B2N2-Doped Dibenzo[a,m]Rubicene: Modular Synthesis, Properties, and Coordination-Induced Color Tunability

B2N2-doped dibenzo[a,m]rubicene (B2N2-DBR) and derivatives possessing two B-N units C-2h-symmetrically on two edges are synthesized on a multigram scale via a two-step modular synthetic route using commercially available indole, aldehyde, and dichloroborane. Photophysical and electrochemical properties, crystal packing, and the reactivity of B2N2-DBR have been investigated. B2N2-DBR showed a larger optical gap and hence blue-shifted absorption and emission with a larger fluorescence quantum yield (Phi = 0.88) and a much smaller Stokes shift than its all-carbon analogue (DBR, Phi = 0.25). The blue-emissive B2N2-DBR derivatives are stable under ambient conditions against water and air but sensitive to nucleophiles such as fluoride and pyridine. B2N2-DBR reversibly interacts with a fluoride ion to bathochromically shift its emission with retention of a high fluorescence quantum yield, while coordination with pyridine quenches its photoluminescence. The marked changes in luminescence properties and optical gap on interaction with a Lewis base along with good chemical stability suggest the application of B2N2-DBR derivatives in colorimetric chemo- and biosensors.

Automated summary

B2N2-DBR and its derivatives were successfully synthesized using a two-step modular synthetic route, showing blue emission with a higher fluorescence quantum yield and stability against water and air but sensitivity to fluoride and pyridine. Interaction with fluoride resulted in a bathochromic shift of emission with retention of high fluorescence quantum yield, while coordination with pyridine quenched its photoluminescence.