Preparation,characterization and biological evaluation of two chiral binuclear copper(II) complexes

Two chiral Cu(II) complexes of [Cu₂(R‐L)₂](PF₆)₂·2C₂H₅OH ( 1 ) and [Cu₂(S‐L)₂](PF₆)₂·2C₂H₅OH ( 2 ) (HL = 2‐(Bis(quinolin‐2‐ylmethyl)amino)‐1‐propanol) were designed and synthesized to serve as chemical nucleases and anticancer drugs. X‐ray crystallography revealed that two complexes contain chiral binuclear cations and PF₆^? anions. The interaction of two complexes with CT‐DNA was researched via various spectroscopic techniques and viscosity measurement, indicating that the complexes were bound to CT‐DNA by a classical intercalation binding mode. In addition, the two complexes exhibited remarkable DNA cleavage activity with an optimal dosage of 10 μM in the absence of any exogenous oxidant agent. Both of the complexes showed excellent in vitro cytotoxicity on A549 cell lines with IC₅₀ values in the low micromolar range. Moreover, complex 2 could damage DNA of A549 cells into fragmentation and then induced cell apoptosis in a dose‐dependent manner, which was demonstrated by comet assay and Hoechst 33342 staining experiment. Further research showed that complex 2 could also induce G₂ and S phase cell cycle arrest.     

Zinc(II)‐N2O2 ligation complex‐based DNA/protein binder and cleaver having enhanced cytotoxic and phosphatase activity

The alkyne arms containing zinc(II) N₂O₂ ligation complexes ( 1 ) and ( 2 ) were prepared from 2,2′‐{cyclohexane‐1,2‐diylbis[nitrilo(E)methylylidene]}bis[5‐(prop‐2‐yn‐1‐yloxy)phenol] (L¹) and 2,2′‐{1,2‐phenylenebis[nitrilo(E)methylylidene]}bis[5‐(prop‐2‐yn‐1‐yloxy)phenol] (L²) and characterized by analytical and various spectral techniques. The molecular geometry of 1 and 2 was optimized by Density Functional Theory (DFT) at B3LYP/6‐311G(d,p) level and compared with literature. The complexes are stable in solution, and their solution structure was assessed using NMR and ESI‐MS spectroscopy. Topological analysis of the electron density and nature of the bonding in the complexes has been determined by using Bader's AIM method. The interaction and binding modes of calf thymus DNA (CT‐DNA) with complexes ( 1 and 2 ) were investigated by using absorption and emission spectral and viscometric studies. The nuclease activity investigated through gel electrophoresis reveals that 1 and 2 exhibits a significant DNA cleavage activity via a hydrolytic pathway and is further confirmed by an experiment performed in the presence of T4 ligase. The protein binding ability of 1 and 2 with bovine serum albumin (BSA) protein evaluated show good protein binding propensity. In‐vitro cytotoxicity of the complexes has shown significant activity against human brain tumor (U87 MG) and breast carcinoma (BT20) cancer cell lines. The comet assay has been used to determine the extent of DNA fragmentation in cancer cells. The phosphatase activity investigated through kinetic measurements establishes that the zinc complexes possess significant hydrolytic efficiency and follow the order 2  >  1 . The DFT calculations have also been carried out to support the proposed mechanistic pathway of catalytic activity.     

Selective oxidation of benzyl alcohol to benzaldehyde, 1‐phenylethanol to acetophenone and fluorene to fluorenol catalysed by iron (II) complexes supported by pincer‐type ligands: Studies on rapid degradation of organic dyes

Hexacoordinated non‐heme iron complexes [Fe^II(L¹)₂](ClO₄)₂ ( 1 ) and [Fe^II(L²)₂](PF₆)₂ ( 2 ) have been synthesized using ligands L¹ = (E)‐2‐chloro‐6‐(2‐(pyridin‐2ylmethylene) hydrazinyl)pyridine and L² = (E)‐2‐chloro‐6‐(2‐(1‐(pyridin‐2‐yl)ethylidene)hydrazinyl) pyridine]. These complexes are highly active non‐heme iron catalysts to catalyze the C (sp³)?H bonds of alkanes. These iron complexes have been characterized using ESI?MS analysis and molecular structures were determined by X‐ray crystallography. ESI ? MS analysis also helped to understand the generation of intermediate species like Fe^III?OOH and Fe^IV=O. DFT and TD?DFT calculations revealed that the oxidation reactions were performed through high‐valent iron center and a probable reaction mechanism was proposed. These complexes were also utilized for the degradation of orange II and methylene blue dyes.     

