Blue‐LED Self‐Assembly‐Assisted Synthesis of New Photostable Organoboron Esters for Live‐Cell Imaging

Abstract

In this work, we report a blue‐LED self‐assembly‐assisted synthesis of novel emissive organoboron esters, achieved in just 30 minutes with quantitative yields. The molecular structure in solution (characterized by ¹H and ¹¹B NMR, and mass spectrometry) was further confirmed via X‐ray molecular diffraction analysis for compound 3, where the boron ion adopts a distorted tetrahedral geometry. The photophysical properties of these molecules were analyzed in solution, revealing that 1, featuring tert‐butyl groups and boron heterocycles with a nitro‐substituent, exhibits superior photostability compared to its derivatives. Photobleaching values showed an inverse correlation with the oxidation potentials of compounds 1–3, except for 4, used as a reference. Mass spectrometry further revealed greater energetic stability of the molecular ion of 1. Notably, compound 3 demonstrated good solubility, high photostability, and adequate biocompatibility, making it a promising fluorescent dye for biomedical applications. Cytotoxicity assays in HEK‐293 cells across different concentrations confirmed its non‐toxic nature. Theoretical calculations further supported the high chemical stability of all compounds, attributing it to a synergistic interaction between electronic and steric effects, which protect the fluorophores by substitution of Schiff bases and formation of boron heterocycles. Additionally, 3 exhibited strong, non‐hazardous blue fluorescence when tested on HEK‐293 and MDA‐MB‐231 cells.