Benzimidazolium salts with 1,4-dihydro-naphtho[1,8-ef]-1,4-diazepine: Synthesis, structure and recognition for copper(II) ion

Article abstract of DOI:10.1016/j.dyepig.2016.12.018

Two new benzimidazolium salts with the same cationic moiety and different anionic moieties 2-[2′-(N-benzyl-benzimidazoliumyl)]-1,4-dihydro-naphtho[1,8-ef]-1,4-diazepine bromide (1) and 2-[2′-(N-benzyl-benzimidazoliumyl)]-1,4-dihydro-naphtho[1,8-ef]-1,4-diazepine hexafluorophosphate (2) were prepared and characterized. The structure of 1 was determined by X-ray single crystal diffraction and ¹H NMR and ¹³C NMR spectroscopy. Selective recognition of 2 for cations (Li⁺, Na⁺, K⁺, NH₄⁺, Ag⁺, Ca²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cr³⁺, Cd²⁺, Al³⁺, Pb²⁺, Hg⁺ and Hg²⁺, and use of their nitrate salts) was investigated by fluorescence and UV/vis titrations in C₂H₅OH/H₂O (v:v?=?1:1) at 25?°C. The response of 2 to Cu²⁺ can be observed through both remarkable fluorescence enhancement and color change under sunlight (from yellow to red). The results indicated that 2 can distinguish Cu²⁺ from other cations via the instrument and naked eyes, and this is greatly convenient in practical operation.