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首页> 外文学位 >The reductive and electro -catalytic properties of two water -soluble cobalt porphyrins investigated by surface -enhanced Raman spectroscopy and electrochemistry.
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The reductive and electro -catalytic properties of two water -soluble cobalt porphyrins investigated by surface -enhanced Raman spectroscopy and electrochemistry.

机译：通过表面增强拉曼光谱和电化学研究了两种水溶性钴卟啉的还原和电催化性能。

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摘要

Electrochemical and surface spectroscopic techniques are utilized to investigate the reductive electrochemistry of two water soluble cobalt porphyrins, cobalt(III)-tetra(4-sulfonatophenyl) porphyrin, CoTSPP, and cobalt(III)-tetra(4-trimethylaniliniumphenyl) porphyrin Co(III)TAPP. The electrochemistry of both porphyrins, at Ag, Au, and Pt working electrodes, Surface-enhanced-Raman scattering spectra and UV/vis absorption spectra of the two redox forms of CoTSPP and CoTAPP are also reported. Voltammetric studies indicate two reductive processes at −0.35 and −1.02 V, vs SCE for CoTSPP, and a single reductive peak at −0.80 V for CoTAPP. A non Faradaic electrochemical wave was observed at −0.68 V in the CV of CoTSPP and this process was established to be an adsorption process.;The reductive intermediates generated at −0.35 and −1.02 V were characterized by potential dependent UV/visible spectroscopy using an optically transparent thin layer electrode. For CoTSPP an intense Soret band was observed at 425 nm when the electrode potential was held at 0.0 V. At −0.3 V the 425 nm Soret band disappeared, replaced by a new band at 412 nm. This 412 nm band persisted in the spectra at potentials more positive than −1.10 V. When the electrode potential was stepped to −1.10 V two bands were observed in the potential dependent UV/vis spectrum; the 412 nm band and a new band at 358 nm. For CoTAPP the Soret band was observed at 427 nm at 0.0 V and shifted to 412 nm when the electrode potential was stepped to −0.8 V. At −1.20 V a split Soret band was observed with wavelengths identical to those observed for CoTSPP. The Soret band at 425 nm has been established to be characteristic of Co porphyrins with the central metal in the 3+ oxidation state. The 412 nm band is indicative of the Co(II) species and the split Soret band at 412 and 358 nm, characteristic of the Co(I) porphyrin. The potential dependent changes are therefore suggestive of a Co(III) to Co(II) transition occurring at −0.35 V and −0.8 V for CoTSPP and CoTAPP respectively, while the transition occurring at −1.10 and −1.20 V for CoTSPP and CoTAPP indicate the Co(II) to Co(I) transition.;Potential dependent shifts in the core sensitive, oxidation state marker band ν4 were also observed for CoTSPP. The ν4 vibration was assigned to the bands at 1374 and 1343 cm−1 in the SERS spectra of CoTSPP and CoTAPP at 0.0 V. For CoTSPP, ν4 shifted from 1374 at 0.0 V to 1364 cm−1 at −0.4 V. This shift has been attributed to a change in the oxidation state of the central metal from Co(III) to Co(II). It was not possible to observe the Co(II) to Co(I) transition for CoTSPP form the potential dependent SERS data.;The catalytic activity of CoTSPP and CoTAPP towards the reduction of cystine and dithiodipropionic acid was also investigated using cyclic voltammetry. Both CoTSPP and CoTAPP catalytically reduced DPA and RSSR at −0.77 and −0.83 V, respectively, on a silver working electrode, in acidic aqueous environments. No catalytic activity was observed when the solution pH was changed from pH 3.0 to pH 10.0.;High Performance Liquid Chromatography and Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry were used to purify the porphyrins and obtain their exact molecular weights.
机译：利用电化学和表面光谱技术研究了两种水溶性钴卟啉，钴（III）-四（4-磺酰基苯基）卟啉，CoTSPP和钴（III）-四（4-三甲基苯胺基苯基）卟啉Co（III）的还原电化学）TAPP。还报道了在Ag，Au和Pt工作电极上的两种卟啉的电化学，CoTSPP和CoTAPP两种氧化还原形式的表面增强拉曼散射光谱和UV / vis吸收光谱。伏安研究表明，相对于SCE，CoTSPP在-0.35和-1.02 V处有两个还原过程，而CoTAPP在-0.80 V处有一个还原峰。在CoTSPP的CV中于-0.68 V处观察到非法拉第电化学波，该过程被确定为吸附过程。-在-0.35和-1.02 V处产生的还原性中间体通过电势依赖性UV /可见光谱进行表征光学透明的薄层电极。对于CoTSPP，当电极电势保持在0.0 V时，在425 nm处观察到强烈的Soret带。在-0.3 V时，425 nm的Soret带消失，被412 nm处的新带所取代。这个412 nm的谱带在光谱上的电势比-1.10 V更正。在电极电势升至-1.10 V时，在与电势相关的UV / vis光谱中观察到两个谱带； 412 nm波段和358 nm处的新波段。对于CoTAPP，在0.0 V时在427 nm处观察到Soret带，当电极电位升至-0.8 V时移至412 nm。在-1.20 V时，观察到了一条分离的Soret带，其波长与CoTSPP观察到的波长相同。 425 nm的Soret谱带已被确定为Co卟啉的特征，中心金属处于3+氧化态。 412 nm谱带指示Co（II）物种以及在412和358 nm分裂的Soret带，这是Co（I）卟啉的特征。因此，电位依赖性变化提示CoTSPP和CoTAPP分别在-0.35 V和-0.8 V发生Co（III）到Co（II）的转变，而CoTSPP和CoTAPP的转变在-1.10和-1.20 V发生，这表明从Co（II）到Co（I）的转变。对于CoTSPP，还观察到了核心敏感的氧化态标记带ν4的电势依赖性变化。在0.0 V的CoTSPP和CoTAPP的SERS光谱中，将ν4振动分配给了1374和1343 cm-1的频带。对于CoTSPP，ν4从0.0 V的1374变为-0.4 V的1364 cm-1的频带。这归因于中心金属的氧化态从Co（III）转变为Co（II）。不可能从潜在的依赖SERS数据观察到CoTSPP从Co（II）到Co（I）的转变。;还使用循环伏安法研究了CoTSPP和CoTAPP对胱氨酸和二硫代二丙酸还原的催化活性。在酸性水环境中，在银工作电极上，CoTSPP和CoTAPP分别在-0.77和-0.83 V时催化还原DPA和RSSR。当溶液的pH值从pH 3.0更改为pH 10.0时，未观察到催化活性。高效液相色谱和基质辅助激光解吸电离飞行时间质谱用于纯化卟啉并获得其确切分子量。

著录项

  • 作者

    Ejeh, David Edo.;

  • 作者单位

    Howard University.;

  • 授予单位 Howard University.;
  • 学科 Chemistry Analytical.
  • 学位 Ph.D.
  • 年度 2000
  • 页码 173 p.
  • 总页数 173
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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