Charge-assisted hydrogen bonding in salts of 2-amino-1H-benzimidazole with 3-phenylpropynoic acid and oct-2-ynoic acid

摘要

The 100K structures of two salts, namely 2-amino-1H-benzimidazolium 3-phenylpropynoate, C7H8N3 +·C9H5O2 -, (I), and 2-amino-1H-benzimidazolium oct-2-ynoate, C7H8N3 +·C8H11O2 -, (II), both have monoclinic symmetry (space group P21/c) and display N-H?O hydrogen bonding. Both structures show packing with corrugated sheets of hydrogen-bonded molecules lying parallel to the [001] direction. Two hydrogen-bonded ring motifs can be identified and described with graph sets R2 2(8) and R4 4(16), respectively, in both (I) and (II). Computational chemistry calculations performed on both compounds show that the hydrogen-bonded ion pairs are more energetically favourable in the crystal structure than their hydrogen-bonded neutral molecule counterparts.