CuN4O2 Chromophore Research Articles

Synthesis, characterization, electrochemical studies and X-ray structures of mixed-ligand polypyridyl copper(II) complexes with the acetate

[Cu(phen)2(CH3COO)](ClO4).2H2O (1) and [Cu(bipy)2(CH3COO)]-(ClO4).H2O (2) {phen = 1,10-phenanthroline, bipy = 2,2?-bipyridine}were synthesized and characterized. The complexes were characterized by employying elemental analyses, infrared and UV-Visible spectroscopy, room temperature magnetic measurements and the crystal structures elucidated using X-ray diffraction experiment. The redox properties of the complexes were also investigated. Both structures have a square pyramidal CuN4O chromophore which exhibit significant distortions due to long Cu-O [2.217(3) ? for (1) and 2.179 (1) for (2)] and Cu-N [2.631(2) ? for (1) and 2.714(1) ? for (2)] bonds. This distortion if further shown by the O-Cu-N bond angles [147.71(8) o for (1) and 153.40(5) o for (2)]. The elemental analyses further support the structural details unveiled by the single crystal X-ray diffraction analysis. The infrared spectra shows the acetate vibrational frequencies at 1587 cm-1,1428 cm-1, 1314 cm-1 for (1) and 1571 cm-1, 1441 cm-1, 1319c m-1 for (2) and the perchlo-rate bands at 1059 cm-1, 720 cm-1 (1) and 1080 cm-1,768 cm-1 (2). The broad d-d bands for the copper ion at 14,514 cm-1(1) and 14,535 cm-1(2) support the adoption of square pyramid geometries. The magnetic moments for the two complexes are 1.83 B.M for (1) and 1.72 B.M for (2). The peak to peak values of the two complexes show that the electrode reactions are quasi-reversibile with ?Ep = 0.023V (1) and 0.025V for (2). In both structures, there are ?-? intermolecular interactions in addition to hydrogen bonding between the units.

Synthesis, crystal structure, properties, and nuclease activity of a new Cu(II) complex [Cu(L)2(Py)2(H2O)] (HL = N-(5-(4-methylphenyl)-[1,3,4]-thiadiazole-2-yl)toluenesulfonamide)

A new N-sulfonamide ligand, N-(5-(4-methylphenyl)-[1,3,4]-thiadiazole-2-yl)toluenesulfonamide (HL) and its Cu(II) complex [Cu(L)2(Py)2(H2O)] (I), have been synthesized. The X-ray crystal structure of the ligand and of complex I have been determined (CIF files CCDC nos. 975153 (HL), 851790 (I)). In I, the Cu2+ ion is five-coordinated, forming a CuN4O chromophore. The ligand acts as monodentate, coordinating the metal ion through a single Nthiadiazole atom. The molecules from the reaction medium (pyridine and water) are also involved in the coordination of the Cu2+ ion. Complex I has a slightly distorted square pyramidal geometry. The complex was characterized by FT-IR, electronic, EPR spectroscopic and magnetic methods. The nuclease activity studies of the synthesized complex confirm his capacity to cleavage the DNA molecule. The ligand has two important roles in the nuclease activity of I: it influence the reactivity of the Cu2+ ion and interact with DNA molecule. The complex interacts with the DNA molecule. Immediately, the Cu2+ ion is reduced to Cu(I), and in the presence of molecular oxygen the formed Cu(I) complex produces reactive oxygen species in close proximity to the double helix.

Nuclease activity and anti-proliferative effect on human cancerous cells of a newly synthesized and characterized mononuclear copper(ii) complex [CuII(L)(fu)2] [L = 2-(2-pyridyl)benzimidazole, fu = furoate

A mononuclear copper(II) complex [CuII(L)(fu)2] (1) [L = 2-(2-pyridyl)benzimidazole, fu = furoate] has been synthesized and characterized by X-ray crystallography. Structural analysis reveals that 1 adopts a distorted square pyramidal geometry with CuN2O3 chromophore. Spectrophotometric and hydrodynamic investigations suggest that the complex binds with DNA in an intercalative mode with a binding constant of (3.19 ± 0.32) × 104 M−1. 1 induces oxidative cleavage of the supercoiled DNA to its nicked circular as well as linear forms. 1 is also proved to be an anti-cancer agent on human keratinocyte cells.

Anionic Amidinourea–Metal(II) Tautomers: MN2O2 or MN4?

