Журнал "Макрогетероциклы"

S. G. Makarov,^a@ G. S. Zabrodina,^a A. V. Cherkasov,^a P. E. Plyusnin,^b,c A. V. Arapova,^a M. A. Katkova,^a and S. Yu. Ketkov^a

^aG. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, 603905 Nizhny Novgorod, Russia

^bA.V. Nikolaev Institute of Inorganic Chemistry RAS, 630090 Novosibirsk, Russia

^cNovosibirsk State University, 630090 Novosibirsk, Russia

^@Corresponding author E-mail: makarsg@mail.ru

DOI: 10.6060/mhc160317m
Macroheterocycles 2016 9(3) 263-267

Recently, many efforts have been made to synthesize various polynuclear compounds as “single-source precursors” to generate the target mixed oxides. To design single-source precursors the lanthanide(III)-copper(II) polynuclear metallamacrocyclic compounds based on glycinehydroxamic acids named as metallacrowns (MC) were prepared. MCs are an exceptional class of supramolecular compounds where the neutral ring consists of five [Cu(II)-N-O] repeated units, and the five hydroximate oxygen atoms encapsulate a Ln(III) ion within the central cavity. The thermal behaviour of MCs was investigated by TGA-DSC analysis in inert atmosphere combined with mass-spectrometry analysis of the evolved gases. Combined (TG-DSC-MS) analyses reveal that the decomposition of Ln(III)[15-MC_CuGlyha-5] complexes is accompanied by a sharp exothermal peak at 190–250 °C. DSC curves of Ln(III)[15-MC_CuGlyha-5] metallacrowns show that the temperature of exothermic stages depend on the nature of lanthanide metal. In these thermal decomposition stages the destruction of the metallacrowns and their hydroxamic ligands were observed as intense signals with m/z=15, 18, 26, 27, 30, 43, 44 in the mass-spectra. According to the X-ray diffraction Nd complex was studied as one of the products of thermolysis at 230 °C isolated as calcium salt. Crystals of [Nd(OAc){15MC_Cu(II)Glyha–5}(H₂O)₂]²⁺·0.5[CN]^-·1.5Cl^-·4.5(H₂O)·0.5Ca(OH)Cl·0.5Ca(CN)Cl belong to triclinic space group P-1 similar to other 15-MC-5 metallacrowns. The Nd³⁺ ion is coordinated by five oxygen atoms of the metallacrown ring in the equatorial plane and two oxygen atoms of the water molecules, two oxygen atoms of the acetate ligand in apical positions. Coordination environment of Ca²⁺ cation with equal probability is comprised of Ca(CN)Cl or Ca(OH)Cl fragment. IR-spectrum of thermal decomposition products, isolated at 230 °C, shows the characteristic bands of original Ln(III)[15-MC_CuGlyha-5] metallacrown and new bands at 2180–2230 cm^-1, corresponding to the vibration of the cyanic and/or isocyanic fragments. Based on literature and experimental data, the metallacrown decomposition scheme, involving oxidation of amine by Cu²⁺ to cyanic group and Lossen rearrangement, was suggested.

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