多吡啶钴(Ⅲ)配合物与Zn2+形成的新型“关-开”荧光探针

近十几年来,对小分子过渡金属配合物与大分子DNA键合与识别机理的研究一直是国际上生物无机化学领域十分活跃的研究课题[1￣3],已发展了一系列具有特定功能的配合物,如DNA结构探针和DNA荧光探针等。与其他类型的金属配合物相比,八面体过渡金属多吡啶配合物具有丰富的光化学和光物理信息,当这些配合物与DNA相互作用时,由于结构匹配或微环境的差异,配合物的光谱特征会出现不同程度的改变,从而达到对DNA的检测。传统的DNA荧光探针有[Ru(bpy)2dppz]2 和[Ru(phen)2dppz]2 (bpy=2,2′-联吡啶,phen=1,10-菲咯啉,dppz=二吡啶[3,2-a∶2′,3′…     

Synthesis,crystal structure,magnetism, and biological activities of an oxo-bridged diiron(III) complex

An unsymmetrical oxo-bridged diiron(III) complex [Fe₂L₂(μ-O)], {H₂L?=?trans-N,N′-bis-(2hydroxy-1-naphthalidehydene)-cyclohexanediamine} has been synthesized and characterized by various physico-chemical techniques. In the complex, each deprotonated bi-anionic L^2? serves as a terminal tetradentate ligand (N₂O₂) and coordinates to one Fe to form a [FeL]⁺ unit. Two [FeL]⁺ units are further linked by an oxo-bridge to construct the binuclear oxo-Fe species with intramolecular Fe–Fe separation of 3.38?Å. Variable-temperature magnetic susceptibility studies revealed a strong antiferromagnetic interaction between two iron centers with J of ?112?cm^?1. The interaction of the complex with CT-DNA was studied by various spectroscopic and viscosity measurements, which indicated that the complex could interact with CT-DNA through intercalation. In addition, the complex is able to cleave pBR322 DNA in the presence of H₂O₂. Furthermore, the interaction of the compound with BSA was also investigated, which indicated that the complex could quench the intrinsic fluorescence of BSA by a static quenching mechanism.     

Synthesis,structural characterization and DNA-binding studies of a new cobalt (II) complex: (HAcr)<Subscript>4</Subscript>[Co(Sal)<Subscript>3</Subscript>]

A new cobalt (II) coordination compound was synthesized using proton transfer mechanism. The reaction between CoCl₂·2H₂O, Salicylic acid (H₂Sal) and acridine (Acr) gave a new coordination compound formulated as (HAcr)₄[Co(Sal)₃], which was characterized by elemental analysis, NMR, IR and UV/Vis spectroscopies. The interaction of this complex with DNA has been investigated in vitro using UV absorption, fluorescence spectroscopy, viscosity measurements and gel electrophoresis methods. The intrinsic binding constant has been estimated to be 5.8 × 10⁵ M^?1 using UV absorption. The interaction of DNA–Co (II) complex caused quenching in fluorescence. The binding constant, the number of binding site and Stern–Volmer quenching constant have been calculated to be 7.7 × 10⁴ M^?1, 1.143 and 1.5 × 10⁴ Lmol^?1, respectively. The increase in the viscosity of DNA with increasing the concentration of the Co (II) complex and the observations of other experiments suggest that the cobalt (II) complex binds to DNA by partial intercalation binding mode. Furthermore, the interaction of DNA–Co (II) complex was confirmed using gel electrophoresis studies. Moreover, molecular docking technique predicted partial intercalation binding mode for the complex.     

AT‐Specific DNA Binding of Binuclear Ruthenium Complexes at the Border of Threading Intercalation

The binuclear ruthenium complex [μ‐bidppz(phen)₄Ru₂]⁴⁺ has been extensively studied since the discovery of its unusual threading intercalation interaction with DNA, a binding mode with extremely slow binding and dissociation kinetics. The complex has been shown to be selective towards long stretches of alternating AT base pairs, which makes it interesting, for example, as a model compound for anti‐malaria drugs due to the high AT content of the genome of the malaria parasite P. falciparum. We have investigated the effect of bridging ligand structure on threading intercalation ability and found that length and rigidity as well as the size of the intercalated ring system are all factors that affect the rate and selectivity of the threading intercalation. In particular, we discovered a new DNA‐threading compound, [μ‐dppzip(phen)₄Ru₂]⁴⁺, which appears to be just at the border of being capable of threading intercalation and displays even greater selectivity for AT‐DNA than the parent compound, [μ‐bidppz(phen)₄Ru₂]⁴⁺.     

