1891-17-4Relevant academic research and scientific papers
Divalent metal ion catalyzed reactions of acyl phosphates
Fife, Thomas H.,Pujari, Mahesh P.
, p. 5551 - 5557 (1990)
The hydrolysis of the acyl phosphate, 1,10-phenanthroline-2-carbonyl phosphate, proceeds with a hydroxide ion catalyzed reaction of the dianionic species at high pH, a pH-independent reaction of that species in the pH range 7-10, and a reaction of the zwitterionic species (protonated phenanthroline nitrogen) at pH app = 5.6). The divalent metal ions Cu2+, Ni2+, Co2+, and Zn2+ have a large effect on the rate of hydrolysis. At saturating concentrations of Ni2+, Co2+, and Zn2+ (0.003 M, 50-fold excess over the acyl phosphate), hydroxide ion catalyzed reactions occur that are > 107-fold more favorable at 30°C than in the absence of the metal ions. Likewise, Mg2+ exerts a sizable catalytic effect (> 104), although binding is considerably weaker than with the other metal ions (saturation only occurs at Mg2+ concentrations greater than 0.1 M). The cupric ion promoted OH--catalyzed reaction at 30 °C (0.002 M Cu2+) is (5 × 1010)-fold more favorable than OH- catalysis in the absence of the metal ion. At pH 18O into the carboxylic acid product when the hydrolytic reactions were carried out in 18O-enriched water showed conclusively that C-O bond breaking occurs in the metal ion promoted hydroxide ion and pH-independent processes. Both imidazole and pyridine are catalysts in the hydrolysis of the acyl phosphate, and the imidazole-catalyzed reaction is markedly enhanced by a saturating concentration of Ni2+. The effect of the metal ion is much smaller in the reaction with pyridine; the second-order rate constant for the pyridine reaction is only increased 3-fold by the presence of a saturating concentration of Ni2+. Thus, the strongly chelated metal ions greatly facilitate nucleophilic reactions that occur at the carbonyl carbon of the acyl phosphate rather than metaphosphate elimination or nucleophilic attack at phosphorus.
Solvent extraction of americium(iii) and europium(iii) with tridentate N,N-dialkyl-1,10-phenanthroline-2-amide-derived ligands: extraction, complexation and theoretical study
Cao, Shiwei,Wang, Jieru,Tan, Cunmin,Zhang, Xin,Li, Sa,Tian, Wei,Guo, Hangxu,Wang, Lei,Qin, Zhi
, p. 10560 - 10568 (2016)
The extraction and complexation behavior of soft-hard combined N,N-dialkyl-1,10-phenanthroline-2-amide (PTA) ligands with Am(iii) and Eu(iii) in HNO3 solution was investigated. The effects of acidity of the aqueous solution, shaking time, concentration of the extractant and temperature on the distribution ratios were studied. The extraction ability for both Am(iii) and Eu(iii) was found to decrease with an increase in the length of the substituent alkyl chains, and the highest extractability and selectivity for Am(iii) over Eu(iii) were found for the diethyl-substituted ligand. The separation factor for Am(iii) over Eu(iii) reached around 7.6 at low acidity and high salinity. UV-vis titrations revealed that the dialkyl-substituted tridentate PTAs all predominantly formed 1?:?1 complexes with Eu(iii), which agreed well with the results of slope analyses in the extraction experiments. The stability constants (KEuL) as well as the protonation constants (KH) were also determined by UV-vis titration. Computational chemistry gave a good explanation of the relationship between the alkalinity and the protonation energy of the proposed PTA ligands. Density functional theory (DFT) calculations on the optimized structures of Am(iii) and Eu(iii) complexes with C2-PTA showed that the selectivity may originate from differences in the degree of covalency of the bonds between the metal ions and the donor N atoms, which fits well with the experimental results.
Hybrid bis-histidine phenanthroline-based ligands to lessen aβ-bound cu ros production: An illustration of cu(i) significance
Drommi, Marielle,Esmieu, Charlène,Hureau, Christelle,Rulmont, Clément
, (2021/12/24)
We here report the synthesis of three new hybrid ligands built around the phenanthroline scaffold and encompassing two histidine-like moieties: phenHH, phenHGH and H’phenH’, where H correspond to histidine and H’ to histamine. These ligands were designed to capture Cu(I/II) from the amyloid-β peptide and to prevent the formation of reactive oxygen species produced by amyloid-β bound copper in presence of physiological reductant (e.g., ascorbate) and dioxygen. The amyloid-β peptide is a well-known key player in Alzheimer’s disease, a debilitating and devasting neurological disorder the mankind has to fight against. The Cu-Aβ complex does participate in the oxidative stress observed in the disease, due to the redox ability of the Cu(I/II) ions. The complete characterization of the copper complexes made with phenHH, phenHGH and H’phenH’ is reported, along with the ability of ligands to remove Cu from Aβ, and to prevent the formation of reactive oxygen species catalyzed by Cu and Cu-Aβ, including in presence of zinc, the second metal ions important in the etiology of Alzheimer’s disease. The importance of the reduced state of copper, Cu(I), in the prevention and arrest of ROS is mechanistically described with the help of cyclic voltammetry experiments.
