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(m3-O/H)(HV/V)3} fragment, with one triangular Cu3(m3-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(m3-O)(HV)3(ClO4)7(H2O)9]$8H2O (1), one dodecanuclear, [Cu12(m3-O)2(V)6(ClO4)5(H2O)18](ClO4)3$6H2O (2), and one tetradecanuclear 1D-polymer, {[Cu14(m3-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) A and the Cu(central) ˚ – Cu(bridged external) av. distance is 5.338(3) A. The magnetic properties of the hexanuclear ˚ “Cu3O–3Cu” cluster have been studied, resulting as best fit parameters: g ¼ 2.18(1), J(intra-triangle) ¼ 247.0(1) cm1 and j(central CuII – external CuII) ¼ 5.15(2) cm1 .