Photodissociative Modules that Control Dual-Emission Properties in Donor-π-Acceptor Organoborane Fluorophores

Donor-pi-acceptor fluorophores that consist of an electron-donating amino group and an electron-accepting triarylborane moiety generally exhibit substantial solvatochromism in their fluorescence while retaining high fluorescence quantum yields even in polar media. Herein, we report a new family of this compound class, which bears ortho-P(=X)R-2-substituted phenyl groups (X=O or S) as a photodissociative module. The P=X moiety that intramolecularly coordinates to the boron atom undergoes dissociation in the excited state, giving rise to dual emission from the corresponding tetra- and tricoordinate boron species. The susceptibility of the systems to photodissociation depends on the coordination ability of the P=O and P=S moieties, whereby the latter facilitates dissociation. The intensity ratios of the dual emission bands are sensitive to environmental parameters, including temperature, solution polarity, and the viscosity of the medium. Moreover, precise tuning of the P(=X)R-2 group and the electron-donating amino moiety led to single-molecule white emission in solution.

Automated summary

A new class of donor-pi-acceptor fluorophores with ortho-P(=X)R-2-substituted phenyl groups (X=O or S) as a photodissociation module is reported. The P=X moiety coordinates to the boron atom and undergoes dissociation in the excited state, resulting in dual emission from tetra- and tricoordinate boron species. The intensity ratios of the dual emission bands are sensitive to environmental parameters and single-molecule white emission can be achieved by precise tuning of the P(=X)R-2 group and the electron-donating amino moiety in solution.