Triazole-Linked Quinoline Conjugate of Glucopyranose: Selectivity Comparison among Zn²⁺, Cd²⁺, and Hg²⁺ Based on Spectroscopy, Thermodynamics, and Microscopy, and Reversible Sensing of Zn²⁺ and the Structure of the Complex Using DFT.

ABSTRACT: A water-soluble triazole-linked quinoline conjugate of glucopyranose (L) has been synthesized and characterized, and its single-crystal X-ray diffraction (XRD) structure has been established. Binding of L toward different biologically relevant metal ions has been studied using fluorescence and absorption spectroscopy in HEPES buffer at pH 7.4. The conjugate L detects Zn²⁺ and Cd²⁺ with 30 ± 2 and 14 ± 1-fold fluorescence enhancement, respectively, but in the case of Hg²⁺, only a fluorescence quench was observed. The stoichiometry of the complex is 1:2 metal ion to the ligand in the case of Zn²⁺ and Cd²⁺ resulting in [Zn(L)₂] and [Cd(L)₂], and it is 1:1 in the case of Hg²⁺, as confirmed from their electrospray ionization mass spectrometry (ESIMS) spectra. Zn²⁺ shows greater exothermicity over Cd²⁺, whereas Hg²⁺ shows endothermicity , which supports the differences in their binding strength and the nature of the corresponding complex. L exhibits rod-shaped particles and upon complexation with Zn²⁺, it exhibits sphere-like morphological features in scanning electron microscopy (SEM) images. However, clustered aggregates are observed in Cd²⁺, whereas the [HgL] complex exhibits small fused spherical structures, and therefore the signature of these ions is seen in microscopy images. The computational studies revealed that the syn-[Zn(L)₂] complex is stabilized by 9.7 kcal mol^-1 more than that in the case of anti-[Zn(L)₂] owing to the formation of hydrogen bonds between the two glucosyl moieties within the syn-complex. Among the anions studied, [Zn(L)₂] is sensitive and selective toward the phosphate ion (H₂PO₄ ^-) with a minimum detection limit of 16 ± 2 ppb. Similarly, the [HgL] can act as a secondary sensor for CN^- while also exhibiting reversibility. Based on the input-output characteristics, INHIBIT logic gate was built in the case of Zn²⁺ vs H₂PO₄ ^- and IMPLICATION logic gate was built in the case of Hg²⁺ vs CN^-.

SUBMITTER: Areti S 

PROVIDER: S-EPMC6640762 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature