A series of Keggin-based compounds constructed by conjugate ring-rich pyrazine and quinoxaline derivatives

Abstract

Through the use of conjugate ring-rich pyrazine and quinoxaline derivatives, five new Keggin polymolybdate based compounds, [Ag^I₃L¹₂(H₂O)₂(PMo₁₂O₄₀)] (1), [Ag^I₄L¹₅(SiMo₁₂O₄₀)] (2), [Ag^I₆L²₆(PMo₁₂O₄₀)₂] (3), [Ag^I₂L²₂(C₁₆H₃₆N)₂](SiMo₁₂O₄₀)] (4), [Cu^I₃L²₃(PMo₁₂O₄₀)] (5) (L¹ = 2,3-diphenylpyrazine, L² = 2,3-diphenylquinoxaline, C₁₆H₃₆N = tetrabutylammonium), were synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. In compound 1, three Ag^I ions are fused by two L¹ molecules to form a [Ag₃L¹₂]³⁺ subunit, and these subunits link the PMo₁₂ anions to construct two kinds of 1D chains (I and II). Chains I and II connect to each other by sharing the same PMo₁₂ anions and a 2D grid-like layer is built. The asymmetric unit of compound 2 is linked to form a dimer by sharing Ag ions, and a 1D double strand is formed. The SiMo₁₂ anions connect adjacent 1D double strands through Ag3–O23 bonds and a 2D network is built. In compound 3, there exists a 1D ladder-like double chain with PMo₁₂ anions as linking bars. A 2D layer is formed by linkage Ag2–O24 between adjacent chains. In compound 4, the PMo₁₂ anions act as inorganic linkages to connect adjacent zigzag chains through Ag1–O3 bonds to construct a 2D grid-like layer. In compound 5 two Cu^I–L² lines are fused by PMo₁₂ anions to build a 1D ladder-like chain. Additionally, the electrochemical and photocatalytic properties of the title compounds have been studied.