Abstract Structures of amidinourea–metal complexes have been obscured by subtle tautomerism and crystal waters. To clarify the most stable form of the tautomers, bis(amidinourea)copper(II) anhydride and the alkyl derivatives were synthesized under basic conditions, and the stability of the CuN2O2 chromophore was suggested. From substituent effects of chelations, UV–vis spectra, IR/Raman spectra, and DFT calculations, it was suggested that the bis(amidinourea)copper(II) has a CuN2O2 chromophore, not CuN4 chromophore. The mutual exclusion rule of IR/Raman spectra supported the trans-CuN2O2 chromophore. Systematic calculations on bis(amidinourea)–Cu(II), –Ni(II), –Pd(II), –Zn(II), and –Cd(II) chelates revealed that the robust stability of CuN2O2 chromophores originates from quasi aromaticity in the six-membered chelate rings. cis- or trans-CuN4 stability reported in the early references is suspicious.

Synthesis, crystallographic characterization and catecholase activity of a monocopper(II) and a dimanganese(III) complex with an anionic Schiff base ligand

The mononuclear [CuII(HL)2] (1) and dinuclear [MnIII2(μ1,3-OAc)2L2] (2) [H2L=N-(2-hydroxypropyl)-3-methoxysalicylaldimine] compounds have been synthesized and characterized using microanalytical, spectroscopic and X-ray crystallographic results. Structural analysis reveals a bidentate chelation behavior of the monoanionic HL ligand, having a distorted square planar coordination environment around copper(II) with a CuN2O2 chromophore. In compound 2, each manganese(III) center has a distorted octahedral geometry, with an MnN2O4 chromophore bridged by two acetate ligands in a μ1,3 fashion. Variable-temperature magnetic susceptibility measurements of 2 indicate an antiferromagnetic interaction between the two manganese(III) centers. Both 1 and 2 behave as effective catalysts towards the oxidation of 3,5-di-tert-butylcatechol to its corresponding quinone with molecular oxygen in methanolic solution.

Bis(2-hy-droxy-benzoato-κO)bis-[3-(4-meth-oxy-phen-yl)-4-(4-methyl-phen-yl)-5-(2-pyrid-yl)-4H-1,2,4-triazole-κN,N]copper(II) dihydrate.

In the title complex, [Cu(C7H5O3)2(C21H18N4O)2]·2H2O, the CuII atom is located on a centre of inversion and exists in a tetra­gonally distorted octahedral geometry with a CuN4O2 chromophore. The intra­molecular O—H⋯O hydrogen bond is highly strained due to the mol­ecular geometry and, as a result, is much shorter than expected. Inter­molecular C—H⋯O and C—H⋯O inter­actions are also observed.

μ-Acetato-μ-aqua-μ-hydroxido-bis[(1,10-phenanthroline)copper(II)] dinitrate monohydrate

The triply bridged title dinuclear copper(II) compound, [Cu(2)(C(2)H(3)O(2))(OH)(C(12)H(8)N(2))(2)(H(2)O)](NO(3))(2)·H(2)O, (I), consists of a [Cu(2)(μ(2)-CH(3)COO)(μ(2)-OH)(phen)(2)(μ(2)-OH(2))](2+) cation (phen is 1,10-phenanthroline), two uncoordinated nitrate anions and one water molecule. The title cation contains a distorted square-pyramidal arrangement around each metal centre with a CuN(2)O(3) chromophore. In the dinuclear unit, both Cu(II) ions are linked through a hydroxide bridge and a triatomic bridging carboxylate group, and at the axial positions through a water molecule. The phenanthroline groups in neighbouring dinuclear units interdigitate along the [010] direction, generating several π-π contacts which give rise to planar arrays parallel to (001). These are in turn connected by hydrogen bonds involving the aqua and hydroxide groups as donors with the nitrate anions as acceptors. Comparisons are made with isostructural compounds having similar cationic units but different counter-ions; the role of hydrogen bonding in the overall three-dimensional structure and its ultimate effect on the cell dimensions are discussed.

Structure and spectroscopic study of a novel complex: Tetrakis(benzimidazole)(perchlorato)copper(II)(perchlorate) hemihydrate

