Models for Nonheme Iron Intermediates: Structural Basis for Tuning the Spin States of Fe(TPA) Complexes

Autor:	Lawrence Que, Jinheung Kim, Elizabeth C. Wilkinson, Evan H. Appelman, Yanhong Dong, Yan Zang
Rok vydání:	1997
Předmět:	Ionic radius Spin states Chemistry Stereochemistry Substituent General Chemistry Tris(2-pyridylmethyl)amine Biochemistry Redox Catalysis law.invention chemistry.chemical_compound Crystallography Colloid and Surface Chemistry law Proton NMR Amine gas treating Electron paramagnetic resonance
Zdroj:	Journal of the American Chemical Society. 119:4197-4205
ISSN:	1520-5126 0002-7863
DOI:	10.1021/ja9638521
Popis:	Our efforts to model the oxygen activation chemistry of nonheme iron enzymes have yielded transient intermediates with novel properties. These properties can be dramatically affected by the introduction of a 6-methyl substituent on the pendant pyridines of the tetradentate ligand TPA (TPA = tris(2-pyridylmethyl)amine). A series of Fe(TPA) complexes has thus been synthesized and characterized to provide the structural basis for these dramatic effects. The following complexes have been obtained: [Fe(L)(CH3CN)2](ClO4)2 (1, L = TPA; 2, L = 6-MeTPA; 3, L = 6-Me2TPA; 4, L = 6-Me3TPA) and [Fe(L)(acac)](ClO4)2 (5, L = TPA; 6, L = 5-Me3TPA; 7, L = 6-MeTPA). As indicated by 1H NMR and/or EPR, 1, 5, and 6 with no 6-methyl substituent are low spin, while complexes 2, 3, 4, and 7 with at least one 6-methyl substituent are all high spin, with higher redox potentials than their low-spin counterparts. The ligands with 6-methyl substituents thus favor a metal center with a larger ionic radius, i.e., FeII over FeIII and h...
Databáze:	OpenAIRE
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