Multiple supported Keggin-type polyoxometalate polymer built upon weak copper–oxygen interaction

Two inorganic–organic hybrid compounds based on Keggin-type polyoxotungstates have been synthesized and characterized. X-ray single crystal analysis indicated that both compounds [Cu(bpe)]6[HCu0.5W12O40]·6H2O (1) and [Cu(bpe)]6[PWV3WVI9O40]·8H2O (2) (bpe = trans-1,2-di-(4-pyridyl)-ethylene) exhibit high-dimensional frameworks constructed from Keggin-type anions and from secondary metal coordination groups of Cu-bpe. It is interesting that in two compounds there are eight Cu-bpe fragments to be anchored around one anion via relatively weak Cu–O interactions (Cu–O = 2.482–2.812 Å), respectively. Compound 1 is a three-dimensional framework; while compound 2 represents a two-dimensional structure. The luminescent property, cyclic voltammetry and thermal stability of 1–2 have been investigated.