Synthèse, caractérisation et propriétés magnétiques de polymères de coordination à base du ligand oxalato(2-)

Abstract

In the present work, four new compounds containing the paramagnetic anionic building block [Co (C2O4)3]3- were obtained namely: (C7H11N2)3[Co (C O ) ] (1), III III 2 43 III (C7H11N2)3[Co (C2O4)3]·4H2O (2), K0.7Ag2.3[Co (C2O4)3]·2.5H2O (3) and III III H0.7Ag2.3[Co (C2O4)3]·2H2O (4). Compounds 1 and 2 are organic-inorganic hybrid salts whereas compounds 3 and 4 are nanochanneled silver deficient non-molecular coordination polymers. All these compounds were characterized by various analytical techniques including: melting point measurement, elemental, thermal and Hirshfeld surface analyses, IR, energy dispersive, X-ray spectroscopy, UV-Vis spectroscopy and X-ray diffraction on single crystal and powder. Magnetic behavior and biological evaluation were also carried out. Compounds 1 and 2 are prismatic crystals with dark-green color. They crystallize in triclinic P-1 space group and monoclinic C2/c space group respectively. In these salts, the 3- III trinegative charge of the complex anion [Co (C2O4)3] is compensated by isomer organic cations (C7H11N2) . The bulky cation tris(2-amino-4,6-dimethylpyridinium) favoured the formation of the anhydrous salt 1. By contrast, the small size cation tris(4- dimethylaminopyridinium) rather led to formation of salt 2 with enough spaces hosting molecules of water of crystallisation. The consolidation of the crystal packing is ensured by electrostatic forces, π–π interactions, hydrogen bonding interactions of type N–H···O in 1 and types N–H···O and O–H···O in 2. Compounds 3 and 4 are elongated crystals with dark-green color. They crystallize in the monoclinic system, space group I2/a. In these salts, the trinegative charge of the complex anion [Co (C O ) ] is compensated by pairs of inorganic + III 2 43 3− ions [K0.7Ag2.3]3+ for 3 and [H Ag ] 0.7 2.3 3+ for 4. Their crystal structures feature one- dimensional nano-channels hosting hydrogen-bonded crystallization water molecules. The thermograms revealed that material 1 is anhydrous whereas 2, 3 and 4 are hydrated. The study of the magnetic properties reveals that 1, 2, 3 and 4 present an antiferromagnetic behavior at low temperatures (T < 4 K). These materials react in ethanol medium at room temperature to give pink cobalt(II) microcrystals, thus proving thes behavior of ethanol towards tris(oxalato)cobaltate(III) anionic species. Antimicrobial studies reveal activities on bacterial strains Staphylococcus aureus and Candida albicans 358B while 3 and 4 react favorably against Klebsiella pneumoniae and Staphylococcus aureus.