Crystal structures, proton conductivities and luminescence of two organic-inorganic hybrid materials based on Keggin-type clusters and Cu(II)/Cu(I)-bis(hydroxymethyl)-2,2′-bipyridine complexes

Two proton-conductive and luminescent organic-inorganic hybrid materials, {[Cu(II)(bhmbpy)(H2O)(Cl)0.5(CH3CN)]2[PW(VI)10W(V)2O39]}·4H2O(1) and {H2[Cu(I)(bhmbpy)2(Cl)Cu(I)(bhmbpy)2][PW12O40]}·7H2O (2) (where bhmbpy is bis(hydroxymethyl)-2,2′-bipyridine), were synthesized at room temperature. The two products were characterized by infrared spectroscopy, X-ray single-crystal diffraction, X-ray powder diffraction, elemental and thermogravimetric analyses. The proton conductivities and luminescence of 1 and 2 were studied by using alternating-current impedance spectroscopy and luminescence spectroscopy, respectively. X-ray diffraction analysis revealed that 1 includes a decorated polyanion chain {[Cu(II)(bhmbpy)(H2O)(Cl)0.5(CH3CN)]2[PW(VI)10W(V)2O39]}n and forms a three-dimensional network structure depending on short Cl…Cl contacts and hydrogen-bonding interactions. X-ray diffraction analysis revealed that 2 includes a butterfly-like bi-nuclear copper cluster unit with a Cl-bridge, [Cu(I)(bhmbpy)2(Cl)Cu(I)(bhmbpy)2]+, and forms a three-dimensional network structure depending on hydrogen-bonding interactions. [PW12O40]3– anions fill in the network based on hydrogen-bonding and electrostatic interactions. In them, the bhmbpy acts as a bidentate nitrogen donor ligand in the chelating fashion to coordinate with the Cu(II) center in 1 and the Cu(I) center in 2. The bhmbpy in 2 successfully constrains the Cu(I) within a rigid environment in a tetragonal-pyramidal geometry. The two compounds exhibit good proton conductivity (10−4 S·cm−1) at 100 °C in the relative humidity range 35–98%. Their luminescence behaviors in the solid state at room temperature have also been investigated. Upon excitation at 384 nm, 1 exhibits three emission peaks centered at 439, 507 and 566 nm. When excited at 364 nm, 2 displays three emission peaks centered at 443, 501 and 553 nm.