CuN4O2 Chromophore Research Articles

New Copper Complexes with Antibacterial and Cytotoxic Activity.

The discovery of a new non-toxic metal complex with biological activity represents a very active area of research. Two Cu+2 complexes, [Cu4(L1)4(OH)4(DMF)2(H2O)] (C1) (HL1 = N-(5-ethyl-[1,3,4]-thiadiazole-2-yl)-benzenesulfonamide) and [Cu(L2)2(phen)(H2O)] (C2) (HL2 = N-(5-(4-methylphenyl)-[1,3,4]-thiadiazole-2-yl)-naphtalenesulfonamide), with two new ligands were synthesized. The X-ray crystal structures of the complexes were determined. In both complexes, Cu+2 is five-coordinated, forming a CuN2O3 and CuN4O chromophore, respectively. The ligands act as monodentate, coordinating the metal ion through a single Nthiadiazole atom; for the two complexes, the molecules from the reaction medium (phenantroline, dimethylformamide and water) are also involved in the coordination of Cu+2. The complexes have a distorted square pyramidal square-planar geometry. The compounds were characterized by FT-IR and UV-Vis spectroscopy. Using the microdilution method, the antibacterial activity of the complexes was determined against four Gram-positive and two Gram-negative bacteria, with Gentamicin as the positive control. Cytotoxicity studies were carried out on two tumor cell lines (HeLa, DLD-1) and on a normal cell line (HFL1) using the MTT method and Cisplatin as a positive control. Flow cytometric assessment of apoptosis induced by the complexes on the three cell lines was also performed. Both complexes present in vitro biological activities but complex C2 is more active.

Promising catalytic activity of a mononuclear copper(II) complex: Functional mimic for amine and catechol oxidases

Mononuclear mixed ligand copper(II) complex, [Cu(L)(Hdpa)](ClO4) [(H(L)) = 2-((2-dimethylamino)ethyliminomethyl)phenol, tridentate NNO donor ligand and Hdpa = 2,2′-dipyridylamine] has been isolated. The coordination geometry is best described as (4+1) square pyramidal with CuN4O chromophore. In solid-state, it displays self-assembled inter-pair dimer due to (i) inter-pair π-π anti-parallel stacking, and (ii) NH⋅⋅⋅O intermolecular hydrogen bonding, and in solution also it is maintained. The reversible change of oxidation state (Cu(II) ⇌ Cu(I)) occurs at high positive redox potential. The present complex acts as good catalyst to convert benzylamine to benzaldehyde and 3,5-di-tert-butylcatechol to 3,5-di-tert-butyl-o-quinone, hence mimicking the functional properties of amine (type-2) and catechol (type-3) oxidases.

New Cu+2 Complexes with N-Sulfonamide Ligands: Potential Antitumor, Antibacterial, and Antioxidant Agents.

Nowadays, the discovery of a new non-toxic metal complex with biological activity represents a very active area of research. Two Cu+2 complexes, [Cu(L1)2(H2O)3] (C1) (HL1= N-(5-(4-methylphenyl)-[1,3,4]–thiadiazole–2-yl)-naphtalenesulfonamide) and [Cu(L2)2(py)2(H2O)] (C2) (HL2= N-(5-ethyl-[1,3,4]–thiadiazole–2-yl)-naphtalenesulfonamide), with two new ligands were synthesized. The X-ray crystal structures of the complexes were determined. In both complexes, Cu+2 is five-coordinated, forming a CuN2O3 and CuN4O chromophore, respectively. The ligands act as monodentate, coordinating the metal ion through a single Nthiadiazole atom; for the C2 complex, the molecules from the reaction medium (pyridine and water) are also involved in the coordination of Cu+2. The complexes have a distorted square pyramidal square-planar geometry. The compounds were characterized by FT-IR, electronic EPR spectroscopy, and magnetic methods. The nuclease activity studies confirm the complexes’ capacity to cleave the DNA molecule. Using a xanthine-xanthine oxydase system, the SOD mimetic activity of the complexes was demonstrated. Cytotoxicity studies were carried out on two tumor cell lines (HeLa, WM35) and on a normal cell line (HFL1) using the MTT method, with cisplatin used as a positive control. The antibacterial activity of the complexes was investigated against two Gram-positive and two Gram-negative bacteria, and compared with Amoxicillin and Norfloxacin using the disk diffusion method. Both complexes showed in vitro biological activity but the C2 complex was more active. A lack of in vivo toxicity was demonstrated for the C2 complex by performing hepatic, renal, and hematological studies on Swiss mice.

