Kinetic hydrogen isotope effects for proton transfer between carboxylic acids and the monoprotonated crysptand (2,1,1)H+ in methanol

Cox, Brian G.; Trưởng, Nguyễn Văn; Schneider, Hermann

doi:10.1039/p29830000515

Cited by 8 publications

(2 citation statements)

References 7 publications

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“…and back-titrated with Th(NO 3 ) 4 ·5H 2 O (Merck) in the presence of excess EDTA (Merck, Titriplex III, 0.1 M) and xylenol orange (Merck) as indicator. Dichloroacetic buffer (0.05 M) was used to maintain the p[H] value at 6.5 ± 0.1. Tetrabutylammonium hydroxide (Fluka, 25% in methanol) was used for neutralization of a titrated (ca.…”

Section: Methodsmentioning

confidence: 99%

Allosteric Effects in Polynuclear Triple-Stranded Ferric Complexes

et al. 1997

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The synthesis and iron(III) coordination properties of three tripodal ligands (L 1 , L 2 , and L 3 ) possessing hydroxamate coordination cavities are examined by various methods (ESMS, UV−vis, CD). The ligands rely on a trisamine as anchor, which is extended by an alternating sequence of variable spacers and hydroxamates as ion binding groups. This modular strategy of design is adopted for the compounds' preparation and enables modifications of each structural element independently. The coordination properties of these iron binding molecules and particularly the presence of allosteric effects are examined by classical spectrophotometric titrations in combination with electrospray mass spectrometric measurements (ESMS). A good match between these two methods is observed, as both indicate the formation of three species in thermodynamic equilibrium: mononuclear, binuclear, and trinuclear ferric complexes. The respective stability constants are determined at p[H] = 6.5 ± 0.1 in methanol, and the corresponding distribution curves clearly illustrate the variations from ligand to ligand. These findings demonstrate that subtle structural changes have a pronounced effect on these compounds' coordination properties. Moreover, among the binders studied representatives of opposite cooperative behavior is identified. The observed dependence of the ligands' coordination properties on their structural features are rationalized.

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Section: Methodsmentioning

confidence: 99%

Allosteric Effects in Polynuclear Triple-Stranded Ferric Complexes

et al. 1997

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“…[83][84][85] Tricyclic tetraamines, also called adamanzanes, exhibit analogous properties and were found to be very inert with respect to the proton entrapped in the cavity. [34][35][36] Of particular relevance with respect to the present work are the macrobicyclic diazacycloalkanes [20][21][22]26 and cryptands, 63,71,86 in which the proton is tightly concealed inside an often rigid cavity. Bridged bicyclic structures of this type contain medium to large rings (at least 7-membered) in which the lone pairs on bridgehead nitrogen atoms can point either inward or outward, thus allowing inside or outside protonation.…”

Section: Nmr Spectroscopic Studies Of the Protonationmentioning

confidence: 99%