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Radicals of Free and Zinc(II)‐Coordinated α‐Azophenols
Author(s) -
Kochem Amélie,
Orio Maylis,
Philouze Christian,
Jamet Hélène,
du Moulinet d'Hardemare Amaury,
Thomas Fabrice
Publication year - 2011
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201001011
Subject(s) - chemistry , electron paramagnetic resonance , zinc , radical , redox , delocalized electron , excited state , electrochemistry , density functional theory , schiff base , ligand (biochemistry) , photochemistry , crystallography , inorganic chemistry , computational chemistry , nuclear magnetic resonance , organic chemistry , electrode , biochemistry , physics , receptor , nuclear physics
The tridentate 2‐ tert ‐butyl‐4‐methoxy‐6‐(quinolin‐8‐ylazo)phenol ligand HL has been synthesized and structurally characterized. Its redox activity has been investigated by electrochemical measurements and DFT calculations. Oxidation of HL (irreversible process) affords primarily a hydrogen‐bonded phenoxyl radical, whereas its reduction affords an iminosemiquinonate radical species. The reaction of two equivalents of HL with Zn(OAc) 2 affords the zinc complex Zn(L) 2 , which has been structurally characterized. Its oxidation is easier than that of HL and is reversible. The EPR spectrum of [Zn(L)(L · )] + shows an unresolved ( S = 1/2) signal at g = 2.005, while [Zn(L · )] 2+ exhibits spin triplet resonances (| D | = 0.0118 cm –1 and E / D = 0). The extra delocalization of spin density on the azo group contributes to a lowering of the D value relative to those of Schiff base derivatives. The temperature dependence of the EPR signal and DFT calculations reveal an excited state for the spin triplet and a weak exchange coupling constant J = –2.73 cm –1 .