Electrografting of Diazonium‐Functionalized Polyoxometalates: Synthesis, Immobilisation and Electron‐Transfer Characterisation from Glassy Carbon

Abstract

Polyoxometalates (POMs) are attractive candidates for the rational design of multi-level charge-storage materials because they display reversible multi-step reduction processes in a narrow range of potentials. The functionalization of POMs allows for their integration in hybrid complementary metal oxide semiconductor (CMOS)/molecular devices, provided that fine control of their immobilisation on various substrates can be achieved. Owing to the wide applicability of the diazonium route to surface modification, a functionalized Keggin-type POM [PW11 O39 {Ge(p-C6 H4 -CC-C6 H4 -${{\rm N}{{+\hfill \atop 2\hfill}}}$)}](3-) bearing a pending diazonium group was prepared and subsequently covalently anchored onto a glassy carbon electrode. Electron transfer with the immobilised POM was thoroughly investigated and compared to that of the free POM in solution.

Electron Transfer to a Phosphomolybdate Monolayer on Glassy Carbon: Ambivalent Effect of Protonation

“…The concentration of surface-immobilized K Mo Sn is obtained from the slope of the ip−v relationship at a low scan rate giving Γ = 1.2 × 10 −10 mol/cm 2 , corresponding to the concentration expected for a compact monolayer. 30 On the reverse (backward) scan, broadening of the reoxidation peak is first observed preceding its splitting into two reoxidation peaks with an increase in scan rate, v, at values higher than 1 V s −1 , as shown in Figure 2a. Such behavior may have various chemical origins.…”

“…65 An apparent electron transfer rate constant k et of 500 s −1 was inferred from this procedure, a value similar to that observed for a densely packed monolayer of the tungstic analogue K W Ge (k et = 800 s −1 ). 30 …”

“…In a recent paper, we In particular, we have tested the resistance of the PMo 11 Sn core to the experimental conditions required by Sonogashira-type C−C couplings by coupling it to a ferrocenyl unit. 37 Following a strategy that proved to be successful in the case of tungstates, 30 …”

Polyoxometalate nanostructured gold surfaces for sensitive biosensing of benzo[a]pyrene

“…Deposition of POMs on surfaces has proved to lead to self assembled 2D-ordered arrays of POMs. The availability of organic-inorganic hybrid POMs including reactive residues [16,17] enables their covalent attachment to surfaces to form stable, dense, and well-ordered monolayers. In view of application in the biosensor field, we have chosen to tether the homobifunctionalized [PW 11 O 39 {(SiC 6 H 4 NH 2 ) 2 O}] 3− anion to gold substrate prefunctionalized with a carboxylic acid terminated self-assembled monolayer (SAM) of thiol.…”

Simulating the Favorable Aggregation of Monolacunary Keggin Anions

“…12,13 In addition, the rectangular lacuna in MKAs represents an ideal binding site wherein to anchor a variety of functional moieties and/or linkers: [14][15][16][17] in practice, this somewhat broadens MKAs' versatility with respect to that of PKAs. Notable examples are organic tethers to chromophores; 12,18,19 to (photo)catalytic centres; 13,[20][21][22] to other solid supports such as electrodes, silica, and metal oxides; 9,19,[23][24][25][26] and to distal metal chelating centres, for subsequent incorporation in co-ordination polymers. 26,27 Just as significant as these intrinsic chemical properties is the dynamic behaviour of Keggin anions in solution.…”