Modelling the use of lanthanides(III) as probes at calcium(II) binding sites in biological systems: Preparation and characterization of neodymium(III) and calcium(II) malonamato(-1) complexes |
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| Authors: | Athanassios Panagiotopoulos Spyros P Perlepes Evangelos G Bakalbassis Aris Terzis Catherine P Raptopoulou |
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| Institution: | 1. Department of Chemistry, University of Patras, 265 04 Patras, Greece;2. Laboratory of Applied Quantum Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece;3. Institute of Materials Science, NCSR “Demokritos”, 153 10 Aghia Paraskevi Attikis, Greece |
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| Abstract: | A bioinorganic approach into the problem of the isomorphous substitution of calcium(II) by lanthanide(III) ions in biological systems is discussed. Reactions of malonamic acid (H2malm) with CaII and NdIII sources under similar conditions yielded the compounds Ca(Hmalm)2]n (1), Nd(Hmalm)2(H2O)2]n(NO3)n (2) and Nd(Hmalm)2(H2O)2]nCln·2nH2O (3·2nH2O). Their X-ray crystal structure data show that the malonamate(-1) ligand presents two different ligation modes and coordinates through the two carboxylate and the amide-O atoms, thus bridging three CaII ions in 1 and two NdIII ions in 2 and 3·2nH2O. Complex 1 is a 3D coordination polymer based on neutral repeating units, whereas 2 and 3·2nH2O are 1D coordination polymers based on the same cationic repeating unit. Hydrogen bonding interactions further stabilize the 3D framework structure of 1 and assemble the 1D chains of 2 and 3·2nH2O into 3D networks. The three complexes were characterized spectroscopically (IR, far-IR, and Raman) and the thermal decomposition of 2 and 3·2nH2O was monitored by TG/DTA and TG/DTG measurements. Variable-temperature magnetic susceptibility data for 2 are also reported. The bioinorganic chemistry relevance of our results is discussed. |
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| Keywords: | Calcium(II) complexes Crystal structures Malonamate(-1) complexes Neodymium(III) complexes Spectroscopic probes |
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