Three new mixed‐ligand copper(II) complexes containing glycyl‐l‐valine and N,N‐aromatic heterocyclic compounds: Synthesis,characterization, DNA interaction,cytotoxicity and antimicrobial activity

Three novel copper(II) complexes, [Cu(Gly‐l ‐Val)(HPBM)(H₂O)]·ClO₄·H₂O ( 1 ), [Cu(Gly‐l ‐Val)(TBZ)(H₂O)]·ClO₄ ( 2 ) and [Cu(Gly‐l ‐Val)(PBO)(H₂O)]·ClO₄ ( 3 ) (Gly‐l ‐Val = glycyl‐l ‐valine anion, HPBM = 5‐methyl‐2‐(2′‐pyridyl)benzimidazole, TBZ = 2‐(4′‐thiazolyl)benzimidazole, PBO = 2‐(2′‐pyridyl)benzoxazole), have been prepared and characterized with elemental analyses, conductivity measurements as well as various spectroscopic techniques. The interactions of these copper complexes with calf thymus DNA were explored using UV–visible, fluorescence, circular dichroism, thermal denaturation, viscosity and docking analyses methods. The experimental results showed that all three complexes could bind to DNA via an intercalative mode. Moreover, the cytotoxic effects were evaluated using the MTT method, and the antimicrobial activity of these complexes was tested against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The results showed that the activities are consistent with their DNA binding abilities, following the order of 1 > 2 > 3 .     

Cu(II) and Ni(II)‐1,10‐phenanthroline‐ 5,6‐dione‐amino acid ternary complexes exhibiting pH‐sensitive redox properties

Syntheses, and electrochemical properties of two novel complexes, [Cu(phendio)(L ‐Phe)(H₂O)](ClO₄) ·H₂O (1) and [Ni(phendio)(Gly)(H₂O)](ClO₄)·H₂O (2) (where phendio = 1,10‐phenanthroline‐5,6‐dione, L ‐Phe = L ‐phenylalanine, Gly = glycine), are reported. Single‐crystal X‐ray diffraction results of (1) suggest that this complex structure belongs to the orthorhombic crystal system. The electrochemical properties of free phendio and these complexes in phosphate buffer solutions in a pH range between 2 and 9 have been investigated using cyclic voltammetry. The redox potential of these compounds is strongly dependent on the proton concentration in the range of ? 0.3–0.4 V vs SCE (saturated calomel reference electrode). Phendiol reacts by the reduction of the quinone species to the semiquinone anion followed by reduction to the fully reduced dianion. At pH lower than 4 and higher than 4, reduction of phendio proceeds via 2e^?/3H⁺ and 2e^?/2H⁺ processes. For complexes (1) and (2), being modulated by the coordinated amino acid, the reduction of the phendio ligand proceeds via 2e^?/2H⁺ and 2e^?/H⁺ processes, respectively. Copyright © 2006 John Wiley & Sons, Ltd.     

p‐Toluate‐bridged dinuclear Cu(II) complexes in combination with tridentate chelating ligand: Crystal structure,density functional theory calculation,DNA/protein binding and catecholase activity

The dinuclear Cu(II) complexes [Cu₂(L¹)₂(mb)]?ClO₄ ( 1 ) and [Cu₂(L²)₂(mb)]?ClO₄ ( 2 ) (HL¹ = 2‐[(2‐diethylaminoethylimino)methyl]phenol; HL² = 2‐[1‐(2‐diethylaminoethylimino)propyl]phenol; mb = 4‐methylbenzoate) were synthesized and characterized using X‐ray crystal structure analysis and spectroscopic methods. Complexes 1 and 2 are dinuclear with distorted square pyramidal Cu (II) geometries, where Schiff base coordinates with tridentate (N,N,O) chelating mode and mb bridges two metal centres. Optimized structures and photophysical properties of ligands and complexes were calculated using density functional theory and time‐dependent density functional theory methods using B3LYP functional with 6‐31G (d,p) and LanL2MB basis sets. Interactions of the complexes with bovine serum albumin (BSA) and human serum albumin (HSA) were studied using UV–visible absorption and fluorescence spectroscopies and the calculated values of association constants (M^?1) are 1.7 × 10⁵ ( 1 –BSA), 5.7 × 10⁵ ( 2 –BSA), 1.6 × 10⁵ ( 1 –HSA) and 6.9 × 10⁵ ( 2 –HSA). Interactions of the complexes with calf thymus DNA were also investigated and the binding affinities are 1.4 × 10⁵ and 1.6 × 10⁵ M^?1 for 1 and 2 , respectively. Both complexes catalytically oxidize 3,5‐di‐tert‐butylcatechol to 3,5‐di‐tert‐butylbenzoquinone in the presence of molecular oxygen.     

