Coordination Polymers between 3,4-Dicyano-1,2,5-telluradiazole and N,N,N′,N′-Tetramethylethane-1,2-diamine: The Decisive Role of Chalcogen Bonding

Abstract

One-dimensional coordination polymers [1·2]∞ (two polymorphs) and [12·2]∞ were obtained by cocrystallization of 3,4-dicyano-1,2,5-telluradiazole (1) and N,N,N′,N′-tetramethylethane-1,2-diamine (2). In the presence of Solv (C6H6, C5H5N, or C4H4S), differently colored, depending on the conditions, {[12·2]·Solv}∞ clathrates were isolated: products synthesized in the light were green, whereas those synthesized in the dark were yellow. In {[12·2]·Solv}∞, the Solv molecules occupy cavities formed by methyl groups of 2. With pyridazine, the 1·(1,2-C4H4N2)2 discrete complex was synthesized, and no clathrates/complexes were observed with pyrazine (1,4-C4H4N2) and pyrrole (C4H5N). In the compounds, 2 connects two 1 or 12 by Te···N chalcogen bonding (ChB), which is decisive for their formation according to quantum theory of atoms in molecules (QTAIM), NBO, and Hirshfeld surface analyses. The ChB features orbital contribution/polarization. The second-order perturbation energies are structure-dependent, and those for {[12·2]·Solv}∞ are slightly higher than those for [1·2]∞ and [12·2]∞. Time-dependent density functional theory (TD-DFT) calculations on the X-ray diffraction (XRD) unit cells of green {[12·2]·Solv}∞ do not reproduce their longest-wavelength absorption, which might indicate minor light-induced side products.