Two New Compounds Based on Bi-Capped Keggin Polyoxoanions and Cu-Bpy Cations Contain Both CuII and CuI Complexes: Synthesis, Characterization and Properties

Abstract

Two inorganic-organic hybrid complexes based on bi-capped Keggin-type cluster, {([Cu^II(2,2'-bpy)₂]₂[PMo^VI₈V^V₂V^IV₂O₄₀(V^IVO)₂])[Cu^I(2,2'-bpy)]}∙2H₂O (1) and {[Cu^II(2,2'-bpy)₂]₂[SiMo^VI_8.5Mo^V_2.5V^IVO₄₀(V^IVO)₂]}[Cu^I_0.5(2,2'-bpy)(H₂O)_0.5] (2) (bpy = bipyridine), had been hydrothermally synthesized and structurally characterized by elemental analysis, FT-IR, TGA, PXRD and X-ray single-crystal diffraction analysis. Compound 1 consists of a novel 1-D chain structure constructed from [Cu^I(2,2'-bpy)]⁺ unit linking bi-supported POMs anion {[Cu^II(2,2'-bpy)₂]₂[PMo^VI₈V^V₂V^IV₂O₄₀(V^IVO)₂]}^-. Compound 2 is a bi-capped Keggin cluster bi-supported Cu-bpy complex. The main highlights of the two compounds are that Cu-bpy cations contain both Cu^I and Cu^II complexes. Furthermore, the fluorescence properties, the catalytic properties, and the photocatalytic performance of compounds 1 and 2 have been assessed, and the results show that both compounds are active for styrene epoxidation and degradation and adsorption of Methylene blue (MB), Rhodamine B (RhB) and mixed aqueous solutions.

Keywords: catalysis; crystallographic structure; hydrothermal synthesis; photocatalytic property; polyoxometalates.

Figure 1

The ball-and-stick diagram of the POM supported coordination in compound 1.

Figure 2

Ball-and-stick representation of the 1-D chain (a), the 2-D supramolecular layer structure formed through the Ow…O hydrogen bonds in (H₂O)₂ cluster and two neighboring 1-D chains (b), and the view of 3-D hydrogen-bonded framework with the C-H…O and N-H…O hydrogen bond interactions between two 2-D layers along the bc plane (c) in compound 1.

Figure 3

The molecular structure of {[Cu^II(2,2′-bpy)₂]₂[SiMo₁₁V₃O₄₂]}[Cu^I_0.5(2,2′-bpy) (H₂O)_0.5].

Figure 4

(a) View of the 1-D chain and 2-D layer structures with the π…π interactions and C-H…O hydrogen bond interactions in 2; several hydrogens are omitted for clarity. (b) Combined ball-and-stick and polyhedron representation of {[Cu(1)(2,2′-bpy)₂]₂[SiMo₁₁V₃O₄₂]}^0.5− anion connected to eight adjacent anions through C-H…O and N-H…O hydrogen bonding interactions on the ac plane. (c) Schematic drawing of the 3-D supramolecular topology in 2.

Figure 5

Catalytic activity and product distribution of compounds 1, 2, 4 and 5. (Convn = Styrene conversion; So = styrene oxide; Bzdh = benzaldehyde; others: including benzoic acid and phenylacetaldehyde).

Figure 6

Absorption spectra of the MB and MB + RhB solution under UV-vis irradiation with the presence of compounds 1 and 2 at pH = 3. (a) 1-MB, (b) 2-MB, (c) 1-RhB + MB and (d) 2-RhB + MB. The black, red, blue, green, purple, and light blue lines represent the absorption spectra curves for tests performed at 0, 20, 40, 60, 80, 100, and 120 min, respectively.