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1.
Studies of double‐stranded‐DNA binding have been performed with three isomeric bis(2‐(n‐pyridyl)‐1H‐benzimidazole)s (n=2, 3, 4). Like the well‐known Hoechst 33258, which is a bisbenzimidazole compound, these three isomers bind to the minor groove of duplex DNA. DNA binding by the three isomers was investigated in the presence of the divalent metal ions Mg2+, Co2+, Ni2+, Cu2+, and Zn2+. Ligand–DNA interactions were probed with fluorescence and circular dichroism spectroscopy. These studies revealed that the binding of the 2‐pyridyl derivative to DNA is dramatically reduced in the presence of Co2+, Ni2+, and Cu2+ ions and is abolished completely at a ligand/metal‐cation ratio of 1:1. Control experiments done with the isomeric 3‐ and 4‐pyridyl derivatives showed that their binding to DNA is unaffected by the aforementioned transition‐metal ions. The ability of 2‐(2‐pyridyl)benzimidazole to chelate metal ions and the conformational changes of the ligand associated with ion chelation probably led to such unusual binding results for the ortho isomer. The addition of ethylenediaminetetraacetic acid (EDTA) reversed the effects completely.  相似文献   

2.
Two new complexes, [Ru(phen)2(ppd)]2+ ( 1 ) and [Ru(phen)(ppd)2]2+ ( 2 ) (ppd=pteridino[6,7‐f] [1,10]phenanthroline‐11,13(10H,12H)‐dione, phen=1,10‐phenanthroline) were synthesized and characterized by ES‐MS, 1H‐NMR spectroscopy, and elemental analysis. The intercalative DNA‐binding properties of 1 and 2 were investigated by absorption‐spectroscopy titration, luminescence‐spectroscopy studies, thermal denaturation, and viscosity measurements. The theoretical aspects were further discussed by comparative studies of 1 and 2 by means of DFT calculations and molecular‐orbital theory. Photoactivated cleavage of pBR322 DNA by the two complexes were also studied, and 2 was found to be a much better photocleavage reagent than 1 . The mechanism studies revealed that singlet oxygen and the excited‐states redox potentials of the complex may play an important role in the DNA photocleavage.  相似文献   

3.
Two different zinc sulfite compounds have been prepared through the decomposition of pyrosulfite–­di­thionite ions in aqueous solution, viz. a dimeric complex, di‐μ‐sulfito‐κ3O,O′:O′′;κ3O:O′,O′′‐bis­[(4,4′‐di­methyl‐2,2′‐bi­pyridine‐κ2N,N′)­zinc(II)] dihydrate, [Zn2(SO3)2(C12H12N2)2]·2H2O, (I), which was solved and refined from a twinned sample, and an extended polymer, poly­[[aqua(1,10‐phenanthroline‐κ2N,N′)­zinc(II)]‐μ3‐sulfito‐κ2O:O′:O′′‐zinc(II)‐μ3‐sulfito‐κ3O:O:O′], [Zn2(SO3)2(C12H10N2)(H2O)]n, (II). In (I), the dinuclear ZnII complex has a center of symmetry. The cation is five‐coordinate in a square‐pyramidal arrangement, the anion fulfilling a bridging chelating role. Compound (II) comprises two different zinc units, one being five‐coordinate (square pyramidal) and the other four‐coordinate (trigonal pyramidal), and two independent sulfite groups with different binding modes to the cationic centers.  相似文献   

4.
Two novel chiral ruthenium(II) complexes, Δ‐[Ru(bpy)2(dmppd)]2+ and Λ‐[Ru(bpy)2(dmppd)]2+ (dmppd = 10,12‐dimethylpteridino[6,7‐f] [1,10]phenanthroline‐11,13(10H,12H)‐dione, bpy = 2,2′‐bipyridine), were synthesized and characterized by elemental analysis, 1H‐NMR and ES‐MS. The DNA‐binding behaviors of both complexes were studied by UV/VIS absorption titration, competitive binding experiments, viscosity measurements, thermal DNA denaturation, and circular‐dichroism spectra. The results indicate that both chiral complexes bind to calf‐thymus DNA in an intercalative mode, and the Δ enantiomer shows larger DNA affinity than the Λ enantiomer does. Theoretical‐calculation studies for the DNA‐binding behaviors of these complexes were carried out by the density‐functional‐theory method. The mechanism involved in the regulating and controlling of the DNA‐binding abilities of the complexes was further explored by the comparative studies of [Ru(bpy)2(dmppd)]2+ and of its parent complex [Ru(bpy)2(ppd)]2+ (ppd = pteridino[6,7‐f] [1,10]phenanthroline‐11,13 (10H,12H)‐dione).  相似文献   

