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Syntheses, Structures, and Spectroscopic Properties of Cobalt(III) Complexes Containing 3‐ or 4‐Pyridyl‐Substituted Nitronyl and Imino Nitroxide Ligands
Author(s) -
Ogita Masahiro,
Yamamoto Youhei,
Suzuki Takayoshi,
Kaizaki Sumio
Publication year - 2002
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 - 10.1002/1099-0682(200203)2002:4<886::aid-ejic886>3.0.co;2-z
Subject(s) - chemistry , unpaired electron , moiety , cobalt , radical , nitroxide mediated radical polymerization , crystallography , substituent , methanol , stereochemistry , photochemistry , medicinal chemistry , inorganic chemistry , organic chemistry , polymer , radical polymerization , copolymer
Abstract Several new cobalt(III) complexes incorporating 4,4,5,5‐tetramethyl‐2‐(3‐ or 4‐pyridyl)imidazolin‐1‐oxyl 3‐oxide (NIT n py) ( n = 3 or 4) or 4,4,5,5‐tetramethyl‐2‐(3‐ or 4‐pyridyl)imidazolin‐1‐oxyl (IM n py) have been prepared. The X‐ray crystallographic analyses and the spectroscopic investigations have revealed that the nitronyl or imino nitroxides with the radical character are bound through the pyridyl‐N atom to a Co III center. There are some influences from the radical unpaired electron toward the Co III complex moiety and those from the coordination of the Co III ion toward the nature of these radicals which can be detected by 59 Co NMR and UV/Vis spectroscopy. Such observed changes coincide with the proposed spin density on the N atom of the pyridyl substituent. Furthermore, it was found that trans ‐[Co(acac) 2 (PPh 3 )(NIT4py)] + in methanol was gradually converted into the corresponding IM4py complex, while free NIT4py is stable in methanol. The Co II species formed on the partial decomposition of the NIT4py complex in methanol seems to catalyze the deoxygenation of NIT4py to IM4py.