Wharton Stuart I, Henry John B, McNab Hamish, Mount Andrew R
School of Chemistry, The University of Edinburgh, The Joseph Black Building, King's Buldings, West Mains Road, Edinburgh EH9 3JJ, UK.
Chemistry. 2009;15(22):5482-90. doi: 10.1002/chem.200900097.
Indolo[3,2,1-jk]carbazole (IC) has been synthesised on a gram scale by flash vacuum pyrolysis. In contrast to a previous suggestion, IC is planar and it is also highly fluorescent, with a solution quantum yield of 0.41. Electro-oxidation of IC at a rotating disc electrode resulted in the passage of steady-state currents and the reproducible formation of conducting, redox-active films with constituent species that are also highly fluorescent. Unusually for coupled electroactive N-heterocyclic systems, electrochemical and spectroscopic characterisation revealed the film to consist exclusively of three redox-active (2,2', 5,5' and 2,5' coupled) IC dimers with no polymeric products. Calculations showed this coupling pattern to be consistent with IC radical-cation coupling through the accessible sites of highest unpaired electron density. The unusual combination of a high dimer second oxidation potential and a negligible dimer-dimer coupling rate explains the lack of further coupling. The identities of the dimeric species were confirmed by independent syntheses involving the Suzuki-Miyaura coupling of IC boronic acids as the key step. Electro-oxidation of the IC system therefore offers a ready route to novel conducting, redox-active molecular films and their redox-active, luminescent dimer constituents.
吲哚并[3,2,1-jk]咔唑（IC）已通过快速真空热解以克级规模合成。与之前的观点相反，IC是平面的，并且还具有高荧光性，溶液量子产率为0.41。在旋转圆盘电极上对IC进行电氧化导致了稳态电流的通过以及具有同样具有高荧光性的组成物种的导电、氧化还原活性膜的可重现形成。对于耦合电活性N-杂环体系而言不同寻常的是，电化学和光谱表征表明该膜仅由三种氧化还原活性（2,2'、5,5'和2,5'耦合）的IC二聚体组成，没有聚合物产物。计算表明这种耦合模式与通过最高未配对电子密度的可及位点进行的IC自由基阳离子耦合一致。高二聚体第二氧化电位和可忽略不计的二聚体-二聚体耦合速率的异常组合解释了缺乏进一步耦合的原因。通过以IC硼酸的铃木-宫浦耦合为关键步骤的独立合成，证实了二聚体物种的身份。因此，IC体系的电氧化为制备新型导电、氧化还原活性分子膜及其氧化还原活性、发光二聚体成分提供了一条便捷途径。