Dinuclear Macrocyclic Quinoline Bridged Mercury and Silver Bis(N‐heterocyclic Carbene) Complexes: Synthesis,Structure, and Spectroscopic Studies

Quinoline bridged imidazolium precursors 5,8‐bis(N‐R‐imidazolylidenylmethylene)quinoline PF₆^– salts [H₂L](PF₆)₂ [R = Me ( 1a ), R = naphthylmethyl ( 1b )] were prepared by quaternization of N‐methylimidazole and N‐naphthylmethylimidazole with 5,8‐bis(bromomethyl)quinoline, respectively. Reaction of the imidazolium ligands 1a and 1b with Hg(OAc)₂ and Ag₂O in acetonitrile gave the macrocyclic transition metal carbene complexes [Hg₂L₂](PF₆)₄ ( 2a and 2b ) and [Ag₂L₂](PF₆)₂ ( 3a and 3b ), respectively. All the N‐heterocyclic carbene complexes were characterized in detail by NMR, ESI‐MS, and elemental analysis. Structures of complexes 2a and 3a were determined by X‐ray diffraction studies. Structural studies revealed that the coordination arrangement of the central mercury atom in complex 2a displays a tricoordinate mode and the molecular conformation results in a“closed” form with the bridging quinoline functionality in the macrocycle, whereas the silver complex 3a does not show an coordiantion between the bridging quinoline and the Ag^I ion, which results in an “open” conformation of the macrocycle. The Hg^II and Ag^I NHC complexes showed similar UV absorption and luminescence in acetonitrile solutions.     

DNA binding,cleavage, and cytotoxicity of binuclear phenolate nickel(II) complexes

Three binuclear phenolate complexes, [Ni₂(L¹)₂(OAc)](BPh₄)·DMF (1), [Ni₂(L²)₂(OAc)](BPh₄) (2), and [Ni₂(L³)₂(OAc)](OH)·3H₂O (3), where L¹ = 2-{[bis-(2-hydroxy-ethyl)-amino]-methyl}-4-methyl-phenol, L² = 2-{[bis-(2-hydroxy-ethyl)-amino]-methyl}-4-methoxy-phenol, and L³ = 2-{[bis-(2-hydroxy-ethyl)-amino]-methyl}-4-tert-butyl-phenol), have been synthesized. Single-crystal diffraction reveals that all the metal atoms are in a distorted octahedral geometry. The interactions of the complexes with calf thymus DNA (CT-DNA) have been investigated by UV–vis absorption, fluorescence emission, and circular dichroism spectroscopy and viscosity measurements. Furthermore, DNA cleavage mechanism shows that the complexes may be capable to promote DNA cleavage through oxidative DNA damage pathway, which is indicative of the involvement of hydroxyl radical, singlet oxygen, or singlet oxygen-like entity in the cleavage process. Cytotoxicity studies on the Hela and MCF-7 cancer cell lines show that complexes 1–3 exhibit excellent activity toward the tested tumor cell lines with respect to the standard drug carboplatin, revealing that they have the potential to act as effective metal-based anticancer drugs.     