Aqueous Solution Equilibria and Spectral Features of Copper Complexes with Tripeptides Containing Glycine or Sarcosine and Leucine or Phenylalanine

Copper(II) complexes of glycyl-L-leucyl-L-histidine (GLH), sarcosyl-L-leucyl-L-histidine (Sar-LH), glycyl-L-phenylalanyl-L-histidine (GFH) and sarcosyl-L-phenylalanyl-L-histidine (Sar-FH) have potential anti-inflammatory activity, which can help to alleviate the symptoms associated with rheumatoid arthritis (RA). From pH 2–11, the MLH, ML, MLH-1 and MLH-2 species formed. The combination of species for each ligand was different, except at the physiological pH, where CuLH-2 predominated for all ligands. The prevalence of this species was supported by EPR, ultraviolet-visible spectrophotometry, and mass spectrometry, which suggested a square planar CuN4 coordination. All ligands have the same basicity for the amine and imidazole-N, but the methyl group of sarcosine decreased the stability of MLH and MLH-2 by 0.1–0.34 and 0.46–0.48 log units, respectively. Phenylalanine increased the stability of MLH and MLH-2 by 0.05–0.29 and 1.19–1.21 log units, respectively. For all ligands, 1H NMR identified two coordination modes for MLH, where copper(II) coordinates via the amine-N and neighboring carbonyl-O, as well as via the imidazole-N and carboxyl-O. EPR spectroscopy identified the MLH, ML and MLH-2 species for Cu-Sar-LH and suggested a CuN2O2 chromophore for ML. DFT calculations with water as a solvent confirmed the proposed coordination modes of each species at the B3LYP level combined with 6-31++G**.

DNA BINDING, IN VITRO CYTOTOXICITY AND ANTICANCER DRUG MECHANISM OF COPPER(II) COMPLEX CONTAINING PYRIDYL-TRIAZINE LIGAND

Mononuclear copper(II) complex [Cu(dppt)2(H2O)2](ClO4)2 (1), where dppt is bidentate NpyNtz donor asymmetric ligand (pyridyl-triazine) has been isolated. The X-ray crystal structure of 1 possesses a CuN4O2 chromophore with elongated octahedral geometry. The electronic and EPR spectral properties demonstrate that the solvent molecules strongly interacted in the axial position thereby weakens the CuN4 coordination plane. Absorption and emission spectral and electrochemical measurements clearly show the partial intercalative binding of 1 to calf thymus (CT) DNA. Remarkably, it exhibits potent cytotoxicity (IC50, 3.73 M) against human cervical carcinoma cells (HeLa), which is 4.5 times better than cisplatin and is non-toxic (IC50, >500 M) to normal mouse embryonic fibroblasts cells (NIH 3T3). It blocks cell cycle progression of HeLa cells in G1 phase. FACSverse analysis of 1 is suggestive of ROS (reactive oxygen species) generation and absolutely induces apoptotic cell death in HeLa cells.

Fate of model complexes with monocopper center towards the functional properties of type 2 and type 3 copper oxidases.

Green colored mononuclear copper(II) complexes viz. [Cu(L)(bpy)](ClO4) (1) or [Cu(L)(phen)](ClO4) (2) (where H(L) is 2-((2-dimethylamino)ethyliminomethyl)naphthol) show distorted square pyramidal (4 + 1) geometry with CuN4O chromophore. The existence of self-assembled molecular associations indicates the formation of the dimer. Dimeric nature in solution is retained due to the binding of the substrate, encourages steric match between substrate and Cu(II) active site, which favors electron transfer. Interestingly, both the complexes exhibit high-positive redox potential. Therefore, the presence of self-assembled molecular association along with the positive redox potential enhances the catalytic oxidation of ascorbic acid to dehydroascorbic acid or benzylamine to benaldehyde or catechol to o-quinone thereby model the functional properties of type 2 and type 3 copper oxidases. Notably, catalytic activity is effective when compared with other reported mononuclear copper(II) complexes and even superior to many binuclear copper(II) complexes. Existence of self-assembled molecular association in solution along with high-positive redox potential favors electron transfer process in mononuclear copper(II) complexes and models the functional properties of type 2 and type 3 copper oxidases.

