Spectroscopic screening and binding studies of tripodal amide-thiourea ligands as oxoanion receptors

Roslan, Norashikin and Ngah, Nurziana and Abd Karim, Nurul Huda and Abd Hamid, Shafida and Wan Abdul Khodir, Wan Khartini (2026) Spectroscopic screening and binding studies of tripodal amide-thiourea ligands as oxoanion receptors. Malaysian Journal of Chemistry, 28 (4). pp. 100-120. ISSN 1511-2292 E-ISSN 2550-1658

PDF - Published Version Restricted to Registered users only Download (1MB) | Request a copy

Abstract

The rising levels of toxic oxoanions such as chromate, permanganate, phosphate, and arsenate in aquatic environments pose significant environmental and health concerns, necessitating the development of efficient detection systems. In this study, three tripodal amide–thiourea receptors (AT1- AT3) were synthesized and evaluated as supramolecular hosts for tetrahedral oxoanions. Structural characterization using UV-Vis, FTIR, and NMR spectroscopy confirmed successful formation of the receptors with multiple hydrogen-bonding donor sites. UV–Vis titration studies revealed distinct bathochromic and hypochromic spectral responses upon anion binding, indicating receptor–anion interactions via N–H·O hydrogen bonding. Job plot analysis suggested a predominant 1:1 binding stoichiometry, while binding constants (Kₐ) derived from BindFit ranged from 8.55 × 10² to 1.88 × 10⁴ M⁻¹. AT3 exhibited the highest affinity toward CrO₄²⁻, attributed to enhanced electronic polarization and favourable structural preorganization induced by the –CN substituent. In contrast, the strongly electron-withdrawing –NO₂ group in AT2 significantly decreased electron density at the thiourea binding sites through its negative inductive (–I) and negative mesomeric (–M) effects. This disrupts effective charge delocalization across the receptor framework and reduces the hydrogen bond-donating ability of the –NH moieties, ultimately resulting in weaker anion binding. These findings highlight the critical role of substituent effects in modulating anion recognition and demonstrate that tripodal amide–thiourea systems are promising candidates for selective optical sensing of environmentally relevant oxoanions.

Item Type:	Article (Journal)
Uncontrolled Keywords:	Amide-thiourea receptors, anion recognition, binding constant, oxoanions, supramolecular sensing, UV-Vis titration
Subjects:	Q Science > QD Chemistry
Kulliyyahs/Centres/Divisions/Institutes (Can select more than one option. Press CONTROL button):	Kulliyyah of Science Kulliyyah of Science > Department of Chemistry
Depositing User:	Dr Nurziana Ngah
Date Deposited:	20 Aug 2026 12:18
Last Update:	20 Aug 2026 12:18
Queue Number:	2026-08-Q4837
URI:	http://irep.iium.edu.my/id/eprint/130919

Actions (login required)

View Item