Characterization of Two New Copper(II) Complexes with Saccharinate and Benzimidazole as Ligands

The crystal structure of the complexes [Cu(sac)₂(bzim)₂(H₂O)] ( 1 ) and [Cu(sac)₂(bzim)(H₂O)(EtOH)] · 2 EtOH ( 2 ) (sac = saccharinate anion; bzim = benzimidazole; EtOH = ethanol) was determined by single crystal X‐ray diffractometry. Complex 1 crystallizes in the monoclinic C2/c space group with Z = 8 whereas complex 2 belongs to the triclinic P1 space group with Z = 2. Room temperature magnetic susceptibilities as well as electronic and IR spectra of both complexes were discussed. Their thermal behaviour was investigated by means of TG and DTA methods.     

Oxovanadium(IV) Complexes of tetradentate SCHIFF Bases

The oxovanadium(IV) complexes of the Schiff bases derived from 1,3-diamino-propane-2-ol and salicylaldehyde, 3-aldehydosalicylic acid, 5-chloro-salicylaldehyde, acetyl acetone, and also of the Schiff base derived from 1.3-diaminopropane and salicylaldehyde have been isolated in the pure state and characterized. The structure of these complexes is discussed on the basis of elemental analyses, electronic spectra and magnetic moment values. These complexes are characterized as five co-ordinate compounds having the general formula [VO](L), where, LH₂ = a molecule of dibasic, tetradentate Schiff base. Electronic spectra of the complexes are found to be solvent independent. The compounds are paramagnetic (μ_eff. = 1.76–1.79 B. M.), and are very stable in air.     

Iron(III) Complexes of Tetradentate SCHIFF Bases

The iron(III) complexes of the Schiff bases derived from 1,3-diaminopropane-2-ol and salicylaldehyde (SBH₂), 3-aldehydosalicylic acid (SB′H₂) and acetylacetone (SB″H₂) have been isolated in the pure state and characterized. The structures of these complexes are discussed on the basis of elemental analyses, molecular weights, conductivities and magnetic susceptibilities. The Schiff bases behave as bivalent, tetradentate ligands. Room temperature (30°C) magnetic moments observed for these chelate compounds are lower than the spinonly value for high-spin d⁵ system.     

Copper(II) Complexes with Asymmetrical Schiff Base Ligands Derived from 2‐Acetylpyrazine

New copper(II) complexes of asymmetrical tetradentate Schiff bases containing pyrazine have been prepared and thoroughly characterised by elemental analysis, IR and electronic spectroscopy, mass spectrometry and magnetic measurements. Two alternative methods were used in the isolation of the complexes: template synthesis in the preparation of Cu(SalDpyz)ClO₄ (HSalDPyz = derived from the condensation of salicylaldehyde, acetylpyrazine and 1,2‐ethylendiamine, 2‐methyl‐1,2‐propylendiamine, 1,2‐phenylendiamine) and direct interaction between copper perchlorate and the corresponding Schiff base, as in the isolation of Cu(AEPyz)(ClO₄) (HAEPyz = (Z)‐4‐[2‐{[2‐{[(E)‐1‐(pyrazinyl)ethylidene]amino} ethyl)amino]‐3‐penten‐2‐one)]. [Cu(SalEn)(py)(OClO₃)][Cu(SalEn)(py)]ClO₄ ( 1 ) (SalEn = 4‐(2‐hydroxyphenyl)‐3‐aza‐3‐buten‐1‐amino, py = pyridine), metal precursor in the preparation of Cu(SalEnpyz)(ClO₄) (HSalEnpyz = 2‐{E(2‐{[(E)‐1‐(2‐pyrazinyl)ethylidene]amino}ethyl)imino]methyl}phenol), was crystallographically characterised. The crystal structure of [Cu(AEpyz)]ClO₄ ( 2 ) is also reported.     

Lanthanide(III) Complexes with Pyridine Head Macrocyclic Ligands

The ability of lanthanide(III) ions to form stable complexeswith three different macrocyclic ligands, L¹ , L² and L³ , has been investigated.The Schiff base macrocycle L¹ and its corresponding reduced ligand L² arederived from 2,6-bis(2-formylphenoxymethyl)pyridine and diethylentriamine;the reduced ligand L³ is derived from 2,6-diformylpyridine and N,N-bis(3-aminopropyl)methylamine. Lanthanide nitrate complexes of L¹ and L² have beenprepared by direct reaction between each ligand and the appropriate hydrated lanthanidenitrate; attempts to obtain the corresponding perchlorate complexes have been unsuccessful.All nitrate complexes of L¹ give the expected [1:1, Ln:L¹ ] stoichiometry; however, complexes obtained with L² show a [2:1, Ln:L² ] stoichiometry. Finally, complexation reactions with L³ have been carried out in order to investigatethe coordination capability of this small and flexible ligand towards the Ln(III) ions.     

