BOPAM: Efficient Synthesis of a Bright Asymmetric Bis-Boron Complex and its Dark Side

A new family of unsymmetrical boron chromophores chelated with two BF2 units, named BOPAM, has been developed via a one-pot, three-step reaction starting from commercially available thioamides via i) conversion to amidrazones, ii) condensation with pyrrole aldehydes, and iii) boron chelation. This synthetic pathway has been proven to be highly efficient, having a broad substrate tolerance and giving the BOPAM products high yield. Notably, some of the BOPAM dyes show interesting photophysical properties with fluorescence quantum yields up to 0.98 in toluene. A fine-tuning of their emissive properties has been attained through tailored molecular design strategies guided by in-depth computational investigations. Tailored substitution with electron-donating groups at the BOPAM ring leads to the opening of a non-radiative decay channel involving a dark state and consequently a significant quenching of the fluorescence. The study is complemented by exhaustive steady-state and time-resolved spectroscopic measurements. Novel asymmetrical bisboron pyrrole amidrazone complexes (BOPAM) are developed through a one-pot, three-step reaction, offering an efficient method for constructing functional BOPAM dyes. The approach, using readily available starting materials, demonstrates excellent functional group tolerance. Moreover, the paper highlights how tailored molecular design, informed by thorough computational investigations, allows precise tuning of their emissive properties.image

Automated summary

A new family of unsymmetrical boron chromophores, BOPAM, has been developed through a one-pot, three-step reaction with high efficiency and broad substrate tolerance. Some of the BOPAM dyes exhibit interesting photophysical properties with fluorescence quantum yields up to 0.98 in toluene. Tailored molecular design guided by computational investigations allows precise tuning of their emissive properties.