共查询到20条相似文献,搜索用时 15 毫秒
1.
Ronald R. Ruminski Kristin D.K. Zimmer Kelliann A. Rita Mackenzie A. Knobbe Carrie Dean 《Inorganica chimica acta》2009,362(6):1772-165
New Os(II) complexes including [Os(dpop′)2](PF6)2 (dpop′= dipyrido(2,3-a;3′,2′-j)phenazine) and a series of mixed ligand [Os(dpop′)(N-N)Cl]PF6 (N-N = 2,2′-bipyridine(bpy); 2,2′-bipyrimidine(bpm) and 2,3-bis(2-pyridyl)pyrazine(dpp)) were synthesized. The Os dπ → dpop′ π∗ MLCT transitions for [Os(dpop′)2]2+ are observed at lower energy than for Os dπ → tpy π∗ (tpy = 2,2′:6′,2″-terpyridine) and Os dπ → tppz π∗ (tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine) (The ligand abbreviations tpd, tpp and tpypz have also appeared in the literature for 2,3,5,6- tetrakis(2-pyridyl)pyrazine in addition to tppz.) MLCT transitions in the comparative [Os(tpy)2]2+ and [Os(tppz)2]2+ complexes. The Os dπ → dpop′ π∗ MLCT transitions are observed at lower energy in mixed bidentate ligand N-N systems compared with [Os(dpop′)2]2+. Cyclic voltammetry shows more positive osmium oxidation, and less negative ligand reduction potentials for [Os(dpop′)2]2+ as compared to [Os(tpy)2]2+ and [Os(tppz)2]2+ complexes. The osmium oxidation potentials in mixed ligand [Os(dpop′)(N-N)Cl]+ complexes are at less positive potential than for the [Os(dpop′)2]2+ ion. NMR results show different chemical shifts for ring protons either trans or cis to dpop′ in mixed ligand systems, and also show two geometrical isomers for the [Os(dpop′)(dpp)Cl]+ complex. The [Os(dpop′)(dpp)Cl]+ geometric isomer with the pyrazine ring of dpp trans to dpop′ is found more predominate by 1.0/0.7 over the isomer with the pyrazine ring of dpp cis to dpop′ and that inter-conversion of geometric isomers does not occur in room temperature solution on the NMR timescale. 相似文献
2.
Mauricio Isaacs 《Inorganica chimica acta》2006,359(12):3847-3854
A series of new heteroleptic, tris(polypyridyl)chromium(III) complexes, [Cr(phen)2L]3+ (L = substituted phenanthrolines or bipyridines), has been prepared and characterized, and their photophyical properties in a number of solvents have been investigated. X-ray crystallography measurements confirmed that the cationic (3+) units contain only one ligand L plus two phenanthroline ligands. Electrochemical and photophysical data showed that both ground state potentials and lifetime decays are sensitive to ligand structure and the nature of the solvent with the exception of compounds containing L = 5-amino-1,10-phenanthroline (aphen) and 2,2′-bipyrimidine (bpm). Addition of electron-donating groups in the ligand structure shifts redox potentials to more negative values than those observed for the parent compound, [Cr(phen)3]3+. Emission decays show a complex dependence with the solvent. The longest lifetime was observed for [Cr(phen)2(dip)]3+ (dip = 4,7-diphenylphenanthroline) in air-free aqueous solutions, τ = 273 μs. Solvent effects are explained in terms of the affinity of hydrophobic complexes for non-polar solvent molecules and the solvent microstructure surrounding chromium units. 相似文献
3.
