Anomalous Effect of Intramolecular Charge Transfer on the Light Emitting Properties of BODIPY

Abstract

A new way to approaching highly emissive BODIPY dyes in both solution and solid state is achieved by introducing intramolecular charge transfer (ICT). A hybrid excited state that shows behaviors of both the ICT excited state and local excited state is discovered to be beneficial in avoiding the disturbance from the rotation vibration of the flexible phenyl substituents. Thus, the nonradiative transition process is suppressed, and the fluorescence efficiency goes up. By modification of the excited state, we realize emission enhancement of crystalline BODIPY derivatives with a PLQY from 0.08 to 0.27, and the compound expresses a good potential application prospect in organic semiconductors.

Solid‐State Emission from Mono‐ and Bichromophoric Boron Dipyrromethene (BODIPY) Derivatives and Comparison with Fluid Solution

“…The radiative rate constant ( k RAD =Φ F /τ S =1×10 8 s −1 ) is in good agreement with that ( k SB =1.3×10 8 s −1 ) calculated from the Strickler–Berg expression . Of the literature reports referring to fluorescence from related B‐aryl BODIPY fluorophores, two describe strong emission in fluid solution but a third details weak fluorescence at room temperature . This latter report mentions that emission is recovered in a frozen glass at 77 K.…”

“…As reported for a related compound by Gao et al., 2 is strongly fluorescent in an optical glass at 80 K. Indeed, in 2‐methyltetrahydrofuran (MTHF), which forms a hard glass below 100 K, the fluorescence yield depends markedly on temperature (Figure ). At 80 K, Φ F approaches unity while τ S has a value of 6.5±0.1 ns.…”

“…Loss of fluorescence for 2 is clearly a consequence of the aryl rings appended to the boron centre; the same is true for 3 (Table ). The absence of a polarity effect suggests that intramolecular charge transfer is not responsible for fluorescence quenching . There is, however, a small recovery of emission on increasing the viscosity of the solvent (Figure S19).…”

“…[29] Of the literature reportsr eferring to fluorescencef rom relatedB -aryl BODIPYf luorophores, two describe strong emission in fluid solution [25,30] but at hird details weak fluorescence at room temperature. [31] This latter report mentionst hat emission is recovered in af rozen glass at 77 K.…”

An Intramolecular Charge Transfer and Aggregation Induced Emission Enhancement Fluorescent Probe Based on 2‐Phenyl‐1,2,3‐triazole for Highly Selective and Sensitive Detection of Homocysteine and Its Application in Living Cells

“…It was found that APTC has excellent optical properties such as aggregation‐induced emission enhancement (AIEE) and intramolecular charge transfer (ICT) due to its D‐π‐A structure. It meant that APTC not only was more conducive to fluorescence imaging in living cells, but also had potential applications in many fields such as OLEDs, stimuli‐responsive smart materials and organic semiconductors …”