Water-Assisted Self-Aggregation of Benzimidazole and Triazole Adducts

The manuscript revolves around an interesting observation of solidification of a solution of N-((1-((1-ethyl-1H-benzo[d]imidazol-2-yl)methyl)-1H-1,2,3-triazole-4-yl)methyl)aniline (A6) in the NMR tube after around 12 h. Real-time images showed fibrillar and spherulitic growth with tip branching and side branching, which is thermoreversible. The compound under investigation is unique because it is synthesized to understand the anticancer activity with two pharmacophores, benzimidazole and triazole. Click chemistry is employed for in situ generation of triazole moiety on benzimidazole. Previously, benzimidazole-based compounds have shown self-aggregation-induced gel-like behavior because of hydrogen bonding and/or π-π stacking interactions. In the present case, NMR titrations with D₂O addition showed two distinct changes in the chemical shift for methylene bridges (connecting benzimidazole and triazole ring) and ortho protons of the phenyl ring (attached to triazole ring). Interestingly, a single-crystal X-ray structure shows the absence of hydrogen bonds and π-π stacking while in the presence of only two distinct close contacts, completely correlating NMR data discussed in detail. A similar "molecular origin" for self-aggregation is observed in seven other flexible but regioisomeric compounds, which were designed and synthesized for inducing hydrogen bonding through the removal of N-ethyl group and insertion of aniline and/or fluoro group.