共查询到20条相似文献,搜索用时 15 毫秒
1.
The rhodium(I) complexes TpmsRh(CO)2 (1) and TpmsRh(cod) (2) of the tripodal nitrogen ligand tris(pyrazolyl)methanesulfonate, Tpms−=[(pz)3CSO3]−, catalyze the hydroformylation of 1-hexene. Addition of phosphine has a negative effect on the activity. The hydroformylation activity reaches a maximum at about 60 °C. At temperatures above 80 °C hydrogenation becomes an important secondary reaction. When the catalysis is performed at 60 °C in acetone with 1 or 2 as catalyst precursor all of the rhodium is recovered in the form of the rhodium(III) bis(acyl) complex TpmsRh(CO)(COC6H13)2 (9). A similar behaviour is observed with rhodium(I) complexes bearing the tripodal oxygen ligand LOMe−=[(cyclopentadienyl)tris(dimethylphosphito-P) cobalt O,O′,O″]−. In this case all of the rhodium is transformed into LOMeRh(CO)(COC6H13)2 (10). These hitherto unknown bis(acyl) rhodium(III) complexes show the same catalytic activity as the rhodium(I) starting compounds. 相似文献
2.
Valerio BertolasiAndrea Marchi Lorenza MarvelliRoberto Rossi Claudio Bianchini Isaac de los RiosMaurizio Peruzzini 《Inorganica chimica acta》2002,327(1):140-146
The reaction of the rhenium(V) nitrido complex [Re(N)Cl2(PPh3)2] with the tripodal ligand N(CH2CH2PPh2)3 (NP3) in THF gave [Re(N)Cl2(η2-P,P-NP3)] (1) in which NP3 acts as a tridentate ligand using the nitrogen and two phosphorus donors for coordination. Refluxing 1 in a polar solvent such as ethanol produced [(η4-NP3)Re(N)Cl]Cl (2) in which NP3 acts as a tetradentate ligand. Treatment of complex [Re(O)Cl3(AsPh3)2] containing the [ReO]3+ core with NP3 in THF yielded [ReCl3{η3-N,P,P-(N{CH2CH2Ph2}2{CH2CH2P(O)Ph2})}] (3). Complexes 1 and 3 have been characterized by single-crystal X-ray analyses. 相似文献
3.
A series of monoporphyrinate neodymium (III) complexes stabilized by anionic tripodal ligand (cyclopentadienyl)tris(dimethylphosphito)cobaltate(I) were prepared and characterized by IR, ESI-HRMS, UV-Vis and X-ray diffraction studies. Structural analyses revealed that the Nd3+ ion was seven-coordinate, surrounded by four nitrogen atoms from the porphyrinate dianion and three oxygen atoms from the anionic tripodal ligand. Photoluminescence studies showed that the porphyrinate dianion acting as a sensitizer absorbed the light and transferred the energy to the Nd3+ center, which then allowed the metal ion to emit efficiently at 885 and 1071 nm. The luminescent intensity of the complexes increases when there are strong electronic donating groups on the porphyrin rings but decreases with increasing polarity of the solvents. 相似文献
4.
Iron(II) complexes of the type [Fe(L)(NCS)2] with the tripodal ligand apme (apme = N1-(2-aminoethyl)-N1-(2-pyridyl-methyl)-1,2-ethanediamine) as well as with its derivatives were prepared and structurally characterized. The bond distances thus obtained showed that all complexes investigated were high-spin at the respective temperature. Furthermore [Fe(Me4apme)(NCS)2] was analyzed using Mößbauer spectroscopy that showed that this complex remains in its high-spin state over the entire temperature range. 相似文献
5.
