The sensitive detection and mechanism of Fe-3,5-dimethyl pyrazole fluorescent sensor to diethylenetriamine pentamethylene phosphonic acid: Experimental study and quantum chemical calculation

Diethylenetriamine pentamethylene phosphonic acid (DTPMP) is one of the most commonly used amino organic phosphonates. The existing methods for DTPMP detection are complicated, time-consuming, and cannot detect trace DTPMP in the natural environment. In the present work, the Fe-based 3,5-dimethyl pyrazole fluorescent sensor (Fe-DP) was constructed. The addition of Fe³⁺ to DP solution can greatly decrease the fluorescent intensity of DP, while the addition of different concentrations of DTPMP will restore the fluorescence intensity of DP to different degrees, to achieve quantitative detection of DTPMP, and the detection limit (LOD) of DTPMP was lower as 0.105 μΜ. The Fe-DP fluorescent sensor exhibited excellent anti-interference ability and good stability. Moreover, the fluorescence quenching mechanism of DP by Fe³⁺ was revealed by UV absorption spectrum and Multiwfn wavefunction analysis based on density function theory (DFT). The results revealed that the excitation of DP belonged to local excitation, in which the electrons were donated primarily by the N atom with double bond and redistributed within the pyrazole ring.The fluorescence quenching of adding Fe³⁺ was not caused by resonance energy transfer or charge transfer, which did not belong to dynamic quenching, but due to the ground state complex formed by the coordination of Fe³⁺ and the double bond N atom on the DP pyrazole ring.

Capped Nanojars: Synthesis, Solution and Solid-State Characterization, and Atmospheric CO2 Sequestration by Selective Binding of Carbonate

Nanojars are a class of supramolecular anion-incarcerating coordination complexes that self-assemble from Cu²⁺ ions, pyrazole, and a strong base in the presence of highly hydrophilic anions. In this work, we show that if the strong base (e.g., NaOH or Bu₄NOH) is replaced by a weak base such as a trialkylamine, capped nanojars of the formula [{Cu₃(μ₃-OH)(μ-pz)₃L₃}CO₃⊂{Cu(μ-OH)(μ-pz)}_n] (pz = pyrazolate anion; L = neutral donor molecule; n = 27-31) are obtained instead of the conventional nanojars. Yet, to obtain capped nanojars, the conjugate acid side product originating from the weak base must be separated by transferring it to water either by precipitation of the water-insoluble capped nanojars or by liquid-liquid extraction. Full characterization using electrospray ionization mass spectrometry, UV-vis and variable-temperature ¹H NMR spectroscopy in solution, and single-crystal X-ray diffraction, elemental analysis, and solubility studies in the solid state reveals similarities as well as drastic differences between capped nanojars and nanojars lacking the [Cu₃(μ₃-OH)(μ-pz)₃L₃]²⁺ cap. Acid-base reactivity studies demonstrate that capped nanojars are intermediates in the pH-controlled assembly-disassembly of nanojars. During the self-assembly of capped nanojars, CO₂ is selectively sequestered from air in the presence of other atmospheric gases and converted to carbonate, the binding of which is selective in the presence of NO₃^-, ClO₄^-, BF₄^-, Cl^-, and Br^- ions.

Accessing the inaccessible: discrete multinuclear coordination complexes and selective anion binding attainable only by tethering ligands together

The use of tethers between ligands allows for the preparation of novel multimetallic complexes, not obtainable without tethers, and leads to unexpected properties, such as selective binding of the carbonate vs. sulfate anion by nanojars.

Ligand effects on the structure and magnetic properties of alternating copper(II) chains with 2,2'-bipyrimidine- and polymethyl-substituted pyrazolates as bridging ligands

A novel series of heteroleptic copper(II) compounds of formulas {[Cu2(μ-H2O)(μ-pz)2(μ-bpm)(ClO4)(H2O)]ClO4·2H2O}n (1), {[Cu2(μ-H2O)(μ-3-Mepz)2(μ-bpm)](ClO4)2·2H2O}n (2), and {[Cu2(μ-OH)(μ-3,5-Me2pz)(μ-bpm)(H-3,5-Me2pz)2](ClO4)2}n (3) [bpm = 2,2'-bipyrimidine, Hpz = pyrazole, H-3-Mepz = 3-methylpyrazole, and H-3,5-Me2pz = 3,5-dimethylpyrazole] have been synthesized and structurally characterized by X-ray diffraction methods. The crystal structures of 1 and 2 consist of copper(II) chains with regular alternating bpm and bis(pyrazolate)(aqua) bridges, whereas that of 3 is made up of copper(II) chains with regular alternating bpm and (pyrazolate)(hydroxo) bridges. The copper centers are six- (1) or five-coordinate (2) in axially elongated, octahedral (1) or square-pyramidal (2) environments in 1 and 2, whereas they are five-coordinate in distorted trigonal-bipyramidal surroundings in 3. The values of the copper-copper separations across the bpm/pyrazolate bridges are 5.5442(7)/3.3131(6) (1), 5.538(1)/3.235(1) (2), and 5.7673(7)/3.3220(6) Å (3). The magnetic properties of 1-3 have been investigated in the temperature range of 25-300 K. The analysis of their magnetic susceptibility data through the isotropic Hamiltonian for an alternating antiferromagnetic copper(II) chain model [H = -J∑i=1-n/2 (S2i·S2i-1 + αS2i·S2i+1), with α = J'/J and Si = SCu = 1/2] reveals the presence of a strong to moderate antiferromagnetic coupling through the bis(pyrazolate)(aqua) [-J = 217 (1) and 215 cm(-1) (2)] and (pyrazolate)(hydroxo) bridges [-J = 153 cm(-1) (3)], respectively, whereas a strong to weak antiferromagnetic coupling occurs through the bis-bidentate bpm [-J' = 211 (1), 213 (2), and 44 cm(-1) (3)]. A simple orbital analysis of the magnetic exchange interaction within the bpm- and pyrazolate-bridged dicopper(II) fragments of 1-3 visualizes the σ-type pathways involving the (dx(2)-y(2)) (1 and 2) or d(z(2)) (3) magnetic orbitals on each metal ion, which account for the variation of the magnetic properties in these three novel examples of one-dimensional copper(II) compounds with regular alternating intrachain antiferromagnetic interactions.