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.