Fundamental studies to emerging applications of pyrrole-BF₂ (BOPHY) fluorophores

Abstract

This review highlights the up-and-coming pyrrole-BF2 (BOPHY) fluorophores, with a focus on synthetic procedures, photophysical properties – including structure–property analyses – as well as emerging applications.

A Family of Highly Fluorescent and Membrane-Permeable Bis(BF2) Acyl-Pyridinylhydrazine Dyes with Strong Solid-State Emission and Large Stokes Shifts: The BOAPH Fluorophores

“…Among the various fluorophores, bright tetracoordinate boron-containing dyes are of great current interest because the electron-deficient boron endows them with superior tunable electronic and photophysical properties owing to building structural rigidity. − Whereas lots of boranes such as well-known boron dipyrromethene (BODIPY, Figure ) dyes are highly fluorescent in solution, most of them tend to show weak fluorescence in solid states due to self-absorption, which limits their applications. − Recently, bis­(BF 2 ) chromophores as BODIPY analogues, which often have low LUMO energy levels and excellent photostability due to the attached electron-deficient BF 2 groups, have received much attention. − One such popular fluorophore is the recently developed BOPHY (Figure ). The potential of BOPHY as a novel platform was immediately realized, and its derivatives have been used in a range of applications spanning from bioimaging, probes, solar cells, energy-transfer cascades to photocatalyst. − …”

2-(4-(Dimethylamino)phenyl)-3,3-difluoro-4,6-diphenyl-3,4-dihydro-1,2,4,5,3-tetrazaborinin-2-ium-3-ide

“…Various boron chelates are some of the most common fluorophores, finding widespread practical application in bioimaging [1], as molecular reporters and chemodosimeters [2,3], in sensors [4][5][6], in optoelectronic applications [7][8][9] and others. The most studied are BODIPY 1 [10][11][12] and their structural analogs 2 [13], BOPHY 3 [14], boron difluoride 1,3-diketonates 4 [15] and 1,3-ketoiminates 5 [16]. Difluoroboron derivatives of different types of hydrazones 6 [17], such as N-acylhydrazones 7 [18] and azohydrazones (formazanes) 8 [19] (Figure 1), are also of interest and are being extensively studied at the present time.…”

Synthesis and Spectroscopic Properties of 1,2,3-Triazole BOPAHY Dyes and Their Water-Soluble Triazolium Salts

“…Among them, boron dipyrromethene (BODIPY 1 ) dyes are the most successful due to their tunable photophysical properties. , The success of BODIPY dyes has led to increasing research into novel boron-centered fluorophores. Ziegler et al disclosed BOPHY 2 , a doubly BF 2 -centered fluorescent chromophore with remarkable spectroscopic properties. − Since then, several new double BF 2 coordinated dyes have been introduced. , In recent years, BOIMPY 3 has gained some interest as double BF 2 -coordinated red-emissive and NIR dyes . Recently, our group and Hao’s group independently disclosed bis­(difluoroboron) pyrrole acylhydrazones (BOPAHY 4 ) (Figure ).…”