Supramolecular assembly of binuclear complexes of rare earth elements with polyaminopolycarboxylate and dodecatungstosilicate

Rare earth elements (RE), polyaminopolycarboxylate and dodecatungstosilicate had self-assembled into four new supramolecular salts [RE2(H2CyDTA)2(H2O)12][H2SiW12O40]·nH2O, RE = Y, n = 14 (1); RE = Sm (2), Eu (3), n = 17; RE = Er, n = 16 (4), CyDTA = trans-cyclohexanediaminotetraacetate tetravalent anion, in aqueous solution and they were characterized by elemental analysis, infrared spectroscopy and single-crystal X-ray diffraction. Eight-coordinated RE ion accepts two carboxyl oxygen atoms from two CyDTA and the CyDTA bridges two RE ions, forming a binuclear complex cation, [RE2(H2CyDTA)2(H2O)12]2+. The cations, SiW12O404− anions and lattice water are arranged into three dimensional supramolecular architecture through hydrogen bonds and electrostatic force. Coordination behavior of CyDTA to RE is rather different from that to transition metal ions and different from that without SiW12 presence. Compounds 1 and 2 exhibit ligand-centered luminescence but the intensity decreases; compound 3 shows the characteristic emission of Eu3+ ion and at the same time it retains the ligand-centered luminescence.