Trapped Cyclic Dimeric Oxyanion Assembly by a Urea-Functionalized Receptor: Potent Application in Linear Discriminant Analysis and as Antibacterial Agents

Abstract

The naphthalimide-based linear monourea receptors L 1 and L 2 exhibit anion (oxyanions and halides) binding in the solid and solution states. The receptor L 1 could render fluoride-/hydroxide-induced aerial CO2 fixation efficiently, leading to air-stable assembling of dianions enclosed by n-TBA cations via the formation of an R2 2(8)-type cylindrical dimeric arrangement. The assembly of the anions is stabilized via short-range hydrogen-bonding interactions. A cyclic dimeric assembly of bisulfate anions sealed by the linear tetrameric assembly of the host molecule was also evidenced from the solid-state architecture. Upon addition of excess amounts of chloride and bromide anion, linearly assembled L 1 captured a cyclic chloride–water and bromide–water tetrameric cluster. The ligands were capable of discriminating five relevant anions with 100% classification accuracy in aqueous media on the basis of multivariate pattern analysis. Interestingly, the ligands L 1 and L 2 displayed notable bactericidal activity against the Gram-negative pathogen E. coli MTCC 433 and were nontoxic to cultured human embryonic kidney (HEK 293) cells.

Anion-Induced Intramolecular Cyclization of Urea-Based Receptors: Entrapment of Cyclic [SO4(H2O)42–]n Cluster and Encapsulation of Anions with Varied Dimensionality

“…Previously, our group has already explored numerous receptors ranging from monopodal to tripodal receptors for both solid- as well as solution-phase anion recognition study − and most of our studies were limited to organic solvent medium only; less exploration was done toward selective anion recognition in aqueous medium. So keeping that in mind, in our continuous endeavor toward anion recognition chemistry, herein, we have designed a set of two unsymmetrical dipodal monourea receptors BPU-1 and BPU-2 having pi -acidic terminal substituents, containing the benzimidazole moiety as a signaling unit as well as a hydrogen donor/acceptor site, to investigate their anion recognition behavior in both solid states as well as in solution phase and also to perform fluorimetric sensing study of both the receptors in the presence of various anions in 100% aqueous medium.…”