Solvothermal syntheses, crystal structures, and characterizations of a series of one-dimensional organic-containing gallium polyselenides

Five new gallium polyselenides, namely [1,3-pdaH2][Ga2Se2(Se2)(Se3)] (1) (1,3-pda = 1,3-diaminopropane), [1,4-bdaH2][Ga2Se3(Se2)] (2) (1,4-bda = 1,4-diaminobutane), [Me2NH2]2[Ga2Se2(Se2)2] (3), α-[AEPH]2[Ga2Se2(Se2)2] (4) (AEP = N-(2-aminoethyl)piperazine), and β-[AEPH]2[Ga2Se2(Se2)2] (5), have been synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction, thermogravimetric analyses and solid-state UV-Vis diffuse reflectance spectroscopy. Compound 1 features a one-dimensional (1D) chain of [Ga2Se2(Se2)(Se3)]n2n− constructed by alternating five-membered rings [Ga2Se(Se2)] and six-membered rings [Ga2Se(Se3)] sharing Ga atoms. Compound 2 features a 1D chain of [Ga2Se3(Se2)]n2n− built from alternating four-membered rings [Ga2Se2] and five-membered rings [Ga2Se(Se2)] joined at Ga atoms. Compounds 3, 4 and 5 feature a 1D-[Ga2Se2(Se2)2]n2n− chain made up by fusing five-membered rings [Ga2Se(Se2)] at Ga atoms. The polymorphic noncentrosymmetric compound 4 and centrosymmetric compound 5 were isolated at different temperatures under solvothermal conditions. The absorption edges reveal band gaps of 2.08 eV for 1, 2.32 eV for 2, 2.07 eV for 3, 1.93 eV for 4 and 2.10 eV for 5, respectively. Their thermal stabilities were investigated viathermogravimetric analysis (TGA).