Abstract

An anionic rectangular tetranuclear Cu(II) complex, namely (NH<inf>2</inf>(CH<inf>3</inf>)<inf>2</inf>)<inf>4</inf>[Cu<inf>4</inf>(pzdc)<inf>4</inf>(dpe)<inf>2</inf>]·3H<inf>2</inf>O (1), was successfully synthesized via a solvothermal method using pyrazole-3,5-dicarboxylic acid (H₃pzdc) and 1,2-di(4-pyridyl)ethylene (dpe) as organic linkers. The structure of complex 1 was structurally characterized through single-crystal and powder X-ray diffraction, FT-IR spectroscopy, thermogravimetric technique, and elemental analysis. Owing to the presence of the π-conjugated system in the structure, complex 1 displays promising iodine adsorption behavior. Complex 1 can adsorb iodine vapor with adsorption capacities of 0.12 g·g⁻¹ and 1.20 g·g⁻¹ at room temperature and 80 °C, respectively, which correspond to 0.30 and 4.08 molecules of iodine per formula unit of sample. The adsorption mechanism was investigated using the density functional theory (DFT) calculations in conjunction with PXRD, XPS, FT-IR, and Raman spectroscopy. Raman and XPS spectra confirmed the presence of both molecular iodine (I<inf>2</inf>) and triiodide ions (I<inf>3</inf>⁻), suggesting that the adsorption involves charge-transfer interactions between iodine and electron-rich organic components in the structure.