- Polypyridyl-Based Copper Phenanthrene Complexes: Combining Stability with Enhanced DNA Recognition
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We report a series of copper(II) artificial metallo-nucleases (AMNs) and demonstrate their DNA damaging properties and in-vitro cytotoxicity against human-derived pancreatic cancer cells. The compounds combine a tris-chelating polypyridyl ligand, di-(2-pycolyl)amine (DPA), and a DNA intercalating phenanthrene unit. Their general formula is Cu-DPA-N,N' (where N,N'=1,10-phenanthroline (Phen), dipyridoquinoxaline (DPQ) or dipyridophenazine (DPPZ)). Characterisation was achieved by X-ray crystallography and continuous-wave EPR (cw-EPR), hyperfine sublevel correlation (HYSCORE) and Davies electron-nuclear double resonance (ENDOR) spectroscopies. The presence of the DPA ligand enhances solution stability and facilitates enhanced DNA recognition with apparent binding constants (Kapp) rising from 105 to 107 m?1 with increasing extent of planar phenanthrene. Cu-DPA-DPPZ, the complex with greatest DNA binding and intercalation effects, recognises the minor groove of guanine–cytosine (G-C) rich sequences. Oxidative DNA damage also occurs in the minor groove and can be inhibited by superoxide and hydroxyl radical trapping agents. The complexes, particularly Cu-DPA-DPPZ, display promising anticancer activity against human pancreatic tumour cells with in-vitro results surpassing the clinical platinum(II) drug oxaliplatin.
- Fantoni, Nicoló Zuin,Molphy, Zara,O'Carroll, Sinéad,Menounou, Georgia,Mitrikas, George,Krokidis, Marios G.,Chatgilialoglu, Chryssostomos,Colleran, John,Banasiak, Anna,Clynes, Martin,Roche, Sandra,Kelly, Suainibhe,McKee, Vickie,Kellett, Andrew
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- Effects of the Ligand Structure of Cu(II) Complexes on Oxidative DNA Cleavage
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Cu complexes were synthesized by substituting the hydrogen of the amine group of basic ligand 2,2′-dipicoylamine (dpca) (complex 2) with CH3CO (complex 1), phenyl (complex 3), and methyl (complex 4), respectively, and their DNA cleavage activity was investigated using linear dichroism (LD) and electrophoresis. The DNA cleavage efficiencies of Cu complexes 3 and 4 with phenyl and methyl, which are electron-donating functional groups, turned out to be the highest, and LD magnitudes rapidly decreased at 260 nm. In particular, Cu complex 3 showed a rapid LD magnitude reduction to 63% of the total for 90 min, and to 50% of the total at 12 min. DNA cleavage efficiencies were high in the order of phenyl > methyl > HCH3CO, and the highest DNA cleavage efficiency was observed in the presence of electron-donating groups. The electrophoresis results are also consistent with the changes in LD spectra over time. The Cu complexes (1–4) were found to cleave DNA through oxidative pathways, and the major reaction oxygen species involved in DNA cleavage were the superoxide radical (·O2?), singlet oxygen (1O2), and hydroxyl radical (·OH).
- Han, Ji Hoon,Kim, Ji Hoon,Jung, Maeng-Joon,Kim, Seog K.,Jang, Yoon Jung
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- Understanding the Origin of One- or Two-Step Valence Tautomeric Transitions in Bis(dioxolene)-Bridged Dinuclear Cobalt Complexes
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Valence tautomerism (VT) involves a reversible stimulated intramolecular electron transfer between a redox-active ligand and redox-active metal. Bis(dioxolene)-bridged dinuclear cobalt compounds provide an avenue toward controlled two-step VT interconversions of the form {CoIII-cat-cat-CoIII} ? {CoIII-cat-SQ-CoII}?{CoII-SQ-SQ-CoII} (cat2- = catecholate, SQ·- = semiquinonate). Design flexibility for dinuclear VT complexes confers an advantage over two-step spin crossover complexes for future applications in devices or materials. The four dinuclear cobalt complexes in this study are bridged by deprotonated 3,3,3′,3′-tetramethyl-1,1′-spirobi(indan)-5,5′,6,6′-tetraol (spiroH4) or 3,3,3′,3′-tetramethyl-1,1′-spirobi(indan)-4,4′,7,7′-tetrabromo-5,5′,6,6′-tetraol (Br4spiroH4) with Mentpa ancillary ligands (tpa = tris(2-pyridylmethyl)amine, n = 0-3 corresponds to methylation of the 6-position of the pyridine rings). Complementary structural, magnetic, spectroscopic, and density functional theory (DFT) computational studies reveal different electronic structures and VT behavior for the four cobalt complexes; one-step one-electron partial VT, two-step VT, incomplete VT, and temperature-invariant {CoIII-cat-cat-CoIII} states are observed. Electrochemistry, DFT calculations, and the study of a mixed-valence {ZnII-cat-SQ-ZnII} analog have allowed elucidation of thermodynamic parameters governing the one- and two-step VT behavior. The VT transition profile is rationalized by (1) the degree of electronic communication within the bis(dioxolene) ligand and (2) the matching of cobalt and dioxolene redox potentials. This work establishes a clear path to the next generation of two-step VT complexes through incorporation of mixed-valence class II and class II-III bis(dioxolene) bridging ligands with sufficiently weak intramolecular coupling.
- Boskovic, Colette,Gable, Robert W.,Gransbury, Gemma K.,Hay, Moya A.,Janetzki, Jett T.,Livesay, Brooke N.,Shores, Matthew P.,Starikova, Alyona
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- CO2 fixation by dicopper(ii) complexes in hypodentate framework of N8O2
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A new ligand with N8O2 donors containing three potential metal-binding sites (H2L) and its tricopper(ii) complex 1 are synthesized. The tricopper species is found to be formed from a hypodentate dicopper(ii) complex 2 in basic solutions. Complex 2 may be isolated from the reaction of H2L with a copper source under acidic conditions. Complex 2 can undergo CO2-abstraction to yield an octacopper(ii) complex 3. The single crystal structures of complexes 2 and 3 are characterized by X-ray crystallography. This journal is the Partner Organisations 2014.
- Ho, Yi-Hsueh,Chang, Mu-Chieh,Yu, Kuo-Hsuan,Liu, Yi-Hung,Wang, Yu,Cheng, Yuan-Chung,Chen, Jwu-Ting
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- Development of Gene-Targeted Polypyridyl Triplex-Forming Oligonucleotide Hybrids
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In the field of nucleic acid therapy there is major interest in the development of libraries of DNA-reactive small molecules which are tethered to vectors that recognize and bind specific genes. This approach mimics enzymatic gene editors, such as ZFNs, TALENs and CRISPR-Cas, but overcomes the limitations imposed by the delivery of a large protein endonuclease which is required for DNA cleavage. Here, we introduce a chemistry-based DNA-cleavage system comprising an artificial metallo-nuclease (AMN) that oxidatively cuts DNA, and a triplex-forming oligonucleotide (TFO) that sequence-specifically recognises duplex DNA. The AMN-TFO hybrids coordinate CuII ions to form chimeric catalytic complexes that are programmable – based on the TFO sequence employed – to bind and cut specific DNA sequences. Use of the alkyne-azide cycloaddition click reaction allows scalable and high-throughput generation of hybrid libraries that can be tuned for specific reactivity and gene-of-interest knockout. As a first approach, we demonstrate targeted cleavage of purine-rich sequences, optimisation of the hybrid system to enhance stability, and discrimination between target and off-target sequences. Our results highlight the potential of this approach where the cutting unit, which mimics the endonuclease cleavage machinery, is directly bound to a TFO guide by click chemistry.
- Zuin Fantoni, Nicolò,McGorman, Bríonna,Molphy, Zara,Singleton, Daniel,Walsh, Sarah,El-Sagheer, Afaf H.,McKee, Vickie,Brown, Tom,Kellett, Andrew
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- A novel ditopic ligand derived from 8-hydroxyquinoline: Synthesis, characterisation, and its coordination chemistry with selected metal ions
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A novel multidentate ligand, 5-(bis(pyridin-2-ylmethyl)amino)quinolin-8-ol (HL) was synthesised and characterised. Its coordination modes with a variety of metal ions (Mg2+, Co2+, Cu2+, Zn2+, and Hg2+) were investigated using UV-Vis spectroscopic titration. Among the examined metal ions, coordination ratios (M2+: HL) between the metal ion and the ligand at 1:2, 1:1, and 3:2 were observed due to the ditopic nature of the ligand. In acetonitrile, Mg2+ showed relatively strong fluorescent response upon binding to the ligand among the examined metal ions, Li+, K+, Mg2+, Ca2+, Al 3+, Cu2+, Fe3+, Cr3+, Zn 2+, Co2+, Ni2+, and Hg2+.
