Ionoactive Imines – 1-R-benzimidazol-2-amine Derivatives

A new benzimidazole-based selective and sensitive 'on-off' fluorescence chemosensor for Cu2+ ions and application in cellular bioimaging

Two new twinborn benzimidazole derivates (L and A), which bonded pyridine via the ester space on the opposite and adjacent positions of the benzene ring of benzimidazole respectively, were designed and synthesized. Compound L displayed fluorescence quenching response only towards copper(II) ions (Cu²⁺ ) in acetonitrile solution with high selectivity and sensitivity. However, compound A presented 'on-off' fluorescence response towards a wide range of metal ions to different degrees and did not have selectivity. Furthermore, compound L formed a 1:1 complex with Cu²⁺ and the binding constant between sensor L and Cu²⁺ was high at 6.02 × 10⁴  M^-1 . Job's plot, mass spectra, IR spectra, ¹ H-NMR titration and density functional theory (DFT) calculations demonstrated the formation of a 1:1 complex between L and Cu²⁺ . Chemosensor L displayed a low limit of detection (3.05 × 10^-6  M) and fast response time (15 s) to Cu²⁺ . The Stern-Volmer analysis illustrated that the fluorescence quenching agreed with the static quenching mode. In addition, the obvious difference of L within HepG2 cells in the presence and absence of Cu²⁺ indicated L had the recognition capability for Cu²⁺ in living cells.

A new high selective and sensitive turn-on fluorescent and ratiometric absorption chemosensor for Cu2+ based on benzimidazole in aqueous solution and its application in live cell

A new benzimidazole base turn-on fluorescent and ratiometric absorption chemosensor (L) bearing bidentate ligand for detection of Cu²⁺ was designed and synthesized. Fluorescence and UV-vis spectra studies demonstrated that L can detect Cu²⁺ ions in aqueous solution using fluorescence enhancement and ratiometric absorption sensing over a wide pH range. Both fluorescent and ratiometric absorption sensing of L for Cu²⁺ possessed high selectivity and sensitivity over other competitive metal ions and had low detection limit. Job's plot, mass spectra and DFT calculation indicated the sensing mechanism is the complex formation between L and Cu²⁺ with 1:2 stoichiometry. Fluorescence images of HepG2 in the absence and presence of Cu²⁺ displayed L had cell permeability and detection ability for Cu²⁺ in live cells.