Selective Recognition of Zn²⁺ Ion Using 2,4‐Bis(2‐pyridyl)‐5‐(4‐pyridyl)imidazole: Spectra and Molecular Structure

Abstract

A trisubstituted imidazole, 2,4-bis(2-pyridyl)-5-(4-pyridyl)imidazole (LH) in presence of other cations, selectively binds Zn 2 + ion by exhibiting characteristic absorption and fluorescence spectral behaviors. Upon gradual addition of ZnCl 2 to DMSOsolution of LH, intensity of peak at 318 nm decreased. A new peak appeared at 364 nm along with an isosbestic point at 337 nm. The DMSOsolution of LH upon irradiation with l = 320 nm exhibited an emission peak at 391 nm, which decreased gradually with increase in Zn 2 + ion concentrations. A new emission peak also appeared at 445 nm along with a quasi isoemissive point at 413 nm. The HEPES buffered aqueous DMSO solution (2:8 v/v, pH = 7.4) of free LH, upon excitation with 320 nm radiation gave emission at 396 nm which shifted to 445 nm during incremental additions of Zn 2 + ion. The red shift is due to binding of Zn 2 + ion to LH. The binding is accompanied by deprotonation of acidic hydrogen in imidazole ring and orientation of two 2-pyridyl rings in near-planarity with imidazolate ring. The Zn 2 + ion can be detected with a calculated limit of 6.5 3 10 À7 M. The Job's plot revealed that ligand binds Zn 2 + ion in 1:2 ratios and was further confirmed by single crystal X-ray diffraction method. Results and DiscussionThe selectivity of LHtowards cations in DMSO and HEPES buffered aqueous DMSO solution (pH = 7.4, 2:8, v/v) were exam-[a] N.

Application of 2,4,5‐tris(2‐pyridyl)imidazole as ‘turn‐off’ fluorescence sensor for Cu(II) and Hg(II) ions andin vitrocell imaging

“…Therefore one ligand capturing two bivalent metal ions, can be arrived at from these mass spectral data and, in other words, a binding stoichiometry of 2:1 between metal and L is pertinent for both copper and mercury complexes. The same ratio has also been found for zinc [34] with 2,4-bis(2-pyridyl)-5-(2-pyridyl)imidazole, the positional isomer of L.…”

“…The ligand 2,4,5‐tris(2‐pyridyl)imidazole ( L ) was first synthesized along with two other positional isomers and 2,4‐bis(2‐pyridyl)‐5‐(4‐pyridyl)imidazole has been found to be selective towards Zn(II) ions. [ 34 ] Our initial evaluation of L revealed that it has excellent fluorescence characteristics. By virtue of having five nitrogen atoms, this ligand can coordinate with metal ions and may show selective characteristics towards a specific metal ion(s); therefore, this study has been carried out.…”

“…[ 32,33 ] One such isomer, 2,4‐bis(2‐pyridyl)‐5‐(4‐pyridyl)imidazole has been found to be a sensor for the selective detection of Zn 2+ ion. [ 34 ] This prompted us to examine the utility of L as a metal ion sensor and the results are reported here.…”

A Coumarin-Based Fluorescence Probe for Selective Recognition of Cu2+ Ions and Live Cell Imaging

“…The former could be ascribed to the π -π * transition of the coumarin chromophore, and the latter was attributed to a metal-to-ligand charge transfer (MLCT) caused by binding L and Cu 2+ ion. Based on the isosbestic point at 458 nm, a 1 : 1 stoichiometry for the L and Cu 2+ ion is confirmed by the data of Job's plot ( Figure S1a) [37][38][39][40].…”

Unusual Types of Layered Organic Crystal Hydrates

“…The first article is entirely devoted to organic synthesis and Xray structure determination was performed just to illustrate the molecular structure of the target product (refcode EHUJEY [27]). The second article has been published in the journal on medicinal chemistry and is devoted to the synthesis of drugs to treat leukemia, for which one of molecular structures (SAXDON [28]) has been studied. In the third work, the crystallized substance was not a target product but a ligand (FELRIA [29]) used for the synthesis of the complex of Zn 2+ .…”