We report the synthesis of the Schiff base ligands, 4-[(4-bromo-phenylimino)-methyl]-benzene-1,2,3-triol (A1), 4-[(3,5-di-tert-butyl-4-hydroxy-phenylimino)-methyl]-benzene-1,2,3-triol (A2), 3-(p-tolylimino-methyl)-benzene-1,2-diol (A3), 3-[(4-bromo-phenylimino)-methyl]-benzene-1,2-diol (A4), and 4-[(3,5-di-tert-butyl-4-hydroxy-phenylimino)-methyl]-benzene-1,3-diol (A5), and their Cd(II) and Cu(II) metal complexes, stability constants and potentiometric studies. The structure of the ligands and their complexes was investigated using elemental analysis, FT-IR, UV-Vis, 1H and 13C NMR, mass spectra, magnetic susceptibility and conductance measurements. In the complexes, all the ligands behave as bidentate ligands, the oxygen in the ortho position and azomethine nitrogen atoms of the ligands coordinate to the metal ions. The keto-enol tautomeric forms of the Schiff base ligands A1-A5 have been investigated in polar and non-polar organic solvents. Antimicrobial activity of the ligands and metal complexes were tested using the disc diffusion method and the strains Bacillus megaterium and Candida tropicalis.Protonation constants of the triol and diol Schiff bases and stability constants of their Cu2+ and Cd2+ complexes were determined by potentiometric titration method in 50% DMSO-water media at 25.00 ± 0.02 °C under nitrogen atmosphere and ionic strength of 0.1 M sodium perchlorate. It has been observed that all the Schiff base ligands titrated here have two protonation constants. The variation of protonation constant of these compounds was interpreted on the basis of structural effects associated with the substituents. The divalent metal ions of Cu2+ and Cd2+ form stable 1:2 complexes with Schiff bases.The Schiff base complexes of cadmium inhibit the intense chemiluminescence reaction in dimethylsulfoxide (DMSO) solution between luminol and dioxygen in the presence of a strong base. This effect is significantly correlated with the stability constants KCdL of the complexes and the protonation constants KOH of the ligands; it also has a nonsignificant association with antibacterial activity. 相似文献
6.
We have synthesized the fully unsymmetrical [(6-bromo 2-pyridylmethyl) (6-fluoro 2-pyridylmethyl) (2-pyridylmethyl)] amine tripod FBrTPA. The synthesis involves preparation of the already known [(6-bromo 2-pyridylmethyl) (2-pyridylmethyl)] amine BrDPA, which is obtained either by classical condensation of α-substituted pyridine carboxaldehyde with aminomethyl pyridine, or by a pathway involving the protection/deprotection sequence of this primary amine. This second way is useful for syntheses of monosubstituted DPAs in the cases where α-substituted pyridine carboxaldehydes are unavailable. The crystal structure of the FeCl2 complex shows that the ligand binds in a κ4-N fashion, with however relatively long ligand-to-metal distances. The spectroscopic and electrochemical studies support decoordination of the bromopyridyl substituent in solution, with κ3-N coordination mode of the tripod within a complex displaying a trigonal bipyramidal geometry at the metal centre. This complex reacts easily with dry oxygen to yield an unsymmetrical μ-oxo diferric complex, the structure of which is also reported. 相似文献
7.
Hassen Jaafar 《Inorganica chimica acta》2011,366(1):147-200
We report in this communication the easy preparation of the α-iodo substituted tripods within the series of tris(2-pyridylmethyl)amine ligands, I1TPA, I2TPA and I3TPA, respectively. The characterization of the corresponding FeCl2 complexes in solution is described and structural analysis by X-ray diffraction for I1TPAFeCl2 and I2TPAFeCl2 is also reported. The steric effect of the iodo substituent is evidenced: (i) by elongation of the metal to iodo-pyridine distance within I1TPAFeCl2, which however remains a very stable compound; (ii) by decoordination of one substituted pyridine in I2TPAFeCl2 and I3TPAFeCl3. In I2TPAFeCl2 and in the solid state, this uncoordinated pyridine strongly interacts with the same fragment of the neighbouring molecule, providing an overall dinuclear arrangement for this complex. 相似文献
8.
