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Cadmium(II) Coordination Polymers Based on Substituted Malonic Acid: Synthesis, Characterization and Photoluminescent Properties


Four novel complexes of cadmium(II) with alky/aryl-substituted malonate ligands of formula {[Cd(Memal)(H2O)]6·0.5H2O}n (1), [Cd(Etmal)(H2O)]n (2), [Cd(Butmal)(H2O)]n (3) and [Cd(Bzmal)(H2O)]n (4), (Memal = methylmalonate, Etmal = ethylmalonate, Butmal = butylmalonate and Bzmal = benzylmalonate) have been prepared and characterized by single crystal X-ray analysis. Their luminescence, UV-Vis absorption properties and thermal behaviour were also investigated. Complex 1 is a three-dimensional compound where each metal centre is connected to other four ones leading to a sodalite network with point symbol {42.64}. Each cadmium(II) ion in 1 is seven-coordinate with a water molecule and six oxygen atoms from three Memal ligands building a somewhat distorted pentagonal bipyramidal surrounding. The Memal ligand in 1 adopts a 3-O:2O’:2O”:O’’’ coordination mode. 2-4 are isomorphous compounds with a two-dimensional structure where centrosymmetric double oxo(carboxylate-substituted malonate)-bridged dicadmium(II) units are linked to other four dinuclear entities through anti-anti and anti-syn carboxylate bridges to form a Shubnikov tetragonal layered [4462]-sql net. Each cadmium(II) ion in 2-4 is six-coordinate in a distorted octahedral environment with four carboxylate-oxygen atoms building the basal plane and a water molecule plus another carboxylate-oxygen atom in the axial positions. The substituted malonate ligands in 2-4 exhibit the 4-O:2O’:2O”:O’’’ coordination mode. The tests of the emission spectra of 1-4 show that the length of the side chain influences the pholuminiscence properties of the complexes. Finally, the decays of the luminescence of 1-4 and the respective free substituted malonic acids reveal that the same value of the average life time is observed for 1 (H2Memal) whereas in the case of 2-4, they are greater than that 1 and those of their corresponding acids. The longer decay rates in 2-4 are consistent with the lack of water molecules at the environment of the cadmium(II) ion in them, indicating that the sheet-like structure of 2-4 provides a chemical surrounding with less non-radiative relaxation processes.

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Publication details

The article was received on 20 Apr 2017, accepted on 16 Jun 2017 and first published on 19 Jun 2017

Article type: Research Article
DOI: 10.1039/C7QI00212B
Citation: Inorg. Chem. Front., 2017, Accepted Manuscript
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    Cadmium(II) Coordination Polymers Based on Substituted Malonic Acid: Synthesis, Characterization and Photoluminescent Properties

    M. Déniz, J. Pasán, B. Rasines , P. Lorenzo-Luis, F. Lahoz, C. Vera Gonzales, M. Julve and C. Ruiz-Pérez, Inorg. Chem. Front., 2017, Accepted Manuscript , DOI: 10.1039/C7QI00212B

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