A novel complex tetrakis(benzimidazole)(perchlorato)copper(II)(perchlorate) hemihydrate has been prepared and characterized by single crystal X-ray analysis, FT-IR, Raman and UV–VIS spectroscopy. [Cu(Hbim) 4(ClO 4)](ClO 4)·½H 2O crystallizes in the centrosymmetric space group of triclinic system with two molecules in the asymmetric unit cell. The cupric ion of both independent molecules is coordinated by four nitrogen atoms lying in the basal plane and by an oxygen atom located in the axial position. An extensive network of N H···O hydrogen bonds links the oppositely charged [Cu(Hbim) 4(ClO 4)] + and ClO 4 - units into the 2D supramolecular arrangement parallel to (0 1 1) crystallographic plane. The CuN 4O chromophore adopts a slightly distorted square-pyramidal geometry (SQP), the degree of trigonality ( τ) equals 0.081 and 0.013, for Cu1 and Cu2, respectively. The solid state diffuse-reflectance electronic spectrum shows the principal high-energy band at ca. 19,200 cm −1, which is assigned to the d xy , d xz ≈ d yz → d x 2– y 2 transitions, whereas the shoulder at ca. 16,030 cm −1 can be assigned to the d z 2 → d x 2– y 2 transition. The FT-IR and Raman spectra have been measured and assigned in the range 4000–50 cm −1. The complicated character of the absorption bands arising from the Cl O and N H stretching vibrations confirms the presence of intermolecular hydrogen bonds in crystal. In the far infrared spectrum, the Cu N stretching vibration is assigned at 310 cm −1, while the Cu O stretching vibration contributes mainly to the band at 160 cm −1, which reflects a weak Cu O interaction.

Monodentate coordinated chromate(VI) ion in [Cu(phen)2OCrO3](phen)0.5·4H2O completing the square pyramidal geometry of the copper(II) in the solid state

Novel copper(II) complex of the formula [Cu(phen)2OCrO3](phen)0.5·4H2O (1) (phen = 1,10-phenantroline) was prepared in the crystalline form and characterized by X-ray diffraction and spectroscopic methods (IR-FIR, NIR-Vis–UV, EPR). In the solid state, the CuN4O chromophore adopts a slightly distorted square-pyramidal geometry around the Cu2+ ion with a magnitude of a distortion parameter τ = 0.14. The chromate unit in (1) was found to be a monodentate.

Self-Assembly of an Infinite Copper(II) Chiral Metallohelicate

The self-assembly between a chiral polydentate N8O4 ligand, containing a bis-imidazole unit substituted by 4 l-valine groups, and copper(II) ions leads to an optically pure, infinite M-helical chain. The X-ray diffraction studies revealed that the compound crystallizes in the hexagonal chiral space group P6122 with a single [HValbiim]5− unit coordinating three different copper(II) centers. Cu1 is in a distorted square-pyramidal environment, Cu2 is involved as well in a five-coordinated CuN2O3 chromophore but with a coordination geometry intermediate between a square pyramid and a trigonal bipyramid, and the third copper(II) ion, namely, Cu3, is in a slightly distorted square planar environment defined by three nitrogen atoms and one oxygen atom from two [HValbiim]5− ligands. The resulting double bridge (namely, Cu2−O42′′ and Cu2′′−O42) gives rise to the formation of a hexanuclear entity. The found antiferromagnetic behavior, successfully modeled by an isosceles triangle, is consistent with the strong coup...

Synthesis, crystal structures and DNA-binding properties of two new mononuclear copper(II) complexes

Two mononuclear copper(II) complexes, [Cu(bpy)2(CH3OH)](pic)2 (1) and [Cu(Me2bpy)2(H2O)](pic)2 (2) (bpy = 2,2′-bipyridine; Me2bpy = 4,4′-dimethyl-2,2′-bipyridine; Hpic = 2,4,6-trinitrophenol), were synthesized and characterized by elemental analyses, conductivity measurements, IR, UV–Visible spectroscopy and single crystal X-ray analyses. Both complexes 1 and 2 are mononuclear compounds. The copper atom in complex 1 is in a distorted square pyramidal geometry with a CuN4O chromophore as revealed from the τ value (0.25), while the Cu(II) ion in complex 2 displays a distorted trigonal bipyramidal stereochemistry with τ = 0.72. Hydrogen bonding interactions and π–π stacking interactions link the mononuclear copper complex 1 or 2 into a 1D infinite chain. The interactions of the two mononuclear complexes with herring sperm DNA (HS-DNA) have been studied by UV–visible absorption titration, fluorescence titration and ethidium bromide (EB) displacement experiments. The results suggest that both complexes might bind to DNA by intercalation.