Methyl substituent effect on one‐dimensional copper(II) coordination polymers containing biologically active ligands: Synthesis,characterization, DNA interactions and cytotoxicities

Three novel water‐soluble copper(II) complexes – {[Cu(phen)(trp)]ClO₄·3H₂O}_n ( 1 ), {[Cu(4‐mphen)(trp)]ClO₄·3H₂O}_n ( 2 ) and [[Cu(dmphen)(trp)(MeOH)][Cu(dmphen)(trp)(NO₃)]]NO₃ ( 3 ) (phen: 1,10‐phenanthroline; 4‐mphen: 4‐methyl‐1,10‐phenanthroline; dmphen: 4,7‐dimethyl‐1,10‐phenanthroline; trp: l ‐tryptophan) – have been synthesized and characterized using various techniques. Complexes 1 and 2 are isostructural, and exist as one‐dimensional coordination polymers. Complex 3 consists of two discrete copper(II) complexes containing [Cu(trp)(dmphen)(MeOH)]⁺, [Cu(trp)(dmphen)(NO₃)] and one nitrate anion. The binding interaction of the complexes with calf thymus DNA (CT‐DNA) was investigated using thermal denaturation, electronic absorption and emission spectroscopic methods, revealing that the complexes could interact with CT‐DNA via a moderate intercalation mode. The binding activity of the complexes to CT‐DNA follows the order: 3  >  2 > 1 . The pUC19 DNA cleavage activity of the complexes was investigated in the absence and presence of external agents using the agarose gel electrophoresis method. Especially, in the presence of H₂O₂ as an activator, the pUC19 DNA cleavage abilities of the complexes are clearly enhanced at low concentration. Addition of hydroxyl radical scavenger dimethylsulfoxide shows a marked inhibition of the pUC19 DNA cleavage activity of the complexes. In vitro cytotoxic effect of the complexes was examined on human tumor cell lines (Caco‐2, A549 and MCF‐7) and healthy cells (BEAS‐2B). The potent cytotoxic effect of complex 3 , with IC₅₀ values of 1.04, 1.16 and 1.72 μM, respectively, is greater relative to clinically used cisplatin (IC₅₀ = 22.70, 31.1 and 22.2 μM) against the Caco‐2, A549 and MCF‐7 cell lines.     

N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamato Complexes of Nickel(II) with Phosphorus Donor Ligands

Planar nickel(II) complexes involving N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamate, such as [NiX(nmedtc)(PPh₃)] (X = Cl, NCS; PPh₃ = triphenylphosphine), and [Ni(nmedtc)(P‐P)]ClO₄(P‐P = 1,1‐bis(diphenylphosphino)methane(dppm); 1,3‐bis(diphenylphosphino)propane (1,3‐dppp); 1,4‐bis(diphenylphosphino)butane(1,4‐dppb) have been synthesized. The complexes have been characterized by elemental analyses, IR and electronic spectroscopies. The increased νC–N value in all the complexes is due to the mesomeric drift of electrons from the dithiocarbamate ligands to the metal atom. Single crystal X‐ray structure of [Ni(nmedtc)(1,3‐dppp)]ClO₄·H₂O is reported. In the present 1,3‐dppp chelate, the P–Ni–P angle is higher than that found in 1,2‐bis(diphenylphosphino)ethane‐nickel chelates and lower than 1,4‐bis(diphenylphosphino)butane‐nickel chelates, as a result of presence of the flexible propyl back bone connecting the two phosphorus atoms of the complex.     

