Covalent Immobilization of Redox-Active Fe(κ²-dppe)(η⁵-C₅Me₅)-Based π-Conjugated Wires on Oxide-Free Hydrogen-Terminated Silicon Surfaces

Abstract

Several redox-active Fe(κ 2 -dppe)(η 5 -C 5 Me 5 ) arylacetylide complexes (dppe = 1,2-bis(diphenylphosphino)ethane) featuring a pendant ethynyl (1b−d and 2) or ethenyl (3) group have been grafted on oxide-free hydrogen-terminated silicon (Si−H) surfaces through a covalent interfacial Si−C bond. They form densely packed redox-active monolayers. The chargetransfer process between the terminal redox center and the underlying silicon interface was subsequently studied by cyclic voltammetry. The latter turned out to be strongly dependent on the nature of the spacer linking the organometallic end groups to the silicon surface, the highest charge-transfer rates being obtained for monolayers anchored through conjugated and unsaturated spacers. Although the rates measured were among the highest values obtained for redox-active systems grafted to Si− H surfaces, this study nevertheless suggests that the electron tunnelling is not entirely controlling the interfacial charge-transfer process for the shorter linkers tested. In this respect, strategies to improve further the charge-transfer kinetics of the produced redox-active films are briefly discussed.

Photoactive silicon surfaces functionalized with high-quality and redox-active platinum diimine complex monolayers

“…Such a shift would be rather consistent with a differently coordinated Pt complex, as previously reported for other organometallic monolayers bound to Si(111) surfaces. 17,18 The experimental ratio between the areas under the S 2p and N 1s peaks was estimated at 1.5, which is very close to 4S/2N expected for the terminal Pt complex. Finally, the chemical conversion of PtCl 2 to Ptdithiolene was thought to introduce some oxidation of the underlying silicon surface, as evidenced by the presence of a small peak at a binding energy of 103-104 eV attributable to silicon oxides.…”

Redox-Active Molecular Wires Derived from Dinuclear Ferrocenyl/Ruthenium(II) Alkynyl Complexes: Covalent Attachment to Hydrogen-Terminated Silicon Surfaces

“…These high values, which can be ascribed to the presence of the conjugated bridge between the attached metallic centers and the underlying silicon surface, are considerably higher than those previously reported for ferrocene monolayers 5 and for dinuclear systems bound to Si surfaces through a saturated spacer. 3,26 Comparison with the values determined for Si-2 (Table 2) reveals that replacement of the remote electron-rich "Fe(κ 2 -dppe)(η 5 -C 5 Me 5 )" end group by a much less electron-rich ferrocenyl unit located spatially closer to the Ru(II) center increases the rate of electron-exchange with the surface while keeping approximately constant the k app value ascribed to the second Ru 2+ /Ru 3+ redox couple. Finally, Si-4 showed a significantly different electrochemical stability from Si-3.…”

TD-DFT Benchmark on Inorganic Pt(II) and Ir(III) Complexes

“…For organic molecules, and especially dyes, one may quote the extensive benchmarks performed by Jacquemin et al in the last years, showing how TD-DFT can provide accurate results for such kinds of compounds after inclusion of some specific corrections (especially accounting for solvent effects). [1][2][3][4][5][6][7][8][9][10][11][12][13][14] However, despite increasing use of the same approach for metal complexes, [15][16][17][18][19][20][21][22][23][24][25][26] or in metal cluster chemistry, [27][28][29][30] benchmarks on those compounds remain difficult to perform, especially due to the requested resources. In any case, some preliminary benchmark study provided encouraging results.…”