Heterodinuclear Ruthenium(II) Complexes of the Bridging Ligand 1,6,7,12‐Tetraazaperylene with Iron(II), Cobalt(II), Nickel(II), as well as Palladium(II) and Platinum(II)

The first heterodinuclear ruthenium(II) complexes of the 1,6,7,12‐tetraazaperylene (tape) bridging ligand with iron(II), cobalt(II), and nickel(II) were synthesized and characterized. The metal coordination sphere in this complexes is filled by the tetradentate N,N′‐dimethyl‐2,11‐diaza[3.3](2,6)‐pyridinophane (L‐N₄Me₂) ligand, yielding complexes of the general formula [(L‐N₄Me₂)Ru(µ‐tape)M(L‐N₄Me₂)](ClO₄)₂(PF₆)₂ with M = Fe {[ 2 ](ClO₄)₂(PF₆)₂}, Co {[ 3 ](ClO₄)₂(PF₆)₂}, and Ni {[ 4 ](ClO₄)₂(PF₆)₂}. Furthermore, the heterodinuclear tape ruthenium(II) complexes with palladium(II)‐ and platinum(II)‐dichloride [(bpy)₂Ru(μ‐tape)PdCl₂](PF₆)₂ {[ 5 ](PF₆)₂} and [(dmbpy)₂Ru(μ‐tape)PtCl₂](PF₆)₂ {[ 6 ](PF₆)₂}, respectively were also prepared. The molecular structures of the complex cations [ 2 ]⁴⁺ and [ 4 ]⁴⁺ were discussed on the basis of the X‐ray structures of [ 2 ](ClO₄)₄ · MeCN and [ 4 ](ClO₄)₄ · MeCN. The electrochemical behavior and the UV/Vis absorption spectra of the heterodinuclear tape ruthenium(II) complexes were explored and compared with the data of the analogous mono‐ and homodinuclear ruthenium(II) complexes of the tape bridging ligand.     

Zn(II) and Cu(II) unsymmetrical formamidine complexes as effective initiators for ring‐opening polymerization of cyclic esters

A series of Zn(II) and Cu(II) complexes were synthesized using unsymmetrical N,N′‐ diarylformamidine ligands, i.e. N‐(2‐methoxyphenyl)‐N′‐2,6‐dichorophenyl)‐formamidine ( L1 ), N‐(2‐methoxyphenyl)‐N′‐phenyl)‐formamidine ( L2 ), N‐(2‐methoxyphenyl)‐N′‐(2,6‐dimethylphenyl)‐formamidine ( L3 ) and N‐(2‐methoxyphenyl)‐N′‐(2,6‐diisopropylphenyl)‐formamidine ( L4 ). The complexes, [Zn₂( L1 )₂(OAc)₄] ( 1) , [Zn₂( L2 )₂(OAc)₄] ( 2 ), [Zn₂( L3 )₂(OAc)₄] ( 3 ), [Zn₂( L4 )₂(OAc)₄] ( 4 ), [Cu₂( L1 )₂(OAc)₄] ( 5 ), [Cu₂( L2 )₂(OAc)₄] ( 6 ), [Cu₂( L3 )₂(OAc)₄] ( 7 ) and [Cu₂( L4 )₂(OAc)₄] ( 8 ), were prepared via a mechanochemical method with excellent yields between 95 ‐ 98% by reacting the metal acetates and corresponding ligands. Structural studies showed that both complexes are dimeric with a paddlewheel core structure in which the separation between the two metal centres are 2.9898 (8) and 2.6653 (7) Å in complexes 3 and 7 , respectively. Complexes 1 – 8 were used in ring‐opening polymerization of ε‐caprolactone (ε‐CL) and rac‐lactide (rac‐LA). Zn(II) complexes were more active than Cu(II) complexes, with complex 1 bearing electron withdrawing chloro groups being the most active (k_app = 0.0803 h^‐1). Low molecular weight poly‐(ε‐CL) and poly‐(rac‐LA) ranging from 1720 to 6042 g mol^‐1, with broad molecular weight distribution (PDIs, 1.78 – 1.87) were obtained. Complex 2 gave reaction orders of 0.56 and 1.52 with respect to ε‐CL and rac‐LA, respectively.     

