Search results for "Ion pairs"
showing 9 items of 19 documents
On the Ion-Pair Recognition and Indication Features of a Fluorescent Heteroditopic Host Based on a BODIPY Core
2014
A fluorescent heteroditopic host for ion pairs and zwitterionic species has been synthesized. Its affinity towards a series of anions, cations and ion pairs in acetonitrile has been assessed, and the spectroscopic response has been evaluated. Solid–liquid extraction experiments of inorganic salts, α-amino acids and γ-aminobutyric acid (GABA) into acetonitrile solutions were performed, and the resulting complexes were analyzed by UV/Vis absorption, fluorescence and 1H NMR spectroscopy. The discrimination patterns observed have been rationalized in terms of the molecular topologies of the host and guests.
Weak alkali and alkaline earth metal complexes of low molecular weight ligands in aqueous solution
2008
This work is aimed at reviewing the chemical literature dealing with thermodynamic aspects of the weak complex formation (species with log K values less than about 3) between alkali and alkaline earth metal ions with low molecular weight inorganic and organic ligands in aqueous solution. The following ligands (up to hexavalent anions) were examined in detail: (i) hydroxide, chloride, sulfate, carbonate and phosphate as inorganic, and (ii) carboxylates, amines, amino acids, complexones and nucleotides as organic ligands. The paper also identifies the main reasons responsible for the dispersion of the stability data on ion pairs in the literature. When possible, the trend of stability for the…
A linear Fe-O-Fe unit in bis(dibenzyldimethylammonium) mu-oxo-bis[tribromoferrate(III)].
2006
The title compound, (C 16 H 20 )N) 2 [Fe 2 Br 6 O], crystallizes with one dibenzyldimethylammonium cation and one half of a μ-oxo-bis[tribromoferrate(III)] anion in the asymmetric unit. The bridging oxo group is situated on an inversion centre, resulting in a linear conformation for the Fe-O-Fe unit. The iron(III) cations have tetrahedral geometry, with bond angles in the range 106.8 (1)-112.2 (1)°. The ion pairs are held together by Coulombic forces and C-H···Br hydrogen bonds. Each Br - anion forms one hydrogen bond. No C-H···O hydrogen bonds are found between the O atom in the Fe-O-Fe unit and surrounding counter-cations, consistent with the linear configuration of the Fe-O-Fe unit.
Boolean operations mediated by an ion-pair receptor of a multi-readout molecular logic gate
2013
A heteroditopic BODIPY dye that performs all basic Boolean operations with a cation (K+) and an anion (F-) as inputs and absorption, transmission and fluorescence as outputs is described. The molecular logic gate can also act as a digital comparator between the inputs.
Complexes hétéronucléaires Cp2MM′(Cp)(CO)3 (M Nb, Ta; M′ Mo, W) avec groupes carbonyles pontants et semi-pontants: synthèse et comportement dynam…
1991
Abstract Heteronuclear structures Cp 2 MM′(Cp)(CO) 3 (M Nb, Ta; M′ Mo, W) are obtained by heating Cp 2 MH 3 (M Nb, Ta) with Cp 2 M′ 2 (CO) 6 (M′ Mo, W) or starting from Cp 2 M(CO)H and Cp 2 M′ 2 (CO) 4 . These heterobimetallic complexes show three CO coordination modes: terminal, semi-bridging and bridging. The two cyclopentadienyl groups of the Cp 2 M moiety are anisochronous owing to molecular rigidity; rotation barriers around the MM′ bond have been estimated and are greatest with tantalum derivatives.
The first structurally characterized cationic lanthanide–alkyl complexesElectronic supplementary information (ESI) available: experimental and spectr…
2002
Reaction of rare earth metal–alkyl complexes [Ln(CH2SiMe3)3(THF)2] (Ln = Y, Lu) with B(C6X5)3 (X = H, F) in the presence of crown ethers gives crystallographically characterized ion pairs [Ln(CH2SiMe3)2(CE)(THF)n]+[B(CH2SiMe3)(C6X5)3]– (CE = [12]-crown-4, n = 1; CE = [15]-crown-5 and [18]-crown-6, n = 0).
Rate constants for ion-pair dissociation and association in the anionic two-state polymerization of styrene in THF
1965
Dynamic Refolding of Ion-Pair Catalysts in Response to Different Anions.
2019
Four distinct folding patterns were identified in two foldamer-type urea-thiourea catalysts bearing a basic dimethylamino unit by a combination of X-ray crystallography, solution NMR studies, and computational studies (DFT). These patterns are characterized by different intramolecular hydrogen bonding schemes that arise largely from different thiourea conformers. The free base forms of the catalysts are characterized by folds where the intramolecular hydrogen bonds between the urea and the thiourea units remain intact. In contrast, the catalytically relevant salt forms of the catalyst, where the catalyst forms an ion pair with the substrate or substrate analogues, appear in two entirely dif…
Apolar versus polar solvents: a comparison of the strength of some organic acids against different bases in toluene and in water
2010
The constants of ion-pair formation with 3-nitroaniline (3NO(2)A) for eight halogenoacetic acids (HAAs, 3a-h: TFA, TCA, TBA, DFA, DCA, DBA, MCA, and MBA), and five 2,2-dichloroalkanoic acids containing 3-8 carbon atoms (HAs, 5a-e: DCPA, DCBA, DCMBA, DCVA, and DCOA) have been determined in TOL at 298.1 K. The results obtained brought to evidence for HAAs the formation of ion-pairs with two different stoichiometries (base-acid, 1:1 or 1:2), while in contrast the HAs furnish only the 1:1 pairs. The different steric and electronic requirements of HAAs and HAs seem to be responsible for such an unlikely behavior. At the same time, the acid-catalyzed MRH of the (Z)-phenylhydrazone of 5-amino-3-be…