Diboron-Incorporated Indenofluorene: Isolation of Crystalline Neutral and Reduced States of 6,12-Diboraindeno[1,2-<i>b</i>]fluorene
Bi Youan E. Tra, Yujie Zhao, Andrew Molino, Yifu Ouyang, Chun‐Lin Deng, Colleen McAloon, Noah D. McMillion, Heechan Kim, Chonghe Zhang, Péter Müller, Robert G. Griffin, Robert J. Gilliard
Abstract
The synthesis and redox transformations of 6,12-diboraindeno[1,2- b ]fluorene (DBIF)─a pentacyclic π-system with diboron incorporation─are reported. In notable contrast to the all-hydrocarbon indenofluorenes, a ligand coordination and reduction strategy allows tuning of the electronic structure across four redox states. Accordingly, we introduce an 18π e – neutral DBIF, a 20π e – diradical, a 21π e – radical anion, and a 22π e – dianion, all of which have been isolated and structurally authenticated. The diradicals exhibit diradical character of up to 77% and possess open-shell singlet ground states with thermally accessible triplet states.