Copper(II) complexes of hydroxyflavone derivatives as potential bioactive molecule to combat antioxidants: synthesis,characterization and pharmacological activities

A variety of novel copper complexes were synthesized and characterized of the formulae [Cu(L¹)(OAc)], [CuL²(H₂O)], [CuL³(H₂O)], [CuL⁴(OAc)], [CuL⁵(H₂O)] [CuL⁶], [CuL⁷], [CuL⁸](OAc) and [CuL⁹], where L¹ L⁹ represents Schiff base ligands [derived by the condensation of 5‐hydroxyflavone with 4‐aminoantipyrine (L¹), o‐aminophenol (L²), o‐aminobenzoic acid (L³), o‐aminothiazole (L⁴), thiosemicarbazide (L⁵), 4‐aminoantipyrine‐o‐aminophenol (L⁶), 4‐aminoantipyrine‐o‐aminobenzoic acid (L⁷), 4‐aminoantipyrine‐o‐aminothiazole(L⁸) and 4‐aminoantipyrine‐thiosemicarbazide (L⁹)]. The spectral and magnetic results of the Cu(II) complexes exhibit square planar geometry. The DNA binding properties of copper complexes were studied by using electronic absorption spectra, viscosity and thermal denaturation experiments. The results show that the complexes were interacting with calf thymus (CT DNA). The in vitro antimicrobial activities of the investigated compounds were tested against the bacterial species and fungal species. Superoxide dismutase and antioxidant activities of the copper complexes have also been studied. Copyright © 2011 John Wiley & Sons, Ltd.     

Linear Pyrazole‐bridged Tetra(N‐heterocyclic carbene) Ligands and Their Hexanuclear Silver(I) Complexes

New hybrid ligands are reported that combine two types of popular donor groups within a single linear scaffold, viz., a central pyrazolate bridge and two appended bis(N‐heterocyclic carbene) units; the ligand strands thus provide two potentially tridentate {NCC} compartments. The pyrazole/tetraimidazolium proligands, [H₅L¹](PF₆)₄ and [H₅L²](PF₆)₄ , were synthesized via multi‐step protocols, and the NH prototropy of [H₅L¹](PF₆)₄ was examined by variable temperature (VT) NMR spectroscopy, giving solvent dependent activation parameters (ΔH^? = 27.6 kJ · mol^–1, ΔS^? = –125 J · mol^–1 · K^–1 in [D₃]MeCN; ΔH^? = 40.4 kJ · mol^–1, ΔS^? = –86.9 J · mol^–1 · K^–1 in [D₆]DMSO) that are in the range typical for pyrazoles. Reaction of the proligands with Ag₂O gave hexametallic complexes [Ag₆(L¹)₂](PF₆)₄ and [Ag₆(L²)₂](PF₆)₄ that involve all six potential donor atoms of the ligands, viz. the four C^NHC and two N^pz donors, in metal coordination. X‐ray crystallography revealed a chair‐like central {Ag₆} deck in both complexes but different arrangements of the ligand strands, which goes along with significantly different Ag^I ··· Ag^I distances that indicate more pronounced argentophilic interactions in case of [Ag₆(L¹)₂]^{4 +}.     

Synthesis, characterization and DNA-binding and DNA-photocleavage studies of two Ru(II) complexes containing two main ligands and one ancillary ligand

DNA-binding and DNA-photocleavage properties of two Ru(II) complexes, [Ru(L¹)(dppz)₂](PF₆)₄ (1) and [Ru(L²)(dppz)₂](PF₆)₄ (2) (L¹ = 5,5′-di(1-(triethylammonio)methyl)-2,2′-dipyridyl cation; L² = 5,5′-di(1-(tributylammonio)methyl)-2,2′-dipyridyl cation; dppz = dipyrido[3,2-a:2′,3′-c]phenazine, have been investigated. Experimental results show that the DNA-binding affinity of complex 1 is greater than that of 2, both complexes emit luminescence in aqueous solution, either alone or in the presence of DNA, complex 1 can bind to DNA in an intercalative mode while 2 most likely interacts with DNA in a partial intercalation fashion, and complex 2 serves as a better candidate for enantioselective binding to CT-DNA compared with 1. Moreover, complex 1 reveals higher efficient DNA cleavage activity than 2, during which supercoiled DNA is converted to nicked DNA with both complexes. Theoretical calculations for the two complexes have been carried out applying the density functional theory (DFT) method at the level of the B3LYP/LanL2DZ basis set. The calculated results can reasonably explain the obtained experimental trends in the DNA-binding affinities and binding constants (K_b) of these complexes.     

