Solvothermal synthesis and theoretical study of a polypyridium trimesylate adduct

The title compound (C 9 H 3 O 6 ·C 20 H 17 N 4 ) 4 ·0.5H 2 O 1 was isolated from solvothermal synthesis of 4′-(4-pyridyl)-2,2′:6′,2′-terpyridine (pytpy) and trimesic acid (1,3,5-benzenetricarboxylic acid, H 3 BTC). It was characterized by element analysis, IR, TGA, XRD, X-ray single-crystal diffraction, and spectroscopy properties, together with quantum chemistry calculation of spectrum (UV–vis spectra) through the method b3lyp/6–31 t g (d,p) are also investigated. Single-crystal X-ray diffraction shows 1 possesses a 3-D supramolecular network with 1-D six-fold helical double chains built from protonated (H 3 pytpy) cations and deprotonated (BTC) anions. The maximum of the fluorescent emission bands of 1 is located at 427 nm ( λ ex = 266 nm), with a shoulder at about 390 nm. The result of theoretic calculations confirms that 1 has small HOMO–LUMO energy gap (1.24 eV) and high chemical reactivity. Graphical Abstract The title compound (C 9 H 3 O 6 ⋅C 20 H 17 N 4 ) 4 ⋅0.5H 2 O 1, possessing a 3-D supramolecular network with 1-D six-fold helical double chains, was isolated from solvothermal synthesis of 4′-(4-pyridyl)-2,2′:6′,2′-terpyridine (pytpy) and trimesic acid (1,3,5-benzenetricarboxylic acid, H 3 BTC). The result of theoretical calculations confirms that 1 has small HOMO–LUMO energy gap (1.24 eV) and high chemical reactivity.