Strong Photocurrent Response of Selenoarsenates With Different Transition Metal Complexes as Structure-Directing Agents

Four selenoarsenates with different transition-metal complexes [Co(tren)(2)H]AsSe(4) [tren = tris(2-aminoethyl)amine] (1); [Ni(2)(dien)(4)](As(2)Se(5)) (dien = diethylenetriamine) (2); [Zn(tren)](2)(As(2)Se(5)) (3) and [Mn(tren)](2)(As(2)Se(5)) (4) were solvothermally synthesized in a mixed solvent of organic amine and alcohol solution. The compounds 1-4 have pyramidal/tetrahedral structures (AsSe(3)/AsSe(4)), and contain transition metal (Co(2+), Ni(2+), Zn(2+) and Mn(2+)) complex that form distinct zero-dimensional (0-D) clusters. Arsenic atoms form a tetrahedron in compounds 1 and 2; 1 consists of discrete tetrahedral (AsSe(4)) and transition metal complex [Co(tren)(2)](2+); 2 is composed of an anion [As(2)Se(5)](4-) cluster and transition metal complex [Ni(dien)(2)](2+). In compounds 3 and 4, arsenic atom forms a pyramidal AsSe(3) and the two pyramidal AsSe(3) share a corner connection to form a dimer [As(2)Se(5)](4-); 3 is characterized as a cluster consisting of two unsaturated [Zn(tren)](2+) caiton linked by a dimer (As(2)Se(5))(4-) linkage; in 4, unsaturated [Mn(tren)](2+) caiton is linked to two trigonal-bipyramidal [Mn(tren)]Se via dimer (As(2)Se(5))(4-) to form [Mn(tren)](4)[As(4)Se(10)] cluster. To our knowledge, [Zn(tren)](2)(As(2)Se(5)) (3) is the first zinc selenoarsenate containing the (As(2)Se(5))(4-) anion type. Furthermore, the Mn(2+) ions adopt a trigonal-biyramidal (five-coordinate) and octahedral (six-coordinate) environment. Adding K(2)CO(3)/Cs(2)CO(3) to the synthesis system is necessary and may act as a mineralizer. Several properties of compounds 1-4 have been characterized in our studies, in particular their strong photocurrent response characteristics under visible light irradiation.