Lim Jia Hui, Engelmann Xenia, Corby Sacha, Ganguly Rakesh, Ray Kallol, Soo Han Sen
Energy Research Institute@NTU (ERI@N) , Nanyang Technological University , Interdisciplinary Graduate School , Research Techno Plaza , Singapore 63755.
Division of Chemistry and Biological Chemistry , School of Physical and Mathematical Sciences , Nanyang Technological University , 21 Nanyang Link , Singapore 637371 . Email:
Chem Sci. 2018 Mar 23;9(16):3992-4002. doi: 10.1039/c7sc05378a. eCollection 2018 Apr 28.
The photochemical oxidation of a (TAML)Fe complex using visible light generated Ru(bpy) produces valence tautomers (TAML)Fe ( ) and (TAML˙)Fe ( ), depending on the exogenous anions. The presence of labile Cl or Br results in a ligand-based oxidation and stabilisation of a radical-cationic (TAML˙)Fe complex, which subsequently leads to unprecedented C-H activation followed by nucleophilic substitution on the TAML aryl ring. In contrast, exogenous cyanide culminates in metal-based oxidation, yielding the first example of a crystallographically characterised = 1 [(TAML)Fe(CN)] species. This is a rare report of an anion-dependent valence tautomerisation in photochemically accessed high valent (TAML)Fe systems with potential applications in the oxidation of pollutants, hydrocarbons, and water. Furthermore, the nucleophilic aromatic halogenation reaction mediated by (TAML˙)Fe represents a novel domain for high-valent metal reactivity and highlights the possible intramolecular ligand or substrate modification pathways under highly oxidising conditions. Our findings therefore shine light on high-valent metal oxidants based on TAMLs and other potential non-innocent ligands and open new avenues for oxidation catalyst design.
使用可见光生成的Ru(bpy)对(TAML)Fe配合物进行光化学氧化，会产生价互变异构体(TAML)Fe( )和(TAML˙)Fe( )，这取决于外源阴离子。不稳定的Cl或Br的存在会导致基于配体的氧化，并使自由基阳离子(TAML˙)Fe配合物稳定，随后导致前所未有的C-H活化，接着在TAML芳环上发生亲核取代。相比之下，外源氰化物会导致基于金属的氧化，产生第一个经晶体学表征的 = 1 [(TAML)Fe(CN)]物种的例子。这是一份关于光化学获得的高价(TAML)Fe体系中阴离子依赖性价互变异构的罕见报告，在污染物、碳氢化合物和水的氧化方面具有潜在应用。此外，(TAML˙)Fe介导的亲核芳香卤化反应代表了高价金属反应性的一个新领域，并突出了在高氧化条件下可能的分子内配体或底物修饰途径。因此，我们的研究结果揭示了基于TAMLs和其他潜在非无辜配体的高价金属氧化剂，并为氧化催化剂设计开辟了新途径。
