Probing Frontier Orbital Energies of {Co9(P2W15)3} Polyoxometalate Clusters at Molecule–Metal and Molecule–Water Interfaces

• Published in: Journal of the American Chemical Society Vol. 139; no. 41; pp. 14501 - 14510
• Main Authors: Yi, Xiaofeng, Izarova, Natalya V, Stuckart, Maria, Guérin, David, Thomas, Louis, Lenfant, Stéphane, Vuillaume, Dominique, van Leusen, Jan, Duchoň, Tomáš, Nemšák, Slavomír, Bourone, Svenja D. M, Schmitz, Sebastian, Kögerler, Paul
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 18-10-2017
• Subjects: Condensed Matter; Physics
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.7b07034

Functionalization of polyoxotungstates with organoarsonate coligands enabling surface decoration was explored for the triangular cluster architectures of the composition [CoII 9(H2O)6(OH)3(p-RC6H4AsVO3)2­(α-PV 2WVI 15O56)3]25– ({Co9(P2W15)3}, R = H or NH2), isolated as Na25[Co9(OH)3(H2O)6­(C6H5AsO3)2­(P2W15O56)3]·86H2O (Na-1; triclinic, P1̅, a = 25.8088(3) Å, b = 25.8336(3) Å, c = 27.1598(3) Å, α = 78.1282(11)°, β = 61.7276(14)°, γ = 60.6220(14)°, V = 13888.9(3) Å3, Z = 2) and Na25[Co9(OH)3­(H2O)6­(H2NC6H4AsO3)2­(P2W15O56)3]·86H2O (Na-2; triclinic, P1̅, a = 14.2262(2) Å, b = 24.8597(4) Å, c = 37.9388(4) Å, α = 81.9672(10)°, β = 87.8161(10)°, γ = 76.5409(12)°, V = 12920.6(3) Å3, Z = 2). The axially oriented para-aminophenyl groups in 2 facilitate the formation of self-assembled monolayers on gold surfaces and thus provide a viable molecular platform for charge transport studies of magnetically functionalized polyoxometalates. The title systems were isolated and characterized in the solid state, in aqueous solutions, and on metal surfaces. Using conducting tip atomic force microscopy, the energies of {Co9(P2W15)3} frontier molecular orbitals in the surface-bound state were found to directly correlate with cyclic voltammetry data in aqueous solution.