5.
2‐(2‐Hydroxy‐phenyl)‐4(3H)‐quinazolinone (HPQ), an organic fluorescent material that exhibits fluorescence by the excited‐state intramolecular proton‐transfer (ESIPT) mechanism, forms two different polymorphs in tetrahydrofuran. The conformational twist between the phenyl and quinazolinone rings of HPQ leads to different molecular packing in the solid state, giving structures that show solid‐state fluorescence at 497 and 511 nm. HPQ also shows intense fluorescence in dimethyl formamide (DMF) solution and selectively detects Zn2+ and Cd2+ ions at micromolar concentrations in DMF. Importantly, HPQ not only detects Zn2+ and Cd2+ ions selectively, but it also distinguishes between the metal ions with a fluorescence λmax that is blue‐shifted from 497 to 420 and 426 nm for Zn2+ and Cd2+ ions, respectively. Hence, tunable solid‐state fluorescence and selective metal‐ion‐sensor properties were demonstrated in a single organic material.  相似文献   

6.
A novel ligand 3‐(1H‐imidazo[4,5‐f][1,10]phenanthrolin‐2‐yl)‐4H‐1‐benzopyran‐4‐one (ipbp) and its ruthenium(II) complexes [Ru(bpy)2(ipbp)]2+ ( 1 ) and [Ru(ipbp)(phen)2]2+ ( 2 ) (bpy=2,2′‐bipyridine, phen=1,10‐phenanthroline) were synthesized and characterized by elemental analysis and mass, 1H‐NMR, and electronic‐absorption spectroscopy. The electrochemical behavior of the complexes was studied by cyclic voltammetry. The DNA‐binding behavior of the complexes was investigated by spectroscopic methods and viscosity measurements. The results indicate that complexes 1 and 2 bind with calf‐thymus DNA in an intercalative mode. In addition, 1 and 2 promote cleavage of plasmid pBR 322 DNA from the supercoil form I to the open circular form II upon irradiation.  相似文献   

7.
The title compound, {[Zn4(C8H4O4)3(OH)2(C12H6N2O2)2]·2H2O}n, has been prepared hydrothermally by the reaction of Zn(NO3)2·6H2O with benzene‐1,4‐dicarboxylic acid (H2bdc) and 1,10‐phenanthroline‐5,6‐dione (pdon) in H2O. In the crystal structure, a tetranuclear Zn4(OH)2 fragment is located on a crystallographic inversion centre which relates two subunits, each containing a [ZnN2O4] octahedron and a [ZnO4] tetrahedron bridged by a μ3‐OH group. The pdon ligand chelates to zinc through its two N atoms to form part of the [ZnN2O4] octahedron. The two crystallographically independent bdc2− ligands are fully deprotonated and adopt μ3‐κOO′:κO′′ and μ4‐κOO′:κO′′:κO′′′ coordination modes, bridging three or four ZnII cations, respectively, from two Zn4(OH)2 units. The Zn4(OH)2 fragment connects six neighbouring tetranuclear units through four μ3‐bdc2− and two μ4‐bdc2− ligands, forming a three‐dimensional framework with uninodal 6‐connected α‐Po topology, in which the tetranuclear Zn4(OH)2 units are considered as 6‐connected nodes and the bdc2− ligands act as linkers. The uncoordinated water molecules are located on opposite sides of the Zn4(OH)2 unit and are connected to it through hydrogen‐bonding interactions involving hydroxide and carboxylate groups. The structure is further stabilized by extensive π–π interactions between the pdon and μ4‐bdc2− ligands.  相似文献   

8.
In the title coordination polymer, [Zn2(C14H8N2O4)2(C12H10N2)]n, the asymmetric unit contains one ZnII cation, two halves of 2,2′‐(diazene‐1,2‐diyl)dibenzoate anions (denoted L2−) and half of a 1,2‐bis(pyridin‐4‐yl)ethene ligand (denoted bpe). The three ligands lie across crystallographic inversion centres. Each ZnII centre is four‐coordinated by three O atoms of bridging carboxylate groups from three L2− ligands and by one N atom from a bpe ligand, forming a tetrahedral coordination geometry. Two ZnII atoms are bridged by two carboxylate groups of L2− ligands, generating a [Zn2(CO2)2] ring. Each loop serves as a fourfold node, which links its four equivalent nodes via the sharing of four L2− ligands to form a two‐dimensional [Zn2L4]n net. These nets are separated by bpe ligands acting as spacers, producing a three‐dimensional framework with a 4664 topology. Powder X‐ray diffraction and solid‐state photoluminescence were also measured.  相似文献   

