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

The asymmetric 3,5-disubstituted 1,2,4-triazole ligand H 2 V (5-amino-3-picolinamido-1,2,4-triazole) by reaction with an excess of Cu(ii) perchlorate (Cu : H 2 V being 12 : 1) has produced a novel hexanuclear {Cu 6 (μ 3 -O/H)(HV/V) 3 } fragment, with one triangular Cu 3 (μ 3 -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, [Cu 6 (μ 3 -O)(HV) 3 (ClO 4 ) 7 (H 2 O) 9 ]·8H 2 O (1), one dodecanuclear, [Cu 12 (μ 3 -O) 2 (V) 6 (ClO 4 ) 5 (H 2 O) 18 ](ClO 4 ) 3 ·6H 2 O (2), and one tetradecanuclear 1D-polymer, {[Cu 14 (μ 3 -OH) 2 (V) 6 (HV)(ClO 4 ) 11 (H 2 O) 20 ](ClO 4 ) 2 ·14H 2 O} 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 "Cu 3 O-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 Cu II - external Cu II ) = -5.15(2) cm -1 .