Readily Accessible, Versatile, and Adaptive Biaxially Chiral Chromophores

Abstract

Precisely controlling quantum states is relevant in next-generation quantum computing, encryption, and sensing. Chiral organic chromophores host unique light–matter interactions, which allow them to manipulate the quantized circular polarization of photons. Axially chiral organic scaffolds, such as helicenes or twisted acenes, are powerful motifs in chiral light manipulation. However, these systems usually require complex syntheses and small-scale (10 mg) enantiomer separations, typically complicating systematic investigations of their structure–property relationships. We report here the straightforward synthesis of both enantiomers (R/S) of 10 different axially chiral chromophores. This protocol relies on a readily accessible, enantiomerically pure, and axially chiral contorting element, benzodinaptho[1,4]dioxicine-2,3-diamine (DODA), that we synthesize in two steps with high purity and good yield at gram scale. Subsequent derivation of DODA transfers the chirality from one axis to twist the dominant chromophore around a second, orthogonal axis. Using this biaxial contortion design element, we produce 10 enantiopure biaxial chromophores, without the need for chromatographic separations, and no observable compromise to chiroptical integrity. These chromophores exhibit broadband single-handed absorption without Cotton effects from 265 to 485 nm, indicating chiral excitonic character that forms between the DODA and twisted core chromophore. This platform is responsive to solvent polarity in the excited state, displaying >50 nm bathochromic shifts in the photoluminescence spectra. In addition, this scaffold intensely interacts with changes in pH, which allows us to ultimately access monosignate circular dichroism absorption over a 300 nm range.