•A reusable anionic resin as catalyst for the synthesis of benzimidazole and benzothiazole compounds.•Two compounds were optimized using DFT method, B3LYP/6-311G(d,p)basis set.•HOMO - LUMO and (MEP) of the compounds were studied.•NLO properties of selected two compounds were performed.•Molecular Docking was performed to establish the biological significance. A series of pharmaceutically valuable, functionalized fused heteroaromatic compounds such as benzimidazoles, and benzothiazoles have been synthesized via catalytic cyclocondensation between o-phenylenediamine, or o-aminothiophenol, and aryl aldehydes at ambient conditions. The Amberlite IRA400-Cl anionic resin has proved to be an efficient green catalyst in this protocol. The salient features of this method are the mild condition, easy work-up, an excellent yield of product, green catalyst, and reusability of the catalyst. Theoretical studies on selected compounds have been carried out using Density Functional Theory (DFT) method and Gaussian 09 package, B3LYP 6-311G(d,p) basis set. Molecular docking studies were also performed on selected compounds to determine their pharmaceutical activities. Display omitted