Full Paper http://www.paper.edu.cn ‘‘Click’’ on Conducting Polymer Coated Electrodes: A Versatile Platform for the Modification of Electrode Surfacesa Yan Li, Weixia Zhang, Jing Chang, Jinchun Chen, Guangtao Li,* Yong Ju* Two types of N-substituted pyrroles with azide and terminal alkyne groups have been synthesized and electropolymerized. ‘‘Click’’ chemistry, specifically Huisgen 1,3-dipolar cycloaddition, was used as a general method for functionalization of the polypyrrole films. Several model compounds, including redox active (quinone), bioactive (cholic acid) and recognition elements (carbohydrate and thymi- dine) could easily be attached onto the electrode surfaces without loss of functionality or the elec- troactivity of the underlying conducting polymers. The results suggest that the polypyrrole films are clickable and provide a novel biocompatible and versatile platform for efficient modifications on electrode surfaces. Introduction catalysis.[1,2] A key factor in such investigations and applications is the achievement of an efficient interface The immobilization of functional units, such as electro- between the functional groups and the conductive active, bioactive and biological recognition elements, onto surface.[3,4] conductive surfaces is of enormous interest, both in Compared to various protocols developed for confining studies of functional groups themselves and in numerous functional units onto solid surfaces, electrodeposition of applications ranging from disease diagnosis to electro- conducting polymers offers a simple and attractive appro- ach for such a purpose.[5] Besides their excellent surface confinement capability, such polymers hold promise for Y. Li, W. Zhang, G. Li inducing electrical, electrochemical or optical signals Key Laboratory of Organic Optoelectronics and Molecular accrued from the interaction of functional groups with Engineering, Tsinghua University, Beijing 100084, China their environments, and are particularly suitable for the Fax: þ86 10 6279 2905; E-mail: [email protected] development of high performance bio- or chemosensory Y. Li, Y. Ju systems.[6,7] Key Laboratory of Bioorganic Phosphorus Chemistry and Synthesis of the functionalized monomers followed by Chemical Biology, Tsinghua University, Beijing 100084, China E-mail:[email protected] electropolymerization represents the most straightfor- ward method of creating the above-mentioned function- [7] J. Chang, J. Chen alized electrode systems. Although this strategy is useful Department of Pharmaceutical Engineering, Beijing University of and many functional groups were attached onto con- Chemical Technology, Beijing 100029, China ductive surfaces, the successful implementation of this a : Supporting information for this article is available at the bottom strategy depends to a great extent on the compatibility of of the article’s abstract page, which can be accessed from the the functional units introduced with the electropolymer- journal’s homepage at http://www.mcp-journal.de, or from the ization reaction. In some extreme cases, the polymeriza- author. tion process is completely blocked when substitutes have Macromol. Chem. Phys. 2008, 209, 322–329 322 ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/macp.200700436 转载 中国科技论文在线 http://www.paper.edu.cn ‘‘Click’’ on Conducting Polymer Coated Electrodes: A Versatile Platform ... bulky molecular size[8] or possess a lower oxidation Experimental Part potential than that of the corresponding monomers.[9] Moreover, due to harsh polymerization conditions, this Chemicals approach is critical or problematic for the immobilization Tetrabutylammonium hexafluorophosphate (TBAPF6), cholic acid, [6] of sensitive, valuable biomolecules. 1,10-dibromodecane, 30-azido-30-deoxythymidine (AZT) and pro- A useful alternative to the approach described above is pargyl amine were purchased from Sigma Company. Pyrrole, to establish a reactive conducting polymer, and then to glucose and the solvents were purchased from Beijing Chemicals attach the desired functional groups to polymer surfaces Company. All reagents and solvents were used without further by chemical grafting.[6] Several polymer systems contain- purification, unless otherwise noted. The synthetic protocols for [17] [18] ing reactive amino, carboxyl or active ester groups have N-(10-bromodecyl)pyrrole and glycosyl azide pentaacetate were adapted from published reports. been developed and widely employed for the functiona- lization of electrodes.[10] Nevertheless, the coupling reac- tions used rely on traditional nucleophilic-electrophilic reactions that are susceptible to side reactions.[11] For Instruments instance, the popular N-hydroxysuccinimide ester is prone to hydrolysis before and during the coupling reaction, Infrared spectra were obtained on ITO glass using a Perkin-Elmer which can both reduce coupling yields and make the yields spectrum GX FT-IR system in reflection mode. NMR spectra were 1 irreproducible.