The reaction of ruthenium carbonyl polymer ([Ru(CO)2Cl2]n) with azopyridyl compounds (2,2′-azobispyridine; apy or 2-phenylazopyridine; pap) generated new complexes, [Ru(azo)(CO)2Cl2] (azo = apy, pap). [Ru(apy)(CO)2Cl2] underwent photodecarbonylation to give a chloro-bridged dimer complex, whereas the corresponding pap complex ([Ru(pap)(CO)2Cl2]) was not converted to a dimer. The reactions of the chloro-bridged dimer containing the bpy ligand (bpy = 2,2′-bipyridine) with either apy or pap resulted in the formation of mixed polypyridyl complexes, [Ru(azo)(bpy)(CO)Cl]+. The novel complexes containing azo ligands were characterized by various spectroscopic measurements including the determination of X-ray crystallographic structures. Both [Ru(azo)(CO)2Cl2] complexes have two CO groups in a cis position to each other and two chlorides in a trans position. The azo groups are situated cis to the CO ligand in [Ru(azo)(bpy)(CO)Cl]+. All complexes have azo N-N bond lengths of 1.26-1.29 Å. The complexes exhibited azo-based two-electron reduction processes in electrochemical measurements. The effects of introducing azopyridyl ligands to the ruthenium carbonyl complexes were examined by ligand-based redox potentials, stretching frequencies and force constants of CO groups and bond parameters around Ru-CO moieties. 相似文献
4.
The binding modes of the [Ru(II)(1,10-phenanthroline)(L1L2) dipyrido[3,2-a:2′,3′-c]phenazine]2+ {[Ru(phen)(py) Cl dppz]+ (L1 = Cl, L2 = pyridine) and ([Ru(phen)(py)2dppz]2+ (L1 = L2 = pyridine)} to native DNA is compared to that of the [Ru(II)(1,10-phenanthroline)2dipyrido[3,2-a:2′,3′-c]phenazine]2+ complex ([Ru(phen)2dppz]2+) by various spectroscopic and hydrodynamic methods including electric absorption, linear dichroism (LD), fluorescence spectroscopy, and viscometric titration. All measured properties, including red-shift and hypochromism in the dppz absorption band, nearly perpendicular molecular plane of the dppz ligand with respect to the local DNA helix axis, prohibition of the ethidium binding, the light switch effect and binding stoichiometry, increase in the viscosity upon binding to DNA, increase in the melting temperature are in agreement with classical intercalation of dppz ligand of the [Ru(phen)2dppz]2+ complex, in which both phenanthroline ligand anchored to the DNA phosphate groups by electrostatic interaction. [Ru(phen)(py)2 dppz]2+ and [Ru(phen)(py) Cl dppz]+ complexes had one of the phenanthroline ligand replaced by either two pyridine ligands or one pyridine plus a chlorine ion. They exhibited similar protection from water molecules, interaction with DNA bases, and occupying site that is common with ethidium. The dppz ligand of these two Ru(II) complex were greatly tilted relative to the DNA helix axis, suggesting that the dppz ligand resides inside the DNA and is not perpendicular relative to the DNA helix axis. These observation suggest that anchoring the [Ru(phen)2dppz]2+complex by both phenanthroline is essential for the dppz ligand to be classically intercalated between DNA base-pairs. 相似文献
5.
Mathias Düggeli 《Inorganica chimica acta》2005,358(1):41-49
A series of ligands, where two pinene-bipyridine moieties are either connected directly, or through a p-xylene bridge are investigated with respect to their complexation behaviour in solution. The bridged [5,6]-CHIRAGEN[p-xyl] ligands, which are substituted in 5′ or 6′ positions show self-assembly reactions, which lead to similar supramolecular species as the unsubstituted bis-pinene-bipyridines ligands studied before. The directly connected [5,6]-CHIRAGEN[0] derivatives, which are substituted at positions 5′ or 6′, form mononuclear complexes with helical chirality at the metal centre. 相似文献
6.
