A three-dimensional bimetallic oxide constructed from octamolybdate clusters and copper–ligand cation polymer subunits. A comment on the stability of the octamolybdate isomers

Hydrothermal reactions of CuSO4·5H2O, MoO3 and tetra-2-pyridylpyrazine (tpyrpyz) yield the three-dimensional bimetallic oxide hybrid material [{Cu2(tpyrpyz)}2{z-Mo8O26}]·7H2O (1·7H2O). The framework structure is constructed from {Cu2(tpyrpyz)}n 2nþ cationic polymer chains linked through octamolybdate clusters. The z-isomer of {Mo8O26}42, consisting of four octahedral and four square pyramidal sites is present as the cluster building block. There are now seven isomeric forms of the {Mo8O26}42 cluster, and calculations of their relative energies and interconversions are presented. Crystal data: C48H46Cu4Mo8N12O33 (1·7H2O), monoclinic C2=c; a ¼ 26:678ð1Þ; b ¼ 10:8981ð4Þ; and c ¼ 25:4109ð9Þ A ° , b ¼ 116:855ð1Þ8; V ¼ 6591:2ð4Þ A ° 3, Z ¼ 4; Dcalc ¼ 2:359 g cm23. q 2003 Elsevier B.V. All rights reserved.