- Xie, Xiang,Jiang, Xiujuan,Liu, Jian,Ren, Xingye,Wang, Hongming,Liu, Xiaoming
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- Towards hydroperoxovanadium complexes: The X-ray crystal structure of a peroxovanadium(v) complex containing a V(O2)(RCO2H)(H2O)2 cluster with hydrogen bond inter-linkages
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The molecular structure of the oxo-peroxovanadium complex [VO(O2)(bpaH)]ClO4·2H20, containing the new ligand N,N-bis(2-pyridylmethyl)-β-alanine (bpaH) reveals tight binding of the carboxylic acid function to the vanadium centre through its doubly bonded oxygen; the carboxylic acid proton mediates hydrogen bonding interactions comprising the peroxo group and the two waters of crystallisation, thus providing the basis for the potential formation of a hydroperoxo species.
- Casny,Rehder
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- Zn(II)-DPA Coordinative fluorescent probe for enhancing G4 DNA binding
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Novel dipicolylamino functionalized styryl-carbazole derivative (YCJ) was designed and synthesized. This derivative in combination with Zn(II) has exhibited large fluorescence intensity enhancement and prominent red-shift in absorption spectra with G4 DNA. Systematical analysis indicats that YCJ-Zn(II) complex shows much higher binding affinity and spectral response to G4 DNA than our previously reported styryl-carbazole scaffold (E1) due to the incorporationc of a Zn(II)-DPA moiety which could decrease the carbazole core electron density and consequently enhance the ability to display π-π stacking interaction with G4 DNA. Spectroscopic and molecular docking studies have unraveled YCJ-Zn(II) complex can stack both 3′ and 5′-ends and an associated with partial loop/groove interactions. The application of this Zn(II) complex as a fluorescent agent for living cell imaging was also demonstrated. The conjugation of the Zn-DPA moiety results in good cell permeability, endogenous DNA labeling, which is suitable for monitoring of nucleus activities.
- Bai, Yi-Tong,Gao, Juan-Juan,Lang, Xue-Xian,Li, Hong-Yao,Wang, Hai-Jiao,Wang, Ming-Qi,Yu, Quan-Qi
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- Photocatalytic degradation of dyes by mononuclear copper(II) complexes from bis-(2-pyridylmethyl)amine NNN-derivative ligands
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Photocatalytic degradation of organic pollutant dyes under ultraviolet radiation has emerged as an efficient wastewater treatment. This work describes the application of four mononuclear copper(II) complexes coordinated to NNN ligands: bis-(2-pyridylmethyl)amine (BMPA), N-methylpropanoate-N,N-bis-(2-pyridylmethyl)amine (MPBMPA), N-propanoate-N,N-bis-(2-pyridylmethyl)amine (PBMPA) and N-propanamide-N,N-bis-(2-pyridylmethyl)amine (PABMPA); in the photocatalytic degradation of different dyes: methyl orange (MO), methylene blue (MB), crystal violet (CV), Congo red (CR) and Rhodamine B (RhB). The reactions were carried out under a UV lamp of 250 W, where 100percent of degradation was achieved in 90 min for all complexes using hydrogen peroxide as oxidant. Kinetic experiments were carried out to investigate the photodegradation of the dyes under a UV lamp of 24 W. The reactions followed a zero-order model in relation to the dye, showing that its concentration did not play a significant role in the photocatalysis. The reaction order in relation to hydrogen peroxide varied from 0 to 0.8, from low to high concentrations of oxidant. The light intensity and the intrinsic catalytic activity of the complexes are the most important features for the dye photodegradation pathway.
- Carvalho, Nakédia M. F.,Carvalho, Samira S. F.,Lima, Juliana F.,Rodrigues, Ana Carolina C.
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- Synthesis and properties of a heterobimetallic iron-manganese complex and its comparison with homobimetallic analogues
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Heterobimetallic cofactors containing one manganese and one iron ion have recently been found within the di-metal carboxylate protein family. Herein we report the synthesis and characterization of three binuclear metal complexes with Fe-Fe, Mn-Mn, and Fe-Mn metal composition. All three complexes use the same ligand framework, the BPMP ligand (HBPMP = 2,6-bis[(bis (-2-pyridylmethyl)amine) methyl]-4-methylphenol)) with two additional acetate ligands bridging the two metals. In terms of stability towards metal exchange, the Fe-Mn is more stable than the Mn-Mn complex but less stable than the Fe-Fe complex. Cyclic voltammetry shows that the Fe-Mn complex behaves markedly different than the homobimetallic complexes. The Fe-Mn complex also shows higher reactivity with O2 than both the Fe-Fe and the Mn-Mn counterparts.
- Bedin, Michele,Agarwala, Hemlata,Marx, Jennifer,Schünemann, Volker,Ott, Sascha,Thapper, Anders
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- Enhanced Tb(III) luminescence by d10transition metal coordination
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Three new TbIIIcontaining complexes of a novel heptadentate amide open crown ether ligand [Tb4L2(NO3)10(CH3COO)2] (TbL), [ZnTbL(NO3)5]2·3CH3CN·CH3COOCH2CH3·H2O (TbZnL) and [CdTbL(NO3)5]·4CH3CN (TbCdL), L = 2,2′-((4-((bis(pyridin-2-ylmethyl)amino)methyl)-1,2-phenylene)bis(oxy))bis(N,N-diisopropylacetamide), were step-by-step prepared and structurally characterized. Photophysical properties of the three emitting TbIIIcomplexes have been investigated in detail. A large increase of the quantum yield and lifetime was observed for TbZnL compared with TbL, whereas a moderate increase of the quantum yield and lifetime was observed for TbCdL.
- Song, Xue-Qin,Cheng, Guo-Quan,Liu, Yuan-Ang
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- Optical detection of di- And triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)-dipicolylamine complexes
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Gold nanoparticles covered with a mixture of ligands of which one type contains solubilizing triethylene glycol residues and the other peripheral zinc(II)-dipicolylamine (DPA) complexes allowed the optical detection of hydrogenphosphate, diphosphate, and triphosphate anions in water/methanol 1:2 (v/v). These anions caused the bright red solutions of the nanoparticles to change their color because of nanoparticle aggregation followed by precipitation, whereas halides or oxoanions such as sulfate, nitrate, or carbonate produced no effect. The sensitivity of phosphate sensing depended on the nature of the anion, with diphosphate and triphosphate inducing visual changes at significantly lower concentrations than hydrogenphosphate. In addition, the sensing sensitivity was also affected by the ratio of the ligands on the nanoparticle surface, decreasing as the number of immobilized zinc(II)-dipicolylamine groups increased. A nanoparticle containing a 9:1 ratio of the solubilizing and the anion-binding ligand showed a color change at diphosphate and triphosphate concentrations as low as 10 μmol/L, for example, and precipitated at slightly higher concentrations. Hydrogenphosphate induced a nanoparticle precipitation only at a concentration of ca. 400 μmol/L, at which the precipitates formed in the presence of diphosphates and triphosphates redissolved. A nanoparticle containing fewer binding sites was more sensitive, while increasing the relative number of zinc(II)-dipicolylamine complexes beyond 25% had a negative impact on the limit of detection and the optical response. Transmission electron microscopy provided evidence that the changes of the nanoparticle properties observed in the presence of the phosphates were due to a nanoparticle crosslinking, consistent with the preferred binding mode of zinc(II)-dipicolylamine complexes with phosphate anions which involves binding of the anion between two metal centers. This work thus provided information on how the behavior of mixed monolayer-protected gold nanoparticles is affected by multivalent interactions, at the same time introducing a method to assess whether certain biologically relevant anions are present in an aqueous solution within a specific concentration range.