Synthesis, Crystal Structures and Properties of [Cu(L1)2(py)2(H2O)](H2O)[HL1 = N‐(5‐ethyl‐[1,3,4]–thiadiazole‐2‐yl)‐toluenesulfonamidate] and [Cu(L2)2(py)2(H2O)] [HL2 = N‐(5‐ethyl‐[1,3,4]–thiadiazole‐2‐yl)‐benzenesulfonamidate

AbstractA series of new N‐sulfonamidate ligands and their cooper(II) complexes, [Cu(N‐(5‐ethyl‐[1,3,4]‐thiadiazole‐2‐yl)‐toluenesulfonamidate)2(py)2(H2O)](H2O) (1) and [Cu(N‐(5‐ethyl‐[1,3,4]‐thiadiazole‐2‐yl)‐benzenesulfonamidate)2(py)2(H2O)] (2) have been synthesized and characterized. The X‐ray crystal structures of the complexes 1 and 2 have been determined. In the both two complexes, the Cu2+ ion is five‐coordinated, forming a CuN4O chromophore. The ligands act as monodentate, coordinating the metal ion through a single Nthiadiazole atom. The molecules from the reaction medium (pyridine and water) also participate to the coordination of Cu2+ ion as monodentate ligands. Both two complexes have a slightly distorted square pyramidal geometry. The chemical properties of the complexes have been studied by FT‐IR, electronic and EPR spectroscopic methods.

Synthesis and characterization of some new mono- and binuclear copper(II) ternary complexes; X-ray crystal structure of copper(II)- N -(acetyl)phenylglycinate–imidazole ternary complex

A series of new copper(II) ternary complexes with N-(benzoyl)leucinate and N-(acetyl)phenylglycinate and certain N-heterocyclic ligands (quinoxaline, 2,4,6-tris-(2-pyridyl)-1,3,5-triazine and oxalic acid diimidazolide) have been synthesized and characterized by elemental analysis, IR and EPR spectra as well as thermogravimetric analysis. The structure of bis-(N-(acetyl)phenyl-glycinato)-bis-(imidazole)copper(II) was also characterized by X-ray single crystal analysis. The structure consists of monomeric units, in which the copper atom exists in a square-planar geometry with a CuN2O2 chromophore with two centrosymmetrically related carboxyl oxygens and imidazole nitrogen atoms.

Aquamalonato(1,10-phenanthroline)copper(II) sesquihydrate

In the title compound, [Cu(C3H4O4)(C12H8N2)(H2O)]·1.5H2O, there are two complex mol­ecules and three uncoordinated water mol­ecules in the asymmetric unit. In both complex mol­ecules, the Cu atom is five-coordinated by one bidentate 1,10-phenanthroline mol­ecule, one bidentate malonate dianion and one water mol­ecule, resulting in a distorted square-based pyramidal CuN2O3 chromophore. The structure is stabilized by O—H⋯O hydrogen bonds involving both the coordinated and uncoordinated water mol­ecules.

Poly[aquadi-μ3-dicyanamido-di-μ2-dicyanamido-dicopper(II)

The asymmetric unit of the title compound, [Cu2(C2N3)4(H2O)]n, contains two Cu atoms with CuN6 and CuN4O2 chromophores. The Cu atoms lie on inversion centres and the aqua ligands on a crystallographic twofold rotation axis. Two dicyanamide ligands link the metal ions into an infinite three-dimensional structure.

Crystal structures and electronic properties of three fluxional [Cu(di-2-pyridylamine)2(OXO)]Y complexes

The crystal structures of three bis(dpyam)copper(II) complexes, [Cu(dpyam)2(ONO)](SO4)0.5(H2O) (I), [Cu(dpyam)2(O2CCH3)](ClO4) (II) and [Cu(dpyam)2(O2CCH2CH3)](ClO4) (III) (dpyam = di-2-pyridylamine) have been determined at room temperature by single-crystal X-ray methods. The complexes involve a CuN4O2 chromophore with a symmetric cis-distorted octahedral stereochemistry for I, and an asymmetric cis-distorted octahedral stereochemistry for II and III. In I the copper atom and the oxygen donor atoms of the symmetrically bonded nitrito group lie on a crystallographic C 2 axis. This is the first reported example in the literature of such a complex with this type of stereochemistry, involving the [Cu(dpyam)2(OXO)][Y] series as a whole, where (OXO)− involves an oxoanion. In contrast, complexes II and III involve a distortion of the CuN4O2 chromophore towards a square pyramidal (4 + 1 + 1) stereochemistry. Here, the stereochemistries of I, II and III are compared with other closely related complexes. The highly asymmetric geometry of the CuN4O2 chromophores of II and III suggests that both complexes appear to be static in nature. Electronic spectra of the three complexes involve two bands of similar intensity corresponding to cis-distorted octahedral copper(II) stereochemistry.

