π-Extension of Isoindigos (IIDs) through C—H/N—H Activation and Alkyne Annulation†

Abstract

Isoindigo (IID) is widely used as organic dye and conjugated unit in opto-electronic materials. Functionalization of IID to increase its structural complexity is demanding for obtaining diversity properties. Herein, we developed a direct C—H/N—H activation method of IIDs via double alkyne annulations and synthesized π-extended IIDs with two pairs of 5/7 membered rings. The structure of the π-extended IIDs was characterized and confirmed by 1H NMR, 13C NMR, HRMS and X ray crystal analysis. Their physical properties were characterized by UV-vis absorption, cyclic voltammetry and thermogravimetric analysis. The absorption coefficient of the annulated products enhanced significantly compared with the non-annulated analogue. (Figure presented.).