Search Results (7)

The study of small synthetic models for the highly selective removal of uranyl ions from seawater with amidoxime-containing materials is a valuable means to enhance their recovery capacity, leading to better extractants. An important issue in such efforts is to design bifunctional ligands and study their reactions with trans-{UO₂}²⁺ in order to model the reactivity of polymeric sorbents possessing both amidoximate and another adjacent donor site on the side chains of the polymers. In this work, we present our results concerning the reactions of uranyl and pyrimidine-2-amidoxime, a ligand possessing two pyridyl nitrogens near the amidoxime group. The 1:2:2 {UO₂}²⁺/pmadH₂/external base (NaOMe, Et₃N) reaction system in MeOH/MeCN provided access to complex [UO₂(pmadH)₂(MeOH)₂] (1) in moderate yields. The structure of the complex was determined by single-crystal X-ray crystallography. The U^VI atom is in a distorted hexagonal bipyramidal environment, with the two oxo groups occupying the trans positions, as expected. The equatorial plane consists of two terminal MeOH molecules at opposite positions and two N,O pairs of two deprotonated η² oximate groups from two 1.11000 (Harris notation) pmadH⁻ ligands; the two pyridyl nitrogen atoms and the –NH₂ group remain uncoordinated. One pyridyl nitrogen of each ligand is the acceptor of one strong intramolecular H bond, with the donor being the coordinated MeOH oxygen atom. Non-classical C_aromatic-H⋯X (X=O, N) intermolecular H bonds and π–π stacking interactions stabilize the crystal structure. The complex was characterized by IR and Raman spectroscopies, and the data were interpreted in terms of the known structure of 1. The solid-state structure of the complex is not retained in DMSO, as proven via ¹H NMR and UV/Vis spectroscopic techniques as well as molar conductivity data, with the complex releasing neutral pmadH₂ molecules. The to-date known coordination chemistry of pmadH₂ is critically discussed. An attempt is also made to discuss the technological implications of this work. Full article

Highly anisotropic single-molecule magnets (SMMs) have attracted much interest in the field of molecular magnetism because of their spin features and potential technological applications. Additionally, a great effort has been devoted to the functionalization of such molecule-based systems which are made with ligands containing functional groups suitable to connect SMMs to junction devices or to perform their grafting on surfaces of different substrates. We have synthesized and characterized two lipoic acid-functionalized and oxime-based Mn(III) compounds, of formula [Mn₆(μ₃-O)₂(H₂N-sao)₆(lip)₂(MeOH)₆][Mn₆(μ₃-O)₂(H₂N-sao)₆(cnph)₂(MeOH)₆]}·10MeOH (1) and [Mn₆(μ₃-O)₂(H₂N-sao)₆(lip)₂(EtOH)₆]·EtOH·2H₂O (2) [H₂N-saoH₂ = salicylamidoxime, lip = lipoate anion, cnph = 2-cyanophenolate anion]. Compound 1 crystallizes in the space group Pī of the triclinic system and 2 crystallizes in the space group C2/c of the monoclinic system. In the crystal, neighboring Mn₆ entities are linked using non-coordinating solvent molecules, which are H-bonded to N atoms of –NH₂ groups of amidoxime ligand. In addition, Hirshfeld surfaces of 1 and 2 were calculated to study the variety of intermolecular interactions and the different levels of importance that take place in their crystal lattice; this type of computed study is the first time performed on Mn₆ complexes. The study of the magnetic properties of 1 and 2 through dc magnetic susceptibility measurements reveals the coexistence of ferromagnetic and antiferromagnetic exchange couplings between the Mn(III) metal ions in both compounds, the latter being the predominant magnetic interaction. A spin S = 4 value of the ground state was obtained using isotropic simulations of the experimental magnetic susceptibility data for both 1 and 2. Ac magnetic susceptibility measurements show features typical of slow relaxation of the magnetization in 1 and 2, which indicate that SMM behavior takes place in both compounds. Full article

An efficient and economical treatment technology for heavy metal removal from the electroplating wastewaters is needed for the water purification. Therefore, pure cellulosic materials were derived from two waste fiber (pandanus fruit and durian rind) and conversion of the cellulose into the poly(acrylonitrile)-grafted material was accomplished by free radical grafting system. Thereafter, poly(amidoxime) ligand was produced from the grafted materials. Sorption capacity (q_e) of several toxic metals ions was found to be high, e.g., copper capacity (q_e) was 298.4 mg g⁻¹ at pH 6. In fact, other metal ions, such as cobalt chromium and nickel also demonstrated significant sorption capacity at pH 6. Sorption mechanism played acceptable meet with pseudo second-order rate of kinetic pattern due to the satisfactory correlation with the experimental sorption values. A significant correlation coefficient (R² > 0.99) with Langmuir model isotherm showed the single or monolayer sorption occurred on the surfaces. The reusability study showed that the polymer ligand can be useful up to six cycles with minimum loss (7%) of efficiency and can be used in the extraction of toxic metal ions present in the wastewaters. Therefore, two types of electroplating wastewater were used in this study, one containing high concentration of copper (23 ppm) and iron (32 ppm) with trace level of others heavy metals (IWS 1) and another containing high concentration of copper (85.7 ppm) only with trace level of others heavy metals (IWS 2). This polymeric ligand showed acceptable removal magnitude, up to 98% of toxic metal ions can be removed from electroplating wastewater. Full article