Synthesis,crystal structure,antioxidation and DNA-binding properties of a dinuclear copper(II) complex with bis(N-salicylidene)-3-oxapentane-1,5-diamine

A Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine (H₂L) and its Cu(II) complex, [Cu₂(L)₂]?CHCl₃, have been synthesized and characterized by physicochemical and spectroscopic methods. Single-crystal X-ray analysis revealed that the complex is a centrosymmetric binuclear neutral entity, in which Cu(II) is a five-coordinate in a distorted trigonal bipyramidal geometry. The DNA-binding properties of the free ligand and the complex have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the H₂L and the complex to DNA via the intercalation mode and the binding affinity of the complex were higher than that of the H₂L. The intrinsic binding constants K_b of the ligand and the complex are 2.2 × 10⁴ and 2.7 × 10⁴ M^?1, respectively. Antioxidant assay in vitro shows the Cu(II) complex possesses significant antioxidant activities and better scavenging activity than the H₂L and other antioxidants.     

Copper(II) complex based on a V-shaped ligand, 2,6- bis (2-benzimidazolyl)pyridine: synthesis,crystal structure,DNA-binding properties,and antioxidant activities

A copper(II) complex based on a V-shaped ligand, 2,6-bis(2-benzimidazolyl)pyridine (bbp), has been synthesized and characterized by elemental analysis, molecular conductivity, ¹H NMR, IR, UV-Vis spectra, and X-ray single-crystal diffraction. The crystal structure of [Cu(bbp)₂](pic)₂?·?2DMF (pic?=?picrate) shows copper is six-coordinate forming a distorted octahedron. The interaction between Cu(II) complex and DNA was investigated by spectrophotometric methods and viscosity measurement. The experimental results suggest that the Cu(II) complex binds to DNA via intercalation. Antioxidant assay in vitro also shows that the Cu(II) complex possesses significant antioxidant activities.     

Synthesis,characterization and binding studies of novel diorganotin(IV) complexes of sodium 2‐mercaptoethanesulfonate

Diorganotin(IV) complexes ( 1‐4) of MESNA (sodium 2‐mercaptoethanesulfonate HSCH₂CH₂SO₃Na) and a mixed ligand complex of dibutyltin(IV), 1,10‐phenanthroline and MESNA ( 5 ) were synthesized with thermal and microwave assisted methods. All the complexes were characterized thoroughly with the help of analytical and various spectroscopic techniques viz. FTIR, NMR (¹H, ¹³C, and ¹¹⁹Sn NMR) spectroscopy and ESI‐MS spectrometery. Various spectrophotometric studies were carried out to decipher the binding mode of MESNA and its diorganotin complexes 1 ‐ 5 with calf thymus DNA (CT DNA) and thus, to calculate the binding constant (K_b). Absorption spectrophotometric study confirmed the interaction is through partial intercalation of all the complexes including MESNA, inside the DNA helix and calculated binding constant (K_b) is in the order of 10³ M^‐1. A series of emission spectrophotometric experiments support the results obtained through the absorption spectrophotometric studies. Circular dichroic (CD) spectroscopic analysis and viscosity measurement of CT DNA further complemented the fact that the partial intercalation plays a major role in the interaction of the studied complexes with CT DNA. All the studies corroborated that complex 2 bound to CT DNA with maximum affinity followed by complex 5 among all the complexes. Involvement of hydroxyl radicals as an active species in the cleavage activity of pBR322 plasmid DNA is proved by carrying out agarose gel electrophoretic technique.     

Synthesis,crystal structure and DNA interaction studies of a 2D cadmium(II) coordination polymer constructed from 2-(2-pyridyl)benzimidazole

A new complex associated with Cd²⁺, [Cd(OH-H₂Bdc)(2-Pbim)]_n (1), (OH-H₂Bdc = 5-hydroxyisophthalic acid, 2-Pbim = 2-(2-pyridyl)benzimidazole), has been synthesised under hydrothermal conditions and characterised by elemental analysis, FT-IR spectroscopy, TG/DTG and fluorescence spectrum. Its in vitro cytotoxicity towards four selected tumour cell lines has been evaluated by an microculture tetrozolium assay, the results suggest that complex 1 displays greater inhibition than the free benzimidazole ligand. On the basis of the combination of absorption titration and fluorescence emission titration, the binding mode of complex 1 to calf thymus DNA has been investigated. Complex 1 can interact with the base pairs of double-helical DNA via the combined mode of intercalation and groove binding with larger binding constants.     

