Photoluminescent Porous Modular Lanthanide-Vanadium-Organic Frameworks

Modularmixed metal-organic frameworks with lanthanide centres 2- M-4[M12V24O24(OH)(8)(H(2)hedp)(8)(Hhedp)(16)(H2O)(64+n)]. 88+y(H2O) (M3+ = Y3+, Ce3+, Sm3+, Eu3+, Tb3+, Gd3+, Er3+; H(5)hedp = etidronic acid), have been reported. The compounds have been prepared by (i) slow evaporation of the solvent to afford large single-crystals of the Y3+, Ce3+ and Er(3+)compounds and (ii) facile one-pot synthesis (at ambient conditions) overnight to yield microcrystalline Y3+, Ce3+, Sm3+, Eu3+, Tb3+ and Gd3+ solids. Framework construction has been shown to be modular and based on the self-assembly of cyclic trinuclear [V3O3(OH)(H(2)hedp)(Hhedp)(2)](6-) anionic units with cationic {MO8}) or {MO9} aqua-based lanthanide complexes (with dodecahedral, square antiprismatic or tricapped trigonal prismatic coordination geometries), which gives rise to unprecedented trinodal networks (having and 4-connected nodes) with a total Schafli symbol of (4.8(3).10(2)}(2){4(2).8(4)}{8}(2). The anionic charge of the networks is balanced by highly disordered trivalent lanthanide cations in the channels. The compounds have been studied by single-crystal and powder X-ray diffraction, vibrational spectroscopy (FTIR), thermogravimetry, optical and scanning electron microscopy and elemental analysis. The photoluminescence properties of selected compounds have been investigated. Intriguingly, the co-existence of V4+ and Eu3+ cations in the same material allows the fine tuning of the photoluminescence emission from white to purplish-blue, by changing the excitation wavelength. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)