Efficient Synthesis of Ir-Polyoxometalate Cluster Using a Continuous Flow Apparatus and STM Investigation of Its Coassembly Behavior on HOPG Surface

Taking advantage of a continuous-flow apparatus, the iridium­(III)-containing polytungstate cluster K₁₂Na₂H₂[Ir₂Cl₈P₂W₂₀O₇₂]·37H₂O (<b>1</b>) was obtained in a reasonable yield (13% based on IrCl₃·H₂O). Compound <b>1</b> was characterized by Fourier transform IR, UV–visible, ³¹P NMR, electrospray ionization mass spectrometry (ESI-MS), and thermogravimetric analysis measurements. ³¹P NMR, ESI-MS, and elemental analysis all indicated <b>1</b> was a new polytungstate cluster compared with the reported K₁₄[(IrCl₄)­KP₂W₂₀O₇₂] compound. Intriguingly, the successful isolation of <b>1</b> relied on the custom-built flow apparatus, demonstrating the uniqueness of continuous-flow chemistry to achieve crystalline materials. The catalytic properties of <b>1</b> were assessed by investigating the activity on catalyzing the electro-oxidation of ruthenium tris-2,2′-bipyridine [Ru­(bpy)₃]^2+/3+. The voltammetric behavior suggested a coupled catalytic behavior between [Ru­(bpy)₃]^3+/2+ and <b>1</b>. Furthermore, on the highly oriented pyrolytic graphite surface, 1,3,5-tris­(10-carboxydecyloxy) benzene (TCDB) was used as the two-dimensional host network to coassemble cluster <b>1</b>; the surface morphology was observed by scanning tunneling microscope technique. “S”-shape of <b>1</b> was observed, indicating that the cluster could be accommodated in the cavity formed by two TCDB host molecules, leading to a TCDB/cluster binary structure