Synthesis and properties of fluorescent 4′-azulenyl-functionalized 2,2′:6′,2″-terpyridines

• Main Authors: Adrian E. Ion, Liliana Cristian, Mariana Voicescu, Masroor Bangesh, Augustin M. Madalan, Daniela Bala, Constantin Mihailciuc, Simona Nica
• Format: Article
• Language: English
• Published: Beilstein-Institut 2016-08-01
• Series: Beilstein Journal of Organic Chemistry
• Subjects: azulene; fluorescence; metal binding; synthesis; terpyridine
• Online Access: https://doi.org/10.3762/bjoc.12.171

4′-Azulenyl-substituted terpyridines were efficiently synthesized following the Kröhnke methodology via azulenylchalcone intermediates. These azulenyl-containing terpyridines showed fluorescent emission with a fluorescence quantum yield varying from 0.14, in the case of parent terpyridine, to 0.64 when methyl groups are grafted on the azulenyl seven-membered ring. According to the crystal structures and TDDFT calculations, different twisting of the aromatic constituents is responsible for the observed fluorescent behavior. The electrochemical profile contains one-electron oxidation/reduction steps, which can only be explained on the basis of the redox behavior of the azulene unit. The ability of the 4′-azulenyl 2,2′:6′,2″-terpyridine to bind poisoning metal cations was studied by UV–vis titrations using aqueous solutions of Hg(II) and Cd(II) chlorides as illustrative examples.