多吡啶锌配合物键合与切割DNA研究

The complex of Zn[(phen)(dione)Cl]ClO_4·H_2O(where phen is 1,10-phenanthroline and dione is 1,10-phenan-throline-5,6-dione)has been synthesized and characterized.The interaction of the complex with DNA was investi-gated using UV absorption,fluorescence spectroscopy and electrophoresis measurements.The results show that thecomplex mainly binds to the double helix of DNA with intercalation mode and the binding constant K is 2.4×10~4mol~(-1)·L.Moreover,the complex can efficiently cleave plasmid DNA at physiological pH and temperature.Thecleavage occurs via a hydrolysis mechanism,which is showed by adding radical scavengers,rigorously anaerobicexperiments,analysis for malondialdehyde-like products,and the hydrolysis experiment of BDNPP with a rate con-stant k_(obs)of 5.3×10~(-6)s~(-1).     

Crystal structure,DNA-binding,and fluorescence properties of cadmium(II) complex with N-(2-acetic acid)salicyloyl hydrazone and imidazole

A novel cadmium(II) complex with N-(2-acetic acid)salicyloyl hydrazone (C₉H₈N₂O₄, H₃L) and imidazole (Im) was prepared and characterized. The crystal structures of ligand H₃L and cadmium(II) complex were determined by X-ray single-crystal diffractometry. The complex consists of three binuclear neutral unattached units. One of Cd²⁺ is six-coordinated by the carboxylic O atom, acylic O atom, and azomethinic N atom of one ligand H₃L (HL²⁻ form), carboxylic O atom from the other ligand H₃L by the μ₂-bridging form and N atoms from two imidazoles, but the other five Cd²⁺ ions all are seven-coordinated more than an O atom from coordinated water molecule compared with six-coordinated Cd²⁺. HL²⁻ acts as tridentate ligand forming two stable five-numbered rings and sharing one side in the keto form for each ligand, and the carboxyl groups of two HL²⁻ ligands are coordinated via the μ₂-bridging form. The coordination polyhedron around Cd²⁺ was described as a octahedron or pentagonal bipyramidal. The inter- and intramolecular hydrogen bonds resulted in a three- dimensional network and provided extrastability for the structure. The complex exhibits good fluorescence properties. The complex was also searched for the interaction with CT-DNA by electronic absorption titration and emission titration. The results show that the complex is bound to calf thymus DNA mainly by intercalation.     

Crystal structure of bis(triphenylphosphine) bis(N,N′-dibutylthiourea)silver(I) nitrate

A mixed-ligand silver(I) complex of triphenylphosphine and N,N′-dibutylthiourea (Dbtu), [Ag(Ph₃P)₂(Dbtu)₂]NO₃, is prepared and its structure in the solid state is determined by X-ray crystallography. X-ray structure of this complex shows that it is mononuclear with the silver atom coordinated by two PPh₃ and two dibutylthiourea ligands adopting a distorted tetrahedral geometry. The crystal structure shows the formation of 1-D chains through intermolecular hydrogen bonding interactions between N-H of Dbtu and nitrate ions. The new complex is also characterized by IR and NMR (¹H and ³¹P) spectroscopy. The spectroscopic data are discussed in terms of the nature of bonding. A similar mixedligand complex is also prepared for tetramethylthiourea (Tmtu), but the structure of the resulting compound shows that it is a bis(phosphine) complex, [Ag(PPh₃)₂NO₃] rather than a mixed-ligand complex.     

Crystal Structure, Thermal Analysis and Theoretical Calculation of a One-dimensional Chain Complex [Zn（dafo）2（H2O）2]（NO3）2

Introduction Molecular recognition and molecular self-assemblycarried out by cooperation of the weak interactions(electrostatic reaction, hydrogen bonds, van der Waalsforce, short-range repulsive force, etc) are the commonphenomena in nature. In recent years, the research onsupramolecular complex has been a crossing focus ofseveral subjects such as chemistry, physics, biology,material and information.1 Supramolecular complex hasa wide application foreground in material, catalysis,conductor,…     

Tris(ethyl­enediamine)zinc(II) molybdate(VI), [Zn(en)3][MoO4]

The crystal structure of the title compound, [Zn(C₂H₈N₂)₃][MoO₄], is composed of [MoO₄]²⁻ anions and [Zn(en)₃]²⁺ complex cations (en is ethyl­enediamine), both with symmetry 2, which are held together in a three‐dimensional network via hydrogen‐bonding inter­actions. The [Zn(en)₃]²⁺ cations in the crystal structure exhibit two configurations, viz. Λ(δδδ) and Δ(λλλ), as a pair of enantiomers.     

