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

摘要

Taking advantage of a continuous-flow apparatus, the iridium(III)-containing polytungstate cluster K12Na2H2[Ir2Cl8P2W20O72]center dot 37H(2)O (1) was obtained in a reasonable yield (13% based on IrCl3 center dot H2O). Compound I was characterized by Fourier transform IR, UV-visible, P-31 NMR, electrospray ionization mass spectrometry (ESI-MS), and thermogravimetric analysis measurements. P-31 NMR, ESI-MS, and elemental analysis all indicated I was a new polytungstate cluster compared with the reported K-14[(IrCl4)KP2W20O72] compound. Intriguingly, the successful isolation of I relied on the custom-built flow apparatus, demonstrating the uniqueness of continuous-flow chemistry to achieve crystalline materials. The catalytic properties of 1 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 1. 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 1; the surface morphology was observed by scanning tunneling microscope technique. "S"-shape of 1 was observed, indicating that the duster could be accommodated in the cavity formed by two TCDB host molecules, leading to a TCDB/cluster binary structure.