Synthesis, Structure, Magnetic and Catalytic Competency of a Tetradentate (NNOO) Schiff Base Mediated Dimeric Copper(II) Complex

One dinuclear copper(II) complex {μ-[2,2′-{ethane-1,2-diylbis[(azanylylidene)methanylylidene]}- bis(phenolato)]}-{μ-[2,2′-{ethane-1,2-diylbis[(azanylylidene)methanylylidene]}bis(phenolato)]}- dicopper(II), [Cu2(salen)2] (1) [salen2− = [2,2′-{ethane-1,2-diylbis[(azanylylidene)methanylylidene]}- bis(phenolato)] has been isolated and characterized by X-ray diffraction analysis and spectroscopic studies. X-ray single crystal structure examination revealed that each Cu(II) center in the asymmetric unit of 1 adopts a distorted square planar geometry with a CuN2O2 chromophore, where two asymmetric units are attached through congregation of Salen involving Cu-O bond to form dinuclear molecular unit [Cu2(salen)2]. In crystalline state, these dinuclear entities in 1 are extended through C-H···π interactions and π···π interactions displaying a 3D network structure. The variable-temperature magnetic susceptibility measurement asserted a dominant antiferromagnetic interaction between the copper(II) centers through Cu-O-Cu linkage in 1 with J = -1.46 cm-1. The catalytic efficacy of complex 1 was studied in a series of solvents for the oxidation of styrene and cyclooctene using tert-butyl-hydroperoxide (TBHP) as an active oxidant under mild conditions. The catalytic reaction mixture has been analyzed by gas chromatography and it displayed that the yield of the epoxidation and its selectivity is optimum in acetonitrile medium.

Double end-on azido derivative of a tridentate (NNO) Schiff base dimeric copper(II) complex: synthesis, X-ray structure, magnetic property and catalytic effectiveness

A dimeric copper(II) complex, bis{(2-[1-(aminoethylimino)ethyl]-phenoxo}-di-μ1,1-azido-dicopper(II), [Cu2(L)2(μ2-1,1-N3)2] (1) [L = 2-[1-(aminoethylimino)ethyl]-phenoxo ion], has been isolated using a self-assembly reaction using a 1:1:1 molar ratio of Cu(NO3)2·3H2O, HL and NaN3 in methanol at room temperature and characterized through X-ray diffraction analysis and spectroscopic studies. X-ray structural analysis reveals that 1 consists of two distinct dinuclear molecular units, where each copper(II) center in the individual dinuclear unit adopts a distorted square pyramidal geometry with a CuN4O chromophore ligated through a tridentate (NNO) Schiff base and two N atoms of two different bridging azides in µ1,1-mode. Two Cu(II) centers are linked through double µ2-1,1-N3 bridges to form the dinuclear unit [Cu2(L)2(μ2-1,1-N3)2]. In the crystalline state, the dinuclear units in 1 are associated through weak intermolecular N-H⋯O hydrogen bonds to afford a 2-D sheet structure viewed along the crystallographic a-axis. The small magnitude of the antiferromagnetic interaction (J = –0.45 cm−1) is a result of the long Cu···Cu separation (3.205(2) Å). The catalytic efficacy of 1 was studied in a series of solvents for the epoxidation of alkenes using tert-butyl-hydroperoxide (TBHP) as an efficient oxidant under mild conditions.

A nitrate bridged one-dimensional copper(II) coordination polymer with a tridentate (NNO) Schiff base: synthesis, X-ray structure and catalytic efficacy

A one-dimensional Cu(II) coordination polymer of [Cu(L)(μ-ONO2)]n (1) (HL = 4-methoxy-2-[1-(methylaminoethylimino)methyl]-phenol) with bidentate bridging nitrate has been isolated and characterized by X-ray diffraction analysis and spectroscopic studies. Single crystal X-ray analysis revealed that each copper(II) center in the asymmetric unit of complex 1 adopts a distorted square pyramidal geometry with a CuN2O3 chromophore ligated through a tridentate Schiff base (L) with (NNO) donor sets and two O atoms of bridging nitrate ion. The adjacent copper atoms are connected by bridging nitrate (μ-ONO2) in bidentate fashion affording a 1D coordination polymeric chain structure along the crystallographic b-axis. In the polymeric framework, the Cu…Cu separation is 4.3749(4) A. The catalytic efficacy of complex 1 was studied in a series of solvents for the epoxidation of cyclooctene using tert-butyl-hydroperoxide (TBHP) as an efficient oxidant under mild conditions. The catalytic reaction mixture was analyzed by gas chromatography and the data indicated that the yield of the epoxidation reaction and its selectivity is maximum in acetonitrile medium.

