Design, synthesis and photophysical properties of novel star-shaped truxene-based heterocycles utilizing ring-closing metathesis, Clauson-Kaas, Van Leusen and Ullmann-type reactions as key tools.

Shakeel Alvi,Rashid Ali

doi:10.3762/bjoc.17.96

Abstract

Design, synthesis and properties of polycyclic aromatic hydrocarbons (PAHs) has historically attracted a considerable interdisciplinary interest from both fundamental as well as applied viewpoint on account of their wonderful optoelectronic properties. The scientific interest in two-dimensional star-shaped PAHs particularly in truxene architectures arises because of their high thermal stability, exceptional solubility and ease with which they can be constructed and modified. Therefore, bearing in mind a wide range of applications of truxene and its congeners, herein we reveal three novel distinctly different routes for the generation of C3-symmetric pyrrole-based truxene architectures by means of cyclotrimerization, ring-closing metathesis (RCM), Clauson–Kaas and Ullmann-type coupling reactions as key steps. Moreover, we have also assembled some other interesting heterocyclic systems possessing oxazole, imidazole, benzimidazole, and benzoxazole in the framework of truxene. Additionally, the preliminary photophysical properties (absorption and emission) for these versatile systems has been revealed.

Highlights

The two-dimensional phenylene-based π-conjugated star-shaped architectures has recently attracted a tremendous attention of the researchers across the globe because of their inimitable physiochemical properties, processability and availability [1,2,3,4]
The heptacyclic truxene scaffold possessing three overlapping fluorene units and its congeners are of archetypal interest due to their potential applications ranging from organic thin‐film transistors (OTFTs), Beilstein J
Bearing in mind the importance of the truxene framework, we report diverse C3-symmetric heterocyclic systems possessing the truxene scaffold in their structures by means of cyclotrimerization, ring-closing metathesis, Ullmann-type coupling, Clauson–Kaas, and Van Leusen reactions as crucial transformations

Summary

Introduction

The two-dimensional phenylene-based π-conjugated star-shaped architectures has recently attracted a tremendous attention of the researchers across the globe because of their inimitable physiochemical properties, processability and availability [1,2,3,4]. Compared to the π-conjugated one-dimensional rodshaped architectures, two-dimensional star-shaped systems hold, superior solubility, improve morphological, optical, electrical and film-forming properties because of the involvement of extra dimensionality. Organic light-emitting diodes (OLEDs), dye‐sensitized solar cells (DSSCs), fluorescent probes, organic photovoltaics (OPVs) to the high hole mobility semiconductors, blue lightemitting materials, nonlinear optical materials and so forth [5,6,7]. The high fluorescence quantum yield as well as the excellent photoluminescence quantum efficiency in addition to extraordinary thermal stability are the most significant characteristics of these systems

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Results

Conclusion