1-Azaazulene: A Ligand Moiety for Boron Difluoride (BF) Complexes To Achieve Long-Wavelength Absorption.

1-Azaazulene was adopted as a new ligand moiety for boron difluoride (BF) complexes, resulting in large red shifts of the absorption bands up to 103 nm compared to their isomeric quinoline-based complexes. Such change was attributed to the nonalternant nature of 1-azaazulene, as the complexes maintained the intrinsic 10π-peripheral electronic structure. exhibited the most red-shifted absorption among reported BF complexes containing a phenolic backbone, and the absorption edge of reached the red region.