Bis- and mixed-ligand copper(II) complexes of nalidixic acid the antibacterial drug: Mode of nalidixate coordination determines DNA binding and cleavage and cytotoxicity

The new complexes [Cu(nal)2]∙2H2O 1 and [Cu(en)2(nal)2] 2, where H(nal) is the antibacterial drug nalidixic acid, have been isolated and their X-ray structures successfully determined. The complex 1 possesses a square planar CuO4 chromophore constituted by the pyridone and carboxylate oxygen atoms of nalidixate anion. Complex 2 contains a CuN4O2 chromophore with a tetragonally distorted octahedral geometry, and the trans-axial coordination of two nalidixate anions at longer distances to the CuN4 plane constituted by ethylenediamine is stabilized by a network of H-bonding. DFT studies illustrate the structures and stabilities of complexes. The DNA binding affinity of 2 (Kb, 9.2 (±0.2) × 104 M−1) is higher than that of [Cu(en)2]2+ [Kb, 2.0 (±0.2) × 104 M−1], illustrating that bound nal¯ enhances the DNA binding affinity. DNA docking studies reveal that 2 bound to DNA undergoes interesting coordinative distortions more than 1, causing more significant changes in DNA host. Thus, 2 displays oxidative DNA cleavage (ascorbic acid) more prominent than [Cu(en)2]2+, by generating OH radicals, and shows poor cytotoxicity towards A549 lung cancer cell lines.

Functional models for type-2 and type-3 copper oxidases: Self-assembled molecular association in [Cu(L)(Hdpa)](ClO4) determines the catalytic activity

Mononuclear copper(II) complex [Cu(L)(Hdpa)](ClO4) (1), where H(L) is tridentate NNO donor ligand and Hdpa is 2,2′-dipyridylamine has been isolated. The X-ray crystal structure of 1 possesses a CuN4O chromophore with square pyramidal (4 + 1) coordination geometry. It displays self-assembled molecular association viz., (a) intermolecular NH⋯O hydrogen bonding and (b) inter-pair π-π anti-parallel stacking. The complex is catalytically effective in the oxidation of benzylamine to benzaldehyde and 3,5-di-tert-butylcatechol to 3,5-di-tert-butyl-o-quinone, thus act as a functional model for amine oxidase and catechol oxidase respectively.

Cooperative H-bonds, π⋯π and anion⋯π interactions as driving forces in the construction of novel Cu(II) bis(imidazol-2-yl) supramolecular 3D frameworks

Two new Cu(II) complexes with bis(2-imidazolyl) based ligands, with the formula [Cu(BIM)2(SCN)2]·2H2O (BIM = bis(2-imidazol-2-yl)methane) and [Cu(HBIMAM)2(OH2)2](BF4)4·2H2O (BIMAM = bis(2-imidazol-2-yl)methylaminomethane) have been synthesized and characterized. Both compounds contain mononuclear entities as molecular building blocks (MBBs); neutral [Cu(BIM)2(SCN)2] in compound 1 and cationic [Cu(HBIMAM)2(OH2)2]4+ in compound 2. The coordination around the metal atoms shows a tetragonally-elongated octahedral geometry (CuN4S2 and CuN4O2 chromophores). The Q-band EPR spectra of both compounds are indicative of an essentially dx2-y2 ground state for copper(II) ions. The analysis of the crystal structures of both compounds shows a cooperative relationship between conventional hydrogen bonds and other non-covalent interactions. Thus, in compound 1 concerted π⋯π interactions are the driving force in the construction of one-dimensional frameworks, which are connected through H-bonds to give 3D structure. On the other hand, in compound 2, cooperative XH⋯F (X = N, O) H-bonds and anion⋯π interactions control the arrangement of the supramolecular 3D framework.

