Hexanuclear Cu3O-3Cu triazole-based units as novel core motifs for high nuclearity copper(ii) frameworks

Abstract

The asymmetric 3,5-disubstituted 1,2,4-triazole ligand H2V (5-amino-3-picolinamido-1,2,4-triazole) by reaction with an excess of Cu(ii) perchlorate (Cu:H2V being 12:1) has produced a novel hexanuclear {Cu6(μ3-O/H)(HV/V)3} fragment, with one triangular Cu3(μ3-O/H) group connected to three peripheral single Cu(ii) ions through a cis-cis-trans bridging mode of the ligand, which is the building block of the three structures described here: one hexanuclear, [Cu6(μ3-O)(HV)3(ClO4)7(H2O)9]·8H2O (1), one dodecanuclear, [Cu12(μ3-O)2(V)6(ClO4)5(H2O)18](ClO4)3·6H2O (2), and one tetradecanuclear 1D-polymer, {[Cu14(μ3-OH)2(V)6(HV)(ClO4)11(H2O)20](ClO4)2·14H2O}n (3), the last two containing hexanuclear subunits linked by perchlorato bridges. The Cu-Cu av. intra-triangle distance is 3.352(2) Å and the Cu(central)-Cu(bridged external) av. distance is 5.338(3) Å. The magnetic properties of the hexanuclear "Cu3O-3Cu" cluster have been studied, resulting as best fit parameters: g = 2.18(1), J(intra-triangle) = -247.0(1) cm-1 and j(central CuII-external CuII) = -5.15(2) cm-1.