A single iron porphyrin shows ph dependent switch between "push" and "pull" effects in electrochemical oxygen reduction
Bhunia, Sarmistha,Dey, Abhishek,Dey, Somdatta Ghosh,Mukherjee, Sudipta,Nayek, Abhijit
, p. 14564 - 14576 (2020/11/02)
The "push-pull"effects associated with heme enzymes manifest themselves through highly evolved distal amino acid environments and axial ligands to the heme. These conserved residues enhance their reactivities by orders of magnitude relative to small molecules that mimic the primary coordination. An instance of a mononuclear iron porphyrin with covalently attached pendent phenanthroline groups is reported which exhibit reactivity indicating a pH dependent "push"to "pull"transition in the same molecule. The pendant phenanthroline residues provide proton transfer pathways into the iron site, ensuring selective 4e-/4H+ reduction of O2 to water. The protonation of these residues at lower pH mimics the pull effect of peroxidases, and a coordination of an axial hydroxide ligand at high pH emulates the push effect of P450 monooxygenases. Both effects enhance the rate of O2 reduction by orders of magnitude over its value at neutral pH while maintaining exclusive selectivity for 4e-/4H+ oxygen reduction reaction.
Monitoring helical twists and effective molarities in dinuclear triple-stranded lanthanide helicates
Ryan, Patrick E.,Guenee, Laure,Piguet, Claude
, p. 11047 - 11055 (2013/08/23)
The replacement of terminal benzimidazole-pyridine binding units in the neutral di-tridentate segmental ligand L1 with phenanthroline in L10 reduces the number of torsional degrees of freedom by two units. Reactions of these ligands with trivalent europium or lutetium cations yield structurally similar self-assembled dinuclear triple-stranded [Ln2(Lk)3] 6+ complexes, thus demonstrating that the increased rigidity of the strand in L10 is compatible with its helical twist. With the larger lanthanum cations, the metallic coordination spheres are completed with two terminal axial triflate counter-anions to give [La2(L10)3(CF 3SO3)2]4+. Thermodynamic investigations in acetonitrile confirm the minor constraints produced by the planar phenanthroline unit in L10 leading to comparable effective molarities EMEu,L1 ≈ EMEu,L10 = 10 -3.9(4) M with mid-range EuIII cations. The striking minute effective molarities EMLn,Ln-2H ≈ 10-6-10-9 M obtained upon the replacement of terminal phenanthrolines with structurally analogous fused hydroxyquinolines in L9 can be thus unambiguously assigned to solvation effects, a new tool for controlling complexity in metal-induced self-assembly processes.
Substituted phenanthrolines as antennae in luminescent EuIII complexes
Akerboom, Sebastiaan,Van Den Elshout, Jos J. M. H.,Mutikainen, Ilpo,Siegler, Maxime A.,Fu, Wen Tian,Bouwman, Elisabeth
, p. 6137 - 6146 (2014/01/06)
Eight novel europium(III)-based coordination compounds with 1,10-phenanthroline (phen) ligands with a chloro, methoxy, ethoxy, cyano, carboxylic acid, methyl carboxylate, ethyl carboxylate, and amino substituent on the 2-position have been prepared in yields ranging from 43 to 89 %. Additionally, one lanthanum(III) coordination compound of 2-amino-1,10- phenanthroline has been isolated. All compounds have the general formula [Ln(L)2(NO3)3], except for the compound with the carboxylate ligand, which has the formula [Eu(O2Cphen) 3]. Three of the EuIII complexes as well as the La III compound crystal structures have been determined, all of which show similar N4O6 coordination spheres for the Ln III ion. Seven compounds exhibit bright luminescence that is characteristic of EuIII upon irradiation with near-UV radiation, thus indicating efficient ligand-to-metal energy transfer. The complex with 2-amino-1,10-phenanthroline is nonluminescent. The solid-state photoluminescent quantum yields range from 10 to 79 %, and the luminescence lifetimes vary from 0.43 to 1.57 ms. Analysis of the spectral intensities with the Judd-Ofelt theory shows a significant contribution of nonradiative processes that quench the luminescence of the 5D0 level on EuIII. Eight new EuIII complexes with 1,10-phenanthroline ligands substituted on the 2-position have been prepared, analyzed, and the photoluminescence properties studied. The complex with the 2-chloro substituent exhibits bright photoluminescence with a high quantum yield of 78 %. The complex with the 2-amino substituent is nonluminescent. Copyright
Highly effective recognition of carbohydrates by phenanthroline-based receptors: α- versus β-anomer binding preference
Mazik, Monika,Hartmann, Andre,Jones, Peter G.
scheme or table, p. 9147 - 9159 (2010/04/05)
1H NMR spectroscopic titrations in competitive and non-competitive media, as well as binding studies in two-phase systems, such as phase transfer of sugars from aqueous into organic solvents and dissolution of solid carbohydrates in apolar medi
Phenanthroline unit as a building block for carbohydrate receptors
Mazik, Monika,Hartmann, Andre
, p. 7444 - 7450 (2008/12/22)
(Figure Presented) An acyclic receptor 1, containing phenanthroline- and aminopyridine-based recognition sites, has been established as a powerful carbohydrate receptor. Compared to the previously described acyclic receptors, compound 1 shows significantl
Catalytic Conversions in Water. Part 23: Steric Effects and Increased Substrate Scope in the Palladium-Neocuproine Catalyzed Aerobic Oxidation of Alcohols in Aqueous Solvents
Ten Brink, Gerd-Jan,Arends, Isabel W. C. E.,Hoogenraad, Marcel,Verspui, Goeran,Sheldon, Roger A.
, p. 1341 - 1352 (2007/10/03)
The steric influence of substituents on the 2-and 9-positions of phenanthroline in the (2,9-R2-1,10-phenanthroline)palladium(II)- catalyzed aerobic oxidation of 2-hexanol was investigated by means of high throughput experimentation. (Neocuproine)Pd-(OAc)2 (R=CH 3) was found to be a highly active catalyst for alcohol oxidation in 1:1 water/DMSO mixtures. The catalyst is unique in that it tolerates water, polar co-solvents and a wide variety of functional groups in the alcohol. Turn-over frequencies of > 1500 h-1 were achieved and a series of alcohols was oxidised with 0.1 to 0.5 mol % of catalyst.