Synthesis and Characterization of Two New Schiff Base Ligands and their Complexes with Cobalt(II), Nickel(II) and Copper(II)

Two Schiff base ligands, 2-{E-[(5-phenyl-6H-1,3,4-thiadiazin-2yl)imino]methyne}-1-naphthol (L¹H) and 5-nitro-2-{[(5-phenyl-6H-1,3,4-thiadiazin-2-yl)imino]methyne}phenol (L²H) have been prepared from 5-phenyl-6H-1,3,4-thiadiazin-2-amine (A), 2-hydroxynaphthaldehyde (1) and 2-hydroxy-5-nitrobenzaldehyde (2) Mononuclear Co(II), Ni^II and Cu^II complexes of the ligands have been prepared by using Co^II, Ni^II and Cu^II salts with a 1:2 metal:ligand ratio. It was determined that the bidentate behavior of the ligands is accomplished via the phenolic oxygen and the azomethine nitrogen atoms. The structures of the ligands and their complexes were identified by using elemental analyses, i.r., ¹H-n.m.r. spectra, electronic spectra, magnetic susceptibility measurements and thermogravimetric analyses (t.g.a.).     

Structural and Electrochemical Comparison of Copper(II) Complexes with Tripodal Ligands

A series of copper(II) complexes with tripodal polypyridylmethylamine ligands, such as tris(2-pyridylmethyl)amine (tpa), ((6-methyl-2-pyridyl)methyl)bis(2-pyridylmethyl)amine (Me(1)tpa), bis((6-methyl-2-pyridyl)methyl)(2-pyridylmethyl)amine (Me(2)tpa), and tris((6-methyl-2-pyridyl)methyl)amine (Me(3)tpa), have been synthesized and characterized by X-ray crystallography. [Cu(H(2)O)(tpa)](ClO(4))(2) (1) crystallized in the monoclinic system, space group P2(1)/a, with a = 15.029(7) ?, b = 9.268(2) ?, c = 17.948(5) ?, beta = 113.80(3) degrees, and Z = 4 (R = 0.061, R(w) = 0.059). [CuCl(Me(1)tpa)]ClO(4) (2) crystallized in the triclinic system, space group P&onemacr;, with a = 13.617(4) ?, b = 14.532(4) ?, c = 12.357(4) ?, alpha = 106.01(3) degrees, beta = 111.96(2) degrees, gamma = 71.61(2) degrees, and Z = 4 (R = 0.054, R(w) = 0.037). [CuCl(Me(2)tpa)]ClO(4) (3) crystallized in the monoclinic system, space group P2(1)/n, with a = 19.650(4) ?, b = 13.528(4) ?, c = 8.55(1) ?, beta = 101.51(5) degrees, and Z = 4 (R = 0.071, R(w) = 0.050). [CuCl(Me(3)tpa)][CuCl(2)(Me(3)tpa)]ClO(4) (4) crystallized in the monoclinic system, space group P2(1)/a, with a = 15.698(6) ?, b = 14.687(7) ?, c = 19.475(4) ?, beta = 97.13(2) degrees, and Z = 4 (R = 0.054, R(w) = 0.038). All the Cu atoms of 1-4 have pentacoordinate geometries with three pyridyl and one tertiary amino nitrogen atoms, and a chloride or aqua oxygen atom. Nitrite ion coordinated to the Cu(II) center of Me(1)tpa, Me(2)tpa, and Me(3)tpa complexes with only oxygen atom to form nitrito adducts. The cyclic voltammograms of [Cu(H(2)O)(Me(n)()tpa)](2+) (n = 0, 1, 2, and 3) in the presence of NO(2)(-) in H(2)O (pH 7.0) revealed that the catalytic activity for the reduction of NO(2)(-) increases in the order Me(3)tpa < Me(2)tpa < Me(1)tpa < tpa complexes.     

Iridium (I) and Platinum (II) Complexes with Cyanine Dye Base Ligands

The preparation of cyanine dyes by coordination of cyanine dye bases with transition metals is described. The significance of these complexús for the realization of an excitonic high temperature superconductor is discussed.     

