Orzeł Łukasz, Szmyd Bartłomiej, Rutkowska-Żbik Dorota, Fiedor Leszek, van Eldik Rudi, Stochel Grażyna
Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland.
Dalton Trans. 2015 Apr 7;44(13):6012-22. doi: 10.1039/c4dt03809f.
The nature of chlorophyll interactions with copper(II) ions varies considerably in organic solvents, depending on the dominant coordinative form. Besides formation of the metallo tetrapyrrolic complex, Cu(II) ions can cause oxidation of the pigment, reversible or irreversible, which can lead to the destruction of the macrocyclic structure. All these reaction types can be distinguished within a quite narrow range of reaction conditions. The ability to form new metallo derivatives in either metalation or transmetalation reactions is obviously limited by the concentration of the potential oxidant, but can be secured below this level via suitable composition of the reaction system. The decisive factor in the selection of a specific reaction pathway is the presence of a potential ligand that can affect the reactivity of Cu(II) for example by shifting its redox potential. Spectroscopic and electrochemical studies were performed in order to determine the predominant species of Cu(II) in methanol, nitromethane and acetonitrile in the presence of chloride and acetate ions, as well as to assign their appropriate oxidizing ability. This allowed us to estimate the boundary conditions for the electron transfer processes in chlorophyll-Cu(II) systems. Chlorophyll and its free base can undergo both types of electron transfer processes, however, they reveal different susceptibilities that make this class of ligands quite versatile markers in tuning the reactivity of metal ions in solutions.
在有机溶剂中，叶绿素与铜（II）离子相互作用的性质因主要配位形式的不同而有很大差异。除了形成金属四吡咯配合物外，铜（II）离子还会导致色素发生可逆或不可逆的氧化，这可能会导致大环结构的破坏。所有这些反应类型在相当窄的反应条件范围内都可以区分。在金属化或转金属化反应中形成新的金属衍生物的能力显然受到潜在氧化剂浓度的限制，但可以通过反应体系的适当组成确保在该水平以下。选择特定反应途径的决定性因素是存在潜在配体，例如它可以通过改变铜（II）的氧化还原电位来影响其反应性。进行了光谱和电化学研究，以确定在存在氯离子和醋酸根离子的情况下，甲醇、硝基甲烷和乙腈中铜（II）的主要存在形式，并确定它们相应的氧化能力。这使我们能够估计叶绿素 - 铜（II）体系中电子转移过程的边界条件。叶绿素及其游离碱都可以经历两种类型的电子转移过程，然而，它们表现出不同的敏感性，这使得这类配体在调节溶液中金属离子的反应性方面成为相当通用的标记物。