The iron(III) complexes of the tridentate N3 ligands pyrazol-1-ylmethyl(pyrid-2-ylmethyl)amine (L1), 3,5-dimethylpyrazol-1-ylmethyl(pyrid-2-ylmethyl)amine (L2), 3-iso-propylpyrazol-1-ylmethyl(pyrid-2-ylmethyl)amine (L3) and (1-methyl-1H-imidazol-2-ylmethyl)pyrid-2-ylmethylamine (L4) have been isolated and studied as functional models for catechol dioxygenases. They have been characterized by elemental analysis and spectral and electrochemical methods. The X-ray crystal structure of the complex [Fe(L1)Cl3] 1 has been successfully determined. The complex possesses a distorted octahedral coordination geometry in which the tridentate ligand facially engages iron(III) and the Cl− ions occupy the remaining coordination sites. The Fe-Npz bond distance (2.126(5) Å) is shorter than the Fe-Npy bond (2.199(5) Å). The systematic variation in the ligand donor substituent significantly influences the Lewis acidity of the iron(III) center and hence the interaction of the present complexes with a series of catechols. The catecholate adducts [Fe(L)(DBC)Cl], where H2DBC = 3,5-di-tert-butylcatechol, have been generated in situ and their spectral and redox properties and dioxygenase activities have been studied in N,N-dimethylformamide solution. The adducts [Fe(L)(DBC)Cl] undergo cleavage of DBC2− in the presence of dioxygen to afford major amounts of intradiol and smaller amounts extradiol cleavage products. In dichloromethane solution the [Fe(L)(DBC)Cl] adducts afford higher amounts of extradiol products (64.1-22.2%; extradiol-to-intradiol product selectivity E/I, 2.6:1-4.5:1) than in DMF (2.5-6.6%; E/I, 0.1:1-0.4:1). The results are in line with the recent understanding of the function of intra- and extradiol-cleaving catechol dioxygenases. 相似文献
9.
《Bioorganic & medicinal chemistry letters》2020,30(22):127501
A series of N-benzyl-7-azaindolequinuclidinone (7-AIQD) analogs have been synthesized and evaluated for affinity toward CB1 and CB2 cannabinoid receptors and identified as a novel class of cannabinoid receptor ligands. Structure–activity relationship (SAR) studies indicate that 7-AIQD analogs are dual CB1/CB2 receptor ligands exhibiting high potency with somewhat greater selectivity towards CB2 receptors compared to the previously reported indolequinuclidinone (IQD) analogs. Initial binding assays showed that 7-AIQD analogs 8b, 8d, 8f, 8g and 9b (1 μM) produced more that 50% displacement of the CB1/CB2 non-selective agonist CP-55,940 (0.1 nM). Furthermore, Ki values determined from full competition binding curves showed that analogs 8a, 8b and 8g exhibit high affinity (110, 115 and 23.7 nM, respectively) and moderate selectivity (26.3, 6.1 and 9.2-fold, respectively) for CB2 relative to CB1 receptors. Functional studies examining modulation of G-protein activity demonstrated that 8a acts as a neutral antagonist at CB1 and CB2 receptors, while 8b exhibits inverse agonist activity at these receptors. Analogs 8f and 8g exhibit different intrinsic activities, depending on the receptor examined. Molecular docking and binding free energy calculations for the most active compounds (8a, 8b, 8f, and 8g) were performed to better understand the CB2 receptor-selective mechanism at the atomic level. Compound 8g exhibited the highest predicted binding affinity at both CB1 and CB2 receptors, and all four compounds were shown to have higher predicted binding affinities with the CB2 receptor compared to their corresponding binding affinities with the CB1 receptor. Further structural optimization of 7-AIQD analogs may lead to the identification of potential clinical agents. 相似文献
10.
Reaction of [MoO2(acac)2] with (S is a thioether, S′ a thiophenolate function) yielded the compound Li7(thf)17{MoO}8 · 10thf · hexane, where {MoO}8 represents one 1, three (2, linked, via the oxo group, to [Li(thf)3]+) and two (3a, linked by two [Li(thf)2]+).A mixed-valent variant of 3, (3b, with an additional[Li(thf)3]+ attached to S′), was also identified. The compounds model features pertinent to oxo-transferases containing the molybdopterin cofactor. 相似文献
11.