Synthesis and structural features of copper(II) complexes of N,N,N′,N′-tetramethylethylenediamine with 2-chlorobenzoate1− and 2-hydroxybenzoate1−

Two copper(II) coordination complexes, formulated as [Cu(tmen)(Clba)2] (1) and [Cu(tmen)(Hsal)2·H2O] (2) (where tmen = N,N,N′,N′-tetramethyl ethylenediamine (C6H16N2), Clba1− = 2-chlorobenzoate (C7H4ClO21−), and Hsal1− (C7H5O31− = monoanion of o-hydroxybenzoic acid (salicylic acid)), have been synthesized and characterized by elemental combustion analysis, spectroscopic techniques, thermal studies, and single crystal X-ray analyses. Complex 1 consists of two distinct monomeric units in which the coordination environment around the central copper(II) ion is a distorted octahedron with a CuN2O4 chromophore, constituted by a chelating tmen molecule, and two 2-chlorobenzoate1− anions coordinated through their carboxylate-O atoms in an asymmetrical bidentate fashion. Complex 2 is also a monomer and consists of an CuN2O3 chromophore, in which tmen is coordinated to Cu(II) through its two N atoms in a chelating bidentate fashion, and an aqua-O and the two o-hydroxybenzoate1− (HSal1−) anions are coordinated through one of their carboxylate-O atoms in a monodentate mode, forming a square pyramidal structure. Hydrogen bonding interactions especially of O–H…O, N–H…O, and C–H…Cl types interweave monomeric units and stabilize the overall crystal structures in both complexes. Thermal analysis and antibacterial activities of 1 and 2 against various bacterial strains were also investigated.

Synthesis, crystal structure, DNA cleavage and antitumor activity of two copper(II) complexes with N-sulfonamide ligand

Two Cu(II) complexes, [Cu(L1)2(py)2(H2O] (C1) (HL1 = N-(5-(4-methylphenyl)-[1,3,4]-thiadiazole-2-yl)-naphtalenesulfonamide) and [Cu(HL2)4](OH)2 (C2) (HL2 = N-(5-(4-methoxyphenyl)-[1,3,4]-thiadiazole-2-yl)-toluenesulfonamide) with two new obtained ligands were synthesized. The X-ray crystal structures of the complexes have been determined. In the complex C1, the Cu(II) ion is five-coordinated, forming a CuN4O chromophore and in the complex C2, the Cu(II) ion is four-coordinated, forming a CuN4 chromophore. The ligands act as monodentate, coordinating the metal ion through a single Nthiadiazole atom. For the complex C1, the molecules from the reaction medium (pyridine and water) are also involved in the coordination of the Cu(II) ion. The complexes have a slightly distorted square pyramidal square-planar (C1) and a square-planar (C2) geometry. The compounds were characterized by FT-IR, electronic, EPR spectroscopic and magnetic methods. The nuclease activity studies of the synthesized complexes confirm their capacity to cleavage the DNA molecule. The results of in vitro cell cytotoxicity on three carcinoma cell lines (HeLa, A2780 and A2780cisR) are in concordance with the DNA cleavage study and with the SOD-mimetic activity and indicate that both complexes have antitumor activity. The antitumor activity was compared with Cisplatin and C1 complex demonstrated a higher activity. Both complexes overcame the Cisplatin resistance tence in A2789cisR cells whitout enhanced toxicity on normal fibroblastic cells.

Functional mimics of type-2 and type-3 copper oxidases: Self-assembled molecular association in mononuclear copper(II) complex enhances the catalytic activity

Mononuclear copper(II) complexes [Cu(L1/L2)(pybzim)](ClO4) (1–2), where H(L1)/H(L2) is tridentate NNO donor ligand and pybzim is 2-(2-pyridyl)benzimidazole, have been isolated. The X-ray crystal structure of 1 possesses a CuN4O chromophore with distorted square pyramidal geometry. It displays self-assembled molecular association viz., (a) intermolecular N-H⋅⋅⋅O hydrogen bonding, (b) inter-pair π-π anti-parallel stacking and (c) attractive C-H⋅⋅⋅π non-covalent interactions. The complexes are catalytically effective in the oxidation of ascorbic acid to dehydroascorbic acid, benzylamine to benzaldehyde and 3,5-di-tert-butylcatechol to 3,5-di-tert-butyl-o-quinone, thus modeling the activity of type-2 and type-3 copper oxidases.

