on geometric criteria and quantum mechanical calculations. The pattern of BPDO association yields a two-dimensional CH⋯O hydrogen-bonded array in the BPDO crystal. Each BPDO molecule participates in eight CH⋯O hydrogen bonds, which occur in two distinct pairs as centric R 2 2(8) and acentric R 2 2(12) dimeric linkages whose binding enthalpies are estimated to be −6.7 and −2.3 kcal mol −1, respectively, by AM1 calculations. Self-association via CH⋯O hydrogen bonding of the parent molecule, pyridine N-oxide (PO), is also considered. In solution, PO molecules are postulated to form CH⋯O bonded R 2 2(8) dimers with an estimated binding energy of −5 to −8 kcal mol −1. In the crystal, PO molecules associate to give a three-dimensional network via CH⋯O hydrogen bonding.