Copper(I) 1,2,4-Triazolates and Related Complexes: Studies of the Solvothermal Ligand Reactions, Network Topologies, and Photoluminescence Properties

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Abstract
One-pot solvothermal treatments of organonitriles, ammonia, and CuII salts yielded CuI and 3,5-disubstituted 1,2,4-triazolates. The organic triazolate components were derived from copper-mediated oxidative cycloaddition of nitriles and ammonia, in which a key intermediate 1,3,5-triazapentadienate was isolated as [CuII(4-pytap)2] (4-Hpytap = 2,4-di(4-pyridyl)-1,3,5-triazapentadiene) via controlled solvothermal conditions. This intermediate could also be synthesized by NiII-mediated reactions; however, the final triazoles were obtained only when CuII was employed. Therefore, the reaction mechanism of these reactions was elucidated as follows: nitrile was first attacked by ammonia to form the amidine, which further reacted with another nitrile or self-condensed to yield 1,3,5-triazapentadiene, which was coordinated to two CuII ions in its deprotonated form. A two-electron oxidation of the 1,3,5-triazapentadienate mediated by two CuII ions gave one triazolate and CuI cations. Other in situ ligand reactions, such as C−C bond cleavage and hydrolysis, were also found for the nitriles under these solvothermal conditions. Another remarkable feature of these crystalline CuI triazolates is their simple, typical 3- or 4-connected network topologies. The self-assembly of these nets is presumably controlled by steric hindrance, which is subsequently applied to the rational design of the close-packed 2D networks [CuI(tz)]∞ and [AgI(tz)]∞ (Htz = 1,2,4-triazole), as well as the porous 3D network [CuI(etz)]∞ (Hetz = 3,5-diethyl-1,2,4-triazole). The interesting photoluminescence properties of these coinage d10 metal complexes were also investigated.

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