A hexa-quinoline basedC₃-symmetric chemosensor for dual sensing of zinc(ii) and PPi in an aqueous mediumviachelation induced “OFF–ON–OFF” emission

Abstract

A quinoline-based C3-symmetric fluorescent probe (1), N,N',N''-((2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene))tris(1-(quinolin-2-yl)-N-(quinolin-2-ylmethyl)methanamine), has been developed which can selectively detect Zn2+ without the interference of Cd2+via significant enhancement in emission intensity (fluorescence "turn-ON") associated with distinct fluorescence colour changes and very low detection limits (35.60 × 10-9 M in acetonitrile and 29.45 × 10-8 M in 50% aqueous buffer (10 mM HEPES, pH = 7.4) acetonitrile media). Importantly, this sensor is operative with a broad pH window (pH 4-10). The sensing phenomenon has been duly studied through UV-vis, steady-state, and time-resolved fluorescence spectroscopic methods indicating 1 : 3 stoichiometric binding between 1 and Zn2+ which is further corroborated by 1H NMR studies. Density functional theoretical (DFT) calculations provide the optimized molecular geometry and properties of the zinc complex, 1[Zn(ClO4)]33+, which is proposed to be formed in acetonitrile. The results are in line with the solution-state experimental findings. The single crystal X-ray study provides the solid state structure of the trinuclear Zn2+ complex showing solubility in an aqueous buffer (10 mM HEPES, pH = 7.4). Finally, the resulting trinuclear Zn2+ complex has been utilized as a fluorescence "turn-OFF" sensor for the selective detection of pyrophosphate in a 70% aqueous buffer (10 mM HEPES, pH = 7.4) acetonitrile solvent with a nanomolar detection limit (45.37 × 10-9 M).

Methylene Spacer Mediated Detection Switch Between Copper and Zinc Ions by Two Coumarin‐Pyrene Based Chemosensors

“…Chemosensors L1 and L2 were selective for Cu 2+ and Zn 2+ ions, respectively, most probably due to the difference in conjugation imparted by the methylene spacer. In case of L2 , rigidity of the resultant zinc complex was greatly enhanced which is the primary reason for the emission enhancement [40,43] . In contrast, when a Cu 2+ ion binds with L1 , emission quenching takes place due to its paramagnetic nature [35] …”

“…In case of L2, rigidity of the resultant zinc complex was greatly enhanced which is the primary reason for the emission enhancement. [40,43] In contrast, when a Cu 2 + ion binds with L1, emission quenching takes place due to its paramagnetic nature. [35]…”

“…[8,42] Zinc actively aids in cell growth and cell division, [28] nerve conduction [11] and synthetic reactions of proteins and nucleic acids. [43] Zinc disorders can lead to various types of syndromes including Alzheimer's decease, [44] prostate cancer, [45] infantile diarrhoea, [46] and weakening of the immune system. [47] Pyrene has gained significant interest in sensing and recognition field due to its excellent photophysical properties.…”

“…Zinc is involved in various enzymatic reactions while also takes part in diverse catalytic reactions [8,42] . Zinc actively aids in cell growth and cell division, [28] nerve conduction [11] and synthetic reactions of proteins and nucleic acids [43] . Zinc disorders can lead to various types of syndromes including Alzheimer's decease, [44] prostate cancer, [45] infantile diarrhoea, [46] and weakening of the immune system [47] …”

Subtle structural variation in azine/imine derivatives controls Zn2+sensitivity: ESIPT-CHEF combination for nano-molar detection of Zn2+with DFT support

“…Bhalla et al 38 have reported a hexaphenylbenzene derivative to recognise Zn 2+ in aqueous media. Out of several notable efforts at Zn 2+ sensing, 39,40 however, few are based on the ESIPT approach. 41,42 Herein, an imine (L1) and three azine (L2, L3 and L4) derivatives have been synthesised and structurally characterised by single crystal X-ray diffraction analysis.…”