9.
In the novel title binuclear zinc(II) Schiff base complex, bis­(μ‐11‐thio­semicarbazonoindeno[1,2‐b]quinoxaline‐8‐carboxylato)bis­[(dimethyl sulfoxide)zinc(II)] dimethyl sulfoxide tri­solvate, [Zn2(C17H9N5O2S)2(C2H6OS)2]·3C2H6OS, each ZnII atom is five‐coordinated and situated in a distorted square‐pyramidal environment, coordinated by two L2− ligands and one dimethyl sulfoxide mol­ecule. Each L2− ligand, which coordinates to two ZnII atoms, has two parts. One part, acting in a tridentate chelating mode, coordinates to one ZnII atom through two N atoms and one S atom, while another part coordinates to another ZnII atom through a monodentate carboxylate group. The whole complex has a dimeric structure. The coordination mode of the nearly planar L2− ligand is quite different from the most common mode for Schiff bases.  相似文献   

10.
Two new ZnII(μ‐4,4′‐bipy) coordination polymers with acetate anions, [Zn(4,4′‐bipy)(AcO)2] ( 1 ) and [Zn2(4,4′‐bipy)(AcO)4] ( 2 ), have been synthesized. The compounds were characterized with elemental analysis, IR‐, 1H NMR‐, 13C NMR spectroscopy and studied by thermal analysis, fluorescence measurements and x‐ray crystallography. The structural studies of compound 1 suggest the structure is a coordination polymer of zinc(II) consisting of linear double chains formed by bridging 4,4′‐bipy ligand and connection of the acetate‐bridged centrosymmetric [Zn2(OAc)2]2+ nodes.  相似文献   

11.
This work demonstrates a selection criteria that determines whether molecular assembly occurs through a one‐step or stepwise manner in ligand‐bridged dinuclear zinc(II) (Zn2+) complex formation, which is associated with the π stacking of building blocks. The building blocks of carbazole ligands ( L1 and L4 ) that contain two imidazole moieties at the 3,6‐positions form 4:2 complexes (i.e., [ L ]4?(Zn2+)2) at a molar ratio of 0.50 ([Zn2+]/[ L ]0=0.50), thereby providing π stacking between the carbazole ligands. At the molar ratio of 0.67 ([Zn2+]/[ L ]0=0.67), the 4:2 complexes change to 3:2 complexes (i.e., [ L ]3?(Zn2+)2) with no π‐stacked carbazole unit. In contrast, when the imidazole groups in L1 are replaced with benzoimidazole groups ( L3 ), L3 also yields the 4:2 complex [( L3 )4?(Zn2+)2] at a molar ratio of 0.50. However, there is no structural transition from ( L3 )4?(Zn2+)2 to other complex species above a molar ratio of 0.50. Similarly, when two imidazole groups are introduced into the carbazole ring at 2,7‐positions ( L5 ), L5 also gives the 4:2 complex [( L5 )4?(Zn2+)2] that shows no structural transition to other complex species at a higher molar ratio.  相似文献   

12.
The title compound, [Zn3(C9H21SiS)6] or [(iPr3SiS)Zn(μ‐SSiiPr3)2Zn(μ‐SSiiPr3)2Zn(SSiiPr3)], is the first structurally characterized homoleptic silanethiolate complex of zinc. A near‐linear arrangement of three ZnII ions is observed, the metals at the ends being three‐coordinate with one terminally bound silanethiolate ligand. The central ZnII ion is four‐coordinate and tetrahedral, with two bridging silanethiolate ligands joining it to each of the two peripheral ZnII ions. The nonbonding intermetallic distances are 3.1344 (11) and 3.2288 (12) Å, while the Zn...Zn...Zn angle is 172.34 (2)°. A trimetallic silanethiolate species of this type has not been previously identified by X‐ray crystallography for any element.  相似文献   

