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Novel bi- and tetranuclear CoII, NiII, CuII and ZnII complexes having diazine bridging units have been prepared and characterised on the basis of analytical and spectroscopic
techniques. With the help of electronic spectra and magnetic moment measurements, it is predicted that the CoII and NiII complexes have octahedral geometry while CuII and ZnII...
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Surface charge-transfer complex formed by TiO2 and phenols has showed a great potential in visible-light photocatalysis. However, back electron transfer limits the charge transfer efficiency and the activation of phenols in surface complex. Herein, we disclosed the efficient activation of phenols in surface complex by introducing the base. Both hom...
Citations
... The literature reports the synthesis and complexing properties of several hybrid macrocycles. Budagumpi et al. [30] report the synthesis of polyaza macrocycle based on pyrazole and phthalazine as well as the corresponding Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ complexes. Altmann et al. [31] communicated the elaboration of novel cyclophane consisting of methylene-bridged imidazolium and pyrazole-moieties and its dinuclear-nickel(II) complex. ...
The synthesis of tree new macrocycles with two pyrazole–tetrazole subunits and a lateral arm is described. These macrocycles were characterized by NMR, FT-IR and UV–Vis spectroscopies as well as elemental analysis and mass spectrometry. The complexing properties of these compounds toward some heavy metal ions Pb2+, Co2+, Cd2+, Zn2+ and Cu2+ were investigated by liquid–liquid extraction. The obtained results show, that all macrocycles possess good ability to extract these heavy metal cations, except, the macrocycle MIII with an aromatic side chain which showed a weak potency. At the competitive conditions, all macrocycles presented some selectivity towards the extraction of Cd2+. In addition, the ability of these macrocycles to extract the cadium cation is affected by the pH of the solution.
... The pyrazolic macrocycles represent a family of the polydentate structures, and they have attracted considerable attention since 1970. 1 These macrocycles contain sp 2 hybridized nitrogen donors having an intermediate character between the hard and the soft bases according to Pearson's principle. 2 This allows them to possess the unusual property of being able to form not only stable complexes with transition metal cations [3][4][5] such as the acyclic pyrazolic ligands, [6][7][8][9][10] but also with alkali cations. [11][12][13][14][15] They were also found in the catalyst field as copper complexes for the oxidative polymerization of 2,6-dimethylphenol. ...
Two novel symmetrical macrocycles containing four pyrazolic units, with two different side arms were synthesized and characterized. Their antibacterial activity was investigated by determining the inhibition zone diameter in agar gel and minimal inhibitory concentration. The obtained results show that the tetrapyrazolic macrocycle with a hydroxyl group in its side chain presents the best inhibitory effect against all tested bacterial strain. Molecular geometries, HOMO–LUMO analysis and molecular electrostatic potential of macrocycles are investigated by theoretical calculations with B3LYP/6-31G* level. The molecular electrostatic potential surface showed that the presence of electrophile site in the lateral arms of these macrocycles enhances the antibacterial activity of such compounds.
... Organic macrocycles with 1H-pyrazole units have taken much more of interest in the past years due to coordination properties of this small heterocycle. [1][2][3][4] They are characterized by a central hydrophilic cavity in which, depending on its diameter, metal cations are selectively bound. Over the last decade, several tetrapyrazolic macrocycles have been synthesized. ...
... Thin layer chromatography was carried out on silica gel pre-coated plates (Merck; 60 A F 254 ) and spots AC. Spin resonances are reported as chemical shifts (δ) in parts per million (ppm) and referenced to the residual peak as an internal standard of the solvent employed, as follow: CDCl3 7.27 ppm ( 1 H NMR), 77 ppm ( 13 C NMR, central band), DMSO-d 6 2.50 ppm ( 1 H NMR, central band), 39.5 ppm ( 13 C NMR, central band). Spin multiplicity is indicated by s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet. ...
The synthesis of three macrocycles, containing four pyrazolic units, with different side arms is described and the crystal structure of one of the intermediate compounds is also presented. The complexing properties of these compounds towards alkaline metal ions (Cs+, K+, Na+ and Li+) was studied by the liquid–liquid extraction process. The percentage values of extraction were determined by atomic absorption measurements and UV spectroscopy. These macrocycles extract selectively K+ and highlight the good effect of using a long side chain bearing a donor group, on the percentage of extraction of the alkali cations K+, Na+ and Li+. They also showed a good antibacterial against Gram-positive and Gram-negative microorganisms with minimum inhibitory concentrations at the range of 32–64 μg/mL.
... These transitions have been red shifted by 17–25 and 30–35 nm, respectively, upon complexation indicating coordination of azomethine group. The electronic spectrum of Co II complex shows an intense band at 560 nm, which is a characteristic d–d transition band for Co II complexes with octahedral geometry [28]. Three distinguishable d–d bands at 495, 550, and 665 nm are observed for the Ni II complex suggesting octahedral geometry [29, 30]. ...
