Two dimensional coordination polymer of pb(II) complex with m-sulfanilic acid: synthesis, characterization, electrical conductivity, adsorption properties and Hirshfeld surface analysis

Abstract

This study presents the synthesis, structure and characterization of a novel two-dimensional coordination polymer (CP) constructed from Pb(II) ions and m-sulfanilic acid. The CP was characterized using various techniques, including element analysis, FTIR-, UV-Visible spectrometry, TG- DTA analysis, powder and single-crystal X-ray diffraction. The crystal structure of the catena-(bis(µ3-3-aminobenzenesulfonato)lead(II)) complex shows that each lead(II) ion is surrounded by two nitrogen atoms and six oxygen atoms from the amino and sulfonate groups of the 3-aminobenzenesulfonate ligands. Importantly, the lead(II) ions have a stereochemically active lone pair of electrons, which results in a distorted coordination geometry. This distortion, known as hemidirected coordination, arises from the uneven distribution of ligands around the lead ion due to the influence of the lone pair. Its electrical conductivity was measured, revealing its potential for electronic applications. Adsorption properties were evaluated for gas N₂. The BET surface area was calculated to be 383.108 m²/g, with a monolayer capacity of 4.2 mmol/g and a C value of 120. The molecular cross-sectional area for nitrogen was taken as 0.162 nm²/molecule. The porosity (ε) of the sample was determined to be 0.65, considering both open and closed pores. Additionally, Hirshfeld surface analysis provided insights into intermolecular interactions within the CP, primarily O—H/H—O interactions (32.1%), H—H interactions (24.8%), and C—H/H—C interactions (16.7%). Pb—O/O—Pb interactions contribute 10.1%, and O—C/C—O interactions contribute 7.3%. Other interactions, such as Pb—N/N—Pb, O—O, O—N/N—O, Pb—H/H—Pb, and Pb—C/C—Pb, contribute smaller percentages. The Continuous Symmetry Measure (CSM) analysis of the lead complex indicates a nearly symmetric structure with slight distortions, as evidenced by its coordination number of 7.7369 and a distortion index of 0.02089. Bond Valence Sum (BVS) analysis confirms that the lead ion is in an oxidation state close to + 2, with a total BVS of 1.87.