Synthesis,structural characterization and catalytic activities of dicopper(II) complexes derived from tridentate pyrazole‐based N2O ligands

A group of a diverse family of dinuclear copper(II) complexes derived from pyrazole‐containing tridentate N₂O ligands, 1,3‐bis(3,5‐dimethylpyrazol‐1‐yl)propan‐2‐ol (Hdmpzpo), 1,3‐bis(3‐phenyl‐5‐methyl pyrazol‐1‐yl)propan‐2‐ol (Hpmpzpo) and 1,3‐bis(3‐cumyl‐5‐methylpyrazol‐1‐yl)propan‐2‐ol (Hcmpzpo), were synthesized and characterized by elemental analysis, IR spectroscopy and three of them also by single‐crystal X‐ray diffraction. Three complexes, [Cu₂(pmpzpo)₂](NO₃)₂·2CH₃OH ( 3 ·2CH₃OH), [Cu₂(pmpzpo)₂](ClO₄)₂ ( 4 ) and [Cu₂(cmpzpo)₂](ClO₄)₂·2DMF ( 7 ·2DMF), each exhibits a dimeric structure with a inversion center being located between the two copper atoms. The metal ion is coordinated in a distorted square planar environment by two pyrazole nitrogen atoms and two bridging alkoxo oxygen atoms. Both complexes 1 ·CH₃OH·H₂O and 3 ·2CH₃OH were investigated in anaerobic conditions for the catalytic oxidation of 3,5‐di‐tert‐butylcatechol (3,5‐DTBC) to the corresponding quinone (3,5‐DTBQ), for modeling the functional properties of catechol oxidase. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis,Crystal Structure and Photoluminescence Property of Zinc(II), Cadmium(II), and Lead(II) Complexes with Bidentate Ligand: 1‐(1‐Imidazolyl)‐4‐(imidazol‐1‐ylmethyl)benzene (IIMB)

Assembly of bidentate ligand 1‐(1‐imidazolyl)‐4‐(imidazol‐1‐ylmethyl)benzene (IIMB) with varied metal salts of Zn^II, Cd^II and Pb^II provide three new complexes, [Zn(IIMB)₂](ClO₄)₂·2H₂O ( 1 ), [Cd(IIMB)₂(SCN)₂] ( 2 ) and [Pb(IIMB)₂(SCN)](SCN) ( 3 ). Single crystal X‐ray diffraction studies revealed that complexes 1 and 2 display a similar one‐dimensional double stranded chain structure, while complex 3 is a slight distorted rhombohedral grid network with (4,4) topology. The results indicate that the coordination geometry of the metal ion and the counter anion have great impact on the structure of the complexes. In addition, the photoluminescence properties of ligand IIMB and complexes 1 – 3 were studied in the solid state at room temperature.     

Co(II), Cu(II) and Zn(II) dinuclear complexes of a polypodal ligand containing phenolate and pyridyl donor groups

Acetate and perchlorate dinuclear metal complexes of Co(II), Cu(II) and Zn(II) with the cresolate polypodal ligand having mixed phenolate and pyridyl pendant functionalities, H₃L, have been synthesized. The complexes were characterized by microanalysis, LSI mass spectrometry, IR, UV–Vis spectroscopy, magnetic studies and conductivity measurements. Crystal structures of H₃L, [Cu₂(HL)(OAc)(H₂O)₂](OAc)·1.5H₂O and [Zn₂L(CH₃OH)₃](ClO₄)CH₃OH·2H₂O complexes, have been also determined.     

