Ion pairing using PGSE diffusion methods

Pregosin, Paul S.

doi:10.1016/j.pnmrs.2006.09.001

Cited by 141 publications

(51 citation statements)

References 168 publications

(219 reference statements)

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“…Indeed, the diffusion coefficients listed in Table 2 clearly demonstrate that the picrate anion is not ionpaired to the oligomer. [37] The diffusion coefficient for this counterion (d = 8.93 ppm) is concentration-independent and its value is close to that of simple alkylammonium salts (e.g. hexylammonium picrate) and in comparison much higher than the one measured for the oligomers present in the same CD 2 Cl 2 solution.…”

Section: ð1þsupporting

confidence: 54%

Counterion‐Dependent Proton‐Driven Self‐Assembly of Linear Supramolecular Oligomers Based on Amino‐Calix[5]arene Building Blocks

Pappalardo¹,

Villari²,

Slovak³

et al. 2007

Chemistry A European J

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Self-assembly of a calix[5]arene bearing a 12-aminododecyl pendant group on the lower rim into supramolecular oligomers through intermolecular iterative inclusion events is readily triggered by contact with acid solutions and is reversed to the amino monomer precursor by treatment with a base. 1H NMR data are consistent with the formation of head-to-tail assemblies derived from endo-cavity inclusion of the alkylammonium moiety. Diffusion NMR and light-scattering studies provide evidence for the presence of oligomers in solution and show that different counterions and concentrations result in different oligomer sizes, whereas ESI-MS and SEM investigations, respectively, indicate that self-assembly also takes place in the gas phase and in the solid state. The growth of these supramolecular oligomers is concentration-dependent; however, as a consequence of the saline nature of the monomer, it also shows a distinct counterion-dependence owing to ion-pairing/solvation effects.

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Section: ð1þsupporting

confidence: 54%

Counterion‐Dependent Proton‐Driven Self‐Assembly of Linear Supramolecular Oligomers Based on Amino‐Calix[5]arene Building Blocks

Pappalardo¹,

Villari²,

Slovak³

et al. 2007

Chemistry A European J

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“…The relative orientation of the anion-cation and the fraction of dissociated ion pairs (a) as a function of the concentration were investigated for 1 a-PF 6 , 1 b-PF 6 , 3 a-PF 6 , and 3 b-PF 6 working in CD 2 Cl 2 by means of the nuclear Overhauser effect (NOE) [19] and PGSE [9] NMR experiments. The assignment of 1 H and 13 C resonances, propedeutic to NOE and PGSE studies, was performed by using multinuclear and multidimensional NMR spectroscopies (see Experimental Section).…”

Section: Nmr Spectroscopic Investigationmentioning

confidence: 99%

“…For these ionic NLO chromophores, ion pairing in a solvent such as CH 2 Cl 2 could be relevant, consequently, we also report an investigation of the effect of different counterions (C 12 H 25 SO 3 À , I À , or PF 6 À ) and of the concentration on their second-order NLO response, by the use of a combination of EFISH and 1 H and 19 F pulsed field gradient spin echo (PGSE) NMR [9] techniques. DFT/time-dependent-DFT (TDDFT) calculations have been performed on the selected systems to provide insight into the electronic properties of these systems and to rationalize some of the experimentally observed trends.…”

Section: Introductionmentioning

confidence: 99%

Cyclometalated Ir^III Complexes with Substituted 1,10‐Phenanthrolines: A New Class of Efficient Cationic Organometallic Second‐Order NLO Chromophores

