Twocomponent polymer films of palladium and fulle

Authors: Monika WysockaŻołopa Krzysztof Winkler Suresh Gadde Francis D’Souza

Publish Date: 2010/12/30

Volume: 16, Issue: 1, Pages: 65-74

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Abstract

Redox active films have been generated via electrochemical reduction in a solution containing palladiumII acetate and fulleropyrrolidine with covalently linked crown ethers viz benzo15crown5 and benzo18crown6 In these films fullerene moieties are covalently bonded to palladium atoms to form a polymeric network Films show ability to coordinate alkali metal cations from the solution Therefore in solutions containing salts of alkali metal cations benzo15crown5C60/Pd and benzo18crown6C60/Pd films are doped with cations coordinated by crown ether moiety and anions of supporting electrolyte which enter the film to balance positive charge These films are electrochemically active in the negative potential range due to the reduction of the fullerene moiety Reduction of the polymer is accompanied by the transport of supporting electrolyte ions between solution and solid phase In solution containing alkali metal salts the process of film reduction is accompanied by the transport of anions from the film to the solution In the presence of tetraalkylammonium salts transport of cations from the solution to the film takes place during the polymer reductionStudy of fullerene derivatives has rapidly grown in recent years due to their practical applications covering diverse applications Several synthetic approaches have been developed to prepare a variety of fullerene derivatives For example a series of fulleropyrrolidine derivatives were synthesized by 13dipolar cycloaddition to C60 1 2 3 4 5 6 7 8 9 10 This procedure has been used to link a crown ether moiety to fulleropyrrolidine 11 12 13 14 15 16 17 18 19 20 21 It was shown 11 12 13 14 21 that crown etherbearing fulleropyrrolidine possesses interesting electrochemical and photophysical propertiesCrown ethers exhibit ability to complex cations of alkali and alkali earth metals 22 23 24 Hence they have been widely used in the construction of alkali metal detectors Recently conjugated conducting polymers functionalized with crown ether substituents have been used as new materials for alkali metal ion detection 25 26 27 28 29 30 These materials can be used for fabrication of allsolid sensing electrodes 31Recently we developed an electrochemical procedure for the formation of twocomponent fullerene films based on the electroreduction carried out in a solution containing fullerene 32 33 34 35 36 or fullerene derivatives 37 38 39 40 and various transition metal complexes In these polymers fullerene moieties are covalently bonded to transition metal atoms or their complexes to form a polymeric network These materials exhibit electrochemical activity in the negative potential range due to rich electroreduction of the fullerene moieties Films containing fullerene derivatives with covalently attached redox probe ferrocene zinc porphyrin or singlewall carbon nanotubes additionally show electrochemical activity at positive potentials 37 38 39 In this case the oxidation of electrondonating redox groups attached to the main backbone of the polymer is responsible for the anodic redox activityThe process of reduction or oxidation of polymeric fullerenebased materials is accompanied by the transport of chargecompensating counterions within the matrix 33 37 The overall control of charge percolation through the electroactive material is governed by the transport of these counter ions It was found that different factors can influence the rate of ion transport through the polymeric layer The degree of solvent swelling 41 42 43 size of supporting electrolyte ions 33 and morphology of the polymeric material 44 are the most important factors that determine the redox properties of the layerPalladium acetate Aldrich Pdac2 and C60 SES Houston TX or Southern Chemical Group were used as received The supporting electrolytes tetranbutylammonium perchlorate nBt4NClO4 lithium perchlorate LiClO4 lithium hexafluoroarsenate LiAsF6 lithium tetrafluoroborate LiBF4 potassium hexafluorophosphate KPF6 and cesium hexafluoroarsenate CsAsF6 Sigma Chemical Co were used as received Acetonitrile 999 and toluene 999 were used as received from Aldrich Chemical CoTo 100 ml of dry toluene C60 100 mg 0138 mmol 5 eq of 4′formylbenzo15crown5 205 mg 0694 mmol 45 and 3 eq of sarcosine 37 mg 0416 mmol were added and the mixture was refluxed for 4–5 h Solvent was removed under vacuum and the crude compound was adsorbed onto silica gel and was purified on a silica gel column using toluene and ethyl acetate 9010 v/v as eluent yielding ~30 Electrospray ionuzation EIS mass in CH2Cl2 matrix was calculated as 10433 found 1044 the 1H NMR 300 MHz CDCl3 in ppm δ 744s 1H phenyl H 712 d 1H phenyl H 690 d 1H phenyl H 495 d 1H CH fulleropyrrolidine ring 484 s 1H CH fulleropyrrolidine ring 427 d 1 H CH fulleropyrrolidine ring 375–430 m 16 H crown CH2 and 281 s 3 H NCH3

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