| Abstract
| - A series of phenoxyl radical complexes of zinc(II) have beengenerated in solution and, in one instance,isolated as solid material (5) in order to study theirspectroscopic features by EPR, resonance Raman, andUV−visspectroscopy. They serve as model complexes for the active form ofthe copper containing fungal enzyme galactoseoxidase. The complexes[Zn(L1H2)]BF4·H2O(1),[Zn(L2H2)]BF4·H2O(2), [Zn(L2H)] (2a),[Zn(L3)(Ph2acac)](3),[Zn(L4)(Ph2acac)] (4),and [Zn(L4)(Me-acac)] (6) weresynthesized from solutions ofZn(BF4)2·4H2O andthecorresponding ligand (L1H3 =1,4,7-tris(3,5-tert-butyl-2-hydroxybenzyl)-1,4,7-triazacyclononane;L2H3 = 1,4,7-tris(3-tert-butyl-5-methoxy-2-hydroxybenzyl)-1,4,7-triazacyclononane;L3H =1,4-dimethyl-7-(3,5-di-tert-butyl-2-hydroxybenzyl)-1,4,7-triazacyclononane; L4H =1,4-dimethyl-7-(3-tert-butyl-5-methoxy-2-hydroxybenzyl)-1,4,7-triazacyclononane, Ph2acac- =1,3-diphenyl-1,3-propanedionate, and Me-acac- =3-methyl-2,4-pentanedionate).Complexes 2, 3·0.5toluene·1n-hexane, and 4 were structurallycharacterized by single-crystal X-ray crystallography.An electrochemical investigation of these complexes inCH3CN and/or CH2Cl2solution revealed that the coordinatedphenolate ligands undergo reversible one-electron oxidations withformation of coordinated phenoxyl radicals.Synthetically, the microcrystalline, paramagnetic(μeff = 1.7 μB), solid material of[Zn(L4)(Ph2acac)]PF6(5) wasproduced by one electron oxidation of 4 by 1 equiv offerrocenium hexafluorophosphate in dryCH2Cl2. Oxidationof coordinated phenol pendent arms in 1, 2, and2a occurs at significantly higher potentials and isirreversible.Electronic (UV−vis), electron paramagnetic resonance (EPR), andresonance Raman (RR) spectra of the radicalshave been studied in solution and allow the description of theelectronic structure of these coordinated phenoxylradical complexes.
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