Synthesis,characterization, and crystal structure of three cobalt(II) complexes with Schiff bases derived from rimantadine

By condensation of rimantadine and substituted salicylaldehyde, three new Schiff bases, HL¹, HL² and HL³, were synthesized. Then, a mixture of one of the new ligands and cobalt(II) chloride hexahydrate in ethanol led to 1, 2, and 3, respectively. These complexes were characterized by melting point, elemental analysis, infrared spectra, molar conductance, thermal analysis, and single-crystal X-ray diffraction analysis. X-ray diffraction analysis reveals that 1 crystallizes in the orthorhombic system, Pbcn space group; each asymmetric unit consists of one cobalt(II) ion, two deprotonated ligands, and one lattice water. The central cobalt is four coordinate via two nitrogens and two oxygens from the corresponding Schiff base ligand, forming a distorted tetrahedral geometry. Complexes 2 and 3 crystallize in the monoclinic system, P2₁/c space group; each asymmetric unit consists of one cobalt(II), two corresponding deprotonated ligands, one lattice water, and one methanol. The central cobalt is also four-coordinate via two nitrogens and two oxygens from the corresponding Schiff base ligand, forming a distorted tetrahedral geometry.     

Spectrophotometric study of coproporphyrin-I complexes of copper(II) and cobalt(II)

The reagent 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) was used for the spectrophotometric determination of copper(II) and cobalt(II) in the presence of pyridine and imidazole catalysts. Optimum conditions were investigated and the methods were applied to the determination of parts per billion levels of copper(II) and cobalt(II). The Sandell sensitivities of the recommended procedures were 0.568 μm cm⁻² and 0.464 μg cm⁻² (for A = 0.001) for copper and cobalt, respectively. The relative standard deviations were 2.0% for copper and 1.0% for cobalt. The kinetics of the reaction of CPI with copper(II) and cobalt(II) in the presence of the catalysts and the influence of the temperature were studied, and their kinetic constants determined.The influence of light on the photodecomposition of CPI was also studied.     

Synthesis,structures and magnetic properties of copper (II) and cobalt (II) complexes containing pyridyl-substituted nitronyl nitroxide and 3,5-dinitrobenzoate

Four new metal-radical complexes - [Cu(NIT3Py)₂(DTB)₂] 1, [Co(NIT3Py)₂(DTB)₂(CH₃OH)₂] 2, [Cu(NIT4Py)₂(DTB)₂(H₂O)₂] 3, [Co(NIT4Py)₂(DTB)₂(H₂O)₂] 4, (NIT3Py = 2-(3^′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide], NIT4Py = 2-(4^′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide], DTB = 3,5-dinitrobenzoic anion) have been synthesized by using transition metal ions, nitronyl nitroxide radicals as spin carriers, and incorporating 3,5-dinitrobenzoic acid (DTB) as a coligand.     

Synthesis and characterization of copper(II) complexes with 3-methylpicolinic acid. Crystal and molecular structure of bis (3-methylpicolinato- N,O )(4-picoline)copper(II)

Copper(II) complexes of 3-methylpicolinic acid (3-MepicH), namely [Cu(3-Mepic)₂] · 2H₂O (1) and [Cu(3-Mepic)₂(4-pic)] (2) were prepared and characterized by IR spectroscopy and thermal analysis (TGA/DTA). Crystal structure for 2 was determined by X-ray crystal structure analysis. 1 was prepared by reaction of copper(II) sulfate pentahydrate and 3-methylpicolinic acid in aqueous solution, while 2 was prepared by recrystallization of 1 from 4-picoline solution. Structure analysis revealed square-pyramidal copper(II) coordination and N,O-chelating mode of 3-methylpicolinic acid in 2. Copper(II) is coordinated by two 3-Mepic ligands in the basal plane of a square pyramid and by 4-picoline in the apical position. Crystal packing of 2 is dominated by weak intermolecular C–H ··· O hydrogen bonds and π ··· π stacking interactions forming a complex three-dimensional supramolecular architecture.     