Synthesis,Antibacterial Activities and Nuclease Properties of Ternary Copper(II) Complex Containing 2‐(2′‐Pyridyl)benzothiazole and Glycinate

A new ternary complex [Cu(PBT)(Gly)(H₂O)]ClO₄ (PBT=2‐(2′‐pyridyl)benzothiazole, and Gly=glycinate) has been synthesized and characterized by elemental analysis, molar conductivity, and IR methods. The complex, structurally characterized by single‐crystal X‐ray crystallography, shows a slightly distorted square‐pyramidal coordination geometry in which two nitrogen atoms of PBT and the carboxylate oxygen atom O and the amino nitrogen atom N of Gly bind at the basal plane, a water molecule is coordinated at the apical position. The complex, Cu(ClO₄)₂ and free PBT were each tested for their ability to inhibit the growth of two Gram(?) (Escherichia coil, Salmonella) and two Gram(+) (Bacillus subtilis, Staphylococcus aureus) microorganisms. The complex showed good antibacterial activities against the microorganisms compared with free PBT and Cu(ClO₄)₂. The interaction between the complex and calf thymus DNA in aqueous solution was investigated using electronic spectroscopy, fluorescence spectroscopy, circular dichroic spectroscopy, and viscosity measurements. Results suggest that the complex could bind to DNA by an intercalative mode. In addition, the result of agarose gel electrophoresis showed that the complex can cleave the plasmid DNA by hydroxyl radicals and singlet oxygen‐like species under the condition of physiological pH and room temperature.     

Synthesis,DNA binding,nuclease activity and cytotoxic studies of a wheel‐shaped octanuclear copper(II) complex based on 1,2,4‐triazole

The antitumor activity shown by many platinum complexes has produced a strong interest in research of new organometallic compounds. Among the metal compounds synthesized and tested, copper compounds have received considerable attention because of their cytotoxic activity against solid tumors. A novel wheel‐shaped octanuclear copper(II) complex with a 1,2,4‐triazole derivative ligand formulated as [Cu₈L₄](ClO₄)₈?11H₂O ( 1 ) (L = 3,5‐bis((bis(2‐hydroxylethyl)amino)methyl)‐4 H‐1,2,4,‐triazole‐4‐amine) has been synthesized and structurally characterized. In 1 , eight Cu atoms are linked through 1,2,4‐triazole units and alkoxide bridges to form a centrosymmetric octanuclear Cu(II) metallomacrocycle. The interaction of complex 1 with calf thymus DNA has been studied using UV absorption, fluorescence and circular dichroism spectroscopies, viscosity measurements and cyclic voltammetry. The apparent binding constant (k_app) value for 1 is 1.59 × 10⁵ M^?1. Furthermore, complex 1 displays efficient oxidative cleavage of supercoiled DNA in the presence of external agents, the rate constant for the conversion of supercoiled to nicked DNA being 2.67 × 10^?5 s^?1. Interestingly, cytotoxicity studies on the MCF‐7 human breast cancer cell line show that the IC₅₀ value of 1 is less than that of cisplatin for the same cell line, revealing that it has the potential to act as an effective metal‐based anticancer drug. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis,Characterization and Molecular Structure of Ternary Cu(II) Complex with 1, 4, 8, 9‐Tetraazatriphenylene and L‐Phenylaninate

The complex [Cu(L‐Phe)(TATP)(H₂O)]ClO₄.0.5H₂O has been synthesized and investigated by elemental analysis, molar conductivity, spectroscopic and X‐ray diffraction methods, where TATP= 1,4,8,9‐tetraazatriphenylene and L‐phe = L‐phenylaninate group. The complex crystallizes in the triclinic space group PI with two molecules in a unit cell of dimensions a=0.5730(l), b = 1.0190(2), c = 2.1430(4), α= 97.50 (1)°, β = 95.33(3)°, γ= 102.85(1)°, V= 1.1998(4) nm³, R₁ = 0.0360, wR₂ = 0.0400. The crystal contains two independent [Cu(L‐Phe) (TATP)(H₂O)]⁺ complexes Cu1 and Cu2, having essentially the same distorted square‐pyramidal structure, where each Cu(II) ion coordinates two nitrogen atoms of TATP and the amino nitrogen and carboxylate oxygen atoms of L‐Phe in the equatorial positions and one water oxygen at an axial position.     