Effendy Claudio Pettinari Massimo Ricciutelli Allan H. White 《Inorganica chimica acta》2005,358(13):4009-4018
1:2, 1:1, 3:2 and 6:2 AgX:L adducts (where L is a tridentate phosphine, in detail: 1,1,1-tris(diphenylphosphinomethyl)ethane (Me-triphos) and bis(2-diphenylphosphinoethyl)phenylphosphine (Ph-triphos), X = O3SCF3, O3SCH3, BF4 or O2CCF3) have been synthesized and characterized by IR, NMR (1H, 31P and 19F) and ESI MS spectroscopy. The stoichiometry of the complexes is strongly dependent on the ligand to metal ratio employed and also on the nature of the counterion. 31P NMR (solution) data also show the complexes existing in solution, in some cases, however, disproportionating to adducts of different nuclearity. Oligonuclear species have been detected through ESI MS spectroscopy that has been demonstrated as a powerful tool for the identification of the solution species. AgBF4:Me-triphos (1:2) has been structurally characterized as [Ag(P,P′-Me-triphos)2](BF4) · H2O · 7/2 MeOH, while Ag(O3SCF3): Ph-triphos: H2O (6:2:4) is a spectacular two-dimensional polymer. 相似文献
12.
The tris(pyrazolyl)amine ligands: tris[2-(1-pyrazolyl)methyl]amine (tpma), tris [3,5-dimethyl-1-pyrazolyl)methyl]amine (tdma), tris[2-(1-pyrazolyl)ethyl]amine (tpea), tris[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine (tdea) and bis(pyrazolyl)amine ligands: bis[2-(1-pyrazolyl)ethyl]amine (bpea) and bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine (bdea) react with [RhCl(cod)]2 in presence of NaBF4 (tpma, tdma and bdea) or AgBF4 (tpea, tdea and bpea) to lead to [Rh(cod)L] (BF4) (L=tpma (1), tdma (2), bdea (3), tpea (4), tdea (5) and bpea (6)). These complexes have been characterised by elemental analyses, conductivity, IR, 1H and 13C NMR spectroscopy and liquid mass (with electrospray) spectrometry. The 1H NMR spectra of 1, 2 show the presence of two isomers in solution in a 3:1 ratio (coordination κ2 or κ3 type) in a thermodynamic equilibrium. The steric bulk of cyclo-octa-1,5-diene causes it to prefer the κ2 mode of bonding as majority. Similar to previous published results, complexes 4 and 5 exist in a sole form in solution (probably κ2 isomer). Finally, the complexes 3 and 6 are fluxional. A NMR study shows that this fluxional process is not frozen at 183 K. 相似文献
13.
Jasmina M. Dimitri? Markovi? Zoran S. Markovi? Jugoslav B. Krsti? 《Journal of inorganic biochemistry》2009,103(5):723-730
Spectroscopic (UV/visible and IR) and theoretical studies were used to assess relevant interaction of fisetin, a tetrahydroxylated flavone molecule, and trivalent aluminium in a wide range of buffered aqueous solutions. The chelation sites, stoichiometry, stability and the dependence of the complexes structures on pH and aluminium/fisetin mole ratios were defined. Obtained results implicated successive formation of two complexes with aluminium(III)-fisetin stoichiometries of 1:1 and 2:1. Considering the fisetin molecular structure, results of vibrational analysis and theoretical calculations, it is possible to implicate 3-hydroxyl-4-carbonyl and 3′4′-dihydroxyl groups as those with the possible chelating power. The equilibrium geometries were optimized in vacuum at the B3LYP/6-31G(d) level of theory, which predict structural modifications between the ligand molecule in free state and in the complex structure. The theoretical model has been validated by both vibrational and electronic spectroscopies. 相似文献
14.