Valore

Cariati

Dragonetti

et al. 2010

Chemistry A European J

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Cyclometalated cationic Ir(III) complexes with substituted 1,10-phenanthrolines (1,10-phen), such as [Ir(ppy)(2)(5-R-1,10-phen)]Y (ppy=cyclometalated 2-phenylpyridine; R=NO(2), H, Me, NMe(2); Y(-)=PF(6) (-), C(12)H(25)SO(3) (-), I(-)) and [Ir(ppy)(2)(4-R,7-R-1,10-phen)]Y (R=Me, Ph) are characterized by a significant second-order optical non linearity (measured by the electrical field induced second harmonic generation (EFISH) technique). This nonlinearity is controlled by MLCT processes from the cyclometalated Ir(III), acting as a donor push system, to pi* orbitals of the phenanthroline, acting as an acceptor pull system. Substitution of cyclometalated 2-phenylpyridine by the more pi delocalized 2-phenylquinoline (pq) or benzo[h]quinoline (bzq) or by the sulfur-containing 4,5-diphenyl-2-methyl-thiazole (dpmf) does not significantly affect the mubeta absolute value, which instead is affected by the nature of the R substituents on the phenanthroline, the higher value being associated with the electron-withdrawing NO(2) group. By using a combined experimental (the EFISH technique and (1)H and (19)F PGSE NMR spectroscopy) and theoretical (DFT, time-dependent-DFT (TDDFT), sum over states (SOS) approach) investigation, evidence is obtained that ion pairing, which is controlled by the nature of the counterion and by the concentration, may significantly affect the mubeta values of these cationic NLO chromophores. In CH(2)Cl(2), concentration-dependent high absolute values of mubeta are obtained for [Ir(ppy)(2)(5-NO(2)-1,10-phen)]Y if Y is a weakly interacting anion, such as PF(6) (-), whereas with a counterion, such as C(12)H(25)SO(3) (-) or I(-), which form tight ion-pairs, the absolute value of mubeta is lower and quite independent of the concentration. This mubeta trend is partially due to the perturbation of the counterion on the LUMO pi* levels of the phenanthroline. The correlation between the mubeta value and dilution shows that the effect of concentration is a factor that must be taken into careful consideration.

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“…[6] Diese Salze waren "traditionelle" Organokatalysatoren für enantioselektive Henry-oder Mannich-Reaktionen und die Hydrophosphonylierung von Aldehyden (Schema 1). [6,7] [9] Die dreidimensionale Struktur in Lösung -und besonders das Wasserstoffbrückennetzwerk -könnten mithilfe homonuclearer NOE-SY-Experimente beschrieben werden. Diese Untersuchungen würden außerdem zur Charakterisierung der auftretenden "Ionenpaarbildung" beitragen, da unklar ist, ob Komplex [1][OPh](HOPh) 2 als Ionenpaar korrekt beschrieben werden kann.…”

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Ladungsunterstützte supramolekulare Katalyse

Rix

Lacour

2010

Angewandte Chemie

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Ion pairing using PGSE diffusion methods

Cited by 141 publications

References 168 publications

Counterion‐Dependent Proton‐Driven Self‐Assembly of Linear Supramolecular Oligomers Based on Amino‐Calix[5]arene Building Blocks

Counterion‐Dependent Proton‐Driven Self‐Assembly of Linear Supramolecular Oligomers Based on Amino‐Calix[5]arene Building Blocks

Cyclometalated Ir^III Complexes with Substituted 1,10‐Phenanthrolines: A New Class of Efficient Cationic Organometallic Second‐Order NLO Chromophores

Ladungsunterstützte supramolekulare Katalyse

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Ion pairing using PGSE diffusion methods

Cited by 141 publications

References 168 publications

Counterion‐Dependent Proton‐Driven Self‐Assembly of Linear Supramolecular Oligomers Based on Amino‐Calix[5]arene Building Blocks

Counterion‐Dependent Proton‐Driven Self‐Assembly of Linear Supramolecular Oligomers Based on Amino‐Calix[5]arene Building Blocks

Cyclometalated IrIII Complexes with Substituted 1,10‐Phenanthrolines: A New Class of Efficient Cationic Organometallic Second‐Order NLO Chromophores

Ladungsunterstützte supramolekulare Katalyse

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Cyclometalated Ir^III Complexes with Substituted 1,10‐Phenanthrolines: A New Class of Efficient Cationic Organometallic Second‐Order NLO Chromophores