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)nO‐ 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. A series of figure‐eight‐shaped cyclic naphthalenes with different tethers were synthesized, and their CPL properties were investigated. Compounds with short tether showed remarkable boosting of the glum (0.010–0.016). The proximate figure‐eight luminophore promotes elongation of the magnetic transition dipole moment that results in significant increases in glum.