Highly Fluorescent Bipyrrole‐Based Tetra‐BF₂ Flag‐Hinge Chromophores: Achieving Multicolor and Circularly Polarized Luminescence

Abstract

This study reports the facile syntheses of tetra‐boron difluoride (tetra‐BF2) complexes, flag‐hinge‐like molecules that exhibit intense green‐to‐orange luminescence in solution and yellow‐to‐red emission in the solid states. Single‐crystal structure analysis and density functional theory calculations suggested a bent structure of this series of compounds. The complexes also exhibited excellent optical properties, with quantum yields reaching 100 % and a large Stokes shift. These properties were attributed to the altered bending angle of the molecule in the S1 excited state. As the rotational motion was suppressed around the 2,2′‐bipyrrole axis, atropisomers with axial chirality were formed, which are optically resolvable into (R) and (S)‐enantiomers through a chiral column. The atropisomers thus function as circularly polarized luminescent (CPL) materials, in which the color (green, green‐yellow, and yellow) can be varied by controlling the aggregation state. This rational design of multi‐BF2 complexes can potentially realize novel photofunctional materials.

Recent Advances in Highly Fluorescent Hydrazine-Inserted Pyrrole-Based Diboron-Anchoring Fluorophores: Synthesis and Properties

“…Owing to the important advantages discussed above, asymmetric bisboron-anchoring BOPPY chromophores quickly attracted attention because of their advantageous photophysical properties and their promising framework as building blocks and functional materials. 47 48 49 50 For example, in 2022, Ono and co-workers 47 reported a new family of BOPPY dimers as flag-hinge chromophores; these were synthesized from premodified diformyl-2,2′-bipyrroles, and showed good multicolor and circularly polarized emission. Shen and co-workers 48 developed B–O–B-bridged BOPPY dimers by reacting 3,5-dimethylpyrrole-2-carbaldehyde with 2,3-dihydrazinoquinoxaline, with subsequent boron complexation.…”

Solvent-dependent dual emission processes in charge-transfer excited states of phenothiazine-triphenyltriazine conformers

“…TA spectroscopy TA spectra were measured by the pump-probe method [20][21][22]. For a probe pulse, we generated a white light pulse by focusing the signal light (1200 nm) from another OPA (Light Conversion, TOPAS-Prime) on a sapphire crystal (3 mm thickness).…”

Highly efficient luminescence from boron β-dialdiminates and their π-conjugated polymers in both solutions and solids: significant impact of the substituent position on luminescence behavior

“…Four-coordinated boron complexes, as represented by boron dipyrromethene (BODIPY) derivatives, have attracted tremendous attention because of their efficient luminescence, tunability of functionality, and extensive applicability. 6 Recently, a growing number of studies have reported a wide variety of fourcoordinated boron complexes with advantageous properties, [7][8][9][10][11] involving AIE, 12 stimuli-responsive luminescence, 13 thermally activated delayed fluorescence, 14 circularly polarized luminescence, 15,16 and near-infrared emission. 17 We have also developed luminescent b-diiminate boron complexes which provide the AIE-and CIE-active molecules, polymers, [18][19][20] and chromic luminescent materials.…”