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.

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 NH(4)I produced a novel framework compound Tb(DMSO)(8)[Ag(2)(mu-I)(3)I(2)]Ag(5)(mu(3)-I)(4)(mu-I)(4) (3) involving alternate layers of discrete Tb(DMSO)(8) cation, Ag(2)I(5) anion and a 2D microporous sheet of the composition Ag(5)I(8), whereas similar reaction of 2 yielded [Tb(DMF)(8)]Ag(6)(mu(4)-I)(2)(mu(3)-I)(2)(mu-I)(5) (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) (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.