Data Sheet 1_Copper complexes containing o-phenylenediamine-based pentadentate ligands catalyze TEMPO-mediated alcohol oxidation.pdf

A set of o-phenylenediamine-based pentadentate ligands having pyridine and quinoline binding sites was prepared in this work. The weak metal-binding abilities of anilinic nitrogen atoms and rigid chelate structure of the o-phenylenediamine skeleton serve as unique metal coordination properties of the ligand library presented herein. In addition to variations in the pyridine and quinoline binding sites, the non-coordinating alkyl groups (CH3 or CH2Ph) in the ligand structure cause significant differences in the coordination structures of copper(II) complexes. In the aerobic alcohol oxidation reaction in the presence of CuBr and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), the ligand donating fewer electrons, namely, N-benzyl-N,N’,N’-tris(2-quinolylmethyl)-1,2-phenylenediamine (Bn-TQPHEN, L4), exhibited greater activity than N-methyl-N,N’,N’-tris(2-pyridylmethyl)-1,2-phenylenediamine (Me-TPPHEN, L1). Thus, the present study proposes future directions for the utilization of pentadentate ligands and their relevance to redox-active copper metalloenzymes.