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Synchrotron powder structure of a new layered lanthanide-organic network

2009; De Gruyter; Volume: 224; Issue: 5-6 Linguagem: Inglês

10.1524/zkri.2009.1132

2366-1798

Luís Cunha‐Silva, Duarte Ananias, Luís D. Carlos, Filipe A. Almeida Paz, João Rocha,

Chemical Synthesis and Characterization

Abstract The hydrothermal synthesis and detailed structural characterisation of layered materials formulated as [Ln(H 2 cmp)] · x H 2 O [where H 5 cmp = (carboxyme thyl)iminodi(methylphosphonic acid) and x < 1; Ln 3+ = Nd 3+ ( 1 ) and Eu 3+ ( 2 )] are reported. Compounds were isolated as microcrystalline powders and the crystal structure of 1 was determined by ab initio methods from high-resolution synchrotron powder X-ray diffraction (PXRD) data collected at the European Synchrotron Radiation Facility (ESRF, Grenoble, France – beam lines BM01a and BM01b). The structure of 2 was refined by conventional PXRD, starting from the atomic coordinates of 1 . Materials contain a single Ln 3+ metal centre in highly distorted dodecahedral coordination geometry. Connectivity through H 2 cmp 3– anionic ligands leads to undulated tapes of Ln 3+ running parallel to the b -axis [closest inter-Ln distances of 4.203(3) and 4.170(3) Å for 1 and 2 ] which coalesce into layers, 2 ∞ [Nd(H 2 cmp)], extended in the bc plane. The presence of a terminal protonated phosphonate group seems to induce the formation of the layers. Topologically, the structure is a 8-connected uninodal plane net, which can be further envisaged as two periodic self-penetrated (4,4) nets. The photophysical properties of the Eu 3+ -bearing material were studied at room temperature (with and without vacuum). The two materials have been further stud ied using thermogravimetric analysis (TGA), vibrational spectroscopy (FT-IR) and CHN elemental analyses.