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 [1 2 •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 (C 6 H 6 , C 5 H 5 N, or C 4 H 4 S), differently colored, depending on the conditions, {[1 2 •2]• Solv} ∞ clathrates were isolated: products synthesized in the light were green, whereas those synthesized in the dark were yellow. In {[1 2 •2]•Solv} ∞ , the Solv molecules occupy cavities formed by methyl groups of 2. With pyridazine, the 1•(1,2-C 4 H 4 N 2 ) 2 discrete complex was synthesized, and no clathrates/complexes were observed with pyrazine (1,4-C 4 H 4 N 2 ) and pyrrole (C 4 H 5 N). In the compounds, 2 connects two 1 or 1 2 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 {[1 2 •2]•Solv} ∞ are slightly higher than those for [1•2] ∞ and [1 2 •2] ∞ . Time-dependent density functional theory (TD-DFT) calculations on the X-ray diffraction (XRD) unit cells of green {[1 2 •2]•Solv} ∞ do not reproduce their longest-wavelength absorption, which might indicate minor light-induced side products.