Synthesis and their property of fluorene-phenyls conjugated molecules containing ferrocene

Conjugated compounds with ferrocene as the side group (6), in the backbone (7) and as the end groups (8) were synthesized by Suzuki coupling reaction. The chemical structures of these compounds were verified by NMR and MS. The fluorescence of 6, 7 and 8 in THF were strongly quenched by ferrocene via an intramolecular photoinduced electron transfer (PET) process. However, adding oxidant such as dilute solution of KMnO₄ a.q. into the solution of 6, 7 and 8, respectively, the fluorescent intensity of these compounds were increased and can be up to 75 times. The fluorescence amplification and response time to oxidant were affected by the position and numbers of ferrocene in these conjugated compounds. The results show that fluorescence enhancement is linear with concentration of oxidant and rapidly responds to oxidant when one ferrocene exists in conjugated structures. Response time becomes slow and fluorescence enhancement is quadratic with concentration of oxidant when there are two ferrocenes in one conjugated molecule.