Synthesis, properties and structure of copper(II) complexes of quinolyl azo derivatives of pyrazole-5-one(thione)

The interaction of 5-methyl-2-phenyl-4-[(8-quinolylhydrazono)]pyrazol-3-one (2) and 5-methyl-2-phenyl-4-(8-quinolylhydrazono)pyrazole-3-thione (4) with copper(II) acetate monohydrate under reflux in ethanol results in the formation of copper(II) azo chelates incorporating CuN4O2 (5) and CuN3S2 (6) chromophores. All the compounds were characterized with FT-IR, EPR, X-ray absorption spectroscopy and magnetic measurements. The structures of complexes 5 and 6 were determined by X-ray single-crystal diffraction. Complex 5 adopts a pseudo-octahedral geometry with a cis disposition of the oxygen atoms around the copper(II) centre, whilst in 6 the copper(II) ion displays a square-pyramidal geometry with a {N3S2} ligand environment.

Synthesis, and structural characterization of mixed ligand copper(II) complexes of N,N,N′,N'-tetramethylethylenediamine incorporating carboxylates

Two ternary copper(II) complexes of N,N,N′,N'-tetramethylethylenediamine (tmen = C6H16N2) with benzoic acid and p-aminobenzoic acid, having the formula [Cu(tmen)(BA)2(H2O)2] (1), and [Cu(tmen)(pABA)2]. 1/2 CH3OH (2) {(Where BA1− = benzoate1− (C6H5CO21−), pABA1− = p-aminobenzoate1- (p-H2NC6H5CO21−)} have been prepared and characterized by elemental combustion analysis, Uv–Visible spectroscopy, FT-IR spectroscopy, thermal, and single crystal X-ray diffraction analyses. The complex 1 is a monomer with distorted octahedral geometry. In its CuN2O4 chromophore, the Cu(II) centre is coordinated by two N atoms of a symmetrically chelating tmen ligand, by two carboxylate-O atoms from two monodentate benzoate1− anions, and by two apical aqua-O atoms, which define the distorted octahedral structure. The complex 2 is a monomer with a distorted square planar coordination geometry. In CuN2O2 chromophore, tmen is coordinated to Cu(II) ion in a chelating bidentate fashion, while the two p-aminobenzoate1- anions coordinate to Cu(II) centre through their carboxylate-O atoms in a monodentate manner, forming a square planar structure. The observed difference between asymmetric ѵas(OCO) and symmetric ѵs(OCO) stretching IR vibrations of the carboxylate moieties for 1 and 2 is 220 cm−1 and 232 cm−1, respectively, which suggests monodentate coordination mode (Δν OCO>200) of the carboxylate groups to Cu(II) ion. Thermogravimetric studies of 1 indicates removal of two water molecules at 171 °C, elimination of a tmen upto 529 °C and of two benzoate groups upto 931 °C. In tga curve of 2, methanol is lost upto 212 °C, while tmen is lost from 212 to 993 °C. The antibacterial activities of these new compounds against various bacterial strains were also investigated.

Syntheses and Structures of Monomeric and Dimeric Ternary Complexes of Copper(II) with 2,2′‐Bipyridyl and Carboxylate Ligands

The syntheses and crystal structures of Cu(C10H8N2)(C9H7O2)(H2O) (1) and [Cu2(C10H8N2)2(C7H6NO2)3(C7H7NO2)]·Cl·3H2O (2) are described [C10H8N2 = 2,2′‐bipyridine (bipy), C9H7O2– = cinnamate anion (cinn–), C7H6NO2– = p‐amino benzoate anion (paba–), and C7H7NO2 = p‐amino benzoic acid (Hpaba)]. Complex 1 [triclinic, space group P1 (no. 2), a = 12.0357 (7) Å, b = 13.8799 (8) Å, c = 16.3225 (9) Å, α = 84.916 (3)°, β = 88.551 (3)°, γ = 67.877 (3)°, V = 2516.0 (2) Å3, Z = 4] contains two molecules in the asymmetric unit: both feature a distorted square‐pyramidal CuN2O3 chromophore arising from the coordination of a bidentate bipy ligand, two monodentate cinn– anions, and a water molecule to the metal ion. The cation in complex 2 [orthorhombic, space group P212121 (no. 19), a = 13.5061 (10) Å, b = 18.1441 (11) Å, c = 18.9671 (13) Å, V = 4648.1 (5) Å3, Z = 4] is dimeric with square pyramidal CuN2O3 and CuN3O2 metal coordination polyhedra: each metal ion is coordinated by a bidentate bipy ligand and two bridging paba– anions; the apical coordination site of one is occupied by an O‐bonded paba– anion and the other by an N‐bonded Hpaba neutral molecule. The cation in 2 is isomeric with the previously reported [Cu2(C10H8N2)2(C7H6NO2)2(C7H7NO2)2]2+ cation, in which both apical Hpaba molecules are N‐bonded to their metal ions.

