Co II/ZnII-(L-tyrosine) magnetic metal-organic frameworks

Three chiral coordination polymers assembled from L-tyrosine (L-tyr) and cobalt, cobalt/zinc and zinc salts, with a new three-dimensional (3D) structure and formulated as [M(L-tyr)] n (M = Co, Co/Zn, Zn) have been prepared by mild hydrothermal synthesis. These three compounds are isostructural, crystallize with monoclinic symmetry in the C2 space group and possess four crystallographically unique metal sites in tetrahedral (two) and octahedral (two) coordination environments resulting in two slightly distinct edge-sharing metal dimers with L-tyr linking the metal atoms in pillars. These features result in a dense framework. The study of the magnetic properties of the cobalt-bearing solid reveals a ferromagnetic exchange interaction within the Co 2+ dimers. The racemic compound of dl-tyrosine and cobalt was also synthesized and its structure characterized. The crystal structure of chiral isomorphous metal-organic frameworks, [M(L-tyrosine)]n, (M = Co, Zn, Co/Zn) features tetrahedral and octahedral metal sites, resulting in two slightly different edge-sharing metal dimers, with L-tyrosine linking the metal atoms in pillars and forming a dense framework. In the dimers, a ferromagnetic exchange interaction couples the Co 2+ ions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.We acknowledge Fundação para a Ciência e a Tecnologia, Fundo Social Europeu, Ciencia 2007, Fundo Europeu de Desenvolvimento Regional (FEDER), Quadro de Referência Estratégico Nacional (QREN), COMPETE (grants PEst-C/CTM/LA0011/2011, PTDC/QUI/ 65805/2006, FCOMP-01-0124-FEDER-007424 and SFRH/BPD/43789/2008). The Aveiro-Zaragoza collaboration was supported by the Integrated Spanish-Portuguese Action (grant PT2009-0131). The work in Zaragoza was supported by the Ministry of Economy and Competitivity through grants MAT2007-61621, MAT2011-27233-C02-02 and CONSOLIDER CSD2007-00010.Peer Reviewe