Synthesis of ferrocene-grafted poly(p-phenylene-ethynylenes) and control of electrochemical behaviors of their thin films.
New ferrocene-coated poly(p-phenylene-ethynylenes) (PPEs) with end capping groups of protected thiol were prepared by a palladium-catalyzed Sonogashira coupling reaction. Ferrocene groups were covalently attached to polymers A and B through ethylene oxide tethers and to polymer C through methylene tethers. Polymers A and B are soluble in common solvents such as tetrahydrofuran (THF), chloroform, methylene chloride, acetone, dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), and polymer C is soluble in toluene, THF, chloroform, and methylene chloride. Polymers A-C display low quantum yield, caused by electron-transfer quenching of ferrocene groups as electron donors. The polymer thin films were prepared through incubation of gold electrodes in THF solutions containing the polymers for 2 days. Ferrocene in thin films of polymers A and B display significantly faster electron-transfer rate than that of polymer C. Hydrophilic ethylene oxide side chains of polymers A and B decrease formal potential of tethered ferrocene groups because of electron-donating effect from ethylene oxide side chains, which stabilizes the ferrocenium ion and leads to a cathodic shift of the redox wave.
Xue
Cuihua
C
Department of Chemistry, Michigan Technological University, Houghton, Michigan 49931, USA.
Chen
Zhen
Z
Wen
Ya
Y
Luo
Fen-Tair
FT
Chen
Jian
J
Liu
Haiying
H
D000480:Alkynes / Q000138:chemical synthesis* / Q000737:chemistry; D004563:Electrochemistry; D004987:Ethers / Q000138:chemical synthesis* / Q000737:chemistry; D005296:Ferrous Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D005453:Fluorescence; D008567:Membranes, Artificial; D000075163:Metallocenes; D016252:Microscopy, Scanning Tunneling; D008968:Molecular Conformation; D010316:Particle Size; D012680:Sensitivity and Specificity; D012996:Solutions / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013499:Surface Properties
D000480:Alkynes; D004987:Ethers; D005296:Ferrous Compounds; D008567:Membranes, Artificial; D000075163:Metallocenes; D012996:Solutions; C436384:phenyleneethynylene; C004998:ferrocene