Role of aromatic vs. aliphatic amine for the variation of structural, electrical and catalytic behaviors in a series of silver phosphonate extended hybrid solids

Four inorganic-organic hybrid silver phosphonate compounds, [Ag(C10H8N2)(H4hedp)] (1), [Ag2(C10H8N2)(H3hedp)]·2H2O (2), [C4H12N2][Ag4(H2hedp)2] (3) and [C4H12N2][Ag10(H2hedp)4(H2O)2]·2H2O (4) (H5hedp = 1-hydroxyethane-1,1-diphosphonic acid), have been prepared by virtue of the variable amine-directed hydrothermal strategy. The subsequent roles of coordinated aromatic amine (4,4'-bipyridine) and coordination-free templated aliphatic amine (piperazine) are studied. The connectivity of the silver ions, diphosphonate units (hedp) and bipyridine moiety can give rise to the one-dimensional structure of 1 and two-dimensional layer structure of 2. In contrast, the silver ions and diphosphonate units are connected to form the tetrameric and pentameric silver cluster units in compound 3 and 4, respectively. Such clusters are rare examples of fundamental building units in the piperazine templated two-dimensional silver based layer structures. The room temperature dielectric studies show the extremely high dielectric permittivity of the amine templated compounds (3 and 4) compared to amine coordinated structures (1 and 2). The synthesized compounds also participate in various heterogenous catalytic reactions acting as active Lewis acid catalysts that are observed for the first time in the amine-templated metal organophosphonates. The observed band gaps and dielectric values suggest that compounds 3 and 4 are more promising candidates for electronic applications, while compounds 1 and 2 are comparatively better Lewis acid catalysts.

Colossal Dielectric Responses from the Wide Band Gap 2D-Semiconducting Amine Templated Hybrid Framework Materials

Two unprecedented organic amine templated silver organophosphonate hybrid solids have been synthesized hydrothermally by varying the molar ratio of the reactants. Both of the compounds consist of novel tetra- and penta-nuclear silver phosphonate basic building units. The dielectric constants are extremely large due to the charge separation of anionic metal phosphonate frameworks and cationic templated piperazine moieties in the compounds, as found for the first time in a hybrid organophosphate family. The conductivity and UV-visible absorption studies provide strong evidence about the semiconducting nature of the present compounds.

The presence of mixed-valent silver in the uranyl phenylenediphosphonate framework

A 2-D silver uranyl phosphonate presents both Ag⁺ and Ag⁰ atoms in the free space between the adjacent layers and the incorporation of the mixed-valent silver sites results in the quenching of the fluorescent emission.