Solid- and Solution Phase Transformations in Novel Hybrid Iodoplumbate Derivatives Templated by Solvated Yttrium Complexes

Solvated yttrium iodide precursors [Y(L)(8)]l(3) [L = dimethylformamide (DMF) or dimethylsulf oxide (DMSO)], prepared in situ by stirring Y-3(PrOH)(4) in DMF/DMSO, react with 3 equiv of Pbl(2) in the presence of NH(4)l to give novel hybrid derivatives based on either a one-dimensional (1D) straight chain, [Y(DMF)(8)][Pb-3(mu-l)(9)](1 infinity) center dot DMF (1), or discrete pentanuclear iodoplumbates, [Y(DMSO)(8)](2)[(DMSO)(2)Pb-5(mu(3)-l)(2)(mu-l)(8)l(6)] (2a). The complex 2a and a closely related [Y(DMSO)(8)][Y(DMSO)(7)(DMF)][(DMSO)(2)Pb-5(mu(3)-l)(2)(mu-l)(8)l(6)] (2b) were obtained in good yield by solution phase transformation of 1 in DMSO under slight different conditions. Derivatives 1 and 2 also undergo unique solid-state transformation in a confined environment of paratone to give 1D polymers based on zigzag iodoplumbate chains; crystals of 1 transform into [Y(DMF)(6)(H2O)(2)][Pb-3(mu(3)-l)(mu-l)(7)l](1 infinity) (3) via an exchange reaction, whereas those of 2a and 2b are converted into [Y(DMSO)(7)][Pb-3(mu(3)-l)(mu-l)(7)l](1 infinity) (4) via a decomposition pathway. The trifurcate H-bonding between water ligands on yttrium cation and iodide of the iodoplumbate anion plays a pivotal role in transforming the straight 1D polymeric Pb-l chain of 1 into a zigzag chain in 3. The thermogravimetry-differential thermal analysis studies indicate that complexes with DMF ligands are thermally more stable than those with DMSO ones, the mixed DMF-H2O ligand complex 3 being the most stable one because of the presence of strong H-bonding. Diffuse-reflectance UV-visible spectral analyses of 1-4 show an optical band gap in the 1.86-2.54 eV range, indicating these derivatives as potential semiconductors. In contrast to non-emissive 3 and 4, derivatives 1, 2a, and 2b show remarkable luminescent emission with peak maxima at 703 nm, assigned as an iodine 5p-lead 6s to lead 6p charge transfer (XM-M-CT).