Crystal-to-crystal transformations in heterometallic yttrium(III)-copper(I) iodide derivatives in a confined solvent-free environment: influence of solvated yttrium cations on the nuclearity and dimensionality of iodocuprate clusters

The solvated yttrium iodide precursors Y(L)(8)]I(3) (L = DMSO or DMF), prepared in situ by stirring YI(3)(Pr(i)OH)(4) in DMSO or DMF, react with CuI in the presence of NH(4)I to give ionic hetero-metallic species Y(DMSO)(8)]Cu(2)(mu-I)I(4)] (1) and Y(DMF)(8)]Cu(4)(mu(3)-I)(2)(mu-I)(3)I(2)] (2) in excellent yields. Re-crystallization of 1 from DMF afforded the mixed-solvate complex Y(DMSO)(6)(DMF)(2)]CuI(3)]I] (3). Compounds 2 and 3 undergo unique crystal-to-crystal transformation via progressive substitution of DMF by water molecules in a confined, solvent-free environment. Thus, crystals of 3 transform into Y(DMSO)(6)(H(2)O)(2)]CuI(3)]I] (4), whereas a discrete ion-pair assembly of 2 is first converted into a 1-D zig-zag structure Y(DMF)(6)(H(2)O)(2)](3+)Cu(7)(mu(4)-I)(3)(mu(3)-I)(2)(mu-I)(4)(I)](1infinity)(3-) (5) and finally into a 2-D sheet containing mixed-valent copper atoms, Y(DMF)(6)(H(2)O)(3)](3+)Cu(I)(7)Cu(II)(2)(mu(3)-I)(8)(mu-I)(6)](2infinity)(3-) (6). The bi- and tetrafurcate H-bonding between water ligands on yttrium and iodides of the Cu-I cluster plays a pivotal role in the evolution of structures 4-6. Formation of a wide range of iodocuprate structures in 1-6, from discrete mono-, di- or tetranuclear units to one- and two-dimensional extended arrays, reflects the influence of solvated yttrium cations on the nuclearity and dimensionality of Cu-I clusters. TG-DTA-MS studies and DFT calculations for these complexes have also been carried out in order to determine their thermal stability and have insight about aforesaid transformations.