Marzia Bellei Shu-pao Wu James A. Cowan Marco Sola 《Journal of inorganic biochemistry》2010,104(6):691-696
The reaction thermodynamics for the one-electron reduction of the [2Fe-2S] cluster of both human ferredoxin and various surface point mutants, in which each of the negatively charged residues Asp72, Glu73, Asp76, and Asp79 were converted to Ala, have been determined by variable temperature spectroelectrochemical measurements. The above are conserved residues that have been implicated in interactions between the vertebrate-type ferredoxins and their redox partners. In all cases, and similar to other 2Fe-ferredoxins, the reduction potentials are negative as a result of both an enthalpic and entropic stabilization of the oxidized state. Although all Hs Fd mutants, with the exception of Asp72Ala, show slightly higher E°′ values than that of wild type Hs Fd, according to expectations for a purely electrostatic model, they exhibit changes in the ?H°′rc values that are electrostatically counter-intuitive. The observation of enthalpy-entropy compensation within the protein series indicates that the mutation-induced changes in ?H°′rc and ?S°′rc are dominated by reduction-induced solvent reorganization effects. Protein-based entropic effects are likely to be responsible for the low E°′ value of D72A. 相似文献
7.
Reaction of phenol with an alkylthiolate-ligated double cubane complex effects phenolate substitution at the terminal positions; the product can be isolated as its benzyltriethylammonium salt. The phenolate cluster possesses unaltered magnetic properties and blue shifted optical spectra, and undergoes ligand exchange reactions with electrophiles as expected for terminal phenolate substitution. Increased isotropic proton NMR shifts and large negative shifts in corresponding first and second reduction potentials are consistent with increased donation of electron density to the [MoFe3S4]3+ cores for phenolate versus thiophenolate terminal ligands to iron. Similar behavior has been observed for Fe4S4, Fe2S2 and MoS2Fe systems. 相似文献
8.
Manas Sutradhar Tannistha Roy Barman Michael G.B. Drew 《Inorganica chimica acta》2010,363(13):3376-117
The present work reports the chemistry of a few oxidovanadium(IV) and (V) complexes of the ONS chelating ligand S-benzyl-β-N-(2-hydroxyphenylethylidine) dithiocarbazate (H2L). Major objective of this work is to arrive at some general conclusions about the influence of binding environment generated by the replacement of an O-donor center by a S-donor point in a ligand (of a similar arrangement of the other O- and N-donor points) on the redox behavior and on the structural features of comparable [VO(OEt)(ONS)] and [VO(OEt)(ONO)] complexes. Synthesis, characterization by various physicochemical techniques (UV-Vis, IR, EPR and elemental analysis), exploration of electrochemical activity of the oxidovanadium(V) complex [VVO(OEt)L] (1), the mixed ligand complex [VVO(N-O)L] (3) (where N-O is the mono anion of 8-hydroxyquinoline) and a binuclear complex [VVO(OEt)L]2(μ-4,4′-bipy) (2) are reported. Similar studies on of mixed ligand oxidovanadium(IV) complexes of the formula [VVO(N-N)L] (4,5) (where N-N = 2,2′-bipy and o-phen) are also presented here. The [VVO(OEt)L] complex is pentacoordinated and distorted square pyramidal, while the [VIV(N-N)L] complexes are hexacoordinated and octahedral. Structural features of the complex 1 were compared with the corresponding aspects of the previously reported analogous complex [VVO(OEt)(ONO)] (1′). 相似文献
9.
10.
Ruthenium phosphine complexes with a CO ligand [Ru(tpy)(PR3)(CO)Cl]+ (tpy = 2,2′:6′,2″-terpyridine, R = Ph or p-tolyl), were prepared by introduction of CO gas to the corresponding dichloro complexes at room temperature. New carbonyl complexes were characterized by various methods including structural analyses. They were shown to release CO following the addition of several N-donors to form the corresponding substituted complexes. The kinetic data and structural results observed in this study indicated that the CO release reactions proceeded in an interchange mechanism. The molecular structures of [Ru(tpy)(PPh3)(CO)Cl]PF6, [Ru(tpy)(P(p-tolyl)3)(CO)Cl]PF6 and [Ru(tpy)(PPh3)(CH3CN)Cl]PF6 were determined by X-ray crystallography. 相似文献
11.
12.
