Synthesis and Properties of 1‐(Dialkylstannyl)‐1,4‐diphenyl‐1,3‐butadiene Fused with a Dibenzobarrelene and the Corresponding Pentaorganostannate

Abstract

Abstract1‐(Dialkylstannyl)‐1,4‐diphenyl‐1,3‐butadiene derivatives that fuse with a dibenzobarrelene were synthesized by the reaction of the dilithium salt, prepared by the treatment of the corresponding tellurium analogue with BuLi, with R2SnCl2 (R=Me or Bu). When Me2SnCl2 was used, a Me−Bu exchange (Bu is from BuLi) was observed. The dimethyl‐, butylmethyl‐, and dibutylstannyl derivatives exhibit weak fluorescence in solution and the solid state. The dibutylstannyl derivative reacted with BuLi in THF to give a pentaorganostannate, which was characterized by means of 119Sn NMR and UV‐vis spectroscopies. Their optical properties were analyzed with TD‐DFT calculations. The first excitation of dialkylstannyl derivatives is assigned to the π‐π* excitation, and an intersystem crossing from the relaxed S1 state to a triplet state was suggested. The calculations show that the dark red color of the pentaorganostannate is ascribed to the excitation from the hypervalent Sn−C bonds (σ) to the π* orbital of the 1,4‐diphenyl‐1,3‐butadiene moiety.