The first example of a novel fluoranthene-embedded; doubly fused expanded porphyrin was synthesized via a [3 + 2] condensation of a newly synthesized fluoranthene-based tripyrrane with a readily available bithiophene diol in CH₂Cl₂; under mild acid-catalyzed conditions and an inert atmosphere at room temperature; followed by DDQ oxidation in open air.

Abstract

The first example of a novel fluoranthene-embedded doubly fused expanded porphyrin was synthesized by [3 + 2] condensation of newly synthesized fluoranthene-based tripyrrane with readily available bithiophene diol in CH₂Cl₂ under mild acid-catalyzed inert atmosphere conditions at room temperature, followed by DDQ oxidation in open air. 1D and 2D NMR spectroscopy and MALDI-TOF analysis indicated that the two thiophene rings of the bithiophene moiety were inverted and the inner C's of the two inverted thiophene rings were involved in bond formation with adjacent pyrrole N's to generate two fused tripentacyclic rings as a part of macrocyclic framework. DFT optimized structure revealed that the macrocycle was highly contorted and adopted saddle-like structure and the fluoranthene unit in the macrocycle was deviated by an angle of 58.34° with respect to the “mean plane” defined by four meso-carbons. The macrocycle showed broad and ill-defined absorption bands in the 300–750 nm region and electrochemical studies revealed that the macrocycle was easier to oxidize, indicating the electron-rich nature of the fluoranthene embedded doubly fused expanded porphyrin. DFT/TD-DFT studies were in agreement with the experimental observations.