Elena Ioachim 《Inorganica chimica acta》2006,359(9):2599-2607
A series of complexes [(N-N)Re(CO)3X]n (N-N = 6,6′-diaryl-4,4′-bipyrimidine, axial ligand X = Cl, MeCN, 4-phenyl-pyridine, or t-Bu-pyridine) have been synthesized and characterized. The substituent aryl on the bipyrimidine, as well as the axial ligand X, has important effects on the properties of these complexes. The co-planarity of the 4,4′-bipyrimidine core and its substituents contributes to the extent of π-electron delocalization and, hence, to the redox and spectroscopic properties of the complexes. The complexes exhibit Re-to-bpm metal-to-ligand charge transfer absorptions in the range of 379-464 nm, which are red-shifted with the increase in the delocalization in the substituted bpm ligand and the increase in the donor character of the axial ligand. The electrochemical data support metal-based oxidations (from +1.07 to +1.40 V) and ligand-based reductions (from −0.62 to −0.75 V) and correlate well with those obtained by UV-Vis spectroscopy. The X-ray crystal structures of two of the complexes have also been investigated. 相似文献
13.
Stella Vitt Kesen Ma Eberhard Warkentin Johanna Moll Antonio J. Pierik Seigo Shima Ulrich Ermler 《Journal of molecular biology》2014
The reversible redox reaction between coenzyme F420 and H2 to F420H2 is catalyzed by an F420-reducing [NiFe]-hydrogenase (FrhABG), which is an enzyme of the energy metabolism of methanogenic archaea. FrhABG is a group 3 [NiFe]-hydrogenase with a dodecameric quaternary structure of 1.25 MDa as recently revealed by high-resolution cryo-electron microscopy. We report on the crystal structure of FrhABG from Methanothermobacter marburgensis at 1.7 Å resolution and compare it with the structures of group 1 [NiFe]-hydrogenases, the only group structurally characterized yet. FrhA is similar to the large subunit of group 1 [NiFe]-hydrogenases regarding its core structure and the embedded [NiFe]-center but is different because of the truncation of ca 160 residues that results in similar but modified H2 and proton transport pathways and in suitable interfaces for oligomerization. The small subunit FrhG is composed of an N-terminal domain related to group 1 enzymes and a new C-terminal ferredoxin-like domain carrying the distal and medial [4Fe-4S] clusters. FrhB adopts a novel fold, binds one [4Fe-4S] cluster as well as one FAD in a U-shaped conformation and provides the F420-binding site at the Si-face of the isoalloxazine ring. Similar electrochemical potentials of both catalytic reactions and the electron-transferring [4Fe-4S] clusters, determined to be E°′ ≈ − 400 mV, are in full agreement with the equalized forward and backward rates of the FrhABG reaction. The protein might contribute to balanced redox potentials by the aspartate coordination of the proximal [4Fe-4S] cluster, the new ferredoxin module and a rather negatively charged FAD surrounding. 相似文献
14.
Akhilesh Kumar Singh 《Inorganica chimica acta》2007,360(10):3456-3461
A new distorted square planar (two CuN2 planes making an angle of ∼43°) copper(II) complex [Cu(L4)] · 0.5EtOH · 0.5MeOH (1) of a deprotonated tetradentate pyridine amide ligand [H2L4 = N,N′-bis(2-pyridinecarboxamide)-2,2′-biphenyl] has been synthesized and structurally characterized. Absorption and EPR spectroscopic properties have also been studied. The E1/2 values (CuII/CuI redox process) of the title complex along with a selected group of structurally characterized CuN4 pyridine amide complexes with systematically varied structural, electronic/steric, and chelate-ring size effects, imposed by the coordinating ligands, have been determined and the observed trend has been rationalized. 相似文献
15.
