Disorder and polymorphism in Cu(II)-polyoxometalate complexes: Cu-1.5(H2O)(7.5)PW12O40center dot 4.75H(2)O, cis- & trans-Cu-2(H2O)(10)SiW12O40center dot 6H(2)O

SR Bajpe and S Henke and JH Lee and PD Bristowe and AK Cheetham, CRYSTENGCOMM, 18, 5327-5332 (2016).

DOI: 10.1039/c5ce02088c

Three highly crystalline Cu(II)-polyoxometalate (POM) complexes, Cu-1.5(H2O)(7.5)PW12O40center dot 4.75H(2)O and cis-and trans-Cu-2(H2O)(10)SiW12O40center dot 6H(2)O, were successfully synthesized and characterized by single crystal and powder X-ray diffraction as well as thermogravimetric analysis. All complexes feature octahedrally coordinated, Jahn-Teller-distorted Cu-II centres, which are coordinated by one terminal oxygen atom of the POM anion and five water molecules. The crystal structure of Cu-1.5(H2O)(7.5)PW12O40center dot 4.75H(2)O, reveals four-fold disorder at one of the two Cu-sites, whereas Cu-2(H2O)(10)SiW12O40center dot 6H(2)O crystallizes in two fully-ordered polymorphic forms: a monoclinic structure containing an angled cis configuration of the Cu-POM- Cu molecule and a triclinic structure containing a linear trans configuration. Density functional theory (DFT) calculations show that the cis polymorph of Cu-2(H2O)(10)SiW12O40center dot 6H(2)O is more stable than the trans form by about 30 kJ mol(-1).

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