In Situ Construction of Three Anion-Dependent Cu(I) Coordination Networks as Promising Heterogeneous Catalysts for Azide-Alkyne Click Reactions

Three Cu(I) coordination networks, namely, {[Cu-2(bpz)(2)(CN)X]center dot CH3CN}(n), (X = Cl, 1; I, 3), {[Cu-6(bpz)(6)(CH3CN)(3)(CN)(3)Br]center dot 2OH center dot 14CH(3)CN}(n), (2, bpz = 3,3',5,5'-tetramethyl-4,4'-bipyrazole), were prepared by using solvothermal method. The cyanide ligands in these networks were generated in situ by cleavage of C-C bond of MeCN under solvothermal condition. The structures of these networks are dependent on halogen anions. Complex 1 is a ladderlike structure with mu(2)-CN- as rung and mu(2)-bpz as armrest. The Cl- in 1 is at terminal position but does not extend the one-dimensional (1D) ladder to higher dimensionalities. Complex 2 is a three-dimensional (3D) framework comprised of novel planar [Cu3Br] triangle and single Cu nodes, which are extended by mu(2)-bpz and mu(2)-CN- to form a novel (3,9)-connected gfy network. Density functional theory calculations showed that single-electron delocalization of Br atom induces the plane structure of [Cu3Br]. Complex 3 also possesses a similar ladderlike subunit as in 1, but the I- acts as bidentate bridge to extend the ladder to 3D framework with a four-connected sra topology. The three networks show notable catalytic activity on the click reaction. The compared catalytic results demonstrate that complex 2 possesses the best catalysis performance among three complexes, which is ascribed to the largest solvent-accessible void (porosity: 2 (29.4%) > 1 (25.7%) > 3 (17.6%)) and the more Cu(I) active sites in 2. The present combined structure-property studies provide not only a new synthetic route to obtain a new kind of catalyst for click reaction but also the new insights on catalyst structure-function relationships.