Condensation of 1H-pyrazole-3,5-dicarboxylic hydrazide with 1H-indole-2,3-dione (isatin)
yield the compartmental ligand, which is capable of encapsulating two transition metal ions
namely CoII, NiII, CuII, and ZnII. The ligand is a binuclear hexadentate chelate with N4O2
donating sites. The pyrazole core provides the diazine fragment, which serves as an endogenous
bridge between the two metal centers. In CoII and NiII complexes, the ligand is in the imidol
form and the subsequent coordination through the imidol oxygen. In other complexes, the
lactonic oxygen takes part in ligation. All the complexes are non-electrolytes and soluble in
DMSO, DMF, and acetonitrile. Spectral and magnetic studies along with analytical data
suggest octahedral geometry for the CoII and NiII complexes, whereas the CuII and ZnII
complexes are assigned square pyramidal geometry. The CuII and NiII complexes show one
electron redox behavior and the rest are electrochemically inactive.
The structural diversity of Co(II) metal centers is known to influence their physico-chemical properties. A novel 2D Co(II)-MOF {[Co5(HL)4(dpp)2(H2O)2(µ-OH)2]∙21H2O}n has been designed and synthesized by adopting mixed ligand strategy, using 1,3-di(4-pyridyl)propane (dpp) co-linker with a flexible spacer H3L (H3L: 5-(2 Carboxybenzyloxy)isophthalic acid). Co(II)-MOF features a 2D-network which is further interpenetrated among the equivalent sets and therefore results in a 3D supramolecular network. Topologically, the entire network can be viewed as a (3,4,8)-connected three nodal net with the extended point symbol of {4.5.7}4{412.52.710.94}{52.8.92.10}2, duly assigned to the novel topological type smm2. The functional utility of Co(II)-MOF is demonstrated by employing it towards Oxygen Evolution Reaction (OER) in a photoelectrochemical cell, exhibiting appreciable photocurrents of up to 5.89 mA/cm² when used as an anode in a photoelectrochemical cell, while also displaying encouraging electrocatalytic currents of 9.32 mA/cm2 (at 2.01 V vs. RHE) for the OER. Moreover, detailed Electrochemical Impedance Spectroscopy (EIS) studies confirm enhanced charge transfer kinetics and improved conductivity under illumination with minimal effect of interfacial phenomena. This work provides a reference for the expanding field of research into applications of MOF materials, and establishes MOF materials as favorable candidates for sustainable and efficient design of electrodes for water splitting.
This review covers the different methods for the synthesis of
group XII metal−NHC complexes with five- and six-membered NHC systems
that have different N-heterocyclic cores: viz., imidazole, triazole, tetrazole,
pyridine-fused imidazole, ruthenocene-fused imidazole, pyrimidine, and
benzimidazole. Moreover, this review focuses on the structural divergence
of group XII metals toward NHCs and their interesting intramolecular
interactions as well as their suitable applications in the field of catalysis and
carbene transfer. Several Zn−NHC complexes were used as catalysts in lactide
polymerization because of their stability and suitable stereochemically diverse
topologies. The structural diversity of both single- and double-site chelates of
group XII metals, which bear NHC ligands, was reviewed. In particular, we
aim to evaluate the widely adopted Et2Zn, ZnCl2, Me2Cd, and Hg(II) acetate
techniques for the preparation of group XII metal(II)−NHC complexes and
their subsequent catalysis (Zn−NHCs) as well as carbene transfer reactions (Hg−NHCs).
Novel CoII, NiII, CuII and ZnII complexes of the polynucleating oxaza macrocyclic ligand (LH4) derived from the 2:2 condensation of pyrazole-3,5-dicarbohydrazide and 2,6-diformyl-4-methylphenol have been synthesized.
Ligand and complexes were characterized on the basis of elemental analysis, IR, 1HNMR, UV–Visible, magnetic susceptibility, ESR and conductivity measurements, FAB-mass and thermal analysis. Present ZnII and CuII complexes are binuclear in nature with octahedral geometry, where as CoII and NiII complexes are tetranuclear with square-planar geometry. CuII and CoII complexes are paramagnetic whereas ZnII and NiII complexes are diamagnetic. Only the copper complex has shown redox property in the applied potential range while the ligand
and other complexes are found to be electrochemically innocent.
The novel phenol and phthalazine-based symmetric compartmental 26-membered polyaza macropolycyclic ligand LH2, was synthesised, incorporating 2,6-diformyl-p-cresol and 1,4-dihydrazinophthalazine via 1:1 condensation. Its coordination behaviour with CuII and ZnII ions was investigated. The tetranuclear complexes [M4μ(Cl2)(L)Cl4]·2H2O exhibited aremarkably high stability, suggesting that, along with the large number of nitrogen donors available for metal binding, deprotonated phenolic functions were also involved in binding the metal ion. Incorporation of the bridging units into the macrocyclic cavity influenced electronic communications between the metal ions.