- Reinke, Lena,Bartl, Julia,Koch, Marcus,Kubik, Stefan
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- Four new copper(II) complexes with di-substituted s-triazine-based ligands
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In this paper, two di-substituted triazine-based ligands, 6-chloro-N,N,N′N′-tetrakis-pyridin-2-ylmethyl-[1,3,5]triazine-2, 4-diamine (L1), and 6-chloro-N,N′-bis-pyridin-2-ylmethyl-N,N′-bis- thiophen-2-ylmethyl-[1,3,5]triazine-2,4-diamine (L2), have been prepared. Reaction of CuCl2·2H2O and Cu(NO3) 2·3H2O with L1 and L2 results in the formation of [Cu2Cl4(L1)]·3MeOH (compound 1), [Cu 4(NO3)8(L1)2]·2.07CH 2Cl2·0.93MeOH (compound 2), [Cu2Cl 4(L2)2] (compound 3) and [Cu(NO3) 2(L2)]·CH2Cl2 (compound 4), respectively, which have been fully characterized and determined by single-crystal X-ray crystallography, FT-IR, elemental analysis, thermogravimetric measurement and magnetic susceptibility. The dinuclear compound 1 shows strong π-π interactions between the neighboring pyridine rings. The nitrate-π (1,3,5-triazine ring) interaction with the distance of 2.755 in compound 2, is the closest contact reported so far. Compounds 3 and 4 are mononuclear copper(II) compounds, in which none of thiophene rings coordinates with copper(II) ion. In addition, the different orientations of two thiophene rings in compounds 3 and 4 lead to the π-π and CH 2Cl2-π (thiophene ring) interactions in compound 4, but not in compound 3.
- Chu, Jinfeng,Chen, Wei,Su, Guangxun,Song, Yu-Fei
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- Iron(iii) complexes of multidentate pyridinyl ligands: Synthesis, characterization and catalysis of the direct hydroxylation of benzene
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Three multidentate ligands, L1-L3, derived from bis(pyridin-2-ylmethyl)amine (L1) were synthesized. Reaction of these ligands with FeCl3·6H2O in methanol led to the formation of the iron complexes Fe1-Fe3 (Fe1: [FeL1Cl3]; Fe2: [FeL2Cl3]; Fe3: [FeL3Cl3]) in good yields. These complexes have been fully characterized. The structures of complexes Fe1-Fe3 have been determined using X-ray single crystal diffraction analysis. Electrochemical investigation revealed that complex Fe3 partially converts to Fe4 ([FeL3Cl2]PF6) by the replacement of one of its three chlorides with its pendant triazolyl group in solution. Fe4 was also synthesized by dechlorination using AgPF6 as the Cl- abstractor and its composition was further confirmed by both elemental analysis and X-ray single crystal diffraction analysis. All four complexes catalyze the direct hydroxylation of benzene to phenol with hydrogen peroxide as an oxidant in a mixed medium of water and acetonitrile. The reactivity of the complexes correlates well with their reduction potentials. The more negative the potential, the more reactive (high conversion rate) the catalysts. These complexes catalyze not only the oxidation of benzene, but also the further oxidation of the product, phenol. In the oxidation, a radical mechanism is certainly involved but an alternative pathway may also exist. This journal is
- Xu, Beibei,Zhong, Wei,Wei, Zhenhong,Wang, Hailong,Liu, Jian,Wu, Li,Feng, Yonggang,Liu, Xiaoming
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- Synthesis, characterization and antimicrobial activity of nickel(II) complexes of tridentate N3 ligands
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The desire to develop new antimicrobial agents against the rising threat of extensive antibiotic resistance led to the exploration of many natural and synthetic compounds. Herein, we report the isolation and structural characterization of nickel(II) complexes of the type [Ni(L)2]2+ (1 and 2) of tridentate N3 ligands such as bis(pyridin-2-ylmethyl)amine (L1) and 1-(1-methyl-1H-imidazol-2-yl)-N-(pyridin-2-ylmethyl)methanamine (L2). Both the complex cations of [Ni(L1)2]2+ (1) and [Ni(L2)2]2+ (2) possess a distorted octahedral coordination geometry in which Ni(II) is chelated to two equivalents of the tridentate L1 and L2 ligand in facial coordination, respectively. Complexes 1 and 2 exhibit the bands in the visible region in UV–Vis spectra and peaks in the downfield region in paramagnetic NMR spectra suggesting the octahedral coordination geometry of the complexes in solution as well. Further, complexes 1 and 2 were evaluated for their antimicrobial activity against various clinical pathogens. With in vitro studies, complex 1 displayed activity against Vibrio parahaemolyticus and V. alginolyticus, Staphylococcus aureus, Candida albicans, and Salmonella typhi, and complex 2 displayed activity against S. aureus, S. typhi, and C. albicans. In addition, with in vivo studies, complex 1 was effective in inhibiting Vibrio infection in brine shrimp larvae while having no toxicity on the larvae. We believe these results will encourage medicinal chemists to further the study on metal complexes against multi-resistant pathogens.
- Arunkumar, Manivel,Bhunia, Sarmistha,Chari, Nithya,Das, Athulya,Rajeev, Anjana,Sankaralingam, Muniyandi
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- Microwave-assisted synthesis of N,N-bis-(2-pyridylmethyl)amine derivatives. Useful ligands in coordination chemistry
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Microwave-assisted synthesis of the ligands N,N-bis-(2-pyridylmethyl)amine (BMPA), N-(methylpropanoate)-N,N-bis-(2-pyridylmethyl)amine (MPBMPA), N-(propanamide)-N,N-bis-(2-pyridylmethyl)amine (PABMPA), PNBMPA (N-(3-propionitrile)-N,N-bis-(2-pyridylmethyl)amine), N-(3-aminopropyl)-N,N-bis-(2-pyridylmethyl)amine (APBMPA), and lithium N-(proponoate)-N,N-bis-(2-pyridylmethyl)amine (LiPBMPA) are reported. High yields and short reaction time were obtained for condensation and Michael addition.
- Pimentel, Luiz Claudio F.,de Souza, Andréa Luzia F.,Fernández, Tatiana López,Wardell, James L.,Antunes
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- Molecular structure of mononuclear azido- and dicyanamido-Cu(II) complexes
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A new series of mononuclear azido- and dicyanamido-Cu(II) complexes, [Cu(L)(N3)]ClO4 where L = pdpa {N-(2-aminopropyl)-N,N-bis(2-pyridylmethyl)amine}, Me3tren {tris(N-methyl-2-aminoethyl)amine} and Me6trien (1,1,4,7,10,10-hexamethyltriethylenetetraamine) and Cu(L)(C2N3)2 with L = pmedien (N,N,N′,N″,N″-pentamethyldiethylenetriamine) and Me2dpt (N,N-dimethyldipropyltriamine) were synthesized and structurally characterized by electronic and IR spectroscopy as well as by X-ray. Single crystal X-ray diffraction analysis of the complexes [Cu(pdpa)(N3)]ClO4 (1), [Cu(Me3tren)(N3)]ClO4 (2) and [Cu(pmedien)(C2N3)2] (3) reveals their monomeric nature. The structures of the complexes 1 and 2 derived from the blocking tripod tetraamines pdpa and Me3tren consist of isolated [Cu(L)(N3)]+ cations and Cl O4- counter ions. The copper centers are penta-coordinated by the four N of the amine ligands with the monodentate azido ligand occupying the apical site in distorted trigonal bipyramidal (TBP) geometry. Complex 1 exhibits π-π stacking interaction between the pyridyl groups. In the neutral complex 3, where the blocking ligand, pmedien is a linear tridentate amine the penta-coordinate geometry of the complex was achieved by the three planar amine-N and two terminal nitrile-N atoms from the two dicyanamide groups; one N in the basal position from the first dicyanamido group and one N at the apical position from the second group. The coordination polyhedron around the copper center may be described as an axially elongated square pyramidal (SP). The visible spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Cu(II) centers.
- Mautner, Franz A.,Landry, Christine N.,Gallo, August A.,Massoud, Salah S.
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- LMCT transition-based red-light photochemotherapy using a tumour-selective ferrocenyl iron(iii) coumarin conjugate
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A rationally designed iron(iii) complex (2a) with pendant ferrocene and naturally occurring coumarin (esculetin) shows LMCT transition-based mitochondria-targeted red-light (600-720 nm) induced apoptotic toxicity against cancer cells but remains innocuous in the dark and to normal cells.
