Ferrocenyl Chalcone with 2-Anthracenyl Group (2-Anth-C(O)CH=CHFc): Electrochemical and Fluorescent Properties

Scheme 1. Some ferrocenyl chalcones bearing polycyclic aromatic hydrocarbon fluorophores Ferrocenyl chalcones (Fc-Ar, Fc-C(O)CH=CHAr and Ar-Fc, Ar-C(O)CH=CHFc), in which ferrocenyl (Fc) and aromatic (Ar) groups are linked by an enone bridge (-CH=CHC(O)-), are versatile compounds exhibiting antiplasmodial and antitumor activities, fluorescent and electrochemical properties, and molecular chemosensor activity. Ferrocenyl chalcones bearing the fluorophores such as 2-naphthalene, 9-anthracene, 1-pyrene, and N-ethyl carbazole, are regarded as good candidates for new fluorescent material (Scheme 1). However, ferrocenyl chalcones containing 9-anthracene and 2-naphthalene derivatives have been reported as being not fluorescent, while those containing 1-pyrene and N-ethyl carbazole derivatives are fluorescent. It means that the ferrocenyl group, known as an effective quencher of exited states, is therefore not the only reason why they are non-fluorescent. Some derivatization of fluorophores can also disable fluorescence, as demonstrated by 2acetylanthracene being fluorescent while 9-acetylanthracene is not. In this study, a ferrocenyl chalcone with a 2-anthracenyl group (2-Anth-C(O)CH=CHFc, 2Anth-Fc), an analogue of 9Anth-Fc, was prepared. Unlike 9Anth-Fc, 2Anth-Fc is fluorescent and its fluorescence was investigated in relation to its solvent’s polarity. Its electrochemical properties were also studied and the local geometry of 2Anth-Fc is suggested from H NMR results.