Development of a Class of Easily Scalable, Electron-Deficient, Core-Extended Benzo-Fused Azadipyrromethene Derivatives

We have developed a new synthetic strategy for the preparation of a series of isoindolin-1-imines and isoindolin-1-ones from aromatic ketones and phthalonitrile. Self-condensation reactions of these isoindolin-1-imines led to the formation of a novel class of benzo-fused, highly electron-deficient core-extended azadipyrromethene chromophores (“MB-DIPY”). The influence of temperature, catalyst, and the template ions, on the self-condensation reaction rate, yield, and stereoselectivity, was examined in detail. New chromophores (sodium, zinc, and metal-free compounds) were characterized by NMR, UV-Vis, fluorescence, high-resolution mass spectroscopies, and in many cases, X-ray crystallography. Their redox properties were probed by electrochemical and spectroelectrochemical approaches that revealed the remarkable electron-accepting nature of the new systems. Stepwise one- and two-electron reduction of the new MB-DIPYs and their zinc complexes was investigated by spectroscopic and spectroelectro-chemical metho...