Effects of methoxy substituents on self-assembly and gelation performance of benzamide-based organogelators

Low-molecular-weight organogelators (LMOGs) have gained widespread attention for their unique properties and potential applications across various fields. However, the discovery of most LMOGs has largely been serendipitous. The molecular structural diversity and complexity of LMOG self-assembly mechanisms posed significant challenges for elucidating the structure-property relationship. Herein, a series of LMOGs derived from methoxy-substituted benzamide-based compounds were synthesized via a one-step condensation reaction, with the methoxy-substitution position fine-tuned. Gelation studies revealed that para-substituted and 3,4-substituted derivatives were efficient LMOGs that could self-assemble and gel various organic solvents, with a minimum gelation concentration below 2.54% w/v. Furthermore, the relationships between molecule structures and gelation properties were studied, and their self-assembly mechanisms were explored. In addition, theoretical calculations were performed to optimize monomer/dimer structures, map electrostatic potential ESP and non-covalent interaction NCI surfaces, and compute dipole moments, HOMO-LUMO gaps, and dimer binding energies, thereby providing molecular insights into the structure-gelation relationship. Both the experimental and theoretical results confirmed that the substitution pattern, particularly the para- or 3,4-dimethoxy arrangement, is more favorable for self-assembly in the benzamide structure.