Synthesis,crystal structure,Hirshfeld surfaces,and spectral properties of Cu(II) and Co(II) complexes with 3-phenoxymethyl-4-phenyl-5-(2-pyridyl)-1,2,4-triazole

A new asymmetrical substituted triazole, 3-phenoxymethyl-4-phenyl-5-(2-pyridyl)-1,2,4-triazole (L) and its complexes, cis-[Cu₂ L ₂Cl₄]·2CH₃CN (1) and trans-[CoL ₂Cl₂]·2H₂O·2CH₃CN (2), have been synthesized and characterized by IR, single-crystal X-ray diffraction, thermogravimetric analyses and Hirshfeld surfaces. In the structure, two L are mainly stabilized by an intermolecular C–H?N hydrogen bond. In 1 (or 2), each L involves a doubly-bidentate (or chelating bidentate) coordination mode through one pyridine and two nitrogens (or one) of triazole, respectively. Complex 1 has a distorted trigonal bipyramidal [CuN₃Cl₂] core with two cis Cl^? while 2 shows a distorted octahedron [CoN₄Cl₂] with two trans Cl^?. We also prepared molecular Hirshfeld surface and fingerprint plot for L, 1 and 2, which revealed the influence of different metals on coordinate of L.     

Synthesis, structure and magnetic properties of cobalt(II) and copper(II) coordination polymers assembled by phthalate and 4-methylimidazole

New coordination polymers [M(Pht)(4-MeIm)₂(H₂O)]_n (M=Co (1), Cu (2); Pht²⁻=dianion of o-phthalic acid; 4-MeIm=4-methylimidazole) have been synthesized and characterized by IR spectroscopy, X-ray crystallography, thermogravimetric analysis and magnetic measurements. The crystal structures of 1 and 2 are isostructural and consist of [M(4-MeIm)₂(H₂O)] building units linked in infinite 1D helical chains by 1,6-bridging phthalate ions which also act as chelating ligands through two O atoms from one carboxylate group in the case of 1. In complex 1, each Co(II) atom adopts a distorted octahedral N₂O₄ geometry being coordinated by two N atoms from two 4-MeIm, three O atoms of two phthalate residues and one O atom of a water molecule, whereas the square-pyramidal N₂O₃ coordination of the Cu(II) atom in 2 includes two N atoms of N-containing ligands, two O atoms of two carboxylate groups from different Pht, and a water molecule. An additional strong O-H?O hydrogen bond between a carboxylate group of the phthalate ligand and a coordinated water molecule join the 1D helical chains to form a 2D network in both compounds. The thermal dependences of the magnetic susceptibilities of the polymeric helical Co(II) chain compound 1 were simulated within the temperature range 20-300 K as a single ion case, whereas for the Cu(II) compound 2, the simulations between 25 and 300 K, were made for a linear chain using the Bonner-Fisher approximation. Modelling the experimental data of compound 1 with MAGPACK resulted in: g=2.6, |D|=62 cm⁻¹. Calculations using the Bonner-Fisher approximation gave the following result for compound 2: g=2.18, J=-0.4 cm⁻¹.     

Novel 2-aminoimidazole-4-one complexes of copper(II) and cobalt(II): Synthesis,structural characterization and cytotoxicity

A series of 2-aminosubstituted (5Z)-3-phenyl-5-(pyridine-2-ylmethylene)-3,5-dihydro-4H-imidazole-4-ones (L) was prepared by the reaction of the corresponding 2-alkylthio-3,5-dihydro-4H-imidazole-4-ones with morpholine or piperidine in the presence of ytterbium(III) triflate. The resulting ligands were subsequently reacted with CuCl₂·2H₂O and CoCl₂·6H₂O to give the corresponding copper(II) and cobalt(II) complexes, respectively. Analysis revealed that the complexes were formed with an LMCl₂ (M = Cu, Co)-type composition in all cases. The structures of the three cobalt complexes prepared in this way were determined by X-ray crystallography. The results revealed that the cobalt ions in these complexes were tetrahedrally coordinated to two chloride anions and two nitrogen atoms from the pyridine and imidazole moieties of the ligand. The electrochemical properties of the ligands and their complexes were evaluated by cyclic voltammetry, and the results revealed that the first stage in the reduction of the Co(II) and Cu(II) complexes involved the reversible formation of the corresponding Co(I) and Cu(I) complexes, respectively. The cytotoxicity activities of the organic ligands and their complexes were evaluated against several cancer cell lines, including MCF-7, A549 and HEK293 cells. The copper complexes of the organic ligands bearing a phenyl or allyl moiety at their N(3) position together with a piperidine substituent at the 2-position of their imidazolone ring exhibited the greatest cytotoxicity of all of the compounds tested in the current study.     