[12] Therefore, it is highly desirable and recorded at 300 MHz on a JOEL JNM ECA300 spectrometer. H NMR useful to develop novel polymer systems containing more chemical shifts are given in ppm relative to TMS. The ESI-MS was efficient reactive groups, which allow post-function- measured on a Bruker Esquire-LC ion trap mass spectrometer operated in positive mode. The fluorescence measurements were alization on the electrode not only easily and selectively carried out using a Fluorescene Spectrometer (Perkin-Elmer, LS55). under mild reaction conditions, but also in high yields without by-products. As a result of our continuous interest in the design and functionalization of conducting polymer coated sur- Synthesis faces,[9,10b] we were attracted by the recent development of click chemistry, especially the copper (I) catalyzed N-(10-Azidodecyl)pyrrole (1) Huisgen reaction between azide and terminal alkyne. This 1,3- dipolar cycloaddition reaction is recognized as the best N-(10-Bromodecyl)pyrrole (412 mg, 2 mmol) was heated in dry example of click chemistry and can be performed to give a DMF (35 mL) with sodium azide (650 mg, 10 mmol) for 20 h quantitative yield, in multiple solvents (including water) at 90 8C. The mixture was then cooled to room temperature and and in the presence of various functional groups, as well as added to a separating funnel containing 60 mL of a saturated aqueous solution of NaCl. The mixture was extracted with under mild reaction conditions.[13] Over the past few years, Et O(3Â 40 mL). The solvent was then evaporated and the product due to its efficiency and simplicity, this spring-loaded 2 purified by chromatography on a silica gel column with 4% ethyl reaction has been proved to be a promising candidate for acetate in petroleum as an eluent, yielding compound 1 (410 mg, [14] preparing biointerface designs and functional poly- 83% yield) as a light yellow oil. [15] mers. The azide, alkyne and the resulting triazole groups IR (KBr): 2 926.8, 2 954.0, 2 095.0, 1 500.1, 1 281.7, 1 043.6, are thermally stable and inert during electrooxidative 721.2 cmÀ1. [16] 1 processes. It is conceivable that, if the electrodeposition H NMR (CDCl3): d ¼ 6.66 (2H, t, H-b), 6.13 (2H, t, H-a), 3.86 (3H, t, of conjugated polymers and the power of click chemistry NCH2), 3.25 (3H, t, CH2N3), 1.75 (2H, m, NCH2CH2), 1.60 (2H, are combined, a useful method would be developed for m, N3CH2CH2), 1.26–1.34 (14H, m, aliphatic H). þ creating an efficient interface between the functional ESI-MS (þ): m/z ¼ 249 [M þ H] . groups and the conductive surface. N-[10-(Propargyl ether)decyl]pyrrole (2) Based on the above, two types of N-substituted pyrrole monomers bearing azide and terminal alkyne groups To a CH3CN solution (25 mL) of propargyl alcohol (112 mg, 2 mmol) respectively were synthesized. The pyrrole subunit KOH (140 mg, 2.5 mmol) was added. The mixture was stirred for about 10 min and then N-(10-bromodecyl)pyrrole (412 mg, was used for the formation of the conducting polymer 2 mmol) was added. The resulting solution was stirred for 10 h at films anchored to an electrode. The azide and alkyne room temperature and evaporated under vacuum. The residue groups served as reactive sites for the covalent binding of was extracted with Et2O and washed with deionized water, dried functional units. Herein we report the preparation of two over MgSO4, concentrated in a vacuum, and purified by column types of clickable polypyrrole-based conducting polymer chromatography with 2% ethyl acetate in petroleum to give the films and demonstrate their potential application as a compound 2 as a colorless oil in 75% yield. biocompatible and versatile platform for efficient mod- IR (KBr): 2 926.8, 2 954.0, 2 095.0, 1 500.1, 1 281.7, 1 043.6, ification of electrode surfaces. 721.2 cmÀ1. Macromol. Chem. Phys. 2008, 209, 322–329 ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.mcp-journal.de 323 中国科技论文在线 http://www.paper.edu.cn Y. Li, W. Zhang, J. Chang, J. Chen, G. Li, Y. Ju 1 À3 H NMR (CDCl3): d ¼ 6.66 (2H, t, H-b), 6.13 (2H, t, H-a), 3.86 (3H, t, monomers was increased to 20 Â 10 M and the system NCH2), 3.25 (3H, t, CH2N3), 1.75 (2H, m, NCH2CH2), 1.60 (2H, electropolymerized by successive scanning in a potential range. m, N3CH2CH2), 1.26–1.34 (14H, m, aliphatic H). After the polymerization, the polymer was rinsed with fresh ESI-MS (þ): m/z ¼ 262 [M þ H]þ. acetonitrile and characterized by electrochemical and spectral methods. Synthesis of Cholic Acid Derived Propargyl Amide (5) Cholic acid (0.816 g, 2 mmol), DCC (0.794 g, 2.2 mmol) and HOBt (0.297 g, 2.2 mmol) were dissolved in 6 mL of dry DMF. After General Procedure for the Modification of the 10 min of stirring at 0 8C, propargyl amine (0.110 g, 2.0 mmol) was Polypyrrole Coated Electrode added and the mixture was kept at ambient temperature for 20 h. Afterwards, the solution was separated from precipitate and Cycloaddition reactions were carried out by immersing the azide poured into 30 mL of ethyl acetate.