Experimental and theoretical studies of the redox potentials of cyclic nitroxides.
The redox potentials of 25 cyclic nitroxides from four different structural classes (pyrrolidine, piperidine, isoindoline, and azaphenalene) were determined experimentally by cyclic voltammetry in acetonitrile, and also via high-level ab initio molecular orbital calculations. It is shown that the potentials are influenced by the type of ring system, ring substituents and/or groups surrounding the radical moiety. For the pyrrolidine, piperidine, and isoindolines there is excellent agreement (mean absolute deviation of 0.05 V) between the calculated and experimental oxidation potentials; for the azaphenalenes, however, there is an extraordinary discrepancy (mean absolute deviation of 0.60 V), implying that their one-electron oxidation might involve additional processes not considered in the theoretical calculations. This recently developed azaphenalene class of nitroxide represents a new variant of a nitroxide ring fused to an aromatic system and details of the synthesis of five derivatives involving differing aryl substitution are also presented.
Blinco
James P
JP
Australian Research Council Centre of Excellence for Free Radical Chemistry and Biotechnology, School of Physical and Chemical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland, 4001, Australia.
Hodgson
Jennifer L
JL
Morrow
Benjamin J
BJ
Walker
James R
JR
Will
Geoffrey D
GD
Coote
Michelle L
ML
Bottle
Steven E
SE
D000097:Acetonitriles / Q000737:chemistry; D000465:Algorithms; D001372:Aza Compounds / Q000737:chemistry; D003497:Cyclic N-Oxides / Q000737:chemistry*; D004563:Electrochemistry; D054833:Isoindoles / Q000737:chemistry; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D010880:Piperidines / Q000737:chemistry; D011759:Pyrrolidines / Q000737:chemistry
D000097:Acetonitriles; D001372:Aza Compounds; D003497:Cyclic N-Oxides; D054833:Isoindoles; D010880:Piperidines; D011759:Pyrrolidines; C032727:piperidine; C032519:pyrrolidine; C032159:acetonitrile