A rare ferromagnetically coupled asymmetric doubly azido bridged copper(II) dimer with an N, N, O donor Schiff base

A new end-to-end (EE) doubly azido bridged dinuclear complex [Cu 2L 2(μ 1,3-N 3) 2] ( 1) [where L = ( E)-4-(2-(dimethylamino)ethylimino)-1,1,1-trifluoropentan-2-one)] has been synthesized and characterized by elemental and spectroscopic techniques. Single crystal X-ray diffraction analysis reveals that the dimeric complex possesses a center of inversion. Each copper atom in 1 is in a distorted square pyramidal geometry with a CuN 4O chromophore as revealed from the τ value, 0.19. The four basal positions are occupied by two imine N and one keto O atom of the Schiff base and one N atom from the azide anion. Another N atom from a coordinated azide occupies the apical position. Temperature dependent magnetic susceptibility of 1 was fitted using the Bleaney–Bowers expression which led to the parameters J = 13.6 cm −1 and R = 3.4 × 10 −5. It indicates a ferromagnetic interaction through the double azido bridges connecting the individual copper Schiff base units.

Bis(2,2′-bipyridine-κ2N,N′)(hippurato-κO)copper(II) perchlorate dihydrate

In the title complex, [Cu(C9H8NO3)(C10H8N2)2]ClO4·2H2O, the CuN4O2 chromophore exhibits a square-pyramidal geometry that is distorted towards octa­hedral owing to an intra­molecular Cu⋯O contact from the double-bond carboxyl­ate O atom. The cations, anions and solvent water mol­ecules are linked by hydrogen bonds into a linear chain running along the b axis.

Three new dinuclear bis-μ-azido-bridged Cu(II) compounds with di-2-pyridylamine as a ligand: Syntheses, X-ray structure and magnetic measurements

Three new dinuclear copper(II) compounds: [Cu 2(dpyam) 2(μ 1,1-N 3) 2(O 2CH) 2] ( 1), [Cu 2(dpyam) 2(μ 1,1-N 3) 2(O 2CCH 3) 2] ( 2) and [Cu 2(dpyam) 2(μ 1,1-N 3) 2(O 2CCH 2CH 3) 2] ( 3) have been synthesized and characterized crystallographically and spectroscopically. Compounds 1, 2 and 3 consist of a dinuclear unit in which both Cu(II) ions are connected through two end-on azido bridges providing a distorted square pyramidal geometry with a CuN 4O chromophore. The Cu⋯Cu separations are 3.195, 3.200 and 3.247 Å for compounds 1, 2 and 3, respectively. The magnetic properties have been measured in the range from 5 to 300 K and correlated with the molecular structures. All three compounds show a medium to weak ferromagnetic exchange interactions between the Cu(II) ions dominated by the bridging azido ligands, with a singlet-triplet splitting ( J) of 63.3, 63.8 and 5.1 cm −1, for compounds 1, 2 and 3, respectively. A large zero-field splitting of about 0.4 cm −1 is observed in the EPR for compounds 1 and 2.

Coordination chemistry of copper(II) complexes with N4, N4S2, and N4O2 donor macrocyclic ligands: Biological aspects—antifungal, synthesis, spectral studies, and magnetic moments

Three macrocyclic ligands and their complexes with copper(II) salts (with anions Cl−, NO 3 − , and NCS−) were prepared and investigated using a combination of microanalytical analysis, melting point, molar conductance measurement, magnetic susceptibility measurement, and electronic, IR and ESR spectral studies. Ligands L1, L2, and L3 having N4, N4O2, and N4S2 core, respectively, and all the donor atoms of these ligands are bonded with Cu, which is confirmed by a seven-line pattern observed at half-field in the frozen (H2O: MeOH = 10: 1 at pH 10) solution ESR spectrum. The polycrystalline ESR data (g ∥ = 2.20–2.27, g ⊥ = 2.01–2.05, and A ∥ = 120–270) of all the complexes together with the high asymmetry geometry suggest that all complexes appear to be near the static distortion (CuN4O2 and CuN4S2 chromophore geometry). The electronic spectra of the complexes involve two bands at the same intensity corresponding to a cis-distorted octahedral geometry. A common structural feature of both ligand L2 and ligand L3 is that two different donor atoms at five-membered heterocyclic aromatic ring due to this N4O2 and N4S2 chromophore form stable six-membered chelate rings with metals via these two, Cu-O and Cu-S, new interactions comparatively to the first macrocyclic ligand, which has four-membered N,N′-chelate rings. The cyclic voltammetric studies point to a two-step electron transfer indicating the reduction of the two copper atoms to copper(I), i.e., Cu(III)Cu(II) ⇄ Cu(II)Cu(I) ⇄ Cu(I)Cu(0). The molar conductance for the complexes corresponds to 1: 2 and is nonelectrolyte in nature. The magnetic moment (μeff) of the complexes lie in the range between 1.80–1.96 μB. Finally, these complexes were screened for their antimicrobial activity against Aspergillus-niger of fungal strains.