Synthesis, Crystal Structures and Magnetic Properties of Trinuclear {Ni2Ln} (LnIII = Dy, Ho) and {Ni2Y} Complexes with Schiff Base Ligands

The reaction of the Schiff base ligand o-OH-C6H4-CH=N-C(CH2OH)3, H4L, with Ni(O2CMe)2∙4H2O and lanthanide nitrate salts in a 4:2:1 ratio lead to the formation of the trinuclear complexes [Ni2Ln(H3L)4(O2CMe)2](NO3) (Ln = Dy (1), Ho (2), and Y (3)) which crystallize in the non-centrosymmetric space group Pna21. The complex cation consists of the three metal ions in an almost linear arrangement. The {Ni2Ln} moieties are bridged through two deprotonated Ophenolato groups from two different ligands. Each terminal NiII ion is bound to two ligands through their Ophenolato, the Nimino atoms and one of the protonated Oalkoxo groups in a distorted octahedral. The central lanthanide ion is coordinated to four Ophenolato oxygen from the four ligands, and four Ocarboxylato atoms from two acetates which are bound in the bidentate chelate mode, and the coordination polyhedron is biaugmented trigonal prism, which probably results in a non-centrosymmetric arrangement of the complexes in the lattice. The magnetic properties of 1–3 were studied and showed that 1 exhibits field induced slow magnetic relaxation.

Synthesis, IR spectroscopic and structural studies of erbium and nickel complexes with N,N'-tetraethyl-N''-trifluoroacetylphosphoroustriamide

A synthesis procedure was developed and a new carbacylamidophosphate type ligand N,N'-tetraethyl-N''-trifluoroacetylphosphoroustriamide (CF3C(O)NHP(O)(NC2H5)2, HL) that contains C(O)NP(O) chelating fragment was isolated in the crystalline state. A mononuclear erbium complex [Er(HL)3(NO3)3] and a tetranuclear nickel complex [Ni4L4(OCH3)4(CH3OH)4] were isolated in the crystalline state. The suggestion about the type and coordination mode of the ligand in complexes was made based on IR spectroscopic investigations: deprotonated (acido-) form in bidentate manner in nickel complex and neutral form in monodentate manner in erbium complex. According to X-ray structural studies, different coordination modes of the ligand in complexes were determined: bidentate chelate manner via the oxygen atoms of the phosphoryl and carbonyl groups of the ligand with the formation of six-membered chelate cycles in case of nickel complex and monodentate manner via the oxygen atom of the phosphoryl group of the ligand in case of erbium complex, the coordination polyhedron of which was interpreted as a distorted three-handed trigonal prism.

Molecular and Supramolecular Structures of Cd(II) Complexes with Hydralazine-Based Ligands; A New Example for Cyclization of Hydrazonophthalazine to Triazolophthalazine

Molecular and supramolecular structures of two polymeric and one trinuclear Cd(II) complex with hydralazine-type ligands were presented. Self-assembly of E-1-(2-(thiophen-2-ylmethylene)hydrazinyl)phthalazine (HL) and CdCl2 gave the 1D coordination polymer [Cd(H2L)Cl3]n*H2O, 1, in which the Cd(II) ion is hexa-coordinated with one cationic monodentate ligand (H2L+) and five chloride ions, two of them acting as connectors between Cd(II) centers, leading to the formation of a 1D coordination polymer along the a-direction. Using DFT calculations, the cationic ligand (H2L+) could be described as a protonated HL with an extra proton at the hydrazone moiety. Repeating the same reaction by heating under reflux conditions in the presence of 1 mL saturated aqueous KSCN solution, the ligand HL underwent cyclization to the corresponding [1,2,4]triazolo[3,4-a]phthalazine-3(2H)-thione (TPT) followed by the formation of [Cd(TPT)(SCN)2]n*H2O, 2, a 1D coordination polymer. In this complex, the Cd(II) is coordinated with one NS-donor TPT bidentate chelate and two bridged μ(1,3)-thiocyanate ions connecting the Cd(II) centers forming the 1D polymer array along the b-direction. Heating E-2-(1-(2-(phthalazin-1-yl)hydrazono)ethyl)phenol HLOH with CdCl2 under reflux condition gave the trinuclear complex [Cd3(Hydralazine)2(H2O)2Cl6], 3, indicating the hydrolysis of the hydrazonophthalazine ligand HLOH during the course of the reaction. Due to symmetry considerations, there are only two different Cd(II) centers having CdN2Cl3O and CdN2Cl4 coordination environments. Hirshfeld topology analysis was used to analyze the solid-state supramolecular structure of the studied complexes.

