Use of Ferrocenyl Surfactants of Varying Chain Lengths To Study Electron Transfer Reactions in Native Montmorillonite Clay

Abstract

A series of ferrocenyl surfactants was tested as model compounds to study electron transfer reactions involving structural Fe(III) in clay minerals. The surfactants contain trimethylammonium headgroups, ferrocene tail groups, and intervening hydrocarbon chain lengths of one, six, or 11 carbons. Two factors considered to be decisive for electron transfer were addressed: (1) physical access of the surfactant ferrocene to the reactive sites through hexagonal holes in the clay lattice by X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) and (2) thermodynamic favorability of the overall oxidation/reduction reaction based on experimentally determined oxidation/reduction potentials. In suspensions of clay with the longer chain surfactants, (ferrocenylhexyl)trimethylammonim (FHTMA+) and (ferrocenylundecyl)trimethylammonium (FUTMA+), where electron transfer may be expected to be favored by both factors, physical accessibility, and thermodynamic favorability, ferroecene oxidation was observed by diffuse reflectance infrared spectroscopy (DRIFT), ultraviolet-visible spectroscopy (UV-vis), and visual color changes. In contrast, the shorter chain length surfactant, (ferrocenylmethyl)trimethylammonium (FMTMA+), did not participate in electron transfer with the clay, as substantiated by UV-vis and no visible color changes. Rigid conformation and/or higher oxidation/reduction potential than clay Fe can accountforthe lack of reaction. The utility and limitations of using these surfactants as model compounds is discussed.

K-10 montmorillonite: An efficient and reusable catalyst for the aerobic CC bond cleavage of α-substituted ketones

“…The dimension of the hexagonal cavity in the tetrahedral layer is about 5Å [44]. To the best of our knowledge, no data has been reported concerning the kinetic diameter of 2-methylcyclohexanone but for cyclohexane and trimethylbenzene, these diameters are 6.0 and 7.3Å, respectively [45].…”

A New Insight of Graphene oxide-Fe(III) Complex Photochemical Behaviors under Visible Light Irradiation

“…6a). The excited GO ( E 0 (GO/ RGO) = −0.85 V vs NHE)41 preferentially donates an electron to the structural Fe(III) ( E 0 (structural Fe(III)/Fe(II)) = 0.44 V vs NHE)/surface Fe(III)/exchangeable Fe 3+ ( E 0 (Fe 3+ /Fe 2+ ) = 0.77 V vs NHE)42 instead of oxygen because of E(O 2 (1 M)/O 2 .− ) = −0.155 V vs NHE)43. So the photo-induced electron would preferentially transfer to Fe(III) which has higher redox potential than O 2 .…”

Ferrocene and ferrocenium modified clays and their styrene and EVA composites

“…Another type of ferrocene-containing surfactants for clays has also been reported [15]: a series of ferrocenyl surfactants was tested as model compounds to study electron transfer reactions involving structural Fe(III) in the clay mineral. The surfactants contained trimethyl ammonium headgroups, ferrocene tail groups, and an intervening hydrocarbon spacer of 1, 6 or 11 carbons.…”

“…Neutral ferrocene is yellow in solution while the positively charged ferrocenium is blue [15]. A color change after oxidation with sulfuric acid is an indication of the oxidation of ferrocene.…”