Neuman Nicolás I, Albold Uta, Ferretti Eleonora, Chandra Shubhadeep, Steinhauer Simon, Rößner Paul, Meyer Franc, Doctorovich Fabio, Vaillard Santiago E, Sarkar Biprajit
Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstrasse 34-36, Berlin 14195, Germany.
Instituto de Desarrollo Tecnológico para la Industria Química, INTEC, UNL-CONICET Paraje El Pozo, Santa Fe, Argentina.
Inorg Chem. 2020 Nov 16;59(22):16622-16634. doi: 10.1021/acs.inorgchem.0c02550. Epub 2020 Nov 5.
Two Co(III) complexes ( and ) of new corrole ligands (5,15-bis(-methylcarboxyphenyl)-10-(-methylcarboxyphenyl)corrole) and (5,15-bis(-nitrophenyl)-10-(-methylcarboxyphenyl)corrole) with two apical pyridine ligands have been synthesized and thoroughly characterized by cyclic voltammetry, UV-vis-NIR, and EPR spectroscopy, spectroelectrochemistry, single-crystal X-ray diffraction studies, and DFT methods. Complexes and possess much lower oxidation potentials than cobalt(III)--pentafluorophenylcorrole (Co(tpfc)) and similar corroles containing pentafluorophenyl (CF) substituents, thus allowing access to high oxidation states of the former metallocorroles using mild chemical oxidants. The spectroscopic (UV-vis-NIR and EPR) and electronic properties of several oxidation states of these complexes have been determined by a combination of the mentioned methods. Complexes and undergo three oxidations within 1.3 V vs FcH/FcH in MeCN, and we show that both complexes catalyze water oxidation in an MeCN/HO mixture upon the third oxidation, with (TOF) values of 1.86 s at 1.29 V () and 1.67 s at 1.37 V (). These values are five times higher than previously reported TOF values for CF-substituted cobalt(III) corroles, a finding we ascribe to the additional charge in the corrole macrocycle due to the increased oxidation state. This work opens up new possibilities in the study of metallocorrole water oxidation catalysts, particularly by allowing spectroscopic probing of high-oxidation states and showing strong substituent-effects on catalytic activity of the corrole complexes.
合成了两种带有两个顶端吡啶配体的新型卟吩配体（5,15-双（-甲基羧基苯基）-10-（-甲基羧基苯基）卟吩）和（5,15-双（-硝基苯基）-10-（-甲基羧基苯基）卟吩）的Co(III)配合物（和），并通过循环伏安法、紫外-可见-近红外光谱和电子顺磁共振光谱、光谱电化学、单晶X射线衍射研究以及密度泛函理论方法对其进行了全面表征。配合物和的氧化电位比钴（III）-五氟苯基卟吩（Co(tpfc)）和含有五氟苯基（CF）取代基的类似卟吩低得多，因此使用温和的化学氧化剂就可以使前者金属卟吩达到高氧化态。通过上述方法的结合，确定了这些配合物几种氧化态的光谱（紫外-可见-近红外和电子顺磁共振）和电子性质。配合物和在乙腈中相对于FcH/FcH在1.3 V范围内经历三次氧化，并且我们表明两种配合物在第三次氧化时在乙腈/H₂O混合物中催化水氧化，在1.29 V（）时的周转频率（TOF）值为1.86 s⁻¹，在1.37 V（）时为1.67 s⁻¹。这些值比先前报道的CF取代的钴（III）卟吩的TOF值高五倍，我们将这一发现归因于由于氧化态增加导致卟吩大环中额外的电荷。这项工作为金属卟吩水氧化催化剂的研究开辟了新的可能性，特别是通过允许对高氧化态进行光谱探测并显示出卟吩配合物催化活性上强烈的取代基效应。
