Structural analysis of intramolecular 1,5-type O⋯O and S⋯O interactions in diethyl 2-oxo and diethyl 2-thioxo-1H benzo[d]imidazole-1,3(2H)-dicarboxylate: Experimental and theoretical study

Four compounds derived from 2-hydroxy and 2-mercaptobenzimidazole were synthesized and characterized by FT-IR spectroscopy, nuclear magnetic resonance and elemental analysis. Two of the resulting compounds –diethyl 2-oxo-1H benzo[d]imidazole-1,3(2H)-dicarboxylate and diethyl 2-thioxo-1H benzo[d]imidazole-1,3(2H)-dicarboxylate– were crystallized and analyzed by X-ray diffraction. The former presented intermolecular interactions of bidentate hydrogen-bonds and the formation of R22(10) rings via C–H⋯OC, resulting in a stacking arrangement while the latter had a zig-zag arrangement due to the intermolecular aromatic interaction C–H⋯OC. A computational conformational study was made to support and explain the resulting structures stabilities. Furthermore, a QTAIM analysis was performed to study the nature of the intramolecular 1,5-type O⋯O and S⋯O interactions.