Fang Yuanyuan, Senge Mathias O, Van Caemelbecke Eric, Smith Kevin M, Medforth Craig J, Zhang Min, Kadish Karl M
Department of Chemistry, University of Houston , Houston, Texas 77204-5003, United States.
Inorg Chem. 2014 Oct 6;53(19):10772-8. doi: 10.1021/ic502162p. Epub 2014 Sep 25.
Electrochemical studies of the oxidation of dodecasubstituted and highly nonplanar nickel porphyrins in a noncoordinating solvent have previously revealed the first nickel(III) porphyrin dication. Herein, we investigate if these nonplanar porphyrins can also be used to detect the so far unobserved copper(III) porphyrin dication. Electrochemical studies of the oxidation of (DPP)Cu and (OETPP)Cu show three processes, the first two of which are macrocycle-centered to give the porphyrin dication followed by a Cu(II)/Cu(III) process at more positive potential. Support for the assignment of the Cu(II)/Cu(III) process comes from the linear relationships observed between E1/2 and the third ionization potential of the central metal ions for iron, cobalt, nickel, and copper complexes of (DPP)M and (OETPP)M. In addition, the oxidation behavior of additional nonplanar nickel porphyrins is investigated in a noncoordinating solvent, with nickel meso-tetraalkylporphyrins also being found to form nickel(III) porphyrin dications. Finally, examination of the nickel meso-tetraalkylporphyrins in a coordinating solvent (pyridine) reveals that the first oxidation becomes metal-centered under these conditions, as was previously noted for a range of nominally planar porphyrins.
先前在非配位溶剂中对十二取代且高度非平面的镍卟啉氧化进行的电化学研究揭示了首个镍（III）卟啉双阳离子。在此，我们研究这些非平面卟啉是否也可用于检测迄今未观察到的铜（III）卟啉双阳离子。对（DPP）Cu和（OETPP）Cu氧化的电化学研究显示有三个过程，其中前两个是以大环为中心，生成卟啉双阳离子，随后在更正的电位下发生Cu（II）/Cu（III）过程。对Cu（II）/Cu（III）过程归属的支持来自于观察到的E1/2与（DPP）M和（OETPP）M的铁、钴、镍和铜配合物中心金属离子的第三电离电位之间的线性关系。此外，还在非配位溶剂中研究了其他非平面镍卟啉的氧化行为，发现镍中-四烷基卟啉也能形成镍（III）卟啉双阳离子。最后，在配位溶剂（吡啶）中对镍中-四烷基卟啉的研究表明，在这些条件下首次氧化以金属为中心，正如先前对一系列名义上平面的卟啉所指出的那样。