Syntheses,Crystal Structures,and Properties of Three Copper(II) Complexes Constructed by 4‐(4,6‐Bis(1H‐pyrazol‐1‐yl)‐1,3,5‐triazin‐2‐yl)morpholine

Three copper(II) complexes of the polydentate N‐donor ligand [4‐(4,6‐bis(1H‐pyrazol‐1‐yl)‐1,3,5‐triazin‐2‐yl)morpholine] (L) with chlorides, nitrates, and perchlorates as anions, namely, [CuCl₂(L)] · 0.5(MeCN) ( 1 ), [Cu(NO₃)₂(H₂O)(L)] · (MeCN) ( 2 ), and [Cu(L)₂](ClO₄)₂ · (MeCN) ( 3 ) were synthesized and structurally characterized by IR, elemental analysis and X‐ray crystallographic analysis. In these complexes, the L ligand binds the copper(II) cation in the tridentate N₃ form. The coordination arrangement around the central copper(II) atom is distorted square‐pyramidal in 1 but it is distorted octahedral in 2 and 3 . The interesting noncovalent interactions such as hydrogen bonds, π–π stacking, and anion–π interactions present in the solid‐state structures are discussed. The crystal results reveal that the counteranions play important roles in determining the diverse structures of these complexes. Moreover, the PXRD, TG, DRS, and fluorescence properties of compounds 1 – 3 were investigated.     

DFT Calculations,Spectroscopic Studies,Biological Activity and Non Linear Optical Properties (NLO) of Novel Ternary Cu(II)‐Chelates Derived from 5‐Acetyl‐4‐hydroxy‐2H‐1,3‐thiazinedione

New ternary Cu(II)‐chelates with the general formula [ML L′(H₂O)_x] (NO₃)_y x (H₂O), x = 0–2 and y = 0–1, (L) = 5‐acetyl‐4‐hydroxy‐2H‐1,3‐thiazine‐2,6(3H)‐dione with in the presence of a secondary ligand (L′) [N,O‐donor; 8 hydroxyquinoline or N,N‐donor; 1,10‐phenanthroline and diethethylendiamine]. Characterization of the synthesized complexes was established based on elemental analysis, molar conductance, magnetic susceptibility measurements, spectral (infrared, electronic, mass, ¹H‐NMR and ESR) as well as thermal gravimetric analysis (TGA). The complexes exhibited octahedral and square planer geometry. The antimicrobial activity for the studied complexes was tested for different kind of organisms. The geometrical and non‐linear optical parameters of the studied complexes 1–3 are investigated theoretically at the B3LYP/GENECP level of theory. The optimized geometries of the studied complexes are non‐planner as indicated from the dihedral angles. The natural charge population (core, valence and Rydberg), exact electronic configuration, total Lewis, and total non‐Lewis is computed and discussed in terms of natural bond orbitals (NBO) analysis. The calculated E_HOMO and E_LUMO energies at the same level of theory of the studied complexes were used to calculate the global properties; hardness (η), global softness (S), electrophilicity (ω) and electronegativity (χ). The total dipole moment (μ_tot), total and anisotropy of polarizability (? α ?), (Δα) and first hyperpolarizability (? β ?) values were calculated and compared with urea as a reference compound. From the values of the computed first hyperpolarizability (? β ?), the ligand and the studied complexes show promising optical properties.     

Stereoselective Synthesis of [5‐[4,4,4,4′,4′,4′‐Hexafluoro‐N‐(2‐hydroxyethoxy)‐D‐valine]]‐ and [5‐[4,4,4,4′,4′,4′‐Hexafluoro‐N‐(2‐hydroxyethoxy)‐L‐valine]cyclosporin A

