Self-assembly of 1D metalloporphyrin array within pseudo-hexagonal channels of polyoxometalates

Self-assembly of the robust Keggin cluster [SiW12O40](4) and metalloporphyrin building blocks [M(TpyPH(n))](n+) under hydrothermal conditions gives two new organic-inorganic hybrid solid compounds. The hydrothermal reactions of H4SiO4 center dot 12WO(3)center dot xH(2)O, Cu(NO3)(2)center dot 2.5H(2)O, meso-tetra(4-pyridyl)porphine (H(2)TpyP) and H2O at 200 degrees C for 72 h yield a solid compound [Cu(TpyPH(3))](2)[Cu(TpyPH(2))][SiW12O40](2)center dot 8H(2)O (1). Using ZnCl2 instead of Cu(NO3)(2)center dot 2.5H(2)O in the syntheses leads to the crystallization of a compound [Zn(TpyPH(4))(H2O)][SiW12O40]center dot 3H(2)O (2). Both compounds consist of discrete anionic alpha-[SiW12O40](4) clusters, cationic metalloporphyrins and crystalline water molecules. Hydrogen bonds, pi-pi aromatic interactions and CH center dot center dot center dot pi interactions in these two new hybrid solids lead to the formation of 3D framework structures. Pseudo-hexagonal channels are formed by polyoxometalates and are occupied by one-dimensional metalloporphyrin arrays. Both compounds were characterized by single crystal Xray, UV-Vis, IR spectroscopy and thermogravimetric analysis. (C) 2011 Elsevier B.V. All rights reserved.