- Banerjee, Samya,Bhattacharyya, Arnab,Hussain, Akhtar,Sarkar, Tukki
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- Cucurbit[7]uril-improved recognition by a fluorescent sensor for cadmium and zinc cations
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The host–guest interaction of cucurbit[7]uril (Q[7]) with the new fluorescent sensor guest molecule (BIBPAH+), formed by alkylation of the secondary amine site in N,N-bis(2-pyridylmethyl)amine with 2-(bromomethyl)benzimidazole, was investigated by fluorescence and 1H NMR spectroscopy. The results indicate the formation of an inclusion complex in a 1:1 ratio with an association constant of Ka?=?(2.9?±?0.7) × 105 L ? mol?1. There is minimal difference in the fluorescence intensities upon the introduction of each of Mn2+, Ni2+, Co2+, Cr3+, Ho3+ and Lu3+. However, the emission was slightly quenched on the addition of Cu2+ or Fe3+ whether Q[7] is present or not. Further investigation showed that encapsulation of BIBPAH+ in Q[7] improves Cd2+ and Zn2+ recognition by enhancing the fluorescence intensity, leading to an improvement in the limits of detection. In contrast, comparative parallel experiments in which Cu2+, Mn2+, Ni2+, Co2+, Fe3+, Cr3+, Ho3+ or Lu3+ were substituted for Zn2+ or Cd2+ resulted in minimal changes in the fluorescence that occurs for the corresponding metal-free system. The natures of the encapsulated Zn2+ and Cd2+ complexes have been investigated using fluorescence and 1H NMR spectroscopy as well as by quantum chemistry.
- Geng, Qing-Xia,Cong, Hang,Tao, Zhu,Lindoy, Leonard F.,Wei, Gang
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- Synthesis, spectroscopic studies, thermal analyses, biological activity of tridentate coordinated transition metal complexes of bi(pyridyl-2-ylmethyl)amine]ligand
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A new tridentate acyclic pincer ligand, [bi(pyridin-2-methyl)amine] (bpma, HL), was synthesized and reacted to form complexes with copper(II), nickel(II), iron(II), cobalt(II) and zinc(II) ions. Both the ligand and its complexes were characterized using elemental analysis, molar conductance, infrared, 1H-NMR-spectroscopy, mass and thermal analyses. According to the spectroscopic data, all of the complexes share the same coordination environment around the metal atoms, consisting two nitrogen-pyridine entities, one nitrogen-methylamine entity, one/two water molecules and/or one/two chloride or bromide ions. Complexes also showed molar conductivity according to the presence of two halide anions outer the coordination sphere except Co(II) and Zn(II) complexes are non electrolytes. Analysis indicates that the metal ions have trigonal bipyramidal structure. Cu(II), Ni(II), Fe(II), Co(II), and Zn(II) metal complexes were screened for their antibacterial activity against Bacillus subtilis, Staphylococcus aureus (G+) and Escherichia coli, and Pseudomonas aeruginosa (G-) bacteria. They showed remarkable antimicrobial activity.
- Abd El-Halim, Hanan F.,Mohamed, Gehad G.
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- Complexation of the N,N',O-donor ligand N-trans-(2'-hydroxycyclohexyl)-2-aminomethylpyridine
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The potentially tridentate N,N',O-donor N-trans-(2'-hydroxycyclohexyl)-2-aminomethylpyridine (1) forms ML2 complexes with M(II) = Cu, Ni, and Zn. X-ray crystal structures of the isostructural Ni(II) and Zn(II) complexes confirm bis-tridentate coordination
- Tiwow, Vanny,Lawrance, Geoffrey A.,Maeder, Marcel,Jensen, Paul
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- Evaluation of cobalt complexes with tripod ligands for zinc finger targeting
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Cobalt complexes have been demonstrated to target zinc fingers, as shown by investigations of Doxovir, the trade name of the [CoIII(acacen)(2-Me-Imz)2]+ drug in clinical trials. Mechanistic studies indicate zinc finger disruption by metal coordination to His residues. Other than Doxovir, a few studies have investigated other ligands and geometries for cobalt complexes for zinc finger targeting. Tripod ligands demonstrated good zinc and cobalt chelation. In this manuscript, we report the ability of CoII and CoIII complexes of tri(2-pyridylmethyl)amine and N,N-di(2-pyridylmethyl)glycinate to disrupt zinc fingers. The results obtained by mass spectrometry and X-ray absorption spectroscopy demonstrate that the complexes were able to remove zinc from the zinc fingers. The product was oxidised apo-peptide. In contrast, the ligands themselves were able to remove zinc, and they did not promote oxidation, resulting in free Cys residues. Cobalt finger adducts were not detected for the complexes with tripod ligands unless they were coordinated to planar ligands such as salen or acacen. Studies of the interactions of cobalt complexes with amino acids demonstrated that tripod ligands promote the cysteine reaction, while the salen ligands promote histidine coordination, demonstrating a different mechanism of action. The results reported here are significant for better understanding and further design of zinc finger targeting compounds.
- Aealsteinsson, Heiear Mar,Abbehausen, Camilla,Galuppo, Carolina,Lima, Frederico A.
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supporting information
p. 16143 - 16153
(2020/12/03)
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- CHEMOSELECTIVE SENSITIVITY BOOSTER FOR TAGGING A PEPTIDE, PEPTIDE CONJUGATE, OR SIMILAR REACTIVE MOLECULE
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The invention pertains to chemoselective sensitivity booster for tagging a peptide, peptide conjugate, or similar reactive molecule for analysis of a peptide, protein, antibody, protein bioconjugate, antibody bioconjugate, and similar analytes. The sensitivity booster comprises of sp2 or sp3 nitrogen centers in combination with hydrophobic carbon chains linked with an electrophile or nucleophile for attachment with a peptide, peptide conjugate, or molecules with similar reactivity.
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(2020/12/29)
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- Five nitrogen oxidation states from nitro to amine: Stabilization and reactivity of a metastable arylhydroxylamine complex
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Redox noninnocent ligands enhance the reactivity of the metal they complex, a strategy used by metalloenzymes and in catalysis. Herein, we report a series of copper complexes with the same ligand framework, but with a pendant nitrogen group that spans five different redox states between nitro and amine. Of particular interest is the synthesis of a unprecedented copper(I)-arylhydroxylamine complex. While hydroxylamines typically disproportionate or decompose in the presence of transition metal ions, the reactivity of this metastable species is arrested by the presence of an intramolecular hydrogen bond. Two-electron oxidation yields a copper(II)-(arylnitrosyl radical) complex that can dissociate to a copper(I) species with uncoordinated arylnitroso. This combination of ligand redox noninnocence and hemilability provides opportunities in catalysis for two-electron chemistry via a one-electron copper(I/II) shuttle, as exemplified with an aerobic alcohol oxidation.
- Zsombor-Pindera, Joseph,Effaty, Farshid,Escomel, Léon,Patrick, Brian,Kennepohl, Pierre,Ottenwaelder, Xavier
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supporting information
p. 19023 - 19028
(2020/11/13)
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- Artificial Iron Proteins: Modeling the Active Sites in Non-Heme Dioxygenases
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An important class of non-heme dioxygenases contains a conserved Fe binding site that consists of a 2-His-1-carboxylate facial triad. Results from structural biology show that, in the resting state, these proteins are six-coordinate with aqua ligands occupying the remaining three coordination sites. We have utilized biotin-streptavidin (Sav) technology to design new artificial Fe proteins (ArMs) that have many of the same structural features found within active sites of these non-heme dioxygenases. An Sav variant was isolated that contains the S112E mutation, which installed a carboxylate side chain in the appropriate position to bind to a synthetic FeII complex confined within Sav. Structural studies using X-ray diffraction (XRD) methods revealed a facial triad binding site that is composed of two N donors from the biotinylated ligand and the monodentate coordination of the carboxylate from S112E. Two aqua ligands complete the primary coordination sphere of the FeII center with both involved in hydrogen bond networks within Sav. The corresponding FeIII protein was also prepared and structurally characterized to show a six-coordinate complex with two exogenous acetato ligands. The FeIII protein was further shown to bind an exogenous azido ligand through replacement of one acetato ligand. Spectroscopic studies of the ArMs in solution support the results found by XRD.
