Structure and thermal behaviour of ScK(C2O4)2(H2O)2 and InRb1-x(H3O)x(C2O4)2(H2O)2•0.5(H2O):: Two members of a family of open-framework oxalates with isotypic helical structures and zeolite-like properties

Two new mixed oxalates with an open architecture, ScK(C2O4)(2)(H2O)(2) (I) and InRb0.77(H3O)(0.23)(C2O4)(2)(H2O)(2).0.5(H2O) (II), have been synthesised from precipitation methods at ambient temperature. They crystallize in hexagonal system, space group P6(2)22 (No. 180), Z = 3, with the following unit-cell parameters for I: a = 8.8667(2) angstrom, c = 11.4908(4) angstrom, V = 782.36(4) angstrom(3), for II: a = 9.0148(3) angstrom, c = 11.4645(3) angstrom, V = 806.86(4) angstrom(3). The two structures belong to a family of isotypic helical anionic open-frameworks built from square antiprismatic coordinated metals and bischelating oxalates. The counter-cations K+ and Rb+/H3O+ are located in the tunnels of the framework. The thermal decomposition process has demonstrated zeolite-like properties associated with weakly-bonded water molecules located in the voids of the framework. (c) 2006 Elsevier SAS. All rights reserved.