New Energetic Copper(II) Complexes With Pyrazolyl Type Ligands

Nine Cu^II complexes ( I – IX ) containing the azide ion and bis‐2,6‐(pyrazol‐1‐yl)pyridine (pp), bis‐2,6‐(pyrazol‐1‐yl)pyridine (dmpp), and 2‐(pyrazol‐1‐yl)‐6‐(3,5‐dimethylpyrazol‐1‐yl)pyridine (mpp), which are derivatives of pyrazolylpyridine, were prepared in nonaqueous medium. These complexes were characterized by elemental analyses and IR spectroscopy. Crystals of one of these complexes [CumppClN₃ ( VII )] were prepared in suitable size, and a molecular structure of this complex was obtained with X‐ray diffraction method. Complexes were examined by thermogravimetry and differential scanning calorimetry methods. Thermal decomposition was observed in complexes including two azide groups similar to that seen in explosives. In the complexes containing one azide group, formation of the Cu^I complexes was observed after thermal decomposition of the azide group.     

Copper(II) Complexes with Chiral Diaminodiamido Ligands: Solution and Structural Studies

Abstract

Three diaminodiamido ligands (S,S)-N,N′-bis(prolyl)ethanediamine (ProNN-2), (S,S)-N,N′-bis(N-methylvalyl)ethanediamine (Me₂ValNN-2), and (S,S)-N,N′-bis(N-methylphenylalanyl)-ethanediamine (Me₂PheNN-2) were synthesised and their complex formation equilibria with copper(II) investigated in aqueous solution by potentiometry and, for ProNN-2, by electronic spectrophotometry. ProNN-2 forms the species [CuLH]³⁺, [Cu₂L₂]⁴⁺, [Cu₂L₂H_?2]²⁺ and [CuLH_?2], Me₂PheNN-2 forms the complexes [CuLH]³⁺, [Cu₂L₂H_?2]²⁺ and [CuLH_?2], whereas Me₂ValNN-2 forms the monomer [CuLH_?1]⁺ but not the dimer. The dimeric cation [Cu₂L₂H_?2]²⁺, of Me₂PheNN-2 has severe steric requirements, as demonstrated by the X-ray crystal structure of the complex [Cu₂L₂H_?2]Cl₂· 12H₂O, of the corresponding non-methylated ligand. Since copper(II) complexes of the ligands examined are used as additives to the mobile phase to perform chiral resolution of D,L-amino acids in RP-HPLC, the present results provide valuable clues to an understanding of the mechanism of the enantiomeric separation.     

Efficient Catalytic Reduction of 4-Nitrophenol Using Copper(II) Complexes with N,O-Chelating Schiff Base Ligands

The reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride was used as a model to test the catalytic activity of copper(II) complexes containing N,O-chelating Schiff base ligands. In this study, a series of copper(II) complexes containing respective Schiff base ligands, N′-salicylidene-2-aminophenol (1), N′-salicylidene-2-aminothiazole (2), and N,N′-bis(salicylidene)-o-phenylenediamine (3), were synthesized and characterized by elemental analysis, Fourier transform infrared (FT-IR), UV-Visible (UV-Vis) and electron paramagnetic resonance (EPR) spectroscopies. The results from the 4-nitrophenol reduction showed that 3 has the highest catalytic activities with 97.5% conversion, followed by 2 and 1 with 95.2% and 90.8% conversions, respectively. The optimization of the catalyst amount revealed that 1.0 mol% of the catalyst was the most optimized amount with the highest conversion compared to the other doses, 0.5 mol% and 1.5 mol%. Recyclability and reproducibility tests confirmed that all three complexes were active, efficient, and possess excellent reproducibility with consistent catalytic performances and could be used again without a major decrease in the catalytic activity.     

A Spectroscopic Study of Thorium(IV) Complexes with bidentate SCHIFF Bases

The complexes of thorium(IV) chloride with bidentate SCHIFF bases have been prepared. The analytical data indicate 1:2 stoichiometry. The complexes are yellow in colour, non-electrolytes in DMF and appear to be octahedral. The UV, IR and NMR spectra of the ligands and the complexes are reported.     

