X[mdash ]H[middot][middot][middot][pi ] (phenyl) interactions Theoretical and crystallographic observations

Abstract

XwHÉ É Ép (phenyl) is the interaction of a hydrogen atom with the p-system of an aromatic ring in either an intermolecular or an intramolecular fashion. Although the existence of these types of interaction has gained recent attention in the literature, the geometry is poorly understood. This paper attempts to investigate the preferred geometry and interaction strength for OwH, NwH, NwH`, SwH, sp2 CwH and sp1 CwH interactions with phenyl rings. This has been done through searches of the Cambridge Structural Database, combined with semi-empirical and ab initio molecular orbital calculations. It is found that the classical image of T-shaped geometry is rarely adopted and that the preferred geometry involves direct interaction of XwH with the carbon atoms of the phenyl ring. The binding energy associated with the interaction decreases with the electronegativity of the donor atom X.

Crystal structure of 2,6-diiodo-8-(3-iodophenyl)-phenyl-BODIPY, C19H16BF2I3N2

“…To tally, four kinds of C-H···p in ter ac tions are ob served be tween the hy dro gen at oms and ar o matic heterocycle. The H···cen troid dis tance ranged from 2.6 to 3.6 Å, which is well in side the typical in ter val be tween 2.6 and 4.0 Å [5]. In one of the four bonds (C26-H26···p i3 , C3/C4/C5/C6/N2, i3: -x, 1-y, -z), the hy dro gen atom is be ing attracted in the di rec tion of the ring cen tre.…”

“…In one of the four bonds (C26-H26···p i3 , C3/C4/C5/C6/N2, i3: -x, 1-y, -z), the hy dro gen atom is be ing attracted in the di rec tion of the ring cen tre. This ar range ment is described as a type-II in ter ac tion [5]. Other three C-H···p in ter ac tions are of type-V (C17-H17C···p i3 , C8/C9/C10/C11/ N12, C17-H17C·· ·p i 3 , N2/C6/C7/C8/N12/B11, and C26-H26···p i3 , N2/C6/C7/C8/N12/B11), in which the hy dro gen at oms in ter act with the car bons at the edge of the ac cep tor ring.…”

Crystal structure and properties of l-tryptophanium hydrogen selenite

“…The H2-centroid distance is 2.681 Å , the interaction angle N2-H2Á Á Ácentroid is 127.83°, and the angle between the H2-centroid line and the ring perpendicular is 25.80°. This geometry is described as type III by Malone et al [20]. The same geometry is seen in the intermolecular interaction, C11-H11Á Á Á(N2-C6 centroid), with a slightly larger distance, 3.184 Å , and angle, 131.40°.…”

The Basicity of Unsaturated Hydrocarbons as Probed by Hydrogen‐Bond‐Acceptor Ability: Bifurcated NH+⋅⋅⋅π Hydrogen Bonding

“…[14][15][16][17][18][19] The range of acceptors now includes nitrogen heterocycles [20] and π-ligand transition metal complexes [18] and these types of interactions are beginning to be utilized in crystal engineering. [21] X-H⋯π interactions have also been identified in proteins [19,22,23] and N-H⋯π interactions can be sufficiently strong to affect secondary (folding) structure. [24] Estimations of the strengths of X-H⋯π interactions have typically relied on the determination of the thermodynamics of complexation.…”