Synthesis, characterization, thermal analysis and biological study of new thiophene derivative containing o-aminobenzoic acid ligand and its Mn(II), Cu(II) and Co(II) metal complexes

New ligand containing 2-(2,4-dioxo-4-thiophen-2-yl-butyrylamino)-benzoic acid (HL) merged moiety was synthesized and characterized by FT-IR, elemental analyses, mass spectra and 1H-NMR spectral. In the present study, the attempts were carried to form complexes of HL ligand with some transition metal ions (MnII, CuII and CoII) of well-defined at the (1:1) ratio of the components in the dimethyl sulfoxide (DMSO) solvent. All complexes have been studied by FTIR spectra, elemental analyses, thermal analysis, molar conductivity, electronic spectra and magnetic moment. The HL ligand produced as a bidentate chelate with interactive metal ions. All the results suggested octahedral geometry to complexes and have the formulae [M(HL)(Cl)2(H2O)2].nH2O where M = Mn(II), Cu(II) and Co(II). The IR spectra of the complexes were assigned and compared with the data in literature. The kinetic and thermodynamic results such as E*, ΔH*, ΔS* and ΔG* were calculated based o the TGA/DTG curves using Coats and Redfern and Horowitz and Metzger approximation methods. Furthermore, the resultant complexes were evaluated for the anti-bacterial and anti-fungal potential. KEY WORDS: 2-(2,4-Dioxo-4-thiophen-2-yl-butyrylamino)-benzoic acid, Transition metal complexes, FTIR, TGA, Antimicrobial test Bull. Chem. Soc. Ethiop. 2021, 35(1), 129-140. DOI: https://dx.doi.org/10.4314/bcse.v35i1.11

SÍNTESE, CARACTERIZAÇÃO E ESTUDO DOS PARÂMETROS DE JUDD-OFELT DE COMPOSTOS β-DICETONATOS DE Eu(III) OU Sm(III)

SYNTHESIS, CHARACTERIZATION AND JUDD-OFELT ANALYSIS OF Eu(III) OR Sm(III) β-DIKETONATE COMPLEXES. The lanthanide complexes [Ln(bmdm)3(L)] where Ln(III) = Eu and Sm were synthesized successfully using the diketone (1-(4-methoxyphenyl)-3-(4-tert-butylphenyl) propane-1,3-dione) (bmdm) and (L) = 1,10-phenanthroline (phen), 2,2’-bipyridine (bipy) ligands. The coordination modes were determined as bidentate chelate by the FT-IR. The ground state geometry was determined using the Sparkle/AM1 implemented in MOPAC2016 package. Europium complexes exhibit the characteristic emission bands that arise from 5 D0→7 FJ (J = 0-4); the presence of just one 5 D0→7 F0 line transition means that this site is without the center of inversion.Samarium complexes display transitions at 4 G5/2→6 HJ (J = 5/2; 7/2; 9/2 and 11/2), being the 4 G5/2→6 H9/2 the most intense, indicating that the forced electric dipole mechanism is predominant when compared with the magnetic dipole ones. The intensity parameters Ω2 and Ω4 were calculated according to the emission spectra for Eu(III) and absorption spectra for Sm(III). The high Ω2 values demonstrated that the lanthanide ion in bipy or phen complexes is in a highly polarizable chemical environment. The emission lifetime (τ) increases compared with that of precursor aquo complexes, confirming that the non-radiative quenching is minimized. The low quantum efficiency is a result of NIR emissions and non-radiative transitions of Sm(III).

The syntheses, structures, and magnetic properties of two mononuclear manganese(II) complexes involving in situ hydrothermal decarboxylation

Two new mononuclear compounds [Mn(3-Br-pydc)(H2O)3] (1) and {[Mn(5-Br-pyc)(bipy)(H2O)(Cl)]·2H2O (2) (3-Br-H2pydc = 3-Br-pyridine-2,6-dicarboxylic acid, 5-Br-Hpyc = 5-Br-pyridine-2-carboxylic acid, bipy = 2,2′-bipyridine) have been synthesized by traditional solution reaction and hydrothermal reaction, respectively. In both compounds, the MnII center is six-coordinated in a distorted octahedral geometry, formed by one tridentate chelate 3-Br-pydc dianion and three water molecules in 1, while the coordination sphere consists of one bidentate chelate 5-Br-pyc anion, one bipy, one water molecule, and one chloride anion in 2 (MnNO5 for 1 and MnN3O2Cl for 2). O–H⋯O hydrogen bonds, Br⋯O halogen bonds, and/or π-π stacking assist in the construction of the three-dimensional (3D) network structures of 1 and 2. Notably, the 5-Br-Hpyc ligand was generated in situ by decarboxylation of the 3-Br-H2pydc precursor under hydrothermal conditions. Variable-temperature magnetic susceptibility data in the 2–300 K temperature range indicate weak antiferromagnetic coupling in both 1 and 2.

