Department of Chemical, Sciences and Technology, University of Rome Tor Vergata, Italy.
Analyst. 2011 Dec 7;136(23):4966-76. doi: 10.1039/c1an15069c. Epub 2011 Oct 4.
A comparative study of Pt(II)- and Pt(IV)-porphyrins as novel ionophores for anion-selective polymeric membrane electrodes is performed. Polymeric membranes of different compositions, prepared by varying plasticizers, cationic and anionic additives and Pt porphyrins, have been examined by potentiometric and optical techniques. Pt porphyrin-based devices were found to exhibit enhanced potentiometric selectivity toward iodide ion compared to electrodes based on a typical anion-exchanger (e.g. tridodecylmethylammonium chloride). It is shown that Pt(II)-porphyrins function as neutral anion carriers within the electrode membranes, while those based on Pt(IV)TPPCl(2) operate via a mixed mode carrier mechanism, evidencing also a partial reduction of the starting ionophore to Pt(II)TPP. Spectrophotometric measurements of thin polymeric films indicate that no spontaneous formation of hydroxide ion bridged porphyrin dimers occurs in the membrane plasticized both with high or low dielectric constant plasticizer, due to a low oxophilicity of central Pt. The computational study of various anion-Pt(IV)TPPCl(2) complex formation by means of semi-empirical and density functional theory (DFT) methods revealed a good correlation between calculated and measured ionophore selectivity.
对 Pt(II)-和 Pt(IV)-卟啉作为新型阴离子选择性聚合物膜电极离子载体进行了比较研究。通过电位和光学技术研究了不同组成的聚合物膜，这些膜是通过改变增塑剂、阳离子和阴离子添加剂以及 Pt 卟啉来制备的。基于 Pt 卟啉的器件被发现表现出对碘化物离子的增强的电位选择性，与基于典型阴离子交换剂（例如三辛基甲基氯化铵）的电极相比。结果表明，Pt(II)-卟啉在电极膜中作为中性阴离子载体起作用，而基于 Pt(IV)TPPCl(2)的那些通过混合模式载体机制起作用，还证明了起始离子载体向 Pt(II)TPP 的部分还原。对薄聚合物膜的分光光度测量表明，由于中心 Pt 的低亲氧性，在高介电常数或低介电常数增塑剂均增塑的膜中，不会自发形成桥连卟啉二聚体的氢氧化物离子。通过半经验和密度泛函理论（DFT）方法对各种阴离子-Pt(IV)TPPCl(2)配合物形成的计算研究表明，计算出的和测量出的离子载体选择性之间存在良好的相关性。