- Batyuk, Alexander,Bhowmick, Asmit,Borovik, A. S.,Brewster, Aaron S.,Follmer, Alec H.,Fuller, Franklin D.,Green, Michael T.,Gul, Sheraz,Heinisch, Tillmann,Kern, Jan,Kim, In-Sik,Miller, Kelsey R.,Mittra, Kaustuv,Paretsky, Jonathan D.,Sauter, Nicholas K.,Sutherlin, Kyle D.,Ward, Thomas R.,Yano, Junko
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supporting information
p. 6000 - 6009
(2020/05/01)
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- Dehydroabietyl picolinamide compounds, and preparation method and application thereof
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The invention discloses dehydroabietyl picolinamide compounds, and a preparation method and an application thereof, and belongs to the fields of chemical synthesis and cation detection. The main component dehydroabietic acid of a natural product rosin, which is used as a raw material, undergoes a one-step process to obtain dehydroabietic acid chloride, and the dehydroabietic acid chloride and eachof bis(pyridin-2-yl-methyl)amine, N-(pyridin-2-yl-methyl)pyridine-2-amine, 2-aminomethylpyridine and 2-aminopyridine undergo an amidation reaction to obtain the four dehydroabietylpicolinamide compounds. The compounds have a high-selectivity recognition function on Cu and Fe, the corresponding detection limits are lower than the maximum allowable values of the copper content and the ironcontent specified in drinking water, and the compounds have good biological safety, so the compounds can be used as an ultraviolet and fluorescent probe for identifying copper ions and iron ions, areapplied to related detection of environments, drinking water and biological systems, and have a wide application prospect.
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Paragraph 0050-0053
(2019/12/25)
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- Sensitivity booster for mass detection enables unambiguous analysis of peptides, proteins, antibodies, and protein bioconjugates
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A chemical tag enhances peptide detection by multiple orders in mass spectrometry. The substantial improvement in the peptide mapping along with simplified and enhanced fragmentation pattern enables the unambiguous sequencing of a protein and antibody. The chemoselective sensitivity booster provides a tool for remarkably improved analysis of protein bioconjugates.
- Singudas, Rohith,Reddy, Neelesh C.,Rai, Vishal
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supporting information
p. 9979 - 9982
(2019/08/22)
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- ZINC-BINDER BASED EBNA1-SPECIFIC COMPOUNDS
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The present disclosure relates to compounds useful in the treatment, imaging, and/or diagnosis of Epstein-Barr virus (EBV)-positive cells, such as cancer.
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-
Paragraph 00244-00245
(2019/08/08)
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- Stabilisation of copper(i) polypyridyl complexes toward aerobic oxidation by zinc(ii) in combination with acetate anions: a facile approach and its application in ascorbic acid sensing in aqueous solution
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A new and facile approach to stabilise copper(i) complexes in aqueous solution by the addition of zinc(ii) ions in combination with acetate ions (OAc?) was demonstrated. This stability enhancement toward the aerobic oxidation of copper(i) species was investigated by various techniques including UV-vis spectroscopy, 1H-NMR, FT-IR, and ESI-MS. Our experimental results together with DFT calculations led to a proposed structure of [(adpa)Cu-OAc-Zn(OAc)(H2O)2]+/2+. It was also postulated that zinc(ii) with its Lewis acidity may attract electrons from the Cu centre through the bridging ligands (OAc?), resulting in the lower reactivity of Cu(i) with O2. In addition, this strategy was shown to be applicable to ascorbic acid detection by monitoring a change in the redox states of copper complexes using fluorescence spectroscopy. Moreover, it was demonstrated that the method was sensitive and accurate for the quantitative analysis of ascorbic acid in vitamin C tablets.
- Suktanarak, Pattira,Ruangpornvisuti, Vithaya,Suksai, Chomchai,Tuntulani, Thawatchai,Leeladee, Pannee
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supporting information
p. 997 - 1005
(2019/01/21)
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- Iron-Catalyzed Intramolecular C-H Amination of α-Azidyl Amides
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Iron-catalyzed intramolecular C-H amination of aliphatic azides has recently emerged as a powerful tool for the preparation of nitrogen heterocycles. This paper reports that α-azidyl amides can be converted in high efficacy to imidazolinone compounds via intramolecular C(sp3)-H amination by the action of a simple catalytic system composed of FeCl2 and a β-diketiminate ligand. The reactions provide a simple and atom-economical approach toward polysubstituted imidazolinones.
- Zhao, Xiaopeng,Liang, Siyu,Fan, Xing,Yang, Tonghao,Yu, Wei
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supporting information
p. 1559 - 1563
(2019/03/20)
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- Pd/TiO2-Photocatalyzed Self-Condensation of Primary Amines to Afford Secondary Amines at Ambient Temperature
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Symmetric secondary amines were synthesized by the self-condensation of primary amines over a palladium-loaded titanium dioxide (Pd/TiO2) photocatalyst. The reactions afforded a series of secondary amines in moderate to excellent isolated yields at ambient temperature (30 °C, in cyclopentyl methyl ether). Applicability for one-pot pharmaceutical synthesis was demonstrated by a photocatalytic reaction sequence of self-condensation of an amine followed by N-alkylation of the resulting secondary amine with an alcohol.
- Wang, Lyu-Ming,Kobayashi, Kensuke,Arisawa, Mitsuhiro,Saito, Susumu,Naka, Hiroshi
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supporting information
p. 341 - 344
(2018/12/11)
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- Chemoselective hydrogenation of nitriles to secondary or tertiary amines catalyzed by aqueous-phase catalysts supported on hexagonal mesoporous silica
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The first supported aqueous-phase catalyst for the hydrogenation of nitriles is revealed. The catalyst prepared from Pd(PhCN)2Cl2, water-soluble ligand 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt and mesoporous silica is a highly efficient catalyst for the selective formation of secondary or tertiary amines from aromatic or aliphatic nitriles. The catalytic system is stable and can be recycled and reused three times without loss of activity and selectivity. This environmentally friendly process is, in addition, an attractive alternative to many homogeneous and heterogeneous catalysts because of its easy preparation and the moderate operational conditions under which it is highly active.
- Nait Ajjou, Abdelaziz,Robichaud, André
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- Preparation of the Ru3(CO)8-pyridine-alcohol cluster and its use for the selective catalytic transformation of primary to secondary amines
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The synthesis of pyridine alcohol based ruthenium carbonyl clusters Ru3(hep)2(CO)8 (1), Ru3(hpp)2(CO)8 (2), and Ru3(bhmp-H)2(CO)8 (3) {hep-H = 2-(2-hydroxyethyl)pyridine, hpp-H = 2-(3-hydroxypropyl)pyridine and bhmp-H2 = 2,6-bis(hydroxymethyl)pyridine} has been carried out by the reaction of the corresponding pyridine-alcohol ligands with Ru3(CO)12. Clusters 1-3 have been characterized using elemental analysis, NMR, FT-IR, mass spectrometry and single-crystal X-ray structures. The clusters were explored for the selective catalytic transformation of primary amines into secondary amines using alcohols as the mono-alkylating agents via hydrogen transfer reactions. All three display efficient catalytic activity with 1 being the most effective.
- Singh, Ajeet,Mobin, Shaikh M.,Mathur, Pradeep
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p. 14033 - 14040
(2018/11/23)
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- SENSOR DYES FOR REAL-TIME SENSING OF METAL IONS IN AQUEOUS ENVIRONMENTS
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Provided herein are dyes for detecting and distinguishing metals in a sample, as well as compositions and methods comprising the same.
- -
-
Paragraph 00150; 00151; 00152
(2017/05/02)
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- Nano-sized La0.5Ca0.5CoO3-mediated reduction by nabh4 of aryl nitriles to bis-(benzyl) amines
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Nano-sized La0.5Ca0.5CoO3 perovskite, which was produced via the sol-gel method, was an efficient heterogeneous catalyst in combination with NaBH4 for the rapid chemoselective reduction of aryl nitriles to bis-(benzyl)amines at 40°C in good to excellent yields. The physico-chemical properties of the catalyst were characterized by means of differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and particle size distributions images. The results show that nanoparticles have regular shapes with well-defined crystal faces with an average size of 30 nm.
- Bavandi, Hossein,Shiri, Ali,Tavakkoli, Haman
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p. 3330 - 3334
(2017/05/29)
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- Highly active binuclear Cu(II) catalyst bearing an unsymmetrical bipyridine-pyrazole-amine ligand for the azide-alkyne cycloaddition reaction
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Ligands containing NH groups often show special characteristics. In this paper, a well-defined dinuclear Cu(II) complex bearing an unsymmetrical bipyridine-pyrazole-amine ligand was synthesized by the condensation of N–H to release H2O. Using sodium L-ascorbate as a reductant, the binuclear complex showed excellent activity in 1,3-dipolar cycloaddition reactions between alkynes and azides to obtain 1,4-disubstituted triazoles in 95%–99% isolated yields.
