10.1021/jo048489s.s001 Shunji Ito Shunji Ito Takahiro Kubo Takahiro Kubo Noboru Morita Noboru Morita Tadaaki Ikoma Tadaaki Ikoma Shozo Tero-Kubota Shozo Tero-Kubota Jun Kawakami Jun Kawakami Akio Tajiri Akio Tajiri Azulene-Substituted Aromatic Amines. Synthesis and Amphoteric Redox Behavior of <i>N</i>,<i>N</i>-Di(6-azulenyl)-<i>p</i>-toluidine and <i>N</i>,<i>N</i>,<i>N</i>‘,<i>N</i>‘-Tetra(6-azulenyl)-<i>p</i>-phenylenediamine and Their Derivatives American Chemical Society 2005 dianion diradicals compound amine 1 b azulenyl amphoteric redox materials UV phenylenediamine absorption maxima amines diamine 2 b exhibit electrochemical oxidation species nm Di Amphoteric Redox Behavior toluidine ESR anion radicals electrochemical reduction 2005-03-18 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Azulene_Substituted_Aromatic_Amines_Synthesis_and_Amphoteric_Redox_Behavior_of_i_N_i_i_N_i_Di_6_azulenyl_i_p_i_toluidine_and_i_N_i_i_N_i_i_N_i_i_N_i_Tetra_6_azulenyl_i_p_i_phenylenediamine_and_Their_Derivatives/3295825 <i>N</i>,<i>N</i>-Di(6-azulenyl)-<i>p</i>-toluidine (<b>1a</b>) and <i>N</i>,<i>N</i>,<i>N</i>‘,<i>N</i>‘-tetra(6-azulenyl)-<i>p</i>-phenylenediamine (<b>2a</b>) and their derivatives with 1,3-bis(ethoxycarbonyl) substituents on each 6-azulenyl group (<b>1b</b> and <b>2b</b>) were prepared by Pd-catalyzed amine azulenylation and characterized as a study into new aromatic amines for multistage amphoteric redox materials. The redox behavior of each compound was characterized by cyclic voltammetry. These compounds undergo facile reduction to stable anion radicals and dianion diradicals owing to the resonance stabilization between the 6-azulenyl groups and exhibit electrochemical oxidation depending on the amine subunits. The ESR measurement of anion radicals and a dianion diradical generated by the electrochemical reduction of amine <b>1b</b> and diamine <b>2b</b> revealed that the unpaired electron of these radicals delocalizes over the entire azulene ring including the central nitrogen atoms. UV−vis spectral analysis of amines <b>1a</b>,<b>b</b> and diamines <b>2a</b>,<b>b</b>, taken during the electrochemical reduction, exhibited a gradual decrease of the absorption bands of the neutral species along with an increase of the new absorption maxima at 625, 605, 640, and 610 nm, respectively, with the development of well-defined isosbestic points at 502, 562, 478, and 545 nm, respectively. As indicated by a combined ESR and UV−vis spectral study, the species giving rise to the new absorption maxima are concluded to be the generation of anion radicals and dianion diradicals of aromatic amines and diamines with high thermodynamic stability.