Synthesis of bis-BN-Naphthalene-Fused Oxepins and Their Photoluminescence Including White-Light Emission

A series of novel
bis-BN-naphthalene-fused oxepin derivatives were
synthesized via a Pd-catalyzed tandem reaction from brominated 2,1-borazaronaphthalenes
and cis-bis­(boryl)­alkenes. X-ray crystallographic analysis revealed
that bis-BN-naphthalene-fused oxepins feature a planar framework.
The electronic and photophysical properties of the novel BN-naphthalene-fused
oxepins were investigated by UV–vis and fluorescence spectroscopies
and density functional theory (DFT) calculations, which disclosed
the distinct electronic and photophysical properties of the analogous
hydrocarbon system. Interestingly, dual-fluorescent emissions were
observed upon dissolving N-substituted derivatives 10–14 in dimethyl sulfoxide. Tunable emission colors
especially for white-light emissions can be achieved by controlling
the ratio of solvents, concentration, or temperature using only a
single-molecule compound.