engleski

1D heterometallic [CuIICrIII] oxalate- and chloranilate-bridged chains

The search for new molecule-based magnets is a very active area in advanced materials, since they offer unique design possibilities, from a wise selection of the molecular building blocks, crystal structures exhibiting cooperative magnetism and even the combination of magnetism with a second property of interest. In the design and synthesis of heteropolynuclear complexes, as potentially new functional materials, an important role belongs to the oxalate ion, C2O42−, because of its various possibilities of coordination to metal centers as well as its ability to mediate magnetic interactions between paramagnetic metal ions. Stable mononuclear anionic oxalate complexes as tris(oxalato)metalate anions, [MIII(C2O4)3]3−, are often used as ligands toward another metal ion for the preparation of extended multifunctional systems. The most effective way to tune the magnetic properties of oxalate-based compounds is to act directly on the exchange pathways within the chains/layers. This can be done either by varying metal centres or by modifying the bridging oxalate ligand, by the use of larger bis(bidentate) bridging ligands as the dianion of 2, 5-dihydroxy-1, 4-benzoquinone (H2dhbq) and its derivatives (C6O4X22− = X2An2−). They show coordination modes similar to the oxalate group and present three additional advantages: (i) they are easy to modify or functionalize in order to tune the exchange coupling through them by simply changing the X group (X = H, F, Cl, Br, I, NO2, OH, CN, etc.) ; (ii) their modification does not affect their coordination mode ; (iii) they are able to provide an effective pathway for the exchange interaction. Also, in the 3, 6-dihalo derivates, halogen atom can play a multifuncional role, either at the electronic or at the supramolecular level, on the physical properties of supramolecular system arising from specific XB-oriented organizations. Thus, our recent (magneto)structural studies on oxalate-based metal complexes have been extended to the reactions of the similar, but more stretched, chloranilate dianion and transition metals [1, 2]. Applying the layering technique, using K3[Cr(C2O4)3]·3H2O and [(n-Bu)4N]3[Cr(Cl2An)3] as building blocks in reactions with CuCl2·H2O and 2, 2'-bipyridine, 1D heterometallic oxalate- and chloranilate-bridged {; ; ; [KCrCu2(C2O4)4(bpy)2]·H2O}; ; ; n (1) and {; ; ; [(n-Bu)4N][CrCu(Cl2An)3(bpy)]}; ; ; n (2) chains have been prepared and characterized, respectively.

Heterometallic ; Oxalate-Bridged ; Chloranilate-Bridged ; Single-Crystal X-Ray Diffraction

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