Synthesis, structure and properties of the first organic-templated inorganic-framework Ba(II) perchlorate

The first organic-templated Ba(II) perchlorate with open architecture, [(C6H8N)2Ba(ClO4)4]n (1), has been synthesized in the presence of 3-methylpyridine (3-MP) under hydrothermal conditions. The compound 1 was characterized by single crystal X-ray diffraction, elemental analysis, IR, powder XRD, 1H NMR, TGA and fluorescence spectra. The 12-coordinate Ba(II) ion was located in the center of the irregular icosahedral (BaO12) cage. Then the icosahedral BaO12 cages and the ClO 4 - linkers joined together to form a (4, 4) topology. And the protonated amine molecules were residing in the interlamellar space of the inorganic macro-anionic topology layers in the aAa mode (a = amine, A = anionic layer). The N–H⋯O hydrogen bonds ensure the stability of the structure by mounted the organic molecules to the main body of the inorganic framework. The solid-state fluorescence spectrum of complex 1 exhibits broad emission at 381 nm at room temperature, which is stronger than the free MPP (MPP = 3-methylpyridinium perchlorate). In addition, the two different synthesis methods provide an effectual impetus about applying hydrothermal reaction chemistry to build novel structures.