Addition of various amines to the 3,3‐bis(trifluoromethyl)acrylamides 10a and 10b gave the tripeptides 11a – 11f , mostly as mixtures of epimers (Scheme 3). The crystalline tripeptide 11f ₂ was found to be the N‐terminal (2‐hydroxyethoxy)‐substituted (R,S,S)‐ester HOCH₂CH₂O‐D ‐Val(F₆)‐MeLeu‐Ala‐O^tBu by X‐ray crystallography. The C‐terminal‐protected tripeptide 11f ₂ was condensed with the N‐terminus octapeptide 2b to the depsipeptide 12a which was thermally rearranged to the undecapeptide 13a (Scheme 4). The condensation of the epimeric tripeptide 11f ₁ with the octapeptide 2b gave the undecapeptide 13b directly. The undecapeptides 13a and 13b were fully deprotected and cyclized to the [5‐[4,4,4,4′,4′,4′‐hexafluoro‐N‐(2‐hydroxyethoxy)‐D ‐valine]]‐ and [5‐[4,4,4,4′,4′,4′‐hexafluoro‐N‐(2‐hydroxyethoxy)‐L ‐valine]]cyclosporins 14a and 14b , respectively (Scheme 5). Rate differences observed for the thermal rearrangements of 12a to 13a and of 12b to 13b are discussed.     

Metal Chelates of N‐(2‐pyridylmethyl)iminodiacetate(2‐) Ion (pmda). Part II. Ternary pmda Chelates with M = Co,Cu or Zn and Creatinine as Auxiliary Ligand

The compounds [Cu(pmda)(crea)]·H₂O ( 1 ), [Zn(pmda)(crea)]·H₂O ( 2 ) and [Co(pmda)(crea)(H₂O)]·H₂O ( 3 ) were prepared and characterized by thermal, spectral and X‐ray diffraction methods. In compounds 1 and 2 the M^II coordination is of type 4+1 and approaches to a trigonal bipyramid (71.85 and 86.18 %, respectively) with rather linear N(pmda)‐M^II‐N(crea) trans‐apical angles, but with different longest coordination bond (Cu‐O(pmda) or Zn‐N(apliphatic, pmda), respectively). Both compounds are isotypic and one intra‐molecular interligand N‐H···O interaction reinforces the molecular recogniton crea‐M^II(pmda) chelate. In contrast, the compound 3 exhibits an octahedral coordination, imposed by the 3d⁷ electronic configuration of the cobalt(II) atom, and the crea‐chelate recognition involves the Co‐N(crea) coordination bond and one intramolecular ‘bifurcated’ H‐bonding interaction between one N‐H(crea) bond and one O(pmda) plus the O(aqua) atoms as ‘acceptors’.     

Synthesis and structural and DNA binding studies of mono‐ and dinuclear copper(II) complexes constructed with ─O and ─N donor ligands: Potential anti‐skin cancer drugs

Mononuclear and dinuclear copper(II) complexes with thiophenecarboxylic acid, [Cu(3‐TCA)₂(2,2′‐bpy)] ( 1 ), [Cu(3‐Me‐2‐TCA)₂(H₂O)(2,2′‐bpy)] ( 2 ), [Cu(5‐Me‐2‐TCA)₂(H₂O)(2,2′‐bpy)] ( 3 ) and [Cu₂(2,5‐TDCA)(DMF)₂(H₂O)₂(2,2′‐bpy)₂](ClO₄)₂ ( 4 ) (where 3‐TCA = 3‐thiophenecarboxylic acid; 3‐Me‐2‐TCA = 3‐methyl‐2‐thiophenecarboxylic acid; 5‐Me‐2‐TCA = 5‐methyl‐2‐thiophenecarboxylic acid; 2,5‐TDCA = thiophene‐2,5‐dicarboxylic acid; 2,2′‐bpy = 2,2′‐bipyridyl; DMF = N,N‐dimethylformamide), were synthesized. Compounds 1 – 4 were extensively characterized using both analytical and spectroscopic methods. Additionally, the solid‐state structures of 1 and 4 were unambiguously established from single‐crystal X‐ray diffraction studies. The hexacoordinated Cu(II) centre in 1 (CuO₄N₂) is a distorted octahedral geometry whereas the pentacoodinated 4 (CuO₃N₂) has distorted square pyramidal geometry. Compounds 1 and 4 exhibit intermolecular hydrogen bonding which leads to the formation of two‐ and three‐dimensional supramolecular architectures, respectively. Spectrophotometric and computational investigations suggest that these compounds bind with DNA in minor groove binding such that K_b = 4.9 × 10⁵ M^?1 and K_sv = 3.4 × 10⁵ M^?1, and binding score of ?5.26 kcal mol^?1. The binding affinity of these complexes to calf thymus DNA is in the order 2 > 3 > 4 > 1 . Methyl‐substituted thiophene ring increases the DNA binding affinity whereas unsubstituted thiophene ring DNA binding rate is reduced. The methyl group on the thiophene ring would sterically hinder π–π stacking of the ring with DNA base pairs, and subsequently they are involved in hydrophobic interaction with the DNA surface rather than partial intercalative interaction. Compounds 1 – 4 show pronounced activity against B16 mouse melanoma skin cancer cell lines as measured by MTT assay yielding IC₅₀ values in the micromolar concentration range. The compounds could prove to be efficient anti‐cancer agents, since at a concentration as low as 2.1 μg ml^?1 they exerted a significant cytotoxic effect in cancer cells whereas cell viability was not affected in normal cells.     