A New Polynuclear Copper‐Complex‐Substituted Tungstoarsenate(V)

A new polynuclear copper‐complex‐substituted dimeric tungstoarsenate(V), H₂[{Cu(2,2′‐bpy)}₈(H₂O)₂(AsW₉O₃₄)₂] · 12H₂O ( 1 ) (2,2′‐bpy = 2,2′‐bipydine), was synthesized hydrothermally and its structure was determined by single‐crystal X‐ray diffraction. The title compound has Ci symmetry and consists of two trilacunary Keggin anions [α‐AsW₉O₃₄]^9– supported by eight copper complex cations. The compound was also characterized by IR and fluorescence spectroscopy, TG analysis, and magnetic measurements. The emission spectrum of the compound in solid‐state exhibits a redshift relative to those of Na₈[A‐HAsW₉O₃₄] · 11H₂O and the free ligand 2,2′‐bpy. Magnetic measurements of the compound indicate competing ferro‐ and antiferromagnetic intramolecular coupling among the Cu^II atoms in the cluster anion.     

Dioxygen Activation by Siloxide Complexes of Chromium(II) and Chromium(IV)

The reaction of a tripodal trisilanol with n‐butyllithium and CrCl₂ results in a dinuclear Cr^II complex ( 1 ), which is capable of cleaving O₂ to yield in a unique complex ( 2 ) with an asymmetric diamond core composed of two Cr^IV?O units. Magnetic susceptibility data reveal significant exchange coupling of Cr^II (S=2) in 1 and large zero‐field splitting for Cr^IV (S=1) in 2 owing to strong spin–orbit coupling of the ground state. The Cr^IV?O compound can also be generated using PhIO, and evidence was gathered that although it is the stable product isolated after excessive O₂ treatment, it further activates O₂ to yield an intermediate species that oxidizes THF or Me‐THF. By extensive ¹⁸O labeling studies we were able to show, that in the course of this process ¹⁸O₂ exchanges its label with siloxide O atoms of the ligand via terminal oxido ligands.     

Initial DNA Interactions of the Binuclear Threading Intercalator Λ,Λ‐[μ‐bidppz(bipy)4Ru2]4+: An NMR Study with [d(CGCGAATTCGCG)]2

Binuclear polypyridine ruthenium compounds have been shown to slowly intercalate into DNA, following a fast initial binding on the DNA surface. For these compounds, intercalation requires threading of a bulky substituent, containing one Ru^II, through the DNA base‐pair stack, and the accompanying DNA duplex distortions are much more severe than with intercalation of mononuclear compounds. Structural understanding of the process of intercalation may greatly gain from a characterisation of the initial interactions between binuclear Ru^II compounds and DNA. We report a structural NMR study on the binuclear Ru^II intercalator Λ,Λ‐B (Λ,Λ‐[μ‐bidppz(bipy)₄Ru₂]⁴⁺; bidppz=11,11′‐bis(dipyrido[3,2‐a:2′,3′‐c]phenazinyl, bipy = 2,2′‐bipyridine) mixed with the palindromic DNA [d(CGCGAATTCGCG)]₂. Threading of Λ,Λ‐B depends on the presence and length of AT stretches in the DNA. Therefore, the latter was selected to promote initial binding, but due to the short stretch of AT base pairs, final intercalation is prevented. Structural calculations provide a model for the interaction: Λ,Λ‐B is trapped in a well‐defined surface‐bound state consisting of an eccentric minor‐groove binding. Most of the interaction enthalpy originates from electrostatic and van der Waals contacts, whereas intermolecular hydrogen bonds may help to define a unique position of Λ,Λ‐B. Molecular dynamics simulations show that this minor‐groove binding mode is stable on a nanosecond scale. To the best of our knowledge, this is the first structural study by NMR spectroscopy on a binuclear Ru compound bound to DNA. In the calculated structure, one of the positively charged Ru²⁺ moieties is near the central AATT region; this is favourable in view of potential intercalation as observed by optical methods for DNA with longer AT stretches. Circular dichroism (CD) spectroscopy suggests that a similar binding geometry is formed in mixtures of Λ,Λ‐B with natural calf thymus DNA. The present minor‐groove binding mode is proposed to represent the initial surface interactions of binuclear Ru^II compounds prior to intercalation into AT‐rich DNA.     

