Air-Stable Spirofluorene-Containing Ladder-Type Bis(alkynyl)borane Compounds with Readily Tunable Full Color Emission Properties

A series of air-stable spiro-fused ladder-type boron(III) compounds has been designed, synthesized, and the electrochemistry and photophysical behavior have been characterized. By simply varying the substituents on the pyridine ring and extending the p-conjugation of the spiro framework, the emission color of these compounds can be easily fine-tuned spanning the visible spectrum from blue to red. All compounds exhibit a broad and structureless emission band across the entire visible region, assigned as an intramolecular charge-transfer transition originating from the thiophene of the spiro framework to the pyridine-borane moieties. In addition, these compounds demonstrate high photoluminescence quantum yields of up to 0.81 in dichloromethane solution and 0.86 in doped thin films. Some of the compounds have also been employed as emissive materials, in which solution-processed organic light-emitting devices (OLEDs) with tunable emission colors spanning the visible spectrum from blue, green to red have been realized, demonstrating the potential applications of these boron compounds in OLEDs.