Generation, Isolation, and Characterization of N-(Arylthio)-7-tert-butyl- and N-(Arylthio)-2,7-di-tert-butyl-1-pyrenylaminyl Radicals

Article abstract of DOI:10.1021/jo00091a015

N-(Arylthio)-7-tert-butyl-1-pyrenylaminyl (2) and N-<(4-nitrophenyl)thio>-2,7-di-tert-butyl-1-pyrenylaminyl radicals (3) are prepared by PbO2 oxidation of N-(arylthio)-7-tert-butyl-1-aminopyrenes and N-<(4-nitrophenyl)thio>-2,7-di-tert-butyl-1-aminopyrene, respectively, and studied by ESR and ENDOR spectroscopy.The kinetic ESR study shows that, while aminyls 2 gradually decompose in solution at room temperature, aminyl 3 is quite persistent, even in refluxing benzene, and shows no tendency to dimerize, even at low temperatures.These interesting properties of 3 permit us to isolate 3 as radical crystals in 28-31percent yield.The hyperfine splitting (hfs) constants of 2 and 3, determined by ESR and ENDOR spectroscopic methods, show an extensive delocalization of the unpaired electron onto the pyrene ring.Comparison of the hfs constants of 2 and 3 shows that a more extensive delocalization of the spin into the pyrene ring takes place in 3.This is accounted for in terms of the difference in the conformations of 2 and 3.