- Han, Baofeng,Xiao, Xiao,Wang, Lan,Ye, Wenjing,Liu, Xiaoping
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p. 1446 - 1450
(2016/10/04)
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- With a three-legged biligand the cobalt carbonyl complex and method of preparing the same
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The invention discloses a carbonyl cobalt complex with a three-legged ligand and a preparation method of the carbonyl cobalt complex. The carbonyl cobalt complex has the molecular formula of C19H21ClCoN5O8 or [Co(mapa)(O2CO)]ClO4.H2O, wherein mapa refers to (6-amino-2-pyridylmethyl)bi(2-pyridylmethyl)amine. The structural formula of the carbonyl cobalt complex is shown in a formula (I). The preparation method comprises the following steps: adding [Co(H2O)6](ClO4)2, a three-legged ligand mapa and NaHCO3 into a mixed solvent of H2O and methanol, thereby obtaining a mixed solution; and (2) performing air foaming on the mixed solution, stirring and reacting, performing recrystallization separation on the reaction product, thereby obtaining the carbonyl cobalt complex. The carbonyl cobalt complex and the preparation method thereof provide an important research object for research on coordination chemistry and have extremely high academic value. The structural formula is as shown in the specification.
- -
-
Paragraph 0029-0030; 0064
(2017/04/11)
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- Amide bond cleavage initiated by coordination with transition metal ions and tuned by an auxiliary ligand
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The reaction of ligand L, N,N-bis(pyridin-2-ylmethyl)acetamide, with five transition metal salts, FeCl3·6H2O, CuCl2·2H2O, Cu(ClO4)2·6H2O, ZnCl2 and K2PtCl4/KI, produced five metal complexes, [(μ-O)(FeClL′)(FeCl3)] (1), [CuLCl2] (2), [CuBPA(ClO4)(CHCN)] ClO4 (3), [ZnLCl2] (4) and [PtLI2] (5), where L′ = 1-(2,4,5-tri(pyridin-2-yl)-3-(pyridin-2-ylmethyl)imidazolidin-1-yl)ethanone which formed in situ, and BPA = bis(pyridin-2-ylmethyl)amine. The ligand and complexes were characterized by a variety of spectroscopic techniques including X-ray single crystal diffraction where applicable. Depending on the metal ion and auxiliary ligand of the complex, the acetyl group of the ligand L could be either intact or cleaved. When ferric chloride hexahydrate was used, the deacetylation proceeded even further and a novel heterocyclic compound (L′) was formed in situ. A possible mechanism was proposed for the formation of the heterocyclic compound found in complex 1. Our results indicate that to cleave effectively an amide bond, it is essential for a metal centre to bind to the amide bond and the metal centre is of sufficient Lewis acidity.
- Yang, Yongpo,Lu, Chunxin,Wang, Hailong,Liu, Xiaoming
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p. 10289 - 10296
(2016/07/06)
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- Monooxygenation of an appended phenol in a model system of tyrosinase: Implications on the enzymatic reaction mechanism
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A new tridentate N-donor ligand and its corresponding copper(i) complex have been synthesized to investigate the tyrosinase-like aromatic hydroxylation of an attached phenol. The results of the oxygenation reactions are compared to related systems having attached phenyl and catechol groups, respectively. The title complex is the first system mediating the monooxygenation of a phenol in the absence of an external base. This journal is
- Hamann, Jessica Nadine,Rolff, Malte,Tuczek, Felix
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supporting information
p. 3251 - 3258
(2015/03/05)
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- Synthesis and characterization of copper(ii) complexes with multidentate ligands as catalysts for the direct hydroxylation of benzene to phenol
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Four copper(ii) complexes with multidentate ligands, 1 ([CuL1Cl2]), 2 ([Cu(HL2)Cl2]), 3 ([Cu2(L2)2](ClO4)2) and 4 ([CuL3(HOCH3)ClO4]) {L1 = N,N-bis((pyridin-2-yl)methyl) prop-2-yn-1-amine, HL2 = 2-((((1-methyl-1H-imidazol-2-yl)methyl)(pyridin-2-ylmethyl)amino)methyl)phenol and HL3 = 2-((((1-methyl-1H-imidazol-2-yl)methyl)(pyridin-2-ylmethyl)amino)methyl)-2-t-butyl-phenol} are reported. The complexes were characterized by UV-vis spectroscopy, elemental analysis and electrochemical analysis. Complexes 1 and 3 were further characterized by X-ray single crystal diffraction analysis. The catalytic performances of these complexes were evaluated in the direct hydroxylation of benzene to phenol with hydrogen peroxide as an oxidant in aqueous acetonitrile media. Under optimized reaction conditions, complex 4 with the most negative reduction potential exhibited the highest conversion without considering the dinuclear complex 3. A correlation between the catalytic efficiency and the reduction potentials of these complexes was observed, that is the more negative the reduction potential, the higher the benzene conversion. A radical mechanism for the catalysis was confirmed by the fact that addition of radical scavengers such as TEMPO into the reaction mixture could severely suppress the catalysis.
- Wu, Li,Zhong, Wei,Xu, Beibei,Wei, Zhenhong,Liu, Xiaoming
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p. 8013 - 8020
(2015/05/05)
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- Diiron(III) complexes of tridentate 3N ligands as functional models for methane monooxygenases: Effect of the capping ligand on hydroxylation of alkanes
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A series of non-heme (μ-oxo)bis(μ-benzoato)-bridged diiron(III) complexes of the type [Fe2(O)(OBz)2(L)2] 2+ (1-6), where OBz = benzoate, L = bis(pyridin-2-ylmethyl)amine (L1), N-((6-methylpyridin-2-yl-)methyl)(pyridin-2-yl)methanamine (L2), N,N-dimethyl-N′-(pyrid-2-ylmethyl)ethylenediamine (L3), (1-methyl-1H-imidazol-2-yl)-N-(pyridin-2-ylmethyl)-methanamine (L4), (1H-benzo[o]imidazol-2-yl)-N-(pyridin-2-ylmethyl)methanamine (L5) and bis((1H-benzo[o]imidazol-2-yl)methyl)amine (L6), have been isolated and characterized by means of elemental analysis, spectral and electrochemical methods. They have been studied as catalysts for selective hydroxylation of alkanes using m-choloroperbenzoic acid (m-CPBA) as the oxidant. In acetonitrile/dichloromethane mixed solvent all the complexes display a d-d band characteristic of a triply bridged diiron(III) core, revealing that they retain their identity in solution. Upon replacing a donor atom on the capping ligand by a stronger donor, the E1/2 value of the one-electron Fe IIIFeIII → FeIIIFeII reduction becomes more negative. All the complexes function as efficient catalysts for hydroxylation of cyclohexane, with 390-410 total turnover numbers and good alcohol selectivity (A/K, 9.3-12.8). Adamantane is selectively oxidized (3 /2, 15.7-28.1) to 1-adamantanol and 2-adamantanol, along with a small amount of 2-adamantanone (Total TON, 336-437), and interestingly the 3N capping ligands with the pyridyl donor around the diiron(III) center lead to high 3 /2 bond selectivity.
- Sankaralingam, Muniyandi,Palaniandavar, Mallayan
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p. 171 - 180
(2013/10/22)
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- Two multidentate ligands utilizing triazolyl, pyridinyl and phenolate groups as donors for constructing dinuclear copper(II) and iron(III) complexes: Syntheses, structures, and electrochemistry
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Two multidentate ligands 2,2′-(1,1′-(pyridine-2,6-diylbis(methylene))bis(1H-1,2,3-triazole-4,1-diyl))bis(methylene)bis((pyridin-2-ylmethyl)azanediyl)bis(methylene)diphenol (H2LI) and N,N′-((1,1′-(pyridine-2,6-diylbis(methylene))bis(1H-1,2,3-triazole-4,1-diyl))bis(methylene))bis(1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine) (LII) containing triazolyl, phenolate and pyridinyl groups were prepared by click reaction between diazide and terminal alkynes in the presence of catalyst CuI. Both ligands were reacted with Cu2+and Fe3+salts to give three dinuclear complexes [LICu2](BPh4)2·2DMF (1), [LII(DMF)2Cu2](ClO4)4·H2O (2) and [LII(FeCl2)2](PF6)2(3). All complexes were characterized by IR, UV-Vis spectra and element analysis. X-ray analysis revealed that the Cu2+centers in complexes 1 and 2 adopted the distorted trigonal bipyramidal geometry, and the Fe3+center in complex 3 chose an octahedral geometry. In addition, the electrochemistry of complexes 1-3 was investigated.
