Lanthanide complexes in hybrid halometallate materials: interconversion between a novel 2D microporous framework and a 1D zigzag chain structure of iodoargentates templated by octakis-solvated terbium(III) cation
Résumé
Octakis solvated terbium iodide complexes [Tb(DMSO)(8)]I-3 (1) and [Tb(DMF)(8)]I-3 (2) (DMSO = dimethylsulfoxide; DMF = dimethylformamide) were used as synthons to construct novel iodoargentate fabrics. Reaction of 1 with 6 equivalents of AgI in the presence of NH4I produced a novel framework compound [Tb(DMSO)(8)](2)[Ag-2(mu-I)(3)I-2][Ag-5(mu(3)-I)(4)(mu-I)(4)](2 infinity) (3) involving alternate layers of discrete [Tb(DMSO)(8)](3+) cation, [Ag2I5](3-) anion and a 2D microporous sheet of the composition [Ag5I8](3-), whereas similar reaction of 2 yielded [Tb(DMF)(8)][Ag-6(mu(4)-I)(2)(mu(3)-I)(2)(mu-I)(5)](1 infinity) (4) with a 1D zigzag structure. The two structural forms are completely inter-convertible on mutual exchange of DMSO and DMF ligands, the partial substitution of the former ligand in 3 yielding a mixed-ligand complex [Tb(DMF)(6.7)(DMSO)(1.3)][Ag-6(mu(4)-I)(2)(mu(3)-I)(2)(mu-I)(5)](1 infinity) (5). Single crystal X-ray structures are reported for all the complexes. Thermo-gravimetric analyses of these complexes show that thermal stability decreases in the order 4 > 2 > 3 > 1, whereas the diffuse reflectance spectra of 3 and 4 exhibit an optical band gap of about 3.7 eV, thus revealing the insulator nature of these hybrid iodoargentates. Compared to solvated terbium iodide complexes 1 and 2, the high energy transitions in the excitation spectra of the iodoargentate complexes 3 and 4 are quenched by a process which can best be attributed to the auto-ionization of the carriers in the above materials.