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Synthesis and structural characterization of the oxalate-based compounds with alkyl ammonium cations

Multifunctional properties of the metal-organic coordination polymers can be achieved by combining the intrinsic properties of the host, especially the magnetic ones, with an additional functionalities coming from the selected guest molecules. The oxalate group, C2O42, has been demonstrated to be one of the most versatile ligands used in the preparation of these systems. Due to its various coordination modes towards the metal centres as well as its ability to mediate magnetic interactions between paramagnetic metal ions, a large number of oxalate-based transition- metal species of different nuclearity, connectivity and dimensionality have been synthesized and characterized, many of them having tunable magnetic frameworks. Furthermore, the simplest method to obtain conductive compound is to introduce proton carries directly as counterions such as NH4+, H3O+ and to make proton-conducting pathways composed of hydrogen- bond networks [1]. In previous work, we reported one-dimensional antiferromagnetic oxalate-bridged coordination polymer {; ; ; [NH(CH3)2(C2H5)] [FeCl2(C2O4)]}; ; ; n, showing hydrogen-bonded diethylmethylammonium cationic moieties what lead to a very high room- temperature proton conductivity [2.70×10−4 ( cm) −1 under 93% relative humidity conditions]. Therefore, we have continued to prepare oxalate systems containing various alkyl ammonium cationic components, with the aim of obtaining compounds which, in addition to interesting magnetic properties, also show proton conductivity. In order to obtained such heterometallic complexes, tris(oxalato)metalates, [MIII(C2O4)3]3– (MIII = Cr or Fe), are used as ligands towards second transition metal ion.

coordination polymers ; oxalate complex ; proton ; conductivity

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