13.
Novel 4‐hydroxyquinoline (4HQ) based tautomeric switches are reported. 4HQs equipped with coordinative side arms (8‐arylimino and 3‐piperidin‐1‐ylmethyl groups) were synthesized to access O or N‐selective chelation of Zn2+ and Cd2+ ions by 4HQ. In the case of the monodentate arylimino group, O chelation of metal ions induces concomitant switching of phenol tautomer to the keto form in nonpolar or aprotic media. This change is accompanied by selective and highly sensitive fluorometric sensing of Zn2+ ions. In the case of the bidentate 8‐(quinolin‐8‐ylimino)methyl side arm, NMR studies in CD3OD indicated that both Cd2+ and Zn2+ ions afford N chelation for 4HQ, coexisting with tautomeric switching from quinolin‐4(1H)‐one to quinolin‐4‐olate. In corroboration, UV/Vis‐monitored metal‐ion titrations in toluene and methanol implied similar structural changes. Additionally, fluorescence measurements indicated that the metal‐triggered tautomeric switching is associated with compound signaling properties. The results are supported by DFT calculations at the B3LYP 6‐31G* level. Several X‐ray structures of metal‐free and metal‐chelating 4HQ are presented to support the solution studies.  相似文献   

14.
Aqueous zinc (Zn) batteries have been considered as promising candidates for grid‐scale energy storage. However, their cycle stability is generally limited by the structure collapse of cathode materials and dendrite formation coupled with undesired hydrogen evolution on the Zn anode. Herein we propose a zinc–organic battery with a phenanthrenequinone macrocyclic trimer (PQ‐MCT) cathode, a zinc‐foil anode, and a non‐aqueous electrolyte of a N,N‐dimethylformamide (DMF) solution containing Zn2+. The non‐aqueous nature of the system and the formation of a Zn2+–DMF complex can efficiently eliminate undesired hydrogen evolution and dendrite growth on the Zn anode, respectively. Furthermore, the organic cathode can store Zn2+ ions through a reversible coordination reaction with fast kinetics. Therefore, this battery can be cycled 20 000 times with negligible capacity fading. Surprisingly, this battery can even be operated in a wide temperature range from ?70 to 150 °C.  相似文献   

15.
The asymmetric unit of {[4,7‐bis(2‐amino­ethyl)‐1,4,7‐tri­aza­cyclo­nonan‐1‐yl]acetato}zinc(II) triaqua{μ‐[4,7‐bis(2‐amino­ethyl)‐1,4,7‐tri­aza­cyclo­nonan‐1‐yl]acetato}lithium(I)zinc(II) chloride diperchlorate, [Zn(C12H26N5O2)][LiZn(C12H26N5O2)(H2O)3]Cl(ClO4)2, obtained from the reaction between the lithium salt of 4,7‐bis(2‐amino­ethyl)‐1,4,7‐tri­aza­cyclo­nonane‐1‐acetate and Zn(ClO4)2, contains two ZnII complexes in which each ZnII ion is six‐coordinated by five N‐atom donors and one O‐­atom donor from the ligand. One carboxyl­ate O‐atom donor is not involved in coordination to a ZnII atom, but coordinates to an Li+ ion, the tetrahedral geometry of Li+ being completed by three water mol­ecules. The two complexes are linked via a hydrogen bond between a primary amine N—H group and the carboxyl­ate‐O atom not involved in coordination to a metal.  相似文献   

16.
The Zn complexes bis(acetylacetonato‐κ2O,O′)bis{4′‐[4‐(methylsulfanyl)phenyl]‐4,2′:6′,4′′‐terpyridine‐κN1}zinc(II), [Zn(C5H7O2)2(C22H17N3S)2], (I), and {μ‐4′‐[4‐(methylsulfanyl)phenyl]‐4,2′:6′,4′′‐terpyridine‐κ2N1:N1′′}bis[bis(acetylacetonato‐κ2O,O′)zinc(II)], [Zn2(C5H7O2)4(C22H17N3S)], (II), are discrete entities with different nuclearities. Compound (I) consists of two centrosymmetrically related monodentate 4′‐[4‐(methylsulfanyl)phenyl]‐4,2′:6′,4′′‐terpyridine (L1) ligands binding to one ZnII atom sitting on an inversion centre and two centrosymmetrically related chelating acetylacetonate (acac) groups which bind via carbonyl O‐atom donors, giving an N2O4 octahedral environment for ZnII. Compound (II), however, consists of a bis‐monodentate L1 ligand bridging two ZnII atoms from two different Zn(acac)2 fragments. Intra‐ and intermolecular interactions are weak, mainly of the C—H...π and π–π types, mediating similar layered structures. In contrast to related structures in the literature, sulfur‐mediated nonbonding interactions in (II) do not seem to have any significant influence on the supramolecular structure.  相似文献   

