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

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.