Kaidong Zhang 《Carbohydrate research》2010,345(9):1114-1122
The synthesis of tetrapeptide-based β-turn mimetics containing spirocyclic glucose-templated 3-hydroxyproline hybrids Glc3′(S)-5′(R)(CH2OH)HypH and Glc3′(S)-5′(S)(CH2OH)HypH as proline mimetics is presented. NMR-based conformational analysis of Ac-Leu-d-Phe-[Glc3′(S)-5′(R)(CH2OH)HypH]-Val-NMe2 and Ac-Leu-d-Phe-[Glc3′(S)-5′(S)(CH2OH)HypH]-Val-NMe2 demonstrates the presence of β-turn conformations. Different turn structures were observed by changing the stereochemistry at 5′-position of Glc3′(S)-5′(R)(CH2OH)HypH. The major prolyl amide cis isomer of glucose-protected tetrapeptide Ac-Leu-d-Phe-[Glc(MOM)43′(S)-5′(R)(CH2OMOM)HypH]-Val-NMe211 and glucose unprotected Ac-Leu-d-Phe-[Glc3′(S)-5′(R)(CH2OH)HypH]-Val-NMe213 forms a type VI β-turn conformation. In contrast, the major prolyl amide trans rotamer of tetrapeptide Ac-Leu-d-Phe-[Glc(MOM)43′(S)-5′(S)(CH2OMOM)HypH]-Val-NMe212 conserves a similar β-turn conformation as the Gramicidin S-based peptide fragment Ac-Leu-d-Phe-Pro-Val-NMe216. 相似文献
16.
Novel methyl 4,6-O-benzylidenespiro[2-deoxy-α-d-arabino-hexopyranoside-2,2′-imidazolidine] and its homologue methyl 4,6-O-benzylidene-3′,4′,5′,6′-tetrahydro-1′H-spiro[2-deoxy-α-d-arabino-hexopyranoside-2,2′-pyrimidine] have been synthesized in good yields by reaction of methyl 4,6-O-benzylidene-α-d-arabino-hexopyranosid-2-ulose with 1,2-diaminoethane and 1,3-diaminopropane. The results are completely different from the reaction with arylamines or alkylamines. One-pot synthesis of novel (E)-methyl 4-[hydroxy (methoxy)methylene]-5-oxo-1-alkyl-(4,6-O-benzylidene-2-deoxy-α-d-glucopyranosido)[3,2-b]pyrrolidines has been achieved by the reaction of alkylamines with the butenolide-containing sugar, derived from the aldol condensation of methyl 4,6-O-benzylidene-α-d-arabino-hexopyranosid-2-ulose with diethyl malonate. These sugar-γ-butyrolactam derivatives are potential GABA receptor ligands. 相似文献
17.
Ecto-5′-nucleotidase (eN) is a membrane-bound enzyme that hydrolyzes extracellular nucleoside-5′-monophosphates yielding the respective nucleoside and phosphate. Increased levels of eN expression have been observed in many cancer cells. By increasing extracellular adenosine concentrations, they contribute to their proliferative, angiogenic, metastatic, and immunosuppressive effects. Therefore, eN is of considerable interest as a novel drug target for the treatment of cancer as well as of inflammatory diseases. In this study, we developed, optimized, and applied a highly sensitive radiometric assay using [3H]adenosine-5′-monophosphate (AMP) as a substrate. The reaction product [3H]adenosine was separated from [3H]AMP by precipitation of the latter with lanthanum chloride and subsequent filtration through glass fiber filters. Conditions were optimized to reproducibly collect the [3H]adenosine-containing filtrate used for quantitative determination. Validation of the assay yielded a mean Z′ factor of 0.73, which demonstrates its suitability for high-throughput screening. The new assay shows a limit of detection that is at least 30-fold lower than those of common colorimetric methods (e.g., optimized malachite green assay and capillary electrophoresis-based assay procedures), and it is also superior to a recently developed luciferase-based assay. 相似文献
18.
