Experimental and computational anion binding studies of meso-substituted one-walled phthalimide-based Calix[4]pyrrole

Anion binding studies of meso -substituted one-walled phthalimide-based calix[4]pyrrole ( m-PC4P, 6 ) were investigated through UV-vis spectroscopy in acetonitrile and corroborated by time-dependent den-sity functional theory (TD-DFT) calculations using 6-311G(d) basis set. Notably, to our expectation, the m-PC4P ( 6 ) displayed higher anion binding affinities in comparison to the parent C4P system, probably due to the additional weak CH-anion interactions besides four NH-hydrogen bonds of the C4P framework (supported by 1 H NMR evidence). Herein, we have observed the usual trend with halide anions (used as their tetrabutylammonium salts), i.e. with increase in size of the halides from fluoride to iodide, the an-ion binding affinity decreases. Moreover, with the nitrate anion, appreciable better binding was observed in the case of m-PC4P ( 6 ) as compared to the simple C4P ( 1 ). & COPY; 2023 Elsevier B.V. All rights reserved.

Automated summary

UV-vis spectroscopy and TD-DFT calculations were used to investigate the anion binding of meso-substituted one-walled phthalimide-based calix[4]pyrrole (m-PC4P, 6) in acetonitrile. The results showed that m-PC4P (6) exhibited higher anion binding affinities compared to the parent C4P system, possibly due to additional weak CH-anion interactions besides four NH-hydrogen bonds of the C4P framework. The binding affinity decreased with the increase in halide size from fluoride to iodide, and m-PC4P (6) showed better binding with nitrate anion compared to simple C4P (1).