Synthesis,Crystal Structures,and Anti‐cervical Cancer Activity Evaluation of Three Trinuclear Transition Metal(II) Complexes with N,O‐Donor Schiff Base Ligand

A new bi‐nucleating Schiff base ligand, 2‐(((3‐(dimethylamino)propyl)imino)methyl)‐6‐methoxyphenol (HL₁) was prepared by a one‐pot condensation reaction, which was further used in the construction of three trinuclear Schiff base transition metal(II) complexes [Cu₃(L1)₂(OH)₂(H₂O)₂](NO₃)₂ ( 1 ), [Co₃(L1)₂(OH)₂(H₂O)₂](NO₃)₂ ( 2 ), and [Cu₃(L1)₂(N₃)₄] ( 3 ). Furthermore, a green hand grinding technique was implemented to reduce the particle size of the coordination complexes to generate the nanoscale compounds. The SEM studies reveal the formation of square and spherical particles for nano 1 and 2 , and nanorod for nano 3 . In addition, the anti‐proliferation activity of nano 1 – 3 was detected on the human cervical cancer Hela cells with CCK‐8 assay. The cell viability curves and IC₅₀ values indicated that only nano 1 has anti‐proliferation activity on Hela cells. To further investigate the mechanism of nano 1 induced Hela cell death, the Annexin V‐FITC/PI double staining assay, western blot assay, and ROS level detection was conducted.     

Syntheses,Structures, and Magnetism of Trinuclear Zn2Ln Complexes with 2,6‐Dipicolinoylbis(N,N‐diethylthiourea)

The bifunctional ligand 2,6‐dipicolinoylbis(N,N‐diethylthiourea) (H₂L) readily reacts with mixtures of Zn(CH₃COO)₂ and LnCl₃ in MeOH at ambient temperature with formation of trinuclear heterobimetallic complexes [Zn₂Ln(L)₂(OAc)₃] ( 1a – 1f ) (Ln = Ce, Nd, Sm, Gd, Dy, Er). The X‐ray single‐crystal diffraction and structural studies of the complexes revealed their isostructural nature, in which two doubly‐charged ligands {L^2–} bind two Zn²⁺ ions with the terminal acylthiourea sites and one Ln³⁺ ion with the central 2,6‐pyridinedicarboxamide site. In the complexes, the coordination numbers of Ln^III and Zn^II ions are 9 and 5, respectively. Magnetic properties of the complexes were studied by temperature‐dependent dc magnetic measurements. The observed μ_eff values at room temperature are all closed to the calculated values. Fitting χ_M and M data of [Zn₂Gd(L)₂(OAc)₃] ( 1d ) shows a g_iso value of 1.94.     

Synthesis of Imines via Reactions of Benzyl Alcohol with Amines Using Half‐Sandwich (η6‐p‐cymene) Ruthenium(II) Complexes Stabilised by 2‐aminofluorene Derivatives

A new class of half‐sandwich (η⁶‐p‐cymene) ruthenium(II) complexes supported by 2‐aminofluorene derivatives [Ru(η⁶‐p‐cymene)(Cl)(L)] ( L  = 2‐(((9H‐fluoren‐2‐yl)imino)methyl)phenol ( L ¹ ), 2‐(((9H‐fluoren‐2‐yl)imino)methyl)‐3‐methoxyphenol ( L ² ), 1‐(((9H‐fluoren‐2‐yl)imino)methyl)naphthalene‐2‐ol ( L ³ ) and N‐((1H‐pyrrol‐2‐yl)methylene)‐9H‐fluorene‐2‐amine ( L ⁴ )) were synthesized. All compounds were fully characterized by analytical and spectroscopic techniques (IR, UV–Vis, NMR) and also by mass spectrometry. The solid state molecular structures of the complexes [Ru(η⁶‐p‐cymene)(Cl)(L²)], [Ru(η⁶‐p‐cymene)(Cl)(L³)] and [Ru(η⁶‐p‐cymene)(Cl)(L⁴)] revealed that the 2‐aminofluorene and p‐cymene moieties coordinate to ruthenium(II) in a three‐legged piano‐stool geometry. The synthesized complexes were used as catalysts for the dehydrogenative coupling of benzyl alcohol with a range of amines (aliphatic, aromatic and heterocyclic). The reactions were carried out under thermal heating, ultrasound and microwave assistance, using solvent or solvent free conditions, and the catalytic performance was optimized regarding the solvent, the type of base, the catalyst loading and the temperature. Moderately high to very high isolated yields were obtained using [Ru(η⁶‐p‐cymene)(Cl)(L⁴)] at 1 mol%. In general, microwave irradiation produced better yields than the other two techniques irrespective of the nature of the substituents.     

