Langmuir monolayer of organoalkoxysilane for vitamin B₁₂-modified electrode

In order to develop a novel type of vitamin B₁₂-functionalized electrode, the monolayer properties of the B₁₂ mimics, which have a core structurally identical with the naturally occurring vitamin B₁₂ and seven ester chains on the outside, have been investigated as a mixed monolayer with an organosilane amphiphile. Vitamin B₁₂ derivatives having seven C₈ chains were stably incorporated into the matrix organosilane monolayer, while the short C₃ chain derivatives were easily squeezed out from the matrix monolayer upon compression. Analyses of the molecular areas revealed that the long chain derivatives had a face-on orientation in the matrix monolayer. The mixed monolayers of the vitamin B₁₂ with the long chains and the organosilane amphiphile were transferred as an X-type LB film on a quartz plate that showed reasonable UV absorbance. The monolayer containing the vitamin B₁₂ derivative was similarly immobilized on an ITO electrode. A cyclic voltammetric measurement of this electrode in aqueous solution showed a Co(II)/Co(I) redox couple at - 0.65 V vs. Ag/AgCl which is in good agreement with the corresponding value of the vitamin B₁₂ derivative dissolved in methanol. It indicates that this modified electrode can be used as a reactive electrode with a vitamin B₁₂ function.