17.
We demonstrate the single‐molecule imaging of the catalytic reaction of a Zn2+‐dependent DNAzyme in a DNA origami nanostructure. The single‐molecule catalytic activity of the DNAzyme was examined in the designed nanostructure, a DNA frame. The DNAzyme and a substrate strand attached to two supported dsDNA molecules were assembled in the DNA frame in two different configurations. The reaction was monitored by observing the configurational changes of the incorporated DNA strands in the DNA frame. This configurational changes were clearly observed in accordance with the progress of the reaction. The separation processes of the dsDNA molecules, as induced by the cleavage by the DNAzyme, were directly visualized by high‐speed atomic force microscopy (AFM). This nanostructure‐based AFM imaging technique is suitable for the monitoring of various chemical and biochemical catalytic reactions at the single‐molecule level.  相似文献   

18.
3,4‐Dimethoxy‐trans‐cinnamic acid (Dmca) reacts with zinc sulfate in the presence of 4‐(1H‐pyrazol‐3‐yl)pyridine (L1) or 4,4′‐bipyridine (L2) under hydrothermal conditions to afford two mixed‐ligand coordination complexes, namely tetrakis(μ‐3,4‐dimethoxy‐trans‐cinnamato‐κ2O:O′)bis[[4‐(1H‐pyrazol‐3‐yl)pyridine]zinc(II)] heptahydrate, [Zn2(C11H11O4)4(C8H7N3)2]·7H2O or [Zn2(Dmca)4(L1)2]·7H2O, (I), and catena‐poly[[bis(3,4‐dimethoxy‐trans‐cinnamato‐κO)zinc(II)]‐μ‐4,4′‐bipyridine‐κ2N:N′], [Zn(C11H11O4)2(C10H8N2)]n or [Zn(Dmca)2(L2)]n, (II). The ZnII centres in the two compounds display different coordination polyhedra. In complex (I), the ZnII cation is five‐coordinated with a pseudo‐square‐pyramidal geometry, while in complex (II) the ZnII cation sits on a twofold axis and adopts a distorted tetrahedral coordination environment. Complex (I) features a centrosymmetric binuclear paddle‐wheel‐like structure, while complex (II) shows a chain structure. This study emphasizes the significant effect of the coordination mode of both carboxylate‐group and N‐donor coligands on the formation of complex structures.  相似文献   

19.
A new 1,3,4‐oxadiazole‐containing bispyridyl ligand, namely 5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione (L), has been used to create the novel complexes tetranitratobis{μ‐5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione}zinc(II), [Zn2(NO3)4(C14H12N4OS)2], (I), and catena‐poly[[[dinitratocopper(II)]‐bis{μ‐5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione}] nitrate acetonitrile sesquisolvate dichloromethane sesquisolvate], {[Cu(NO3)(C14H12N4OS)2]NO3·1.5CH3CN·1.5CH2Cl2}n, (II). Compound (I) presents a distorted rectangular centrosymmetric Zn2L2 ring (dimensions 9.56 × 7.06 Å), where each ZnII centre lies in a {ZnN2O4} coordination environment. These binuclear zinc metallocycles are linked into a two‐dimensional network through nonclassical C—H...O hydrogen bonds. The resulting sheets lie parallel to the ac plane. Compound (II), which crystallizes as a nonmerohedral twin, is a coordination polymer with double chains of CuII centres linked by bridging L ligands, propagating parallel to the crystallographic a axis. The CuII centres adopt a distorted square‐pyramidal CuN4O coordination environment with apical O atoms. The chains in (II) are interlinked via two kinds of π–π stacking interactions along [01]. In addition, the structure of (II) contains channels parallel to the crystallographic a direction. The guest components in these channels consist of dichloromethane and acetonitrile solvent molecules and uncoordinated nitrate anions.  相似文献   

20.
The novel title ZnII coordination polymer, poly[bis(μ‐6‐thioxo‐1,6‐dihydropyridine‐3‐carboxylato‐κ2S:O)zinc(II)], [Zn(C6H4NO2S)2]n, consists of two crystallographically independent zinc centers and two 6‐mercaptonicotinate (Hmna) ligands. Each ZnII atom is four‐coordinated and lies at the center of a distorted tetrahedral ZnS2O2 coordination polyhedron, bridged by four Hmna ligands to form a two‐dimensional (4,4)‐network. Each Hmna ion acts as a bridging bidentate ligand, coordinating to two ZnII atoms through the S atom and a carboxyl O atom. The metal centers reside on twofold rotation axes. The coordination mode of the S atoms and N—H...O hydrogen‐bonding interactions between the protonated N atoms and the uncoordinated carboxyl O atoms give the extended structure a wavelike form.  相似文献   

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