Zinc(II) complexes of Triaza and Amidinate ligands: Efficient initiators for the ring‐opening polymerization of ε‐Caprolactone and rac‐Lactide

Zinc complexes supported by tertiary 1,3,5‐triazapenta‐1,3‐dienate ligand (L¹) and N ‐benzoyl‐N′ ‐arylbenzamidinate [aryl =2,6‐diisopropylphenyl (L²), phenyl (L³)] ligands have been synthesized and characterized. The reaction of L¹H with ZnEt₂ affords a mononuclear zinc complex [L¹ZnEt] ( 1 ) in good yield. Tetra nuclear zinc complex [(L¹)₂Zn₄O(OAc)₄] ( 2 ) is prepared by treating L¹H with one equivalent of Zn(OAc)₂ in toluene. Further, dinuclear zinc complexes [L²ZnEt]₂ ( 3 ) and [L³ZnEt]₂ ( 4 ) are obtained in good yields from L²H and L³H with ZnEt₂ in toluene respectively_. The complexes 1–4 have been characterized by ¹H/¹³C NMR spectroscopy and single crystal X‐ray diffraction studies. All of the complexes have been explored for their catalytic activity toward the ring‐opening polymerization (ROP) of ε ‐caprolactone. It has been found that complex 1 is an active catalyst for the polymerization of ε ‐caprolactone in presence of a cocatalyst benzyl alcohol (BnOH). While complex 2 is as active as 1 there is no need for a cocatalyst for the polymerization to proceed. Dinuclear zinc complexes 3 and 4 show very high activity for the ROP of ε ‐caprolactone (CL) and rac ‐lactide (LA) without requiring a cocatalyst. The resultant polymers are found to have very high molecular weight (M _n = 296 X 10³ g mol⁻¹) and relatively narrow polydispersity index compared to 1 and 2 .     

Syntheses,spectral characterization,thermal properties and DNA cleavage studies of a series of Co(II), Ni(II) and Cu(II) polypyridine complexes with some new imidazole derivatives of 1,10-phenanthroline

In the present study three new imidazole derivatives of phen, 2-(4-hydroxy-3,5-diiodophenyl) imidazo[4,5-f][1,10]phenanthroline L¹, 2-(2-hydroxy-3,5-diiodophenyl)imidazo[4,5-f][1,10]phenanthroline L², 2-(4-hydroxy-5-iodo-3-methoxyphenyl)imidazo[4,5-f][1,10]phenanthroline L³ and their nine new polypyridine complexes[M(N–N)₂(L^1–3)](OAc)₂·(nH₂O) where M is Ni(II), Co(II) and Cu(II) and where (N–N)₂ is 2,2′-bipyridine (bpy)₂ or 1,10-phenanthroline (phen)₂ have been synthesized from the reaction of the metal precursor complexes [M(phen)₂(OAc)₂]·(nH₂O) and [M(bpy)₂(OAc)₂]·(nH₂O) with the respective ligands in ethanol and water. The structures of the compounds were determined with the aid of elemental analysis and FT-IR, UV–Vis, ¹H NMR, ESR spectroscopic methods, magnetic measurements and conductance measurements, further analyzed by powder XRD and thermal studies. Elemental analysis data suggested that the complexes have a 1:2:1 molar ratio among the metal and phen or bpy and L¹/L² or L³ ligands. The spectral data show that all the complexes were six coordinated and possess octahedral geometry around the metal ions. The X-band ESR spectrum of the Cu(II) in DMSO solution at room temperature was recorded and observed anisotropic g values indicate the presence of metal ion in an octahedral environment. The powder XRD patterns of complexes recorded in the range (2θ = 0–80°) and average crystallite size (d_XRD) was calculated using Scherrer’s formula. Thermal decomposition profiles of complexes show high decompound temperatures indicating a good thermal stability. Binding of the complexes with calf thymus DNA (CT DNA) has been investigated by gel electrophoresis. The experimental results indicate that the complexes bind to DNA by intercalation mode and found to promote cleavage of plasmid pBR 322 DNA from the supercoiled form I to the open circular form II upon irradiation.     

