Electron Transfer in Ferrocene-Containing Functionalized Chitosan and Its Electrocatalytic Decomposition of Peroxide
Electron Transfer in Ferrocene-Containing Functionalized Chitosan and Its Electrocatalytic Decomposition of Peroxide
复制标题
含二茂铁功能化壳聚糖中的电子转移及其过氧化物的电催化分解
作者：
近年来，具有参与电子转移过程的能力的功能聚合物材料变得越来越重要，特别是在催化剂、生物技术、环境保护和照明领域。1-3至于聚合物催化剂，最近在开发更清洁的可持续系统方面的努力是由从基于石油化工的原料向生物材料的转变所驱动的。4，5鉴于这些发展，似乎很明显，在开发用作聚合物催化剂的天然聚合物（或生物聚合物）方面将发挥关键作用。与合成聚合物相比，天然聚合物的一个独特特征是它们能够被特定微生物降解。6，7壳聚糖是一种丰富的生物聚合物，由其母体多糖甲壳素完全或部分脱乙酰化获得，由于其生物降解性、生物相容性和生物活性，在包括生物医学、农业和环境保护领域的广泛科学研究中引起了极大的兴趣。8-11壳聚糖的大量羟基和氨基不仅为许多化学修饰提供位点，而且是用于锚定各种有机金属络合物的优良官能团，使壳聚糖成为分子催化剂的良好候选者。9，12-14此外，氨基是潜在的碱催化剂。4这些特征允许在操纵壳聚糖方面具有很大的灵活性，并导致作为催化剂的独特潜力。另一方面，含有有机金属单元的大分子将潜在有用的化学、电化学、光学和其他感兴趣的特性与聚合物的性质和加工性结合联合收割机。特别地，二茂铁基聚合物，其是氧化还原活性材料，鉴于其作为电催化剂、化学传感器、改性电极、光敏分子器件和药物的用途，已经受到了极大的关注。19，20-25二茂铁和壳聚糖的共价连接可以为构建新型聚合物系统提供一种方法，其结合了氧化还原活性和生物相容性，并在催化，生物传感器，光致变色器件，非线性光学，抗体诊断测试和癌症研究中的抗增殖化疗剂中开辟了应用。本文合成了含二茂铁的壳聚糖，并研究了其光诱导电子转移过程以及对过氧化物的电催化分解，为壳聚糖在催化、防爆剂、光敏剂、过氧化物传感器等方面的应用奠定了基础。在甲磺酸溶液中，壳聚糖的氨基被质子化，这对于亲核置换反应是不利的。因此，假定取代优先发生在羟基上（参见方案1）。这已经通过FTIR、1H NMR和13 C NMR光谱证实。与起始原料壳聚糖的红外光谱相比，含二茂铁的壳聚糖的红外光谱在约1720 cm-1处显示出强吸收带，其可归属于酯羰基，并且在3085、830、770和740 cm-1附近的谱带对应于双环。1H NMR谱显示出4.2-5.0 ppm范围内的信号，归属于N-部分的质子。在13 C NMR谱中，166 ppm处的信号可归因于二茂铁羰基（CdO）。基于NMR测量，可以计算出取代度为约1。
Functional polymeric materials that have the ability to participate in electron-transfer processes have become increasingly important in recent years, in particular in the fields of catalyst, biotechnology, environmental protection, and illumination. 1-3 As for polymeric catalysts, the most recent efforts in the development of cleaner sustainable systems are being driven by a shift from petrochemical-based feedstocks toward biological materials. 4, 5 Given these developments, it seems clear that there will be a key role to be played in the development of natural polymers (or biopolymers) for use as polymeric catalysts. A unique feature of natural polymers compared with synthetic ones is their ability to undergo degradation by specific microorganisms. 6, 7 Chitosan, an abundant biopolymer obtained from a fully or partially deacetylation of its parent polysaccharide chitin, has attracted significant interest in the broad range of scientific research, including biomedical, agriculture, and environmental protection fields, due to its biodegradability, biocompatibility, and bioactivities. 8-11 A large number of chitosan’s hydroxyl and amino groups not only provide sites for numerous chemical modifications but also are excellent functional groups for the anchoring of a large variety of organometallic complexes, making chitosan a good candidate as a precursor for molecular catalysts. 9, 12-14 Moreover, the amino groups are potential base catalysts. 4 These features allow for great flexibility in manipulating chitosan and leading to a unique potential as a catalyst. 14-16 On the other hand, macromolecules containing organometallic units combine potentially useful chemical, electrochemical, optical, and other interesting characteristics with the properties and processability of polymers. 17-19 In particular, ferrocenebased polymers, which are redox-active materials, have received a great deal of attention in light of their uses as electrocatalysts, chemical sensors, modified electrodes, photoactive molecular devices, and medicine. 19, 20-25 The covalent attachment of ferrocene and chitosan could offer a way for building novel polymeric systems, which combines redox activity and biocompatibility as well as opens applications in catalysis, biosensors, photochromic devices, nonlinear optics, antibodies diagnostic tests, and antiproliferative chemotherapeutic agent in cancer research. Herein, we synthesized the ferrocenecontaining chitosan and investigated the photoinduced electrontransfer processes in this functionalized chitosan as well as the electrocatalytic decomposition of peroxide, which could lead to its applications in catalysis, antiexplosion agent, photosensitizer, peroxide sensor, etc.In methanesulfonic acid solution in our experiment, the amino groups of chitosan are protonated, and this is disadvantageous for the nucleophilic displacement reaction. Therefore, the substitution is supposed to happen preferentially onto the hydroxyl groups (see Scheme 1). This has been confirmed by FTIR, 1H NMR, and 13C NMR spectra. Compared with the IR spectrum of the starting material chitosan, the IR spectrum of ferrocene-containing chitosan shows a strong absorption band at about 1720 cm-1, which can be assigned to the ester carbonyl group, and the bands around 3085, 830, 770, and 740 cm-1 corresponded to the cyclopentadienyl ring. The 1H NMR spectrum exhibited the signals in the range of 4.2-5.0 ppm, assigned to the protons of cyclopentadienyl moieties. In the 13C NMR spectrum, the signal at 166 ppm is attributable to the ferrocenecarbonyl group (CdO). On the basis of the NMR measurements, it can be calculated that the degree of substitution is about 1.