How directional are D–H⋯phenyl interactions in the solid state (D = C, N, O)?

Abstract

In-depth examinations of the Cambridge Structural Database (CSD) for D–H⋯phenyl supramolecular contacts (with D = C, N, O) have been made. Careful analyses of the data found in a 5 Å high and 10 Å wide hemisphere around the phenyl plane reveal that for D = C or N, the CSD hits are preferentially located above the ring, thus indicating that C–H⋯π^phenyl and N–H⋯π^phenyl interactions are preferentially taking place. In contrast, for D = O, the CSD hits cluster near the periphery of the phenyl ring, suggesting that the O–H moiety rather acts as hydrogen-bond acceptor (the phenyl unit behaving as a hydrogen-donor group in this case). These findings are confirmed by inspection of the vertical region (d) above the ring centroid (r = 0–1 Å), as Gaussian-shaped plots are observed for D = C (maximum at d = 2.90 Å) and D = N (maximum at d = 2.55 Å) while the hits are randomly distributed for D = O.