Issue 32, 2021

Rationalizing the effect of benzo-fusion at [a] and [b] positions of BODIPY on fluorescence yields

Abstract

The origin of the large difference of fluorescence yields between benzo[a] and benzo[b] BODIPY derivatives was investigated. The benzo[a]-BODIPY chromophore shows high fluorescence yields while the totally quenched fluorescence of benzo[b]-BODIPYs is observed. Quantum calculations indicated that larger spin–orbit coupling (SOC) and smaller singlet–triplet energy gaps result in non-fluorescence for benzo[b]-BODIPY. Benzo[b]-fusion makes a partial contribution to the HOMO but a full contribution to the HOMO−1, and thus the S1 → S0 and T2 → S0 transitions, involved in HOMO–LUMO and HOMO−1–LUMO, have different characteristics, which leads to spin flipping for intersystem crossing (ISC) and increases the SOC to 1.70 cm−1. However, benzo[a] contributes to HOMO and HOMO−1 equally, and minimizes the SOC between S1 and T2, leading to slow ISC from S1, thus possessing strong fluorescence. These results are useful for the rational design of heavy-atom-free triplet organic chromophores.

Graphical abstract: Rationalizing the effect of benzo-fusion at [a] and [b] positions of BODIPY on fluorescence yields

Supplementary files

Article information

Article type
Paper
Submitted
12 Jul 2021
Accepted
16 Jul 2021
First published
19 Jul 2021

Phys. Chem. Chem. Phys., 2021,23, 17402-17407

Rationalizing the effect of benzo-fusion at [a] and [b] positions of BODIPY on fluorescence yields

N. Xu, Y. Xiao, Z. Ni, L. Gai, Z. Zhou and H. Lu, Phys. Chem. Chem. Phys., 2021, 23, 17402 DOI: 10.1039/D1CP03160K

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