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Linear free‐energy relationships in semiquinone species and their Mn(II) and Cu(II) complexes
Author(s) -
Sloop Joseph C.,
Shultz David A.,
Marcus Mithra Beikmohamadi,
Shepler Benjamin
Publication year - 2012
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1878
Subject(s) - semiquinone , chemistry , metal , transition metal , ligand (biochemistry) , free energy relationship , coupling constant , linear relationship , hyperfine structure , linear correlation , photochemistry , quinone , crystallography , computational chemistry , stereochemistry , atomic physics , reaction rate constant , organic chemistry , kinetics , catalysis , biochemistry , physics , receptor , statistics , mathematics , particle physics , quantum mechanics
Linear free‐energy relationships for a series of functionalized semiquinone ligands and their Mn II ‐ and Cu II hydro‐tris(3‐cumenyl‐5‐methylpyrazolyl) borate complexes were examined. Quinone–semiquinone cycle half‐wave reduction potentials and semiquinone hydrogen hyperfine coupling constants (a H ) were determined and their correlation with Hammett σ parameters reported. A new σ parameter, σ aH , has been proposed. Mn II and Cu II metal complex metal–ligand charge transfer and n → π* UV transitions were found to be modulated by substituents. Satisfactory Hammett correlations between UV transitions and various σ values have been determined and compared in a number of instances. Copyright © 2011 John Wiley & Sons, Ltd.