A novel fluorescent 2,2′-bipyridine derivative prepared by coupling to a fluorescent aminophenazine – fluorescence properties and response toward various cations

Abstract

2,2′-Bipyridine (bpy), a non-fluorescent but good metal-chelating unit, and 2-aminophenazine (2-aphz), a good fluorescent unit, are integrated to give 7-aminodipyrido[3,2-a∶2′,3′-c]phenazine (7-amino-dppz) 1. Compound 1 exhibits an efficient fluorescence at 517 nm (Φ = 0.24, dichloromethane), which is similar to the parent 2-aphz. It is suggested that the orbitals involved in the photoexcitation process are mostly localized on the phenazine unit. However, addition of divalent metal ions such as Mg²⁺, Ca²⁺ and Cu²⁺ causes a noticeable fluorescence response, which is attributed to coordination of these cations to the bpy chelation site of 1. This behaviour indicates that sufficient electronic communication exists between the bpy chelation site and the phenazine fluorophore. 7-(4-tert-Butylbenzoylamino)dppz 2 also showed a fluorescence response towards divalent metal ions.