Coordination properties of 4(5)-hydroxymethylimidazole and 4(5)-hydroxymethyl-5(4)-methylimidazole towards cobalt(II) ions

Two new complexes of imidazole alcohols, 4-hydroxymethylimidazole (4-CH₂OHim) and 4-hydroxymethyl-5-methylimidazole (4-CH₂OH-5-CH₃im), with cobalt(II) of formula [CoL₂(H₂O)₂](NO₃)₂ were obtained. These compounds were described through single X-ray diffraction studies, spectroscopic (Ir. Far-IR, UV-Vis-NIR) and magnetic measurements. In the present complexes imidazole ligands are bidentate coordinating the heterocyclic ring through pyridine-like nitrogen and the oxygen atom of the hydroxymethyl group (chromophore CoN₂O₄). The shape of Co(II) coordination polyhedra is that of a distorted octahedron, with the equatorial plane defined by the 4-CH₂OHim (or 4-CH₂OH-5-CH₃im) bidentate ligands and two water molecules occupying axial positions (i.e. trans to each other). Formation of successive cobalt(II) complexes with 4-CH₂OH-5-CH₃im in aqueous solution was followed quantitatively by potentiometry.     

Complexes of 4- and 5-bromo derivatives of 2-(hydroxymethyl)pyridine with copper(II) and cobalt(II) salts. Synthesis and X-ray crystal structures

Four copper(II) complexes (1–4) and a cobalt(II) complex (5) derived from 4-bromo-2-(hydroxymethyl)pyridine (L¹) or 5-bromo-2-hydroxymethyl)pyridine (L²) with Cu(NO₃)₂·3H₂O, CuCl₂·2H₂O and CoCl₂·6H₂O have been synthesized and their respective crystal structures studied. They show specific influences owing to the different kind of metal cations and counter anions, the hydration as well as the different position of the bromine substitution on both the coordination of the complex unit and the network structure of the crystal lattice. The Cu(II) complexes of L¹ are five-coordinate [Cu(L¹)₂NO₃]NO₃·H₂O (1) and [Cu(L¹)₂Cl]Cl·H₂O (2) species with distorted quadratic pyramidal and trigonal bipyramidal coordination geometries of the N₂O₃ and N₂O₂Cl donor atoms around the Cu(II), respectively. The Cu(II) complexes of L² are six-coordinate [Cu(L²)₂(NO₃)₂] (3) and [Cu(L²)₂Cl(H₂O)]Cl·H₂O (4) species with distorted octahedral coordination geometries of the N₄O₂ and N₂O₃Cl donor atoms. A distorted octahedral coordination geometry of the N₂O₂Cl₂ donor atoms is also found in the complex unit [Co(L²)₂Cl₂] of the Co(II) complex 5 but showing the oxygen atoms of the chelating ligand as well as the chloride ions in a cis-position. Depending on the complex, water molecules and chloride anions are shown to act as stabilizing components of the crystal structure. The comparative structural investigation includes also known structures of the bromine-free ligand analogue 2-(hydroxymethyl)pyridine, illustrating the basic implication of the bromine substitution, mostly perceptible in the different modes of crystal packing.     

Synthesis, crystal structure, spectroscopic and photoluminescence studies of manganese(II), cobalt(II), cadmium(II), zinc(II) and copper(II) complexes with a pyrazole derived Schiff base ligand

Varying coordination modes of the Schiff base ligand H₂L [5-methyl-1-H-pyrazole-3-carboxylic acid (1-pyridin-2-yl-ethylidene)-hydrazide] towards different metal centers are reported with the syntheses and characterization of four mononuclear Mn(II), Co(II), Cd(II) and Zn(II) complexes, [Mn(H₂L)(H₂O)₂](ClO₄)₂(MeOH) (1), [Co(H₂L)(NCS)₂] (2), [Cd(H₂L)(H₂O)₂](ClO₄)₂ (3) and [Zn(H₂L)(H₂O)₂](ClO₄)₂ (4), and a binuclear Cu(II) complex, [Cu₂(L)₂](ClO₄)₂ (5). In the complexes 1-4 the neutral ligand serves as a 3N,2O donor where the pyridine ring N, two azomethine N and two carbohydrazine oxygen atoms are coordinatively active, leaving the pyrazole-N atoms inactive. In the case of complex 5, each ligand molecule behaves as a 4N,O donor utilizing the pyridine N, one azomethine N, the nitrogen atom proximal to the azomethine of the remaining pendant arm and one pyrazole-N atom to one metal center and the carbohydrazide oxygen atom to the second metal center. The complexes 1-4 are pentagonal bipyramidal in geometry. In each case, the ligand molecule spans the equatorial plane while the apical positions are occupied by water molecules in 1, 3 and 4 and two N bonded thiocyanate ions in 2. In complex 5, the two Cu(II) centers have almost square pyramidal geometry (τ = 0.05 for Cu1 and 0.013 for Cu2). Four N atoms from a ligand molecule form the basal plane and the carbohydrazide oxygen atom of a second ligand molecule sits in the apex of the square pyramid. All the complexes have been X-ray crystallographically characterized. The Zn(II) and Cd(II) complexes show considerable fluorescence emission while the remaining complexes and the ligand molecule are fluorescent silent.     

