Unravelling the sensing mechanism of bis-urea macrocycle-based anion receptor: a theoretical study

Understanding how the bis-urea macrocycle molecules can sense different invited anionic substances is becoming increasingly crucial. In this context, we have theoretically studied a new host-guest such as the interaction of 7,13-dibromo-1,4,8,11-tetraazacyclotetradecane-5,12‑dione (BUM) with the anions like SO42−, SO32−, CH3COO−, NO2−, and NO3−. DFT and TD-DFT are used to calculate thermodynamics, electronic structure, electric-field induced properties, and photo-physical characteristics in order to investigate the mechanism of selective sensing of these anions. The free energy change (ΔGads) and adsorption energies (Eads) suggest that these anionic interactions are thermodynamically feasible with strong to moderate adsorption energy with the receptor. The conductivity and sensitivity between the anions can be improved by the external electric field regulated investigation. Because of the intramolecular charge transfer transitions, internal conversions, and related configurational modifications, BUM-SO32− exhibits good fluorescence in the BUM-anion complexes, indicating its significance for practical utility.