- You, Xiuli,Wei, Zhenhong
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supporting information
p. 332 - 339
(2015/02/19)
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- An efficient oxygen evolving catalyst based on a μ-O diiron coordination complex
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A family of oxygen evolving catalysts was investigated, which was based on the most desired first-row transition metal iron. Among them, the highest turnover number of 2380 was obtained in acetate buffer at pH 4.5 with [(TPA)2Fe2(μ-O)(μ-OAc)]3+. This journal is
- Liu, Yongdong,Xiang, Rui,Du, Xiaoqiang,Ding, Yong,Ma, Baochun
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supporting information
p. 12779 - 12782
(2015/05/20)
-
- Low-Molecular-Weight CXCR4 Ligands with Variable Spacers
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Low-molecular-weight CXCR4 ligands based on known lead compounds including the 14-mer peptide T140, the cyclic pentapeptide FC131, peptide mimetics, and dipicolylamine-containing compounds were designed and synthesized. Three types of aromatic spacers, 1,4-phenylenedimethanamine, naphthalene-2,6-diyldimethanamine, and [1,1′-biphenyl]-4,4′-diyldimethanamine, were used to build four pharmacophore groups. As pharmacophore groups, 2-pyridylmethyl and 1-naphthylmethyl are present in all of the compounds, and several aromatic groups and a cationic group from 1-propylguanidine and 1,1,3,3-tetramethyl-2-propylguanidine were also used. Several compounds showed significant CXCR4 binding affinity, and zinc(II) complexation of bis(pyridin-2-ylmethyl)amine moieties resulted in a remarkable increase in CXCR4 binding affinity.
- Narumi, Tetsuo,Aikawa, Haruo,Tanaka, Tomohiro,Hashimoto, Chie,Ohashi, Nami,Nomura, Wataru,Kobayakawa, Takuya,Takano, Hikaru,Hirota, Yuki,Murakami, Tsutomu,Yamamoto, Naoki,Tamamura, Hirokazu
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p. 118 - 124
(2013/02/26)
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- Iron(II) α-aminopyridine complexes and their catalytic activity in oxidation reactions: A comparative study of activity and ligand decomposition
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New well-defined FeII complexes bearing bi- and tridentate α-aminopyridine ligands were synthesized, and their catalytic activity in the oxidation of hydrocarbons and alcohols utilizing peroxide oxidants was investigated. The tridendate bis-(picolyl)amine ligand 6 and its benzylated analogue 7 were converted into complexes [FeII(6)2] OTf2 (96 %, X-ray; OTf= CF3SO3 -) and [FeII(7)2]OTf2 (90 %). The bidentate aminopyridine ligand 8 was converted into [FeII(8) 2(OTf)2] (93 %, X-ray). The new complexes are catalytically active in the oxidation of secondary alcohols and benzylic methylene groups to the corresponding ketones, of toluene to benzaldehyde, and of cyclohexene to cyclohexene oxide (3 mol% catalyst, tBuOOH (4 equiv), RT, 2-6 h, 28 to 85% yield of isolated product). The catalytic oxidation of cyclohexane with ROOH (R=H, tBu) to an alcohol/ketone mixture with low ratio revealed that these oxidations follow largely a radical mechanism, except when [Fe II(6)2]OTf2 was employed and H 2O2 was added slowly. Together with known bi- and tetradendate iron complexes, a comparative study showed slight reactivity differences for the newly prepared complexes, with the highest observed for [FeII(6)2]OTf2 and [FeII(7) 2]OTf2. The reaction of the new complexes with peroxides was followed over time by UV/Visible spectroscopy; this revealed a fast reaction between the two reactants within minutes. Ligand-decomposition pathways were investigated, and revealed that the NCH2 units of the complexes are rapidly oxidized to the corresponding amides NC=O. The iron complex [Fe II(6)2]OTf2 showed no decrease in catalytic activity and a moderate decrease in selectivity when first subjected to oxidative conditions similar to those employed in catalysis. Thus, oxidative ligand deterioration had a marginal effect on the catalytic activity of the iron complex [FeII(6)2]OTf2.
- Lenze, Matthew,Martin, Erin T.,Rath, Nigam P.,Bauer, Eike B.
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p. 101 - 116
(2013/05/22)
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- C-C bond formation and related reactions at the CNC backbone in (smif)FeX (smif = 1,3-di-(2-pyridyl)-2-azaallyl): Dimerizations, 3 + 2 cyclization, and nucleophilic attack; Transfer hydrogenations and alkyne trimerization (X = N(TMS)2, dpma = (Di-(2-pyridyl-methyl)-amide))
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Molecular orbital analysis depicts the CNCnb backbone of the smif (1,3-di-(2-pyridyl)-2-azaallyl) ligand as having singlet diradical and/or ionic character where electrophilic or nucleophilic attack is plausible. Reversible dimerization of (smif)Fe{N(SiMe3)2} (1) to [{(Me3Si)2N}Fe]2(μ-κ3, κ3-N,py2-smif,smif) (2) may be construed as diradical coupling. A proton transfer within the backbone-methylated, and o-pyridine-methylated smif of putative (bMe2 oMe2smif)FeN(SiMe3)2 (8) provides a route to [{(Me3Si)2N}Fe]2(μ- κ4,κ4-N,py2,C-(bMe, bCH2,oMe2(smif)H))2 (9). A 3 + 2 cyclization of ditolyl-acetylene occurs with 1, leading to the dimer [{2,5-di(pyridin-2-yl)-3,4-di-(p-tolyl-2,5-dihydropyrrol-1-ide)}FeN(SiMe 3)2]2 (11), and the collateral discovery of alkyne cyclotrimerization led to a brief study that identified Fe(N(SiMe 3)2(THF) as an effective catalyst. Nucleophilic attack by (smif)2Fe (13) on tBuNCO and (2,6-iPr 2C6H3)NCO afforded (RNHCO-smif)2Fe (14a, R = tBu; 14b, 2,6-iPrC6H3). Calculations suggested that (dpma)2Fe (15) would favorably lose dihydrogen to afford (smif)2Fe (13). H2-transfer to alkynes, olefins, imines, PhNNPh, and ketones was explored, but only stoichiometric reactions were affected. Some physical properties of the compounds were examined, and X-ray structural studies on several dinuclear species were conducted.
- Frazier, Brenda A.,Williams, Valerie A.,Wolczanski, Peter T.,Bart, Suzanne C.,Meyer, Karsten,Cundari, Thomas R.,Lobkovsky, Emil B.
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supporting information
p. 3295 - 3312
(2013/05/08)
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- Heterogeneously catalyzed self-condensation of primary amines to secondary amines by supported copper catalysts
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Self-condensation of primary amines to symmetrically substituted secondary amines could efficiently be promoted by an inexpensive supported copper catalyst, Cu/Al2O3, easily prepared by the reduction of the hydroxide precursor, Cu(OH)x/Al2O3. Various kinds of structurally diverse primary amines including benzylamine, picolylamine, and aliphatic amine derivatives could selectively be converted into the corresponding secondary amines in moderate to excellent yields without any cocatalysts such as bases and stabilizing ligands in 1 atm of Ar or H 2. The reactions in H2 showed higher selectivities to desired secondary amines than those in Ar. The roles of H2 are the promotion of hydrogenation of N-alkylimines and the stabilization of active Cu(0) species. In addition, in the presence of Cu/Al2O3, unsymmetrically substituted secondary amines could efficiently be synthesized by N-alkylation of primary amines with alcohols and reductive amination of aldehydes. The observed catalysis was truly heterogeneous, and the retrieved Cu/Al2O3 catalyst could be reused for self-condensation without a significant loss of its catalytic performance. The reaction mechanism involving dehydrogenation of primary amines and condensation to N-alkylimines followed by hydrogenation, the so-called "borrowing hydrogen pathway", has been proposed. The Royal Society of Chemistry 2013.
