EPR Studies on Carboxylic Esters, 22 [1, 2]. Preparation of New Alkyl Azulenecarboxylates and EPR-spectroscopic Study of Their Radical Anions

Abstract

Five regio-isomeric alkyl azulenecarboxylates were prepared. Additional substituents such as tertbutyl groups or deuterium were introduced in certain positions of the azulene skeleton in order to facilitate the assignment of the proton hyperfine structure (hfs) coupling constants of the EPR spectra. The electrochemical behavior of the esters was studied by means of differential pulse polarography and cyclovoltammetry. In-situ electroreduction of the azulenecarboxylic esters led to the corresponding radical anions, the EPR spectra of which were recorded. The spin density distribution in these non-alternant systems as determined from hfs coupling constants was compared with the results of MO calculations and discussed with respect to the influence of substituents.