A series of 1:1 iron(III) complexes of simple and sterically hindered tridentate 3N donor ligands have been synthesized and studied as functional models for catechol dioxygenases. All of them are of the type [FeLCl3], where L is bis(pyrid-2-yl-methyl)amine (L1), N,N-bis(benzimidazol-2-ylmethyl)amine (L2), N-methyl-N'-(pyrid-2-ylmethyl)ethylenediamine (L3), N,N-dimethyl-N'-(pyrid-2-ylmethyl)-ethylenediamine (L4) and N-phenyl-N'-(pyrid-2-ylmethyl)ethylenediamine (L5). They have been characterised by spectral and electrochemical methods. The X-ray crystal structure of the complex [Fe(L4)Cl3] has been successfully determined. The complex crystallizes in the triclinic space group P1 with a = 7.250(6), b = 8.284(3), c = 12.409(4) angstroms, alpha = 80.84(3) degrees, beta = 86.76(6) degrees, gamma = 72.09(7) degrees and Z = 2. It possesses a distorted octahedral geometry in which the L4 ligand is cis-facially coordinated to iron(III) and the chloride ions occupy the remaining coordination sites. The systematic variation in the ligand donor atom type significantly influences the Lewis acidity of the iron(III) center and hence the binding interaction of the complexes with simple and substituted catechols. The spectroscopic and electrochemical properties of the catecholate complexes generated in situ have been investigated. All the complexes catalyze mainly the oxidative intradiol cleavage of 3,5-di-tert-butylcatechol (H2DBC) in the presence of dioxygen, which is unexpected of the cis-facial coordination of the ligands. The rate of intradiol catechol cleavage reaction depends upon the Lewis acidity of iron(III) center and steric demand and hydrogen-bonding functionalities of the ligands. Interestingly, the electron-sink property of N-phenyl substituent in [Fe(L5)Cl3] complex leads to enhancement in rate of cleavage. All these observations provide support to the substrate activation mechanism proposed for intradiol-cleaving enzymes. 相似文献
15.
Amaury du Moulinet d’Hardemare Stéphane Torelli Guy Serratrice Jean-Louis Pierre 《Biometals》2006,19(4):349-366
The interest in synthetic siderophore mimics includes therapeutic applications (iron chelation therapy), the design of more
effective agents to deliver Fe to plants and the development of new chemical tools in order to study iron metabolism and iron
assimilation processes in living systems. The design of ligands needs a rational approach for the understanding of the metal
ion complexing abilities. The octahedral arrangement of donor atoms is the most favourable geometry, allowing the maximum
possible distance between their formal or partial negative charges. Hexadentate chelators, usually of the tris-bidentate type,
can accommodate the metal coordination sphere and are well-suited to obtain high pFe values. The first part of this review
is dedicated to selected synthetic routes, taking into account (i) the nature of the chelating subunits, connecting groups
and spacers, (ii) the water-solubility and hydrophilic/lipophilic balance, (iii) the chirality and (iv) the possibility of
grafting probes or vectors. In the second part, we discuss the role of the molecular design on complexing abilities (thermodynamics
and kinetics). The bidentate 8-hydroxyquinoline moiety offers an alternative to the usual coordinating hydroxamic acids, catechols
and/or α-hydroxycarboxylic acids groups encountered in natural siderophores. The promizing results obtained with the tris-hydroxyquinoline-based
ligand O-TRENSOX are summarized. O-TRENSOX exhibits a high and selective affinity for Fe(III) complexation. Its efficiency in delivering Fe to plants, iron
mobilization, cell protection, and antiproliferative effects has been evidenced. Other chelators derived from O-TRENSOX (mixed catechol/8-hydroxyquinoline ligands, lipophilic ligands) are also described. Some results question the relevance
of partition coefficients to foresee the activity of iron chelators. The development of probes (fluorescent, radioactive,
spin labelled) based on the O-TRENSOX backbone is in progress in order to get insights in the complicated iron metabolism processes. 相似文献
16.
