High-dimensional mixed-valence copper cyanide complexes: Syntheses,structural characterizations and magnetism |
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Authors: | Samia Benmansour Fatima Setifi Smaïl Triki Franck Thétiot Jean Sala-Pala Carlos J Gómez-García Enrique Colacio |
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Institution: | 1. UMR CNRS 6521, Université de Bretagne Occidentale, BP 809, 29285 Brest, France;2. Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, 46980 Paterna, Spain;3. Département de Chimie, Université Farhat-Abbas, 19000 Sétif, Algeria;4. Departamento de Química Inorgánica, Universidad de Granada, 18071 Granada, Spain |
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Abstract: | Reactions of CuCl2 with different CN complexes in presence of a neutral ancillary ligand lead to two novel mixed-valence Cu complexes CuII(bpy)CuI(CN)3]n, 1 (bpy = 2,2′-bipyridine) and {CuII(tn)2]CuI4(CN)6]}n2 (tn = 1,3-diaminopropane). For compound 1, the asymmetric unit involves two Cu ions Cu1 and Cu2 (CuI and CuII centres, respectively) which strongly differ in their environments. The Cu1 ion presents a CuC4 pseudo-tetrahedral geometry, while the Cu2 ion presents a CuN5 slightly distorted square-pyramidal geometry. The extended structure of 1 is generated by three cyano ligands which differ in their coordination modes. One CN group has a μ3 coordination mode and bridges two CuI and one CuII ion, while the two other CN groups act as μ2 bridges leading to a sophisticated 3-D structure. As for 1, the asymmetric unit of 2 involves three crystallographically different Cu ions (Cu1A and Cu1B, presumably CuI centres, and Cu2 presumably CuII centres). The Cu2 ion presents centrosymmetric CuN4 coordination environments involving four nitrogen atoms from two bidentate tn ligands; while the Cu1A and Cu1B ions are three coordinated to cyano groups. The structure can be described as formed by 18-membered “CuI(CN)]6” planar metallocycles that are connected to their six neighbors to generate 2-D sheets; these sheets stack forming infinite hexagonal channels in which the Cu(tn)2]2+ units are located. Magnetic measurements show an unexpected weak ferromagnetic coupling (θ = 0.239(1) K) of the CuII ions through the long and “a priori diamagnetic” –NC–CuI–CN– bridges in compound 1 and an essentially paramagnetic behavior in compound 2. |
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Keywords: | Copper cyanides Bridging ligands Coordination modes Magnetic properties Mixed-valence |
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