Two new inorganic-organic hybrid materials based on β- and γ-octamolybdate clusters: Synthesis, structure determination and solid-state photochromic properties

Two new hybrid inorganic-organic compounds, namely ((Pr2NH2)-Pr-i)(2)(NH4)(2)[Mo8O26] (1) and (C4H7N2)(4)[Mo8O26(C4H6N2)(2)]center dot 2H(2)O (2), have been synthesized from room temperature, and characterized by vibrational spectroscopies, thermal gravimetric analysis (TGA) and single-crystal X-ray diffraction. Compound (1) contains a beta-octamolybdate anionic cluster (beta[Mo8O26](4-)) stabilized with two ammonium [NH4](+) and two diisopropylammonium [(Pr2NH2)-Pr-i](+) cations. Compound (2) is built upon a gamma-octamolybdate anionic cluster (gamma-[Mo8O26](4-)) functionalized by two neutral 2-methylimidazole (C4H6N2) molecules, and stabilized by four protonated 2-methylimidazolium [C4H7N2](+) cations. Single-crystal X-ray diffraction analyses reveal that the compounds have 2D and 3D supramolecular structures resulting from electrostatic and H-bonding interactions between inorganic and organic entities. Both compounds exhibit distinct solid-state photochromic properties at room temperature which vary with the nature of both the polyoxometalate clusters and the organoammonium cations. (C) 2020 Elsevier Ltd. All rights reserved.