Herein, syntheses, crystal structures, and photoluminescence properties of 24 new ammonia and alkali metal ATCN salts characterized via single-crystal X-ray diffraction are reported. Moreover, ten structure types of these salts have been described, three of which are predominant. Some ATCNs were obtained as two crystalline polymorphs. It was estimated that most ATCN powders exhibited yellow-green fluorescence (at 450-600 nm). For samples that possess fluorescence of low intensity in the solid state, several optical centers of emission exist. It was speculated that the obtained spectral features were due to anion-anion intermolecular interactions. ATCN being a new representative of stable tetracyanoallyl salts is a promising candidate for creation of various 1D, 2D, and 3D supramolecular structures and potential functional materials.
A novel route for synthesis of 2-acyl-1,1,3,3-tetracyanopropenides (ATCN) salts in high yields and excellent purities starting from readily available methyl ketones, malononitrile, bromine, and alkali metal acetates is reported. The starting aryl(heteroaryl) methyl ketones were oxidized to the corresponding α-ketoaldehydes by new a DMSO-NaBr-H2SO4 oxidation system in yields up to 90% within a short reaction time of 8-10 min. The subsequent stages of ATCN preparation are realized in aqueous media without use of any toxic solvents, in accordance with principle 5 of "green chemistry". Lithium, sodium, potassium, rubidium, and cesium 2-benzoyl-1,1,3,3-tetracyanopropenides were characterized by X-ray diffraction analysis. These salts show a good potential for synthesis of five- and six-membered heterocycles and may serve as potentially useful ligands in coordination and supramolecular chemistry.
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