RESUMO
The three-dimensional frameworks infinity(3)[LnCl3(1,4-Ph(CN)2)] of the lanthanides Ln = Sm (1), Gd (2), Tb (3), and infinity(3)[Ln2Cl6(1,4-Ph(CN)2)] for the group 3 metal Y (4) were obtained as single crystalline materials by the reaction of the anhydrous chlorides of the referring rare earth elements with a melt of 1,4-benzodinitrile. No additional solvents were used for the reactions. The dinitrile ligand is strongly coordinating and substitutes parts of the chlorine coordination. The Ln halide structures are reduced to two-dimensional networks, whereas coordination of both nitrile functions to the metal ions renders bridging in the third direction accessible. This enables formation of new metal organic framework (MOF) structure types with the large 1,4-benzodinitrile spacers interlinking infinity (2)[LnCl3] planes. In comparison to 1,4-Ph(CN)2 the mono functional benzonitrile ligand does not constitute framework structures, which is underlined by comparison with a reaction of yttrium chloride with PhCN resulting in the molecular complex [Y2Cl6(PhCN)6] (5) with end-on coordination PhCN ligands. The coordination spheres of the rare earth ions consist of double capped (infinity(3)[LnCl3(1,4-Ph(CN)2)] (1-3)) as well as single capped trigonal prisms (infinity(3)[Ln2Cl6(1,4-Ph(CN)2)] (4)) of chloride ions and N[triple bond]C groups while 5 displays edge sharing pentagonal bipyramids as coordination polyhedra. Sm (1), Gd (2), and Tb (3) exhibit isotypic framework structures with intercrossing dinitrile ligands. The group 3 metal Y (4) gives a framework with a coplanar arrangement of ligands and a lower ligand content. The largest cavities within the MOF structures of 1-4 have diameters of 3.9-8.0 A. All compounds were identified by single crystal X-ray analysis. Mid IR, Far IR, and Raman spectroscopy, microanalyses and simultaneous Differential Thermal Analysis-Thermogravimetry (DTA/TG) were also carried out to characterize the products. Crystal data for infinity(3)[LnCl3(1,4-Ph(CN)2)] (1-3): Pnma, T = 170(2) K; Sm (1): a = 7.172(1) A, b = 22.209(3) A, c = 6.375(1) A, V = 1015.4(3) A(3), R1 for F(o) > 4sigma(F(o)) = 0.032, wR2 = 0.079. Gd (2): a = 7.116(1) A, b = 22.147(4) A, c = 6.345(1) A, V = 1000.0(3) A(3), R1 for F(o) > 4sigma(F(o)) = 0.033, wR2 = 0.085. Tb (3): a = 7.090(2) A, b = 22.140(4) A, c = 6.325(2) A, V = 992.8(3) A(3), R1 for F(o) > 4sigma(F(o)) = 0.025, wR2 = 0.061. Crystal data for infinity (3)[Y2Cl6(1,4-Ph(CN)2)] (4): P1, T = 170(2) K; a = 6.653(2) A, b = 6.799(2) A, c = 9.484(2) A, V = 397.9(2) A(3), R1 for F(o) > 4sigma(F(o)) = 0.027, wR2 = 0.069. Crystal data for [Y2Cl6(PhCN)6] (5): P2(1)/c, T = 170(2) K; a = 9.767 (2) A, b = 12.304(3) A, c = 19.110(4) A, V = 2294.8(8) A(3), R1 for F(o) > 4sigma(F(o)) = 0.041, wR2 = 0.092.
RESUMO
By solvent free syntheses of the rare earth trichlorides LnCl(3), Ln = Pr, Nd, Sm, Eu, Tb with melts of 4,4'-bipyridine two-dimensional frameworks of the formula (2)(infinity)[Ln(2)Cl(6)(4,4'-bipy)(3)] x 2(4,4'-bipy) are obtained, with 4,4'-bipy = C(10)H(8)N(2), 4,4'-bipyridine. 4,4'-Bipyridine acts both as a linker ligand as well as a template and populates all cavities in the structures. The template can be evaporated at temperatures >200 degrees C giving a new high temperature compound with a yet unknown structure. Further heating results in the release of the remaining linking equivalents of the ligand and reformation of LnCl(3). Thus the reaction can be run in cycles if the evaporated ligand is collected. Luminescence in the visible range without quenching by concentration is observed for the lanthanides Eu and Tb, which is identified for Eu(III) with the transitions (5)D(0)-->(7)F(J) and (5)D(4)-->(7)F(J) for Tb(III). The hybrid character of the material is reflected by the additional strong antenna effect of the ligand: main excitation is observed via the 4,4'-bipyridine linkers followed by an energy transfer to the metal centres. It is remarkable that both the template containing MOFs as well as the new high temperature compounds exhibit luminescence properties.