Metallkomplexe mit N2O2S2‐Koordinationssphäre. Synthese und Charakterisierung der Cobalt(II)‐, Nickel(II)‐ und Kupfer(II)‐Komplexe eines 15‐ und eines 16‐gliedrigen N,N′‐bis(2‐hydroxyethyl)‐funktionalisierten makrocyclischen Liganden

Metal Complexes with N₂O₂S₂ Donor Set. Synthesis and Characterization of the Cobalt(II), Nickel(II), and Copper(II) Complexes of a 15‐ and a 16‐Membered Bis(2‐hydroxyethyl) Pendant Macrocyclic Ligand The macrocyclic ligands 6, 10‐bis(2‐hydroxyethyl)‐7, 8, 9, 11, 17, 18‐hexahydro‐dibenzo‐[e, n][1, 4, 8, 12]‐dithiadiaza‐cyclopentadecine ( 1 ) (L¹) and 5, 13‐bis(2‐hydroxyethyl)‐7, 8, 9, 10, 16, 17, 18, 19, 20‐nonahydro‐dibenzo‐[g, o][1, 9, 5, 13]‐dithiadiaza‐cyclohexadecine (L⁴) have been prepared. They form the stable complexes [CoL¹(‐H)CoL¹](ClO₄)₃ ( 2 ), [NiL¹](ClO₄)₂·MeOH ( 3 ), Λ‐[CuL¹](ClO₄)₂·MeOH ( 4a ) and rac‐[CuL¹](ClO₄)₂·MeOH ( 4b ), [NiL⁴](ClO₄)₂ ( 5 ), and [CuL⁴](ClO₄)₂ ( 6 ). The compounds 1 to 6 have been characterized by standard methods and single‐crystal X‐ray diffraction. In the complexes 2 to 6 the metal atoms are octahedrally coordinated by the N₂O₂S₂ donor set of the ligands. L¹ and L⁴ are folded herein along the N···M···S‐ and the N···M···N′‐axes, respectively. This results at the metal atom in a all‐cis‐configuration for the complexes of L¹ and a trans‐N₂‐cis‐O₂‐cis‐S₂‐configuration for the complexes of L⁴. The cobalt(II) complex 2 is a dimer, bridged by a rather short hydrogen bridge of 2.402(12)Å length. The copper(II) complexes of L¹ and L⁴ differ with respect to the Jahn‐Teller‐distortion.     

Cyclometalated platinum(II) complexes bearing o-phenylenediamine derivatives: Synthesis and electrochemical behavior

New cyclometalated Pt(II) complexes bearing 1,2-phenylenediamine (pda) derivatives were synthesized and their chemical and electrochemical properties were investigated. Two Pt complexes, [Pt(bzqn) (pda)](PF₆) (bzqn = benzo[h]quinoline, [1](PF₆): pda = 1,2-phenylenediamine, [2](PF₆): pda = 4,5-dimethyl-1,2-phenylenediamine), were synthesized by the reaction of (Bu₄N)[PtCl₂(bzqn)] with corresponding pda derivatives. The Pt-pda complexes were converted to Pt-bda (bda = 1,2-benzenediamide) complexes by treatment of 2 mol equiv of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and they showed two-step reversible redox couples in cyclic voltammetry. The cyclometalated ligand gave a strong electronic effect to the bda ligand to take place the negative shift of the bda-based redox potentials.