- Kim, Insu,Itagaki, Shintaro,Jin, Xiongjie,Yamaguchi, Kazuya,Mizuno, Noritaka
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p. 2397 - 2403
(2013/09/02)
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- Trifunctional metal ion-catalyzed solvolysis: Cu(II)-promoted methanolysis of N,N-bis(2-picolyl) benzamides involves unusual lewis acid activation of substrate, delivery of coordinated nucleophile, powerful assistance of the leaving group departure
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The methanolyses of Cu(II) complexes of a series of N,N-bis(2-picolyl) benzamides (4a-g) bearing substituents X on the aromatic ring were studied under s s pHcontrolled conditions at 25 °C. The active form of the complexes at neutral s s pH has a stoichiometry of 4:Cu(II): (-OCH 3)(HOCH3) and decomposes unimolecularly with a rate constant kx. A Hammett plot of log(kx) vs σx values has a ?x of 0.80 ± 0.05. Solvent deuterium kinetic isotope effects of 1.12 and 1.20 were determined for decomposition of the 4-nitro and 4-methoxy derivatives, 4b:Cu(II):( -OCH3)(HOCH3) and 4g:Cu(II):( -OCH3)(HOCH3), in the plateau region of the s s pH/ log(kx) profiles in both CH 3OH and CH3OD. Activation parameters for decomposition of these complexes are ΔH≠ = 19.1 and 21.3 kcal mol -1 respectively and ΔS≠ = -5.1 and -2 cal K-1 mol-1. Density functional theory (DFT) calculations for the reactions of the Cu(II):(-OCH3)(HOCH3) complexes of 4a,b and g (4a, X = 3,5-dinitro) were conducted to probe the relative transition state energies and geometries of the different states. The experimental and computational data support a mechanism where the metal ion is coordinated to the N,N-bis(2-picolyl) amide unit and positioned so that it permits delivery of a coordinated Cu(II):(-OCH3) nucleophile to the C=O in the rate-limiting transition state (TS) of the reaction. This proceeds to a tetrahedral intermediate INT, occupying a shallow minimum on the free energy surface with the Cu(II) coordinated to both the methoxide and the amidic N. Breakdown of INT is a virtually barrierless process, involving a Cu(II)-assisted departure of the bis(2-picolyl)amide anion. The analysis of the data points to a trifunctional role for the metal ion in the solvolysis mechanism where it activates intramolecular nucleophilic attack on the C=O group by coordination to an amidic N in the first step of the reaction and subsequently assists leaving group departure in the second step. The catalysis is very large; compared with the second order rate constant for methoxide attack on 4b, the computed reaction of CH3O- and 4b:Cu(II):(HOCH3)2 is accelerated by roughly 2.0 × 1016 times.
- Raycroft, Mark A.R.,Maxwell, Christopher I.,Oldham, Robyn A. A.,Andrea, Areen Saffouri,Neverov, Alexei A.,Brown, R. Stan
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p. 10325 - 10333
(2013/01/15)
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- A fluorescence turn-on H2O2 probe exhibits lysosome-localized fluorescence signals
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A new fluorescence turn-on probe that responds exclusively to H 2O2 exhibits subcellular localized fluorescence staining of lysosomes.
- Song, Dayoung,Lim, Jung Mi,Cho, Somin,Park, Su-Jin,Cho, Jaeheung,Kang, Dongmin,Rhee, Sue Goo,You, Youngmin,Nam, Wonwoo
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experimental part
p. 5449 - 5451
(2012/07/28)
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- A new disubstituted polyacetylene bearing pyridine moieties: Convenient synthesis and sensitive chemosensor toward sulfide anion with high selectivity
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To develop sensitive and selective S2- chemosensors, a new disubstituted polyacetylene (P2) bearing pyridine moieties in the side chains was prepared conveniently through a postfunctional method, the strong green fluorescence of which could be completely quenched by Cu2+ ions at the concentration as low as 2.0 × 10-6 mol/L in diluted solutions. Based on the displacement strategy, by utilizing the much higher stability constant of the complex of S2- and Cu2+, the quenched fluorescence of the solution of P2 by Cu2+ ions could recover upon the addition of trace S2- anions, with the detection limit down to 5.0 × 10-7 mol/L. Moreover, no interference were observed from other anions, including SO32-, HSO 3-, SO42-, ClO4 -, I-, Br-, Cl-, F-, IO3-, HPO42-, PO4 3-, C2O42-, S2O 32-, CO32-, AcO-, CN -, and P2O74-, making P2 a novel, sensitive, and selective sulfide probe.
- Zhang, Liang,Lou, Xiaoding,Yu, Yun,Qin, Jingui,Li, Zhen
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experimental part
p. 5186 - 5193
(2012/04/17)
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- A second-generation photocage for Zn2+ inspired by TPEN: Characterization and insight into the uncaging quantum yields of ZinCleav chelators
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Photocages have been used to elucidate the biological functions of various small molecules and Ca2+; however, there are very few photocages available for other metal ions. ZinCleav-2 (1-(4,5-dimethoxy-2-nitrophenyl)-N,N, N′,N′-tetrakis-pyridin-2-ylmethyl-ethane-1,2-diamine) is a second-generation photocage for Zn2+ that releases the metal ion after a light-induced bifurcation of the chelating ligand. The structure of ZinCleav-2 was inspired by TPEN (N,N,N′,N′-tetrakis(2-pyridylmethyl) ethylenediamine), which is routinely used to sequester metal ions in cells owing to its high binding affinity. Inclusion of a 2-nitrobenzyl chromophore leads to the formation of two more weakly binding di-(2-picolyl)amine (DPA) fragments upon photolysis of the TPEN backbone. The desired ligand was prepared using a modified procedure used to access ZinCleav-1 (1-(4,5-dimethoxy-2-nitrophenyl)-N, N′-dimethyl-N,N′-bis-pyridin-2-ylmethyl-ethane-1,2-diamine). ZinCleav-2 has a conditional dissociation constant (Kd) of ~0.9 fM as measured by competitive titration with a quinoline-based fluorescent sensor for Zn2+. The Kd of the Zn2+ complex of the DPA photoproducts is ~158 nM; therefore, the ΔKd for ZinCleav-2 photocage is ~108. A large ΔKd is required to significantly perturb free metal ion concentrations in biological assays. The quantum yield of photolysis of apo ZinCleav-2 and the [Zn(ZinCleav-2)]2+ complex are 4.7 and 2.3 %, respectively, as determined by HPLC analysis. Proof of concept Zn2+ release upon photolysis of [Zn(ZinCleav-2)]2+ was demonstrated using the fluorescent sensor Zinpyr-1, and the speciation of Zn2+ complexes was simulated using computational methods. The influence of benzylic substituents on the quantum yield of uncaging is also analyzed with the aim of tuning the photochemical properties caged complexes for in vivo experiments.
- Bandara, H. M. Dhammika,Walsh, Timothy P.,Burdette, Shawn C.
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p. 3932 - 3941
(2011/05/11)
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- Mononuclear iron(III) complexes supported by tripodal N3O ligands: Synthesis, structure and reactivity towards DNA cleavage
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A new synthetic route to the known tripodal tetradentate N3O ligand L1 (HL1 = [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine) is reported. The related compounds HLn (n = 2, 3) were prepared by a similar procedure. Treatment of HLn (n = 1-3) with FeCl3·6H2O in hot methanol led to the mononuclear iron(III) complexes [Fe(Ln)Cl2] (1: n = 1, 2: n = 2, 3: n = 3). The solid-state structures of complexes 1 and 2 were determined by X-ray crystallography. [Fe(L1)Cl2] (1) showed effective nuclease activity in the presence of hydrogen peroxide, converting supercoiled plasmid DNA to its linear form.
- Wong, Yee-Lok,Mak, Chun-Yin,Kwan, Hoi Shan,Lee, Hung Kay
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experimental part
p. 1246 - 1253
(2010/07/05)
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- Novel asymmetrically functionalized bis-dipicolylamine metal complexes: Peripheral decoration of a potent anion recognition scaffold
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We report the design and synthesis of a novel class of asymmetrically functionalized, ditopic bis-dipicolylamine (BDPA) ligands. A key feature of this research involved the controlled, sequential functional group decoration of a potent molecular recognition scaffold. Calorimetric screening identified a BDPA analogue as a highly potent (Ka~ 106 M-1) and selective sensor for inorganic phosphate.
- Drewry, Joel A.,Fletcher, Steven,Hassan, Haider,Gunning, Patrick T.
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supporting information; experimental part
p. 5074 - 5077
(2010/04/04)
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