Near‐IR Electrochromic Dihydroindolo(2,3a)carbazole‐Based Macrocycles and Their [b]‐Annulated BODIPY Complexes

Abstract A new class of redox‐active dihydroindolo(2,3a)carbazole( InC )‐based porphyrin‐like macrocycles (thiophene embedded: InCT and p –phenylene embedded: InCB ) and the corresponding [b]‐annulated BODIPY complexes ( InCT BF 2 and InCB BF 2 ) are reported. A facile synthetic methodology is adopted to accomplish the new expanded‐porphyrin‐like macrocyclic systems using the key precursor 11 based on 11,12‐dihydroindolo(2,3a)carbazole building block 4 . In these macrocyclic systems, the subunit 4 is deemed to be a donor and an azafulvene‐extended with π ‐conjugated fragment (thiophene or p ‐phenylene) acts as an acceptor. Single crystal X‐ray structures are obtained for both InCT and InCB . Spectroelectrochemical studies on these macrocycles and their BF 2 complexes display intriguing near‐IR electrochromic properties with reversible multi‐color switching upon cathodic scans at room temperature. InCT BF 2 shows high stability with a radical comproportionation constant ( K c ) of 1.22 × 10 6 . Thiophene and p ‐phenylene subunits in InCT and InCB exhibit ring rotation at room temperature as evident from NMR studies. Such ring rotation is restricted upon BF 2 complexation, and they show unusual stability in acidic conditions.