Small Figure-Eight Luminophores: Double-Twisted Tethered Cyclic Binaphthyls Boost Circularly Polarized Luminescence.

Double-twisted cyclic binaphthyls, in which two naphthalenes are tethered by -O(CH2 )n O- linkage (n=1-3), have been synthesized. X-ray analyses and DFT calculations revealed a tightly constrained stereogenic figure-eight geometry. Tethering of two naphthalenes by short linkage forces a small dihedral angle, and the cyclic binaphthyls with short tether (n=1, 2) exhibit remarkable boosting of the glum value (1.0-1.6×10-2 ) in circularly polarized luminescence (CPL) and unusual glum /gabs ratios (0.93-1.3). These experimental high |glum | values are in accord with the results of excited state TD-DFT calculations, which show transannular interactions and that consequent extensive delocalization occurs throughout the figure-eight π-core. As a result, the present figure-eight luminophore promote the elongation of the magnetic transition dipole moment that results in significant increases in glum values.