Solvothermal Synthesis and Characterization of Polyselenidoarsenate Salts of Transition Metal Complex Cations

The polyselenidoarsenates [Fe(phen)(3)][As(2)Se(6)] (1), [Zn-(phen)(dien)][As(2)Se(6)]center dot 2phen (2), [{Mn(phen)(2)}(2)(mu-eta(2),eta(2)-AsSe(4))](2)-[As(2)Se(6)]center dot H(2)O (3), and [Ni(phen)(3)][As(2)Se(2)(mu-Se(3))(mu-Se(5))] (4) (dien = diethylenetriamine and phen = 1,10-phenanthroline) were prepared by the reaction of As(2)O(3), Se, dien, and phen in the presence of transition metals in a methanol solvent under solvothermal conditions. Compounds 1-3 consist of [As(2)Se(6)](2-) anions with [Fe(phen)(3)](2+), [Zn(phen)(dien)](2+), and [{Mn-(phen)(2)}(2)(mu-eta(2),eta(2)center dot AsSe(4))](+) complex counter cations, respectively. The [As(2)Se(6)](2-) anion is formed from two As(III)Se(3) trigonal pyramids linked through two Se Se bonds. Compound 3 is the first example of a mixed-valent selenidoarsenate(III,V) and exhibits the coexistence of As(III)Se(3) trigonal pyramidal and As(V)Se(4) tetrahedral units. Compound 4 is composed of a helical chain of [As(2)Se(2)(mu-Se(3))(mu-Se(5))(2-)](infinity) and octahedral [Ni(phen)(3)](2+) cations. The [As(2)Se(2)(mu-Se(3))(mu-Se(5))(2-)](infinity) chain is constructed from AsSe(+) units alternatively linked by mu-Se(3)(2-) and mu-Se(5)(2-) bridging ligands. When the structures of compounds 1-4 are compared, the transition metal ions show different structural directing effects during the synthesis of arsenic polyselenides in methanol. Compounds 1, 2, 3, and 4 exhibit semiconducting properties with band gaps of 1.88, 2.29, 1.82, and 2.01 eV, respectively.