Facile approach to benzo[d]imidazole-pyrrolo[1,2-a]pyrazine hybrid structures through double cyclodehydration and aromatization and their unique optical properties with blue emission.

Gi Hun Bae,Na Keum Lee,Ikyon Kim,Jeong Hwa Lee,Suzi Kim,Anuradha Dagar,Jeeyeon Lee

doi:10.1039/d0ra01140a

Abstract

A modular approach to polycyclic N-fused heteroaromatics is described. Acid-catalyzed reactions of various 1-(2-oxo-2-arylethyl)-1H-pyrrole-2-carbaldehydes with several o-phenylenediamines provided facile access to a number of new benzo[d]imidazole-pyrrolo[1,2-a]pyrazine hybrid structures through double cyclodehydration and aromatization. Optical characterization of the synthesized compounds revealed unique emission properties, with deep blue emission in the aggregated and solid states, and a dramatic substituent effect was observed. Fusion of an additional benzene ring into the benzo[4,5]imidazo[1,2-a]pyrrolo[2,1-c]pyrazine scaffold resulted in a remarkable increase in the intensity of blue fluorescence from the solution along with good cell permeability and negligible phototoxicity, indicating the potential for bioimaging applications.

Highlights

Novel organic uorophores are critical tools in biomedical research and play an important role in disease diagnosis and bioimaging applications.1–4 Due to the detrimental aggregationcaused quenching (ACQ) effects of conventional uorophores, various approaches to achieve stable and efficient emission have been explored.5,6 Along this line, aggregation-induced emission (AIE) and aggregation-induced emission enhancement (AIEE) have drawn much attention recently, as dramatic enhancements of emission in the aggregated or solid state have been observed.7–9 AIE luminogens have shown the potential to prevent quenching at high concentrations or in the solid state, practical issues remain, such as solubility and cell permeability, which need to be overcome to facilitate practical applications, in various bioassays.6 the AIE effect has challenged our current understanding of the photophysical properties of photoluminescence
Blue or deep-blue emissive materials are valuable in organic lightemitting diodes (OLEDs), but good blue or deep-blue emitters (AIEgens) are still rare due to their wide energy gaps
We were pleased to nd that desired product 8a was obtained in 80% yield by initial treatment of 5a and o-phenylenediamine in TFA/DMSO at room temperature for 8 h followed by warming at 65 C for an additional 3 h

Summary

Introduction

Novel organic uorophores are critical tools in biomedical research and play an important role in disease diagnosis and bioimaging applications.1–4 Due to the detrimental aggregationcaused quenching (ACQ) effects of conventional uorophores, various approaches to achieve stable and efficient emission have been explored.5,6 Along this line, aggregation-induced emission (AIE) and aggregation-induced emission enhancement (AIEE) have drawn much attention recently, as dramatic enhancements of emission in the aggregated or solid state have been observed.7–9 AIE luminogens have shown the potential to prevent quenching at high concentrations or in the solid state, practical issues remain, such as solubility and cell permeability, which need to be overcome to facilitate practical applications, in various bioassays.6 the AIE effect has challenged our current understanding of the photophysical properties of photoluminescence.

Results

Conclusion