(Z)‑1,2-Di(1-pyrenyl)disilene: Synthesis, Structure, and Intramolecular Charge-Transfer Emission

(Z)-1,2-Di­(1-pyrenyl)­disilene containing bulky 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl (Eind) groups has been obtained as purple crystals by the reductive coupling reaction of the corresponding dibromosilane with lithium naphthalenide. An X-ray crystallographic analysis revealed an Eind- and pyrenyl-meshed molecular gear around the disilene core adopting the Z configuration, in which the two pyrenyl groups intramolecularly interact through the π–π stacking with a distance of 3.635 Å between the centers of the two pyrene rings. The disilene π-system exhibits a π­(Si–Si) → π*­(pyrene) intramolecular charge-transfer (ICT) fluorescence at room temperature, whose wavelengths depend on the solvent polarity. The photophysical properties are theoretically supported by computational studies including excited-state calculations.