Pseudohalide‐directed Assembly of Two Zinc(II) Coordination Polymers with a 3,4‐Bis(3‐pyridyl)‐5‐(4‐pyridyl)‐1,2,4‐triazole Tecton

The zinc(II) pseudohalide complexes {[Zn(L³³⁴)(SCN)₂(H₂O)](H₂O)₂}_n ( 1 ) and [Zn(L³³⁴)(dca)₂]_n ( 2 ) were synthesized and characterized using the ligand 3,4‐bis(3‐pyridyl)‐5‐(4‐pyridyl)‐1,2,4‐triazole (L³³⁴) and ZnCl₂ in presence of thiocyanate (SCN^–) and dicynamide [dca, N(CN)₂^–] respectively. Single‐crystal X‐ray structural analysis revealed that the central Zn^II atoms in both complexes have similar octahedral arrangement. Compound 1 has a 2D sheet structure bridged by bidentate L³³⁴ and double μ_N,S‐thiocyanate anions, whereas complex 2 , incorporating with two monodentate dicynamide anions, displays a two‐dimensional coordination framework bridged by tetradentate L³³⁴ ligand. Structural analysis demonstrated that the influence of pseudohalide anions plays an important role in determining the resultant structure. Both complexes were characterized by IR spectroscopy, microanalysis, and powder X‐ray diffraction techniques. In addition, the solid fluorescence and thermal stability properties of both complexes were investigated.     

Structures and Magnetic Properties of Two Copper(II) Complexes with 2,5‐Dichloro‐3,6‐Dihydroxy‐1,4‐Benzoquinone Dianionic and Tetrachloroquinone Ligand

The polynuclear copper(II) complex [Cu₂(Hdpa)₂(μ‐ClDHBQ)(ClO₄)₂]_n, 1 is bridged by ClDHBQ^?2 (2,5‐dichloro‐3,6‐dihydroxy‐1,4‐benzoquinone dianionic) and 2,2′‐dipyridylamine (Hdpa). In the axial position, Cu is connected with the oxygen atom of ClO. The perchlorate anion may be envisaged as a monodentate O‐bound ligand. Through the bond bridge of O–Cu … O–Cl, the binuclear compound [Cu₂(Hdpa)₂(μ‐ClDHBQ)(ClO₄)₂] is strung together into a long chain compound. Tetrachlorocatechol underwent partial oxidation/hydrolysis/dechlorination processes to produce ClDHBQ^?2. The other mononuclear complex [Cu(Hdpa)(TeCQ)](DMF), 2 , in which tetrachloroquinone (TeCQ) was produced by oxidation of tetrachlorocatechol (TeCC), therefore complex 2 is in the quinone form. The magnetic susceptibility measurements show antiferromagnetic coupling with J = ?11.9 cm^?1, θ = 2.6 K, and g = 2.05 for complex 1. Complex 2 exhibits the typical paramagnetic behavior of s = 1/2.     