Synthesis,crystal structure,and antibacterial activity of mononuclear nickel(II) and cobalt(III) Schiff-base complexes

Four new mononuclear complexes, [Ni(L¹)(NCS)₂] (1), [Ni(L²)(NCS)₂] (2), [Co(L¹)(N₃)₂]ClO₄ (3), and [Co(L²)(N₃)₂]ClO₄ (4), where L¹ and L² are N,N′-bis[(pyridin-2-yl)methylidene]butane-1,4-diamine and N,N′-bis[(pyridin-2-yl)benzylidene]butane-1,4-diamine, respectively, have been prepared. The syntheses have been achieved by reaction of the respective metal perchlorate with the tetradentate Schiff bases, L¹ and L², in presence of thiocyanate (for 1 and 2) or azide (for 3 and 4). The complexes have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1–4 are distorted octahedral geometries. The antibacterial activity of all the complexes and their constituent Schiff bases have been tested against Gram-positive and Gram-negative bacteria.     

Studies on mononuclear chelates derived from substituted Schiff-base ligands (part 6): synthesis and characterization of a new 3-ethoxysalicyliden- p -aminoacetophenoneoxime and its complexes with cobalt(II), nickel(II), copper(II) and zinc(II)

Schiff-base complexes of cobalt(II), nickel(II), copper(II) and, zinc(II) with 3-ethoxysalicyliden-p-aminoacetophenoneoxime (HL) were prepared and characterized on the basis of elemental analyses, IR, ¹H- and ¹³C-NMR, electronic spectra, magnetic susceptibility measurements, molar conductivity and thermogravimetric analyses (TGA). A tetrahedral geometry has been assigned to the complexes.     

Iron(III), cobalt(II,III), copper(II) and zinc(II) complexes of 2-pyridineformamide 3-piperidylthiosemicarbazone

Reduction of 2-cyanopyridine by sodium in the presence of 3-piperidylthiosemicarbazide produces 2-pyridineformamide 3-piperidylthiosemicarbazone, HAmpip. Complexes with iron(III), cobalt(II,III) copper(II) and zinc(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. In addition, the crystal structures of HAmpip, [Fe(Ampip)₂]ClO₄, [Cu(HAmpip)Cl₂]·CH₃OH and [Zn(HAmpip)Br₂]·C₂H₆SO have been determined. Coordination is via the pyridyl nitrogen, imine nitrogen and thiolato or thione sulfur when coordinating as the anionic or neutral ligand, respectively.     

Cyano-bridged bimetallic complexes of copper(II) with tetracyanonickelate(II). Crystal structure of [Cu(dpt)Ni(CN)4]

Five new complexes of composition [Cu(dpt)Ni(CN)₄] (1) (dpt=dipropylenetriamine), [Cu(dien)Ni(CN)₄]·2H₂O (2) (dien=diethylenetriamine), [Cu(N,N′-dimeen)Ni(CN)₄]·H₂O (3) (N,N′-dimeen=N,N′-dimethylethylenediamine), [Cu(N,N-dimeen)Ni(CN)₄]·H₂O (4) (N,N-dimeen=N,N-dimethylethylenediamine) and [Cu(trimeen)Ni(CN)₄] (5) (trimeen=N,N,N′-trimethylethylenediamine) have been obtained by the reactions of the mixture of Cu(ClO₄)₂·6H₂O, appropriate amine and K₂[Ni(CN)₄] in water and have been characterized by IR and UV–Vis spectroscopies and magnetic measurements. The crystal structure of [Cu(dpt)Ni(CN)₄] (1) has been determined by single-crystal X-ray analysis. The structure of 1 consists of a one-dimensional polymeric chain ---Cu(dpt)---NC---Ni(CN)₂---CN---Cu(dpt)--- in which the Cu(II) and Ni(II) atoms are linked by CN groups. The nickel atom is four coordinate with four cyanide-carbon atoms (two cyano groups are terminal and two cyano groups (in cis fashion) are bridged) in a square-planar arrangement and the copper atom is five coordinate with two cyanide-nitrogen and three dpt-nitrogen atoms, in a distorted square-pyramidal arrangement. The temperature dependence of magnetic susceptibility (2–300 K) was measured for compound 1. The magnetic investigation showed the presence of a very weak antiferromagnetic interaction (J=−0.16 cm⁻¹) between the copper atoms within each chain through the diamagnetic Ni(CN)₄ ²⁻ ions.     

