Host-guest interaction of tryptophane with acid-functionalized calix[4]pyrrole: a fluorescence-based study

Functionalized calix[4]pyrroles are at forefront of host-guest aided molecular sensors. They offer unique platform for flexible functionalization to develop receptors suitable for different applications. In this context, calix[4]pyrrole derivative (TACP) was functionalized with an acidic group to investigate its binding behavior with different amino acids. The acid functionalization facilitated host-guest interactions through hydrogen bonding and increase the solubility of ligand in 90% aqueous media. The results indicated that TACP exhibited significant fluorescence enhancement in the presence of tryptophan while no considerable changes were observed with other amino acids. The other complexation properties such as LOD and LOQ were determined to be 25 µM and 22 µM respectively with 1:1 stoichiometry. In addition, the proposed binding phenomena were further confirmed through computational docking studies and NMR complexation study. Overall, this work highlights the potential of acid functionalization in developing molecular sensors for amino acid detection using calix[4]pyrrole derivatives. Communicated by Ramaswamy H. Sarma