Azobenzene Probes For Metal Ions: Molecular Design, Synthesis And Spectroscopic Properties

A series of novel fluorescent probes for metal ions with different receptors were designed and synthesized based on the azobenzene.The UV-visible and fluorescence properties of azobenzene derivatives with non-fluorescent groups in the receptors were investigated. O, N and S atoms were introduced into the receptors respectively as a ligand of metal ions. The cis/trans ratios of these compounds under irradiation of a high-pressure Hg-lamp equipped with a color filter (λ<360 nm), as well as and the effects of metal ions on photoisomerization were studied. The probe A6 was designed to exhibit selectivity to Cu²⁺.Two novel fluorescent probes (C1 and C2) with a receptor containing anthracene group were designed and synthesized for recognition of heavy metal ions. It was found that C1 and C2 show a pronounced fluorescence enhancement response to Hg²⁺, respectively. TheÏ€electrons of the azobenzene probes exhibit photoinduced electron transfer (PET) effects to the fluorescent anthracene group as well as atom S, which was firstly reported in this paper. C4 was designed based on the above studies and it has higher selectivity to Hg²⁺ than C1 and C2.The naphthyl group was also introduced to the azobenzene derivatives connected with 1,3-bis(methylthio)propane and N,N'-dimethylpropane-1,3-diamine, respectively. The fluorescent probe E2 show fluorescence enhancement response to Cu²⁺. The mechanism of this selectivity was proposed with the aid of computational chemistry (program of GAUSSIAN 03).