Trinuclear NiII-LnIII-NiII Complexes with Schiff Base Ligands: Synthesis, Structure, and Magnetic Properties

The reaction of the Schiff base ligand o-OH-C6H4-CH=N-C(CH2OH)3, H4L, with Ni(O2CMe)2∙4H2O and lanthanide nitrate salts in a 4 : 2 : 1 ratio lead to the formation of the trinuclear complexes [Ni2Ln(H3L)4(O2CMe)2](NO3) (Ln = Sm (1), Eu (2), Gd (3), Tb (4)). The complex cations contain the strictly linear NiII-LnIII-NiII moiety. The central LnIII ion is bridged to each of the terminal NiII ions through two deprotonated phenolato groups from two different ligands. Each terminal NiII ion is bound to two ligands in distorted octahedral N2O4 environment. The central lanthanide ion is coordinated to four phenolato oxygen atoms from the four ligands, and four carboxylato oxygen atoms from two acetates which are bound in the bidentate chelate mode. The lattice structure of complex 4 consists of two interpenetrating, supramolecular diamond like lattices formed through hydrogen bonds among neighboring trinuclear clusters. The magnetic properties of 1-4 were studied. For 3 the best fit of the magnetic susceptibility and isothermal M(H) data gave JNiGd = +0.42 cm−1, D = +2.95 cm−1 with gNi = gGd = 1.98. The ferromagnetic nature of the intramolecular Ni···Gd interaction revealed ground state of total spin S = 11/2. The magnetocaloric effect (MCE) parameters for 3 show that the change of the magnetic entropy (−ΔSm) reaches a maximum of 14.2 J kg−1 K−1 at 2 K. A brief literature survey of complexes containing the NiII-LnIII-NiII moiety is discussed in terms of their structural properties.

Crystal structure and characterization of a new copper(II) chloride dimer with methyl(pyridin-2-ylmethylidene)amine

The new copper(II) complex, namely, di-μ-chlorido-bis{chlorido[methyl(pyridin-2-ylmethylidene)amine-κ2 N,N′]copper(II)}, [Cu2Cl4(C7H8N2)2], (I), with the ligand 2-pyridylmethyl-N-methylimine (L, a product of Schiff base condensation between methylamine and 2-pyridinecarbaldehyde) is built of discrete centrosymmetric dimers. The coordination about the CuII ion can be described as distorted square pyramidal. The base of the pyramid consists of two nitrogen atoms from the bidentate chelate L [Cu—N = 2.0241 (9), 2.0374 (8) Å] and two chlorine atoms [Cu—Cl = 2.2500 (3), 2.2835 (3) Å]. The apical position is occupied by another Cl atom with the apical bond being significantly elongated at 2.6112 (3) Å. The trans angles of the base are 155.16 (3) and 173.79 (2)°. The Cu...Cu separation in the dimer is 3.4346 (3) Å. In the crystal structure, the loosely packed dimers are arranged in stacks propagating along the a axis. The X-band polycrystalline 77 K EPR spectrum of (I) demonstrates a typical axial pattern characteristic of mononuclear CuII complexes. Compound (I) is redox active and shows a cyclic voltammetric response with E 1/2 = −0.037 V versus silver–silver chloride electrode (SSCE) assignable to the reduction peak of CuII/CuI in methanol as solvent.