Boke C. de Pater Kees Goubitz Peter H.M. Budzelaar Kees Vrieze 《Inorganica chimica acta》2005,358(2):431-436
The synthesis and the crystal and molecular structure of a unique Rh(III) complex, [RhIII(Br)(acetonyl)2(4′-(4-tbutylphenyl)-2,2′:6′,2″-terpyridine)] (1) are described. The yellow crystals separate from the acetone solution of the starting complex [Rh(Br)(COD)]2 and the ligand 4′-(4-tbutylphenyl)-2,2′:6′,2″-terpyridine after standing at room temperature for a prolonged period of time. The crystals are almost insoluble in all common organic solvents. The single-crystal X-ray structure determination shows that compound 1 is the first Rh-complex with a terdentate nitrogen ligand and two axially oriented, σ-bound acetonyl groups. DFT-calculations on a model complex without the substituent on the terpyridine ligand were carried out and agree very well with the X-ray results, confirming the constitution and geometry of the molecule. 相似文献
19.
García B Garcia-Tojal J Ruiz R Gil-García R Ibeas S Donnadieu B Leal JM 《Journal of inorganic biochemistry》2008,102(10):1892-1900
Experimental studies of the binding interactions of [CuL(NO3)] and [{CuL′(NO3)}2] (HL = pyridine-2-carbaldehyde thiosemicarbazone, and HL′ = pyridine-2-carbaldehyde 4N-methylthiosemicarbazone) with adenine, guanine, cytosine, thymine and their mononucleotides (dNMP), 2-deoxyadenosine-5′-monophosphate, (dAMP), 2′-deoxyguanosine-5′-monophosphate, (dGMP), 2′-deoxycytidine-5′-monophpsphate (dCMP), and thymidine-5′-monophosphate (dTMP) have been carried out in aqueous solution at pH 6.0, I = 0.1 M (NaClO4) and T = 25 °C. The complexation constants of these compounds, calculated by Hildebrand-Benesi plots for the dye binding, D, ([CuL] or [CuL′]) to the nucleobases or nucleotides (P), have shown two linear stretches in adenine, guanine, dAMP and dGMP. The data were analyzed in terms of formation of 1:1 DP and 1:2 DP2 complexes with increasing purine base or nucleotide content. For cytosine and dCMP only 1:1 complexes have been observed, whereas for thymine and dTMP such complex structures were not observed. The [CuL(Hcyt)](ClO4) cytosine derivative has been isolated and characterized. The crystal structure consists of perchlorate ions and [CuL(Hcyt)]+ monomers attached by hydrogen bond, chelate π−ring and anion-π interactions. The Cu2+ ions bind to the NNS chelating moiety of the thiosemicarbazone ligand and the cytosine N13 site (N3, most common notation) yielding a square-planar geometry. A pseudocoordination to the cytosine O12 site (=O2) can also be considered. 相似文献
20.
Condensation of salicylic aldehyde with 8-aminoquinoline afforded (ONN)-tridentate ligand 2-N-(quinoline-8-yl)iminomethylphenol (1), which was obtained as a crystalline solid for the first time and characterized by X-ray diffraction. Reaction between 1 and phenyltrichlorosilane in the presence of triethylamine results in the formation of the 1:1 chelate complex dichloro-[2-N-(quinoline-8-yl)imino-methylphenolato]-phenylsilane (2a) bearing a hexacoordinate silicon atom. The crystal structure of 2a∗CHCl3 reveals a rare coordination pattern: Although carrying two chlorine atoms, the hexacoordinate Si atom coordinates the tridentate ligand’s imine N atom in the trans position to the phenyl group. Silylation of 1 with hexamethyldisilazane and synthesis of dichloro-[2-N-(quinoline-8-yl)iminomethylphenolato]-methylsilane (2b) yielded few crystals of [2-N-(quinoline-8-yl)iminomethylphenolato]-salicylaldiminato-methylsiliconium chloride (2b′) as byproduct. 2b′ is the first structurally characterized main group element complex of salicylaldimine. This bidentate ligand exhibits an unusually strong N → Si coordination. 相似文献