The assembly of POM-induced inorganic–organic hybrids based on copper ions and mixed ligands

Though PMo12, PW12, and BW12 are all Keggin-type POMs, they exhibit different coordination abilities and electron densities under different pH conditions. Therefore, the types of POMs and pH value have effects on the formation of various frameworks. Three inorganic-organic hybrid materials based on Keggin-type polyoxometalates (POMs), [Cu-2(II)(phen)(2)(4,4-bipy)(H4,4-bipy)(2)(H2O)(2)][PMo12O40](2)2H(2)O (1), [Cu-II(phen)(2)(H4,4bipy)][PW12O40]center dot H2O (2), and [Cu-2(II)(phen)(2)(4,4-bipy)(BW12O40)(H2O)(2)](H(2)4,4-bipy)(0.5)3H(2)O (3) (phen=1,10-phenanthroline, 4,4-bipy=4,4-bipyridine), were synthesized using different POMs in the hydrothermal conditions. Compounds 1-3 were characterized by single-crystal X-ray diffraction, IR spectra, elemental analyses, powder X-ray diffraction analyses, and thermogravimetric analyses. Compound 1 presents a two-dimensional (2-D) network containing the Keggin-type [PMo12O40](3-) anion and dinuclear metal-organic units [Cu-2(II)(phen)(2)(4,4-bipy)(H4,4-bipy)(2)(H2O)(2)](3+). Compound 2 is a 2-D architecture constructed from a [PW12O40](3-) and mononuclear metal-organic units [Cu-II(phen)(2)(H4,4-bipy)](3+). In 3, the [BW12O40](5-) anions link [Cu-2(II)(phen)(2)(4,4-bipy)] units to form a one-dimensional (1-D) chain [Cu-2(II)(phen)(2)(4,4-bipy)(BW12O40)(H2O)(2)]; the 1-D chain connects with protonated 4,4-bipy ligands and lattice waters, yielding a 2-D layer. Fluorescence spectra, UV-vis spectra, and electrochemical properties of 1-3 have been investigated.