Sequential transformations in assemblies based on octamolybdate clusters and 1,2-bis(4-pyridyl)ethane

The new hybrid inorganic-organic solids [Mo8O26][H(2)bpe](2) (1), {[Mo8O26(mu-bpe)][H(2)bpe](2)}(n) (2), [Mo8O26(Hbpe)(2)][H(2)bpe] (3), and {[Mo8O26][H(2)bpe](2)}(n) (4) were synthesized under hydrothermal conditions. The crystal structure of 1 contains the discrete octamolybdate beta-isomer, whereas in 3 the inorganic building unit is a functionalized octamolybdate of general formula [Mo8O26X2]((2n-4)). A similar building unit is found in 2 and 4, but forming part of polymeric 1D-arrays. In 2 the polymer is constructed from [Mo8O26(mu-bpe)](4-), and the functionalization of the anionic cluster in 4 occurs through Mo-O-Mo bonds. The sequential hydrothermal 2/3 -> 1 and 1 -> 4 transformations were observed at 145 and 180 degrees C, respectively. However, thermal studies of 1 and 4 revealed that both materials do not suffer any phase transitions below 340 degrees C for 1 or <350 degrees C for 4, indicating that such transformations are possible only under the hydrothermal conditions. An XRPD study as a function of the temperature of 1 also demonstrated the negligible structural changes before 330 degrees C.