Reaction of Amines with 8‐MethylthioBODIPY: Dramatic Optical and Laser Response to Amine Substitution

Abstract

A thorough study of the photophysical and laser properties of 8-aminoboron dipyrromethene dyes was undertaken to determine the role of amine substitution and spatial disposition on the properties of the dyes. It was found that the fluorescent and laser response varied significantly. Although primary amines give rise to highly fluorescent products at the blue edge of the visible region, secondary amines yield nonfluorescent analogues in polar media. The crystal structures of two analogues are reported and described. Steric hindrance and the higher electron-releasing ability of the amine favor the formation of a quenching intramolecular charge-transfer state. Accordingly, boron dipyrromethene derivatives with primary amines exhibited laser emission with efficiencies of up to 44%. Besides, the more efficient derivative was also the most photostable, leading to a significant improvement in the lasing performance with regard to previously reported 8-aminoboron dipyrromethene derivatives. An increase in the solvent polarity, and mainly the presence of tertiary cyclic amines, led to a dramatic decrease or even the loss of the laser action.

Exploring BODIPY Derivatives as Singlet Oxygen Photosensitizers for PDT

“…100 nm) when compared with related 8‐(methylthio)BODIPY 17 , in agreement with the Hammett σ ‐parameter of the groups located at position 8 ( σ p + = −1.81 for NHMe and σ p + = −0.60 for SMe) (76). This effect is mainly attributed to the high contribution of a hemicyanine‐like BODIPY structure in the case of the aminated derivatives (78‐80). Indeed, the higher the electron‐donor capacity of the amine is, the higher the blueshift is, as it is shown by BODIPY 14 with a methyl group ( σ p + = −0.31) involved in the 8‐(methylamino) moiety, in comparison with a propargyl one (with lower electron‐donor strength; σ p + = +0.18) involved in the 8‐(propargylamino) group of BODIPY 15 (Table 1).…”

Toward Prediction of Nonradiative Decay Pathways in Organic Compounds II: Two Internal Conversion Channels in BODIPYs

“…All these molecules are selected from reliable spectroscopic and photophysical studies reported by experimental researchers. 22,24,26,27,29,30,34,35,37,40,45,50,51,59,[62][63][64][65]67 We present the identities of X 1 through X 8 , λ abs , and λ fl of these molecules (compounds 1 through 100) in Tables S1 and S2, their E abs , E fl , and | µ fl | in Tables S3 and S4, and their k fl , k nr , and Φ fl in Tables S5 and S6.…”

“…[127][128][129][130] For BODIPY we follow the experimental evidence that only one of the S 1 → S 0 and S 1 → S 2 (or L a → L b ) ICs is fast enough to be observed, being at least two orders of magnitude faster than any other nonradiative channel. 9,12, 22,24,26,27,29,30,35,42,46,47,50,51,62,64,66,67,[100][101][102]110,152,163 As a result,…”

“…Possible IC channels include the most common relaxation to the ground state (S 1 → S 0 ), the photoinduced isomerization (S 1 → S 1 /S 0 ), and the intramolecular charge transfer (ICT) reaction from a bright donating state to a dark accepting state (S 1 → S 2 or L a → L b ). 9,12, 22,24,26,27,29,30,35,42,46,47,50,51,62,64,66,67,[100][101][102]110,152,163 In the following sections, we will show that all three IC mechanisms are available in BODIPY, also depending on the substituents. Based on sufficient experimental data, our proposed model allows us to predict k fl , k nr , and Φ fl to the desired accuracy, validating its ability in the planned machine learning aided design of BODIPY.…”

“…Unfortunately, this treatment is still expensive given the large size of BODIPY and the multireference character of the far-from-equilibrium molecular configurations. 29,31,37,40,43,45,50,51,54,55,62,70,76,79,85,[87][88][89]91,93,95,98,101,[106][107][108][109]111,[113][114][115][116][117][118][119][120][121][122][123][124][125][126] To further reduce the computational cost, our group proposed and constructed an alternative approach by using a data-driven, semi-empirical model based on a combination of inexpensive quantum chemical calculations and experimental spectroscopic data. 127 Herein we focus on the prediction of a key photophysical quantity, the fluorescence quantum yield (Φ fl ), which is defined as [128][129][130] Φ fl = # of photons emitted # of photons absorbed ,…”