CRYSTAL STRUCTURE AND MAGNETIC MEASUREMENTS OF CIS-DICYANO-BIS (1,10-PHENANTHROLINE)IRON(III) SULFATE

Abstract

The structure of the solvatochromic complex cis-dicyano-bis(1,10-phenanthroline)iron(III) sulfate dihydrate was determined by X-ray diffraction. The complex crystallized in a compressed octahedral conformation with the cyanide ligands cis-bonded. The unit cell contains enantiomeric pairs of the compound with a network of sulfate ions and water molecules stabilized by hydrogen bonding. The magnetic moments of the perchlorate salt dissolved in both water and nonaqueous solvents were probed and found to be in accord with a solvated, low spin [Fe(III)(phen)₂(CN)₂]⁺ ion, (μ_exp = 2.0–2.6 BM, 298K), showing no dependence on the empirical solvent parameters AN, DN, E_T(30) and π?.     

Synthesis and Crystal Structures of Antimony(III) Complexes With a Bis(amino)silane Ligand

Bis(amino)silane bearing bulky substituents on nitrogen, LH₂ [L = Me₂Si(NDipp)₂, Dipp = 2, 6‐diisopropylphenyl] was reacted with nBuLi (ratio 1:1 and 1:2) in toluene. The Me₂Si(LiNDipp)₂ was treated with SbCl₃ in a 1:1 ratio to yield the four‐membered SiN₂Sb ring compound of composition [η²(N,N)‐Me₂Si(NDipp)₂SbCl] ( 1 ). The mono lithiated bis(amino)silane was used to synthesize the monodentate heterotetraatomic complex [(η¹‐Me₂SiNDipp)NHDippSbCl₂] ( 2 ) by the reaction with SbCl₃. The complexes were characterized by ¹H and ¹³C NMR, elemental analysis, IR, and single‐crystal X‐ray structural analysis.     

Diammonium hexakis(thiocyanato‐κN)rhenate(IV) dimethyl sulfone tetrasolvate

The title compound, (NH₄)₂[Re(NCS)₆]·4C₂H₆O₂S, was obtained by solvothermal synthesis as part of a project on rhenium thiocyanate catalysts and starting materials for further aggregation to molecular magnets. The compound is the ammonium salt of octahedral hexakis(thiocyanato‐κN)rhenate(IV) anions, which lie on centres of inversion. The dimethyl sulfone solvent molecules are involved in R₄²(8) and D N—H...O hydrogen‐bonded motifs. N—H...S and S...S short contacts are also present. Hydrogen‐bonded ammonium–dimethyl sulfone layers alternate with layers formed by the complex anion (with S...S short contacts) parallel to (100).     

A Dinuclear Ruthenium(II) Schiff Base Complex with Dissimilar Coordination: Synthesis,Characterization, and Biological Activity

A dinuclear Schiff base Ru^II complex derived from 5‐chlorosalicylaldehyde and 2‐aminopyridine was synthesized. The structure of the compound was analyzed by mass spectrometry as well as IR, UV/Vis, and ¹H NMR spectroscopy, along with chemical analysis,as well as magnetic, cyclovoltammetric and conductivity measurements. Two Ru^II atoms are octahedrally coordinated by azomethine and pyridine nitrogen atoms from two tridentate monobasic Schiff bases and bridging phenol oxygen atoms. The formula of the complex is [Ru₂L₂Cl₂(Et₂NH)(H₂O)] [L = N‐(2‐pyridyl)‐5‐chlorosalicylideneimine and Et₂NH = isodiethylamine]. The Ru^II atoms in the dinuclear neutral complex species have different coordination environments, RuN₃O₂Cl and RuN₂O₃Cl. Interaction with CT DNA showed moderate hydrophobic binding. The compound demonstrates strong activity against methicillin‐resistant Staphylococcus aureus, methicillin‐sensitive Staphylococcus aureus, and especially Enterococcus faecalis. Microbiological tests showed significant inhibition of growth and ability to kill pathogens, similar or even improved compared to reference antibiotics vancomycin.