Cu (II) tyrosinate complexes containing methyl substituted phenanthrolines: Synthesis,X‐ray crystal structures,biomolecular interactions,antioxidant activity,ROS generation and cytotoxicity

In this paper, three new copper (II) complexes, [Cu(4‐mphen)(tyr)(H₂O)]ClO₄ (1) , [Cu(5‐mphen)(tyr)(H₂O)]ClO₄·1.5H₂O (2) and [Cu (tmphen)(tyr)(NO₃)]0.5H₂O (3) (4‐mphen: 4‐methyl‐1,10‐phenanthroline, 5‐mphen: 5‐methyl‐1,10‐phenanthroline, tmphen: 3,4,7,8‐tetramethyl‐1,10‐phenanthroline and tyr: L‐tyrosine), were synthesized and characterized using elemental analyses, FT‐IR, ESI‐MS, cyclic voltammetry and single‐crystal X‐ray diffraction. It was found that the complexes adopt a distorted five‐coordinate square pyramidal geometry. The interaction of the three complexes with calf thymus DNA was also investigated using UV–visible absorption spectra, ethidium bromide and Hoechst 33258 displacement assay and thermal denaturation. The DNA cleavage activity of the complexes, monitored using gel electrophoresis, showed significant damage of the pUC19 plasmid DNA. Binding activity of bovine serum albumin (BSA) reveals that these complexes can strongly quench the fluorescence of BSA through a static quenching mechanism. The results suggested that interaction of the complexes with DNA occurred through a partial intercalation into the minor grooves of DNA. In addition, interaction of the complexes with bovine serum albumin quenched the fluorescence emission of the tryptophan residues of the protein binding constants and thermodynamic parameters were obtained from the fluorescence quenching experiments at different temperatures. Free radical scavenging activities of the complexes were determined by various in vitro assays such as 1,1‐diphenyl‐2‐picryl‐hydrazyl free radicals (DPPH˙) and H₂O₂ scavenging methods. In addition, the cytotoxicity of these complexes in vitro on tumor cell lines (Caco‐2 and MCF‐7) was examined by XTT and showed better antitumor effect on the tested cells. ROS (reactive oxygen species) and comet experiments are consistent with each other and these complexes lead to DNA damage via the production of ROS. The effect of the hydrophobic properties of the synthesized complexes on DNA and BSA binding activities were discussed.     

Syntheses,Structures, Electrochemistry,and Electrocatalysis of Three Copper(II) Coordination Polymers constructed from 5‐[4‐(1H‐Imidazol‐1‐yl)phenyl]‐1H‐tetrazole

Three coordination polymers (CPs) based on the 5‐[4‐(1H‐imidazol‐1‐yl)phenyl]‐1H‐tetrazole ( HL ) ligand, namely, [Cu(μ₂‐ L )(μ₄‐pbda)(H₂O)] ( 1 ), [Cu₂(μ‐Hbtc)(H₂btc)(μ₃‐OH)(μ₄‐ HL )] ( 2 ) and [Cu₅(μ₃‐ L )(μ₄‐ L )(μ₃‐ip)(μ₃‐OH)(H₂O)₂] · 2H₂O ( 3 ) (H₂pbda = 1,4‐benzenedicarboxylic acid, H₃btc = 1,3,5‐benzenetricarboxylic acid, H₂ip = isophthalic acid) were hydrothermally synthesized and structurally characterized. Complex 1 represents “weave”‐type 2D layers consisting of wave‐like 1D chains and 1D straight chains, which are further connected by hydrogen bonds to form a 3D supramolecular structure. Complex 2 exhibits a uninodal (4)‐connected 2D layer with a point symbol of {4⁴ · 6²}, in which the L ligand can be described as μ₅‐bridging and the H₂btc^– ions display multiple kinds of coordination modes to connect Cu^II ions into 1D “H”‐type Cu‐H₂btc chains. In complex 3 , 2D Cu‐ L layers with two kinds of grids and 1D “stair”‐type Cu‐ip chains link each other to construct a 3D {4¹² · 6³} framework, which contains the pentanuclear subunits. Deprotonated degree and coordination modes of carboxylate ligands may consequentially influence the coordination patterns of main ligands and the final structures of complexes 1 – 3 . Furthermore, electrochemical behaviors and electrocatalytic activities of the title complexes were analyzed at room temperature, suggesting practical applications in areas of electrocatalytic reduction toward nitrite and hydrogen dioxide in aqueous solutions, respectively.     

