Supramolecular Assemblies of 3/4-Chlorobenzoic Acid and Amino-Chloropyridine Derivatives: Synthesis, X-ray Diffraction, DFT Calculations, and Biological Screening

Abstract

Organic acids (3-chlorobenzoic acid and 4-chlorobenzoic acid) were treated with 4-amino-2-chloropyridine and 2-amino-4-chloropyridine as coformers for cocrystallization. Acid/base pairs afforded a cocrystal (3-chlorobenzoic acid and 4-amino-2-chloropyridine, compound 1) and molecular salts (2-amino-4-chloropyridinium 3-chlorobenzoate, 2; 2-amino-4-chloropyridinium 4-chlorobenzoate, 3). The products were characterized with the help of FT-IR, UV/visible spectroscopy, PXRD, and SC-XRD. The position of the Cl-substituent on the phenyl ring was explored with respect to proton transfer between acid/base pairs, and its role in supramolecular chemistry is discussed in detail. The existence of supramolecular assemblies was further reproduced using DFT calculations. Further, frontier molecular orbital (FMO), molecular electrostatic potential (MEP), and noncovalent interaction index (NCI) analyses were performed to gain insight into the electronic properties and nature of noncovalent interactions. The prepared compounds were examined for their biological activities against selected Gram-positive and Gram-negative bacterial strains and were also tested as antioxidant agents (DPPH free radical scavenging). Structural parameters determined experimentally and theoretically are within the expected range, and the biological activities of the resultant compounds are moderate.