Copper(II), Nickel(II) and Cobalt(II) Complexes of Dibasic Tridentate Schiff Bases

Complexes of Cu(II), Ni(II) and Co(II) with the Schiff bases derived from o-aminobenzoic acid with salicylaldehyde and its 5-chloro and 5-bromo derivatives have been prepared. The 1:1 (metal-ligand) stoichiometry of these complexes is shown by elemental analysis, gravimetric estimations and conductometric titrations while the structures of the complexes are proved by i.r. spectra and thermogravimetric analysis. The magnetic susceptibility and electronic spectra of Cu(II) complexes indicate the nonplanar binuclear structures while that of Ni(II) and Co(II) show their paramagnetic octahedral geometry. The molar conductance values in nitrobenzene indicate the nonelectrolytic behaviour of the complexes. The results show that the complexes of the type (Cu·L)₂, Ni·L·3H₂O and Co·L·3H₂O are formed having solvent molecule in coordination with the metal ion. The monopyridine and monoammonia adducts of Cu(II) complexes were found to be monomeric.     

Insights into Structure and Biological Activity of Copper(II) and Zinc(II) Complexes with Triazolopyrimidine Ligands

In an attempt to increase the biological activity of the 1,2,4-triazolo[1,5-a]pyrimidine scaffold through complexation with essential metal ions, the complexes trans-[Cu(mptp)₂Cl₂] (1), [Zn(mptp)Cl₂(DMSO)] (2) (mptp: 5-methyl-7-phenyl-1,2,4-triazolo[1,5-a]pyrimidine), [Cu₂(dmtp)₄Cl₄]·2H₂O (3) and [Zn(dmtp)₂Cl₂] (4) (dmtp: 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine), were synthesized and characterized as new antiproliferative and antimicrobial species. Both complexes (1) and (2) crystallize in the P2₁/n monoclinic space group, with the tetrahedral surroundings generating a square-planar stereochemistry in the Cu(II) complex and a tetrahedral stereochemistry in the Zn(II) species. The mononuclear units are interconnected in a supramolecular network through π–π interactions between the pyrimidine moiety and the phenyl ring in (1) while supramolecular chains resulting from C-H∙∙∙π interactions were observed in (2). All complexes exhibit an antiproliferative effect against B16 tumor cells and improved antibacterial and antifungal activities compared to the free ligands. Complex (3) displays the best antimicrobial activity against all four tested strains, both in the planktonic and biofilm-embedded states, which can be correlated to its stronger DNA-binding and nuclease-activity traits.     

Mononuclear and Tetranuclear Copper(II) Complexes Bearing Amino Acid Schiff Base Ligands: Structural Characterization and Catalytic Applications

Two new glycine-Schiff base copper(II) complexes were synthesized. Single crystal X-ray diffraction (SCXRD) allowed us to establish the structure of both complexes in the solid state. The glycine-Schiff base copper(II) complex derived from 2′-hydroxy-5′-nitroacetophenone showed a mononuclear hydrated structure, in which the Schiff base acted as a tridentate ligand, and the glycine-Schiff base copper(II) complex derived from 2′-hydroxy-5′-methylacetophenone showed a less common tetranuclear anhydrous metallocyclic structure, in which the Schiff base acted as a tetradentate ligand. In both compounds, copper(II) had a tetracoordinated square planar geometry. The results of vibrational, electronic, and paramagnetic spectroscopies, as well as thermal analysis, were consistent with the crystal structures. Both complexes were evaluated as catalysts in the olefin cyclopropanation by carbene transference, and both led to very high diastereoselectivity (greater than 98%).     

Structures of Nickel(II) and Copper(II) Complexes of 14-Membered Macrocyclic Quadridentate Ligands

The structures of 41 Ni(II) and 17 Cu(II) complexes of macrocyclic quadridentate ligands have been analyzed, and are discussed about bond lengths, bond angles, conformations, and configurations, upon which many conclusions are formed. The inter- or intra-molecular hydrogen bonds exist among ligands and hydrates in many compounds and play an important role in the structures. There are exhibited two distinct peaks on the histogram of the average Ni-N distances, corresponding to four coordination and six coordination; these average Ni-N distances are 1.95(4) Å and 2.10(5) Å, respectively. The most probable structures of Ni(II) macrocyclic compounds have coordination number six for the metal ion, chair forms for six-membered rings, planar structure for the metal ion and the four donor atoms of the quadridentate ligand and an inversion center at the central metal ion.     

Copper(II) Complexes with N,O-Hybrid Ligands based on Pyridyl-Containing Phospholane Oxides

Russian Journal of Coordination Chemistry - New water-soluble copper(II) bis-N,O-chelate complexes [Cu(L2)2Cl2] (I), [Cu2(L1)2Cl4] (II), and [Cu(L1)2Cl]2[CuCl4] (III) (L1, L2 = pyridyl-containing...