SYNTHESIS AND SPECTRAL CHARACTERISTICS OF THE Ru(III,ІІ), Rh(III) AND Pd(II) COMPLEXES BASED ON N-ALLYLTHIOAMIDES AND PRODUCTS THEIR PROTON- AND IODOCYCLIZATION

The paper shows the possibility of using N-allylthioamides H2L1-H2L3 and products of their proton / iodine cyclization HL4, HL5 as chelating agents in the complexation reactions with Ru(III,II), Rh(III) and Pd(II) ions. As a result, a series of new chelating complexes of [M(HL1-3)Cl2(H2O)2], [M(HL1-3)2(H2O)2]Cl (2), [М(HL1-3)2(H2O)Cl] (3), [Ru(HL1-3)(PPh3)2]Cl (4), K[Pd(HL1-3)Cl2] (5), [Pd(HL1-3)2] (6), [M(L4,5)2(H2O)2]Cl (7), K[Pd(L4,5)Cl2] (8), [Pd(L4,5)2] (9) in which the ligands are coordinated to the metal ions by O,S- or O,N-bidentate chelate manner in a monodeprotonated form, where synthesis, isolated in solid state and characterized by the methods of elemental chemical analysis, 1H NMR, IR and UV-Vis spectroscopy. It was found that HL4,5, when complexed, is converted to the corresponding tautomeric form with O,N-coordination through the oxygen atoms of the deprotonated hydroxyl group and the nitrogen atoms of the dihydrothiazolyl ring. It has been established that the allyl moiety does not participate in the formation of a coordination bond with the Ru (III,II), Rh(III) and Pd(II) ions, which is probably due to the presence in the molecules of ligands of other donor nucleophilic centers located in advantageous position for the formation of six-membered chelated metal cycles. In contrast to complexes 1-9, the compounds of [M(HL6)2(H2O)2Cl2]Cl (10), [Pd(HL6)2Cl2] (11) based on 2-(5-(iodomethyl)-1,3-thiazolidin-2-ylidene) malononitrile (HL6) were obtained with monodentate coordination of the ligand in molecular form, which is caused by the presence of two nitrile groups in the HL6 molecule with sp-hybridization of the nitrogen atomic orbitals, which provides almost linear overlap with the d-orbitals of the metal atom upon formation of CN→M bond. The study of the complex formation of metal chlorides with H2L1-H2L3 by the method of isomolar series and UV-Vis spectra showed that there is interaction in the M: L = 1:1, 1:2, 1:3 molar ratio (in the case of Ru3+, Rh3+ ions) and 1:1, 1:2 (in the case of Pd2+ and Ru2+ ions) which is related to the coordination capacity of metals and their ability to form octahedral (for Ru3+, Rh3+ ions) or square-planar (for Pd2+ ions) coordination unit. The reaction of Ru3+, Rh3+ and Pd2+ ions with HL4, HL5 in the isopropanol solution also occurs in the ratio M:L = 1:1, 1:2, 1:3, however, the titration curves are much less pronounced compared to complexes based on H2L1-H2L3. In the interaction of HL6 with the ions of the above metals, the curve has the appearance of an almost straight line, indicating the so-called "state of unsaturation" of the system in the corresponding concentration range due to the monodentate coordination of HL6. The solubility study of the obtained complexes showed that ionic type compounds 2, 4, 5, 7, 8, 10 were dissolved in methanol, partially (or completely) in ethanol, and at low concentrations (10-3-10-5 mol/l) - in water, while molecular type compounds 1, 3, 6, 11 are soluble in DMSO and DMF only.

Zinc Binding to Fulvic acids: Assessing the Impact of pH, Metal Concentrations and Chemical Properties of Fulvic Acids on the Mechanism and Stability of Formed Soluble Complexes

The aim of the study was defined as a complementary analysis of molecular interactions between zinc (Zn) and fulvic acids (FAs) at a broad pH range (3–7), different metal concentrations (0–50 mg dm−3) and chemical properties of FAs and their impact on the Zn binding mechanism, stability, and efficiency. The results showed that the complexation reaction prevailed at pH 6 and 7, whereas protons exchange dominated interactions at pH 3. Stability constant of the complexes increased along with pH (logK increased from ~3.8 to 4.2). Complexation was preferred by less-humidified structures of lower molecular mass containing more oxygen groups. The number of fluorophores available for Zn(II) increased from pH 3 to 7 by ~44%. Depending on the pH, complexation involved a bidentate chelate, monodentate and bidentate bridging mode. Zn(II) binding was insufficiently modeled by the classic Stern–Volmer equation and well described by the double logarithmic equation (R > 0.94) as well as by a modified Stern–Volmer formula assuming the existence of available and unavailable fluorophore populations (R > 0.98). The fluorescence ratio of different fluorophores was proposed as an indicator of the binding affinity of various structures. A positive relationship was found between the fraction of accessible fluorophores and Zn(II) binding at pH 7 determined based on proton release (R = 0.91–0.97). The obtained results can find application in controlling the mobility and bioavailability of Zn in different conditions.