Novel Copper(I)− and Copper(II)−Guanazolate Complexes: Structure, Network Topologies, Photoluminescence, and Magnetic Properties

Hydrothermal reactions of copper(I) or copper(II) salts with guanazole (3,5-diamino-1,2,4-triazole = Hdatrz) have yielded three novel 3D Cu-guanazolate complexes, that is, [Cu7Br6][Cu(datrz)2] (1), [Cu(datrz)] (2), and [Cu4(datrz)2(OH)2(SO4)2] (3). Complex 1 presents the first example in Cu(I) halide complexes with its Cu(I) bromide units {Cu7Br6}nn+ adopting a 3D network, which is constructed from two unprecedented substructures: the edge-sharing eight-membered {Cu4Br4}n rings and the three-bladed paddle-wheel-like {Cu4Br4}n units. Guanazolate ligands in 1 adopt an unprecedented pentadentate bridging mode and some bromide ligands exhibit a rare umbrella-like μ4 coordination geometry. The first binary Cu(I) guanazolate 2 exhibits a seldom reported two-fold interpenetrated lvt-a net, which can be partially controlled through the fixing effect of inter-ligand hydrogen bonds. Cu(II) complex 3 comprises a rarely encountered 12-connected tetranuclear {Cu4(μ3-OH)2} SBU, which is bridged by guanazolate ligands adopting a peculiar quadridentate coordination mode. This complex displays a non-interpenetrated pcu net, which is first constructed from multinuclear Cu(II) SBUs. Both 1 and 2 exhibit strong, broad, and unstructured emissions with long luminescence lifetimes, which may be assigned to the 3[MLCT] ES, and the 3[MC] or 3[MMLCT] ES could also be possible for 1. Complex 3 exhibits magnetic properties with four Cu(II) centers antiferromagnetically coupled in a tetranuclear array, which enables multiple and strong exchange interactions of J1 = −95.1, J2 = −152.7, and J3 = −55.4 cm−1. All compounds of this study display a medium to high thermal stability, and complex 1 shows the highest one with its structure framework unchanged up to 540 °C. Some significant structure−function correlations are discussed in this study as well.