Harrington JM Winkelmann G Haselwandter K Crumbliss AL 《Journal of inorganic biochemistry》2011,105(12):1670-1674
One method of mobilization of iron by mycorrhizal organisms is through the secretion of small organic chelators called siderophores. Hydroxamate donor chelators are a common type of siderophore that is frequently used by fungal organisms. The primary siderophore that is produced by fungi from the genera Ceratobasidium and Rhizoctonia is the tripodal trishydroxamate siderophore basidiochrome. To gain some insight into the iron uptake mechanisms of these symbiotic fungi, the iron binding characteristics of basidiochrome were determined. It was found that basidiochrome exhibits a log β110 of 27.8 ± 0.1 and a pFe value of 25.0. These values are similar to those of another fungal trishydroxamate siderophore, ferrichrome. The similarity in iron affinity between the two siderophores suggests that the structure of the backbone has little influence in complex formation due to the length of the pendant arms, although the identity of the terminating groups of the pendant arms is likely related to complex stability. The role of basidiochrome in the biogeochemical cycling of iron is also discussed. 相似文献
17.
The reactions of CoCl2 with three equivalents of 2-(phenylimino)pyrrolyl sodium salts, performed under a nitrogen atmosphere, lead to the formation of the Co(III) complexes [Co(κ2N,N′-NC4H3C(H)N-C6H5)3] (2a), [Co(κ2N,N′-NC4H3C(CH3)N-C6H5)3] (2b) and [Co(κ2N,N′-NC16H9C(H)N-C6H5)3] (2c), accommodating three chelating iminopyrrolyl ligands. Complexes 2a-c were obtained in moderate yields, and their characterisation by 1H, 13C NMR and X-ray diffraction show they are diamagnetic and have an octahedral geometry about the cobalt centre, respectively. Uncharacterised products were obtained in the same reaction involving ligand precursors such as 2-(2,6-dimethylphenylimino)pyrrolyl sodium salts, which is attributed to a greater steric hindrance in the coordination of three of these bulkier ligands. The redox behaviour of complexes 2a-c shows an irreversible reduction wave with a peak potential in the range −3.2 to −3.7 V. Upon reduction, the complexes decompose giving rise, in the case of 2a, to a redox pattern compatible with the formation of [Co(κ2N,N′-NC4H3C(H)N-C6H5)2]. 相似文献
18.
Dror Shamir Israel Zilbermann Eric Maimon Alexander I. Shames Dan Meyerstein 《Inorganica chimica acta》2010,363(12):2819-2823
Several new anions were shown to be good stabilizing ligands for , (L = 1,4,8,11-tetraazacyclotetradecane, cyclam) in aqueous solutions. , phosphonates, phosphates, including the biological relevant ATP were shown to have the highest binding constants to the tervalent nickel ion. The results suggest that the charge density of the anion at the binding site and the basicity of the anion are the main factors affecting the binding constant to the central Ni(III) cation. 相似文献
19.
20.
The coordination between Al(III) and sialic acid (N-acetylneuraminic acid, HL, pKa = 2.58 ± 0.01) was studied by potentiometric titrations at 25 °C in aqueous 0.2 M KCl, by 1H NMR, and by electrospray ionization mass spectrometry (ESI-MS). The potentiometric measurements gave the following aluminium complex stoichiometries and stability constants: , log β(AlLH−2) = −6.34 ± 0.02, and log β(AlL2H−1) = −1.14 ± 0.04. The 1H NMR spectra yielded structural information on species . The ESI-MS data confirmed the metal-ligand stoichiometry of the complexes.The metal-ligand speciation at micromolar Al(III) concentrations (i.e., under in vivo conditions) at physiological pH values reveals that considerable amount of Al(III) is complexed. This suggests that the toxic effect of Al(III) towards cellular membranes might be due to its coordination by protein-bound sialic acid. 相似文献