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Oxidative Catalysis by TAMLs: Obtaining Rate Constants for Non‐Absorbing Targets by UV‐Vis Spectroscopy
Author(s) -
Somasundar Yogesh,
Lu Iris C.,
Mills Matthew R.,
Qian Lisa Y.,
Olivares Ximena,
Ryabov Alexander D.,
Collins Terrence J.
Publication year - 2020
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.202000222
Subject(s) - catalysis , spectroscopy , oxidative phosphorylation , ultraviolet visible spectroscopy , chemistry , reaction rate constant , photochemistry , kinetics , organic chemistry , physics , biochemistry , quantum mechanics
Abstract Understanding the catalysis of oxidative reactions by TAML activators of peroxides, i. e. iron(III) complexes of tetraamide macrocyclic ligands, advocated a spectrophotometric procedure for quantifying the catalytic activity of TAMLs for colorless targets ( k II ′, M −1 s −1 ), which is incomparably more advantageous in terms of time, cost, energy, and ecology than NMR, HPLC, UPLC, GC‐MS and other similar techniques. Dyes Orange II or Safranin O (S) are catalytically bleached by non‐excessive amount of H 2 O 2 in the presence of colorless substrates (S 1 ) according to the rate law: − d [S]/ dt = k I k II [H 2 O 2 ][S][TAML]/( k I [H 2 O 2 ]+ k II [S]+ k II ′[S 1 ]). The bleaching rate is thus a descending hyperbolic function of S 1 : v = ab /( b +[S 1 ]). Values of k II ′ found from a and b for phenol and propranolol with commonly used TAML [Fe III { o , o ′‐C 6 H 4 ( N CO N Me 2 CO) 2 CMe 2 } 2 (OH 2 )] + are consistent with those for S 1 (phenol, propranolol) obtained directly by UPLC. The study sends vital messages to enzymologists and environmentalists.