Golden Age of Fluorenylidene Phosphaalkenes–Synthesis, Structures, and Optical Properties of Heteroaromatic Derivatives and Their Gold Complexes

The
substitution of 2,7-dibromo-9-fluorenyl phosphaalkenes with
heteroaromatic substituents (bithiophene, benzothiophene, pyridine)
offers access to interesting push–pull dye molecules. Steric
shielding due to the bulky P-substituent gives marked different reactivities
at the 2- and 7-positions, allowing the synthesis of mixed/asymmetric
derivatives. Further functionalization via gold­(I) coordination was
demonstrated and increased the acceptor character, concomitant with
a red-shifted absorption.