Copper(I) 1,2,4-triazolates and related complexes: Studies of the solvothermal ligand reactions, network topologies, and photoluminescence properties

One-pot solvothermal treatments of organonitriles, ammonia, and Cu-II salts yielded Cu-II 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 [Cu-II(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 Ni-II-mediated reactions; however, the final triazoles were obtained only when Cu-II 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 Cu-II ions in its deprotonated form. A two-electron oxidation of the 1,3,5-triazapentadienate mediated by two Cu-II ions gave one triazolate and Cu-I 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 Cu-I 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 [Cu-I(tz)](infinity) and [Ag-I(tz)](infinity) (Htz = 1,2,4-triazole), as well as the porous 3D network [Cu-I(etz)](infinity) (Hetz = 3,5-diethyl-1,2,4-triazole). The interesting photoluminescence properties of these coinage d(10) metal complexes were also investigated.