The simultaneous use of 2-pyridyl oximes (pyridine-2 amidoxime, H₂pyaox; 2-methyl pyridyl ketoxime, Hmpko) and 1,3,5-benzenetricarboxylic acid (H₃btc) provided access to five new compounds, namely [Zn(H₂btc)₂(H₂pyaox)₂]•2H₂O (1•2H₂O), [Zn(Hbtc)(H₂pyaox)₂]_n (2), [Cu(Hbtc)(H₂pyaox)]_n (3), [Cu(Hbtc)(HmpKo)]_n (4) and [Cu₂(Hbtc)₂(Hmpko)₂(H₂O)₂]•4H₂O (5•4H₂O). Among them, 3 is the first example of a metal-organic framework (MOF) containing H₂pyaox. Its framework can be described as a 3-c uninodal net of hcb topology with the layers being parallel to the (1,0,1) plane. Furthermore, 3 is the third reported MOF based on a 2-pyridyl oxime in general. 2 and 4 are new members of a small family of coordination polymers containing an oximic ligand. 1–5 form 3D networks through strong intermolecular interactions. Dc magnetic susceptibility studies were carried out in a crystalline sample of 3 and revealed the presence of weak exchange interactions between the metal centres; the experimental data were fitted to a theoretical model with the fitting parameters being J = −0.16(1) cm⁻¹ and g = 2.085(1). The isotropic g value was also confirmed by electronic paramagnetic resonance (EPR) spectroscopy. Reactivity studies were performed for 3 in the presence of metal ions; the reaction progress was studied and discussed for Fe(NO₃)₃ by the use of several characterization techniques, including single crystal X-ray crystallography and IR spectroscopy. Full article

The transition metal-catalyzed chemical transformation of organic electrophiles, and organometallic reagents have turned up as an exceedingly robust synthetic tool. The evolution of transition metal catalysts has attained a stage of civilization that authorizes for an extensive scope of chemical bonds formation partners to be combined efficiently. The applications of Cu-based nanoparticles have received great attention owing to the earth-abundant, low toxicity and inexpensive. Due to these characteristics, copper nanoparticles have generated a great deal of interest especially in the field of catalysis. In this study, poly(acrylonitrile) was synthesized by undergoes free-radical initiation process and followed by Beckmann rearrangement with hydroxylamine solution converted into the poly(amidoxime) ligand and anchored the copper onto poly(amidoxime). Cu(II)@PAM was characterized using different techniques such as FTIR, FESEM, EDX, TEM, TGA, DSC, ICP-OES, and XPS analyses. The Cu(II)@PAM showed high stability and high catalytic activity in a wide variety of electrophilic substituted phenols with substituted aryl/benzyl halides. 0.15 mol%, ±3 mg of Cu(II)@PAM could efficiently promote Ullmann reaction to give the corresponding coupling product up to 99 % yields. The complex was easy separated and recovered from the reaction mixture by simple filtration. Full article

The synthesis and characterization of coordination polymers and metal–organic frameworks (MOFs) has attracted a significant interest over the last decades due to their fascinating physical properties, as well as their use in a wide range of technological, environmental, and biomedical applications. The initial use of 2-pyridyl oximic ligands such as pyridine-2 amidoxime (H₂pyaox) and 2-methyl pyridyl ketoxime (Hmpko) in combination with 1,2,4,5-benzene tetracarboxylic acid (pyromellitic acid), H₄pma, provided access to nine new compounds whose structures and properties are discussed in detail. Among them, [Zn₂(pma)(H₂pyaox)₂(H₂O)₂]_n (3) and [Cu₄(OH)₂(pma)(mpko)₂]_n (9) are the first MOFs based on a 2-pyridyl oxime with 9 possessing a novel 3,4,5,8-c net topology. [Zn₂(pma)(H₂pyaox)₂]_n (2), [Cu₂(pma)(H₂pyaox)₂(DMF)₂]_n (6), and [Cu₂(pma)(Hmpko)₂(DMF)₂]_n (8) join a small family of coordination polymers containing an oximic ligand. 9 exhibits selectivity for Fe^III ions adsorption, as was demonstrated by a variety of techniques including UV-vis, EDX, and magnetism. DC magnetic susceptibility studies in 9 revealed the presence of strong antiferromagnetic interactions between the metal centers, which lead to a diamagnetic ground state; it was also found that the magnetic properties of 9 are affected by the amount of the encapsulated Fe³⁺ ions, which is a very desirable property for the development of magnetism-based sensors. Full article

G-quadruplex (G4) nucleic acid structures have been reported to be involved in several human pathologies, including cancer, neurodegenerative disorders and infectious diseases; however, G4 targeting compounds still need implementation in terms of drug-like properties and selectivity in order to reach the clinical use. So far, G4 ligands have been mainly identified through high-throughput screening methods or design of molecules with pre-set features. Here, we describe the development of new heterocyclic ligands through a fragment-based drug discovery (FBDD) approach. The ligands were designed against the major G4 present in the long terminal repeat (LTR) promoter region of the human immunodeficiency virus-1 (HIV-1), the stabilization of which has been shown to suppress viral gene expression and replication. Our method is based on the generation of molecular fragment small libraries, screened against the target to further elaborate them into lead compounds. We screened 150 small molecules, composed by structurally and chemically different fragments, selected from commercially available and in-house compounds; synthetic elaboration yielded several G4 ligands and two final G4 binders, both embedding an amidoxime moiety; one of these two compounds showed preferential binding for the HIV-1 LTR G4. This work presents the discovery of a novel potential pharmacophore and highlights the possibility to apply a fragment-based approach to develop G4 ligands with unexpected chemical features. Full article