A highly selective colorimetric fluorescent probe for detection of Hg2+ and its application on test strips

An efficient fluorescent probe Pyr-Rhy based on pyrazole was developed, which can detect Hg²⁺ in water. Its fluorescence properties were studied by UV-vis and fluorescence spectroscopy, and the study results indicated that this probe can selectively detect Hg²⁺via complexation reaction, and then cause a remarkable color change from colorless to pink and a strong fluorescence enhancement can be observed. Furthermore, this probe showed high sensitivity with the detection limit down to 2.07 × 10⁻⁸ M, and its stoichiometric ratio toward Hg²⁺ ions was 1 : 1. The sensing mechanism was investigated by Job's plot ¹H NMR titrations, and FT-IR spectra analysis, which demonstrated a chelation-enhanced fluorescence (CHEF) mechanism. More importantly, obvious color changes of sensor Pyr-Rhy can be observed when it was impregnated on filter paper testing strips and immersed in Hg²⁺ solution (water as solution), indicating its potential application for trace Hg²⁺ detection in environmental samples.

An efficient fluorescent probe Pyr-Rhy based on pyrazole was developed, which can detect Hg²⁺ in water.

Synthesis, spectroscopy studies, and theoretical calculations of new fluorescent probes based on pyrazole containing porphyrins for Zn(II), Cd(II), and Hg(II) optical detection

New pyrazole-porphyrin conjugates were successfully prepared from a reaction of β-porphyrin-chalcone derivatives with phenylhydrazine in acetic acid followed by an oxidative step. This fast and efficient synthetic approach provided the expected compounds in yields up to 82%. The sensing ability of the new porphyrin-pyrazole derivatives to detect the metal ions Ag(+), Na(+), K(+), Mg(2+), Ca(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Cr(3+) was studied by spectrophotometric and spectrofluorimetric titrations. In the presence of Zn(2+), the conjugates exhibit changes in the emission spectra that are desired for a ratiometric-type fluoroionophoric detection probe. The studies were extended to gas phase, where the pyrazole-porphyrin conjugates show ability to sense metal ions with high selectivity toward Cu(2+) and Ag(+), and in poly(methyl methacrylate) doped films with promising results for Zn(2+) detection.

Pd(II) and Pt(II) Coordination Chemistry with Hybrid Pyridine-Pyrazole Ligands: from 3D-Frameworks Structures in Molecular Complexes

In this paper we studied the reaction of ligands 2-[5-phenyl-1-(3,6,9-trioxodecane)-1H-pyrazol-3-yl]pyridine (L1) and 3,5-bis(2-pyridyl)-1-(3,6,9-trioxodecane)-1H-pyrazole (L2) with [MCl2(CH3CN)2] (M = Pd(ii), Pt(ii)), to obtain monomeric complexes [MCl2(L)] (M = Pd(ii): L = L1 (1), L = L2 (2); M = Pt(ii): L = L1 (3), L = L2 (4)). Additionally, the reaction of [Pd(CH3COO)2] with L1 (5) and L2 (6) was also studied pointing out dimeric structures with bridged acetates between the Pd(ii) atoms. All complexes were characterised by elemental analyses, conductivity measurements, infrared spectroscopy (IR), 1H, 13C{1H}, and 195Pt{1H} NMR spectroscopies, and electrospray ionisation mass spectrometry (MS-ESI(+)). The crystal structure of complex [PtCl2(L1)] (3) was determined by X-ray diffraction methods; it consists of a mononuclear complex where L1 acts as a bidentate chelate ligand. Moreover, we also studied the extended structure observing that the ether, present in the alkyl chain of the ligand, chlorine, and platinum moieties play a fundamental role in the final disposition of the supramolecular structure. All these results show how the design of an appropriate hybrid ligand can strongly influence the structural control of the molecular packing.