Synthesis and Characterization of Poly(ferrocenylsilanes) with Coumarin Side Groups and Their Photochemical Reactivity and Electrochemical Behavior

Abstract

Two novel photoreversible poly(ferrocenylsilanes) (PFS) with coumarin side groups, i.e., halfand whole-substituted poly(ferrocenyl(3-(7-hydroxycoumarin) propyl)methylsilane), are synthesized by transition metal-catalyzed ring-opening polymerization of ferrocenyl(3-chloropropyl) methylsilane monomer and subsequent group exchange and nucleophilic substitution reaction. The two polymers are characterized by elemental analysis, 1 H and 13 C NMR, FTIR, UV-vis, emission spectra, TG, and DSC. Their photochemical reactivity and electrochemical behavior are studied by UV-vis spectra and cyclic voltammetry, respectively. The two PFS polymers, like coumarin derivatives, can undergo reversible photodimerization and photoscission, but the content of coumarin significantly affects their photochemical reactivity and electrochemical properties. The photochemical reaction of coumarin side groups can cause a reversible change of electrochemical behavior of these PFS polymers, i.e., the peak separation ∆E increases with photodimerization and decreases with photoscission again. Cyclic voltammograms indicate that the electrode processes of the films of both original and photo-cross-linked polymers coated on a glassy carbon electrode are diffusion controlled and quasireversible in a wide scan rate range in 0.1 M NaCl aqueous solution at room temperature because of a low rate of mass diffusion and slow rate of the change transfer between the active sites, judged from small kinetic parameters such as surface transfer coefficient Rn R , standard rate constant K s , and apparent diffusion coefficient D app of the electroactive species. Interestingly, the electrode process of the half-/whole-substituted PFS polymer was less reversible than the half-substituted one at high scan rate. Photoirradiation causes the electrode processes of the two coumarin PFS polymers to become less reversible due to the cross-linking of the films. These coumarin PFS polymers may have potential use in many fields because they combine the useful photochemical reactivity with redox activity.

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