Syntheses and crystal structures of two 2D coordination polymers of cobalt(II) and nickel(II) with the Malonate Dianion Ligand

Two 2D complexes, [Co(mal)(phen)(H₂O)₂] (1) and [Ni(mal)(phen)(H₂O)₂] (2) (mal?=?malonate dianion; phen?=?1,10-phenanthroline), have been synthesized by the reaction of Co(ClO₄)₂·6H₂O and Ni(ClO₄)₂·6H₂O with disodium malonate and 1,10-phenanthroline in MeOH/H₂O solution. Their crystal structures have been determined by X-ray diffraction. The structures of Complexes 1 and 2 show that each metal ion is coordinated by one 1,10-phenanthroline, two water molecules and a malonate ligand forming a distorted octahedral environment and each mononuclear fragment forms a 2D supramolecular network through H-bonding interactions.     

cis-bis(Saccharinato)cobalt(II) and -zinc(II) complexes with 2-dimethylaminoethanol: syntheses,crystal structures,spectroscopic and thermal studies

2-Dimethylaminoethanol (dmea) reacted with tetraaqua-bis(saccharinato)cobalt(II) and -zinc(II) in n-butanol to yield the new complexes cis-[Co(sac)₂(dmea)₂] (1), and cis-[Zn(sac)₂(dmea)₂] (2) (sac?=?saccharinate). The complexes were characterized by elemental analyses, IR spectroscopy, DTA-TG and X-ray crystallography. Both complexes are isomorphous and crystallize in the monoclinic space group P2₁/c. The cobalt(II) and zinc(II) ions are coordinated by two neutral dmea ligands and two sac anions in a distorted octahedral environment. The dmea ligand acts as a bidentate N, O donor through the amine N and hydroxyl O atoms, while the sac ligand exhibits non-equivalent coordination, behaving as an ambidentate ligand; one coordinates to the metal via the carbonyl oxygen atom, while the other is N-bonded. The packing of the molecules in the crystals of both complexes is achieved by aromatic π(sac)–π(sac) stacking interactions, C–H?·?π interactions and weak intermolecular C–H?·?O hydrogen bonds involving the methyl groups of dmea and the sulfonyl oxygen atoms of the sac ligands. IR and UV spectra and thermal analysis are in agreement with the crystal structures.     

Synthesis, structural and magnetic properties of diphenoxo-bridged binuclear mixed-ligand Cu(II) complexes

The copper(II) complexes [Cu₂(phen)₂(HL¹)₂] (ClO₄)₂ (1) and [Cu₂(phen)₂(HL²)₂] (ClO₄)₂ (2) synthesized from two potentially tridentate ligands N-(2-hydroxybenzyl) propanolamine (H₂L¹) and N-(5-methyl-2-hydroxybenzyl) propanolamine (H₂L²) have centrosymmetric bis(μ₂-phenoxo)-bridged dicopper(II) structures. Variable temperature magnetic measurements have revealed the existence of relatively weak antiferromagnetic interactions (1: 2J=−212.5, 2: 2J=−337.0 cm⁻¹) with respect to the bridging angles (1: θ=101.47(18)°, 2: θ=102.79(12)°). The results suggest that the distortion index of the Cu(II) atoms (1: τ=0.73, 2: τ=0.53) may be the major factor governing the spin coupling between the copper(II) centers of these diphenoxo-bridged binuclear complexes. The coordination moieties of complex 1 are connected into a 1D linear structure via intermolecular hydrogen bonds between alkoxyl, amine, and perchlorate groups.