AIE‐Active Difluoroboron Complexes with N,O‐Bidentate Ligands: Rapid Construction by Copper‐Catalyzed C−H Activation

Abstract

The development of organic materials with high solid-state luminescence efficiency is highly desirable because of their fundamental importance and applicability in optoelectronics. Herein, a rapid construction of novel BF 2 complexes with N,O-bidentate ligands by using Cu(BF 4 ) 2 •6H 2 O as a catalyst and BF 2 source is disclosed, which avoids the need for pre-composing the N,O-bidentate ligands and features a broad substrate scope and a high tolerance level for sensitive functional groups. Moreover, molecular oxygen is employed as the terminal oxidant in this transformation. A library of 36 compounds as a new class of BF 2 complexes with remarkable photophysical properties is delivered in good to excellent yields, showing a substituent-dependency on the photophysical properties, derived from the -* character of the photoexcited state. In addition, aggregation-induced emission (AIE) is observed and quantified for the brightest exemplars. The excited state properties are fully investigated in solids and in THF/H 2 O mixtures. Hence, a new series of photofunctional materials with variable photophysical properties is reported, with potential applications for sensing, bioimaging, and optoelectronics.

Recent advances in the synthesis of luminescent tetra-coordinated boron compounds

“…Quinazolinone based BF 2 compounds of the framework 165 with various substituents on the phenolate ring also showed the AIEE phenomenon. 168 Naphthyridine 140,164 and pyrimidine 158 based BF 2 compounds were synthesized and studied for their potential applications in biochemistry (166)(167)(168)(169). N,O-chelated naphthyridine based boron compounds 166 and 167 were studied as probes for the detection of phosphate ions.…”

“…The type of aryl group, spacers and mode of coordination had influence on the photophysical properties of the resultant products. 135–169 The Lu group 142,149 synthesized N,O-chelated BF 2 compounds 138–142 (Fig. 17).…”

Asymmetric Core‐Expanded BOPYOs: Facile Synthesis and Optical Properties

“…Fluorophores BODIPY, BOPHY, BOPPY and boranil, etc., which contain NÀ BÀ N, OÀ BÀ O or NÀ BÀ O bridges have been widely investigated because of their outstanding photophysical properties such as tunable emission, high fluorescent quantum yields, and high stability. [1][2][3][4][5][6][7][8][9] Unlike conventional N,N and O,Obidentate organic boron complexes, N,O-bidentate boron complexes, which can be prepared by B-coordination using the ligands 2-(pyridin-2-yl)phenol and its analogues, have only been developed in recent years. The low-symmetry or asymmetric structure of these N,O-bidentate boron complexes gives them unique photophysical properties such as a relatively large Stokes shift, [10][11][12][13][14][15][16][17][18][19] strong emission in solution and/or solid, [14,16,17,[20][21][22][23][24][25][26][27][28][29] NIR absorption and emission, [20,30,31] and anion sensing.…”

“…The first example (Scheme 1 (3-4)) was obtained accidentally in 2008 by condensation and coordination approaches based on imidazolinones and pyrrole-2-carboxaldehyde. [34] The second one, which was synthesized from ortho-hydroxylated substrates and pyrrole in one step (Scheme 1 (5)(6)), is applied as a probe for detecting H + and F À ions. [35] The last one was prepared by condensation, oxidation and coordination reactions from aldehydes and pyrrole (Scheme 1 (7)(8)(9)).…”

“…Fluorophores BODIPY, BOPHY, BOPPY and boranil, etc., which contain N−B−N, O−B−O or N−B−O bridges have been widely investigated because of their outstanding photophysical properties such as tunable emission, high fluorescent quantum yields, and high stability [1–9] . Unlike conventional N,N and O,O‐bidentate organic boron complexes, N,O‐bidentate boron complexes, which can be prepared by B‐coordination using the ligands 2‐(pyridin‐2‐yl)phenol and its analogues, have only been developed in recent years.…”