Bright and bold: Exploring the photophysical properties of push-pull Bimanes

Researchers have recently shown a great interest in the design, synthesis, and use of novel π-conjugated molecules in materials science.^1,2 One type of such molecules, known as push-pull chromophores, feature an electron-donor (D) and an electron-acceptor (A) linked by a π-conjugated system, resulting in intramolecular charge transfer (ICT). The unique properties of push-pull chromophores, including their intense color, dipolar character, electrochemical behavior, crystallinity, intermolecular interactions (π-stacking), and nonlinear optical (NLO) properties, stem from the D-A interaction and the creation of a new low-energy molecular orbital. Push-pull chromophores are versatile and have found applications in various fields.
Recent research by our group, in collaboration with Prof. Levine's lab, has focused on synthesizing and investigating the photophysical properties of a series of novel bimanes as sensors for external analytes.^3–7 Bimanes, with linear extended π-conjugated structures, have the potential to be an excellent scaffold for push-pull chromophores.
Previous studies have shown that N-alkylated or N-unsubstituted bimanes exhibit strong and distinct solvatochromism, making them effective probes for determining solvent polarity, studying solvent effects, and measuring pH.
In this study, we have developed and investigated several push-pull bimane chromophores (1-6) featuring an N,N-dimethylamine group as a donor and three different acceptor groups (-CF₃, -CHO, -NO₂). The synthesis and photophysical properties of these push-pull bimanes will be reported. Overall, our study highlights the potential of push-pull bimane chromophores as effective alternatives to traditional chromophores, paving the way for their utilization in a wide range of applications in materials science and beyond.