Antibacterial Activities and Nuclease Properties of Two New Ternary Copper(II) Complexes with 2‐(4′‐Thiazolyl)‐benzimidazole and 2,2′‐Bipyridine/1,10‐phenanthroline

Two new complexes: [Cu(TBZ)(bipy)Cl]Cl·H₂O ( 1 ) and [Cu(TBZ)(phen)Cl]Cl·H₂O ( 2 ) [TBZ=2‐(4′‐thiazolyl)‐ benzimidazole, phen=1,10‐phenanthroline and bipy=2,2′‐bipyridine] have been synthesized and characterized by elemental analysis, molar conductivity, IR, and UV‐vis methods. Complex 2 , structurally characterized by single‐crystal X‐ray crystallography, crystallizes in the monoclinic space group P2₁/c in a unit cell of a=0.85257(12) nm, b=2.5358(4) nm, c=1.15151(13) nm, β=118.721(8)°, V=2.183.2(5) nm³, Z=4, D_c=1.624 g·cm⁻³, µ=1.367 mm⁻¹. The complexes, free ligands and chloride copper(II) salt were each tested for their ability to inhibit the growth of two gram‐positive (B. subtilis and S. aureus) and two gram‐negative (Salmonella and E. coli) bacteria. The complexes showed good antibacterial activities against the microorganisms. The interaction between the complexes and calf thymus DNA in aqueous solution was investigated adopting electronic absorption spectroscopy, fluorescence spectroscopy, viscosity measurements and cyclic voltammetry. Results suggest that the two complexes can bind to DNA by intercalative mode. In addition, the result of agarose gel electrophoresis suggested that the complexes can cleave the plasmid DNA at physiological pH and room temperature. Mechanistic studies with different inhibiting reagents reveal that hydroxyl radicals, and a singlet oxygen‐like copper‐oxo species are all involved in the DNA scission process mediated by the complexes.     

Nucleic Acid Biosensor for Detection of Human Immunodeficiency Virus Using Aquabis(1,10‐phenanthroline)copper(II) Perchlorate as Electrochemical Indicator

The electrochemical behavior of aquabis(1,10‐phenanthroline)copper(II) perchlorate [Cu(H₂O)(phen)₂]·2ClO₄, where phen=1,10‐phenanthroline, on binding to DNA at a glassy carbon electrode (GCE) and in solution, was described. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) results showed that [Cu(H₂O)(phen)₂]²⁺ had excellent electrochemical activity on the GCE with a couple of quasi‐reversible redox peaks. The interaction mode between [Cu(H₂O)(phen)₂]²⁺ and double‐strand DNA (dsDNA) was identified to be intercalative binding. An electrochemical DNA biosensor was developed with covalent immobilization of human immunodeficiency virus (HIV) probe for single‐strand DNA (ssDNA) on the modified GCE. Numerous factors affecting the probe immobilization, target hybridization, and indicator binding reactions were optimized to maximize the sensitivity and speed of the assay. With this approach, a sequence of the HIV could be quantified over the range from 7.8×10^?9 to 3.1×10^?7 mol·L^?1 with a linear correlation of γ=0.9987 and a detection limit of 1.3×10^?9 mol·L^?1.     

2,5‐Bis(2‐(diphenylphosphino)phenyl)‐1,3,4‐oxadiazole ligands and their Cu(I) complexes for Sonogashira coupling reaction

Two diphosphane ligands – 2,5‐bis(2‐(diphenylphosphino)‐5‐R)phenyl)‐1,3,4‐oxadiazole ( L1 , R = H, L2 , R = OMe) and their binuclear complexes, L1Cu and L2Cu , were prepared and characterized. The molecular structures of L1Cu and L2Cu , as perchlorate salts, were established by X‐ray crystallography, which showed them to be binuclear complexes with each Cu atom tetrahedrally coordinated by two P atoms and two N atoms. The ligands and their Cu(I) complexes catalyzed Sonogashira coupling reactions of iodobenzene with phenylacetylene in the presence of K₂CO₃ under Pd‐free conditions. Coupling reactions catalyzed by L1 or L2 with Cu(MeCN)₄ClO₄ in situ exhibited better yields than those by the corresponding Cu(I) complexes L1Cu or L2Cu . Detailed studies showed L1 or L2 with Cu(MeCN)₄ClO₄ to be suitable catalysts for the coupling reaction of terminal alkynes and aryl halides. The coupling reactions of aryl iodides with electron‐withdrawing groups showed better results. Copyright © 2014 John Wiley & Sons, Ltd.