Synthesis, crystal structure and characterization of new biologically active Cu(II) complexes with ligand derived from N-substituted sulfonamide

A new N-sulfonamide ligand (HL1 = N-(5-(4-methoxyphenyl)-[1,3,4]–thiadiazole–2-yl)-toluenesulfonamide) and two Cu(II) complexes, [Cu(L1)2(py)2] (C1) and [Cu(L2)2(py)2(H2O)] (C2) (HL2 = N-(5-(4-methylphenyl)-[1,3,4]–thiadiazole–2-yl)-benzenesulfonamide) were synthesized. The X-ray crystal structures of the complexes were determined. In the complex C1, the Cu(II) ion is four-coordinated, forming a CuN4 chromophore and in the complex C2, the Cu(II) ion is five-coordinated, forming a CuN4O chromophore. The ligand acts as monodentate, coordinating the Cu(II) ion through a single Nthiadiazole atom. The molecules from the reaction medium (pyridine and water) are also involved in the coordination of the Cu(II) ion. The complexes C1 and C2 are square-planar and a slightly distorted square pyramidal, respectively. The compounds were characterized by FT-IR, electronic, EPR spectroscopic and magnetic methods. The nuclease binding activity studies of the synthesized complexes confirm their capacity to cleave the DNA molecule. The cytotoxicity studies were carried out on melanoma cell line WM35 which confirm that both compounds inhibit the growth of these cells. They have a higher activity compared to a platinum drug, carboplatin. A new N-sulfonamide ligand (HL1= N-(5-(4-methoxyphenyl)-[1,3,4]–thiadiazole–2-yl)-toluenesulfonamide) and two Cu(II) complexes, [Cu(L1) 2 (py) 2 ] and [Cu(L2) 2 (py) 2 (H 2 O)] (HL2= N-(5-(4-methylphenyl)-[1,3,4]–thiadiazole–2-yl)-benzenesulfonamide) were synthesized.The X-ray crystal structures of the complexes have been determined. Interaction of complexes with the DNA molecule and cytotoxicity studies were carried out.

Design of a mononuclear copper(II)-phenanthroline complex: Catechol oxidation, DNA cleavage and antitumor properties

A mononuclear copper(II) complex [Cu(phen)(OH2)2(NO3)](NO3) (1) [phen=1,10-phenanthroline] has been synthesized and structurally characterized by different spectroscopic characterization methods including single crystal X-ray diffraction study. X-ray crystal structure analysis shows that 1 adopts square pyramidal geometry with CuN2O3 chromophore and the molecule crystallises in P21/n space group. 1 has been evaluated as model system for the catechol oxidase enzyme by using 3,5-di-tert-butylcatechol (DTBC) as the substrate in methanol medium, revealing that 1 exhibits greater catalytic activity with Kcat value 3.91×103h−1 compared to a few copper(II) complexes of the same class. Electrochemical analysis suggests that the mononuclar Cu(II) complex mimics the catechol oxidase enzyme in methanolic medium through radical pathway. The complex cleaves the double strand of pBR 322 plasmid DNA in a concentration-dependent manner so as for the DNA to change from super coiled form to both nicked circular and linear forms. The complex is cytotoxic to the human hepatocarcinoma cell HepG2, as revealed in MTT assay. AO/EB and Hoechst 33528 fluorescent staining techniques were used to find the mode of cell death. Interestingly, AO/EB and Hoechst stained cells observed at IC50 concentration shows that 1 brings about conformational change on DNA to induce apoptosis which would be the basis underlying its cytotoxic property.