The 35Cl NQR spectra and structure of pentafluorophenyltetrachlorophosphorane C6F5PCl4

The low temperature structure of C₆F₅PCl₄ was confirmed by ³⁵Cl NQR measurements as ψ-trigonal bipyramidal, with the C₆F₅ group axial. Discrepancies were found with previously reported data, possible causes of these are discussed.     

Mechanistic Studies of Metal Aqua Ions: A Semi‐Historical Perspective

A semi‐historical review of the establishment of the nature of metal aqua ions ranging from the alkali metal ions to the lanthanides and the mechanism of water exchange and ligand substitution on them is presented.     

The inclusion of pyronine B and pyronine Y by beta- and gamma-cyclodextrins A kinetic and equilibrium study

Equilibrium and temperature-jump spectrophotometric studies show that the mono-cation of pyronine B (PB) is included by beta- and gamma-cyclodextrins (CD and CD) to form the labile complexes PB. CD, PB. CD and (PB)₂. CD in water. The equilibrium, kinetic and structural aspects of these complexes and those formed by pyronine Y are discussed in conjunction with data characterizing the inclusion of other dyes by cyclodextrins.     

The solvation of the dioxouranium(VI) ion by dimethyl sulfoxide

The species UO₂(DMSO) ₅ ²⁺ is shown from¹H NMR studies to be the predominant dioxouranium(VI) species existing in dilute anhydrous acetonedimethyl sulfoxide (DMSO) solutions, and this result is compared with data reported for the analogous water-acetone-dimethyl sulfoxide system. Complete line-shape analyses of exchange-modified¹H NMR line shapes indicate that the mechanism for DMSO exchange on UO₂(DMSO) ₅ ²⁺ is probably of theD orI _D type. A typical set of rate parameters arek _ex (260°K) =273±14 sec^–1, H ^#=38.9±0.5 kJ-mole^–1, and S ^#=–47.5±1.8 J-^oK^–1-mole^–1 for a solution in which [UO₂(DMSO)₅ ²⁺], [DMSO], and [d ₆ acetone] are, respectively, 0.01155, 0.0875, and 13.00 moles-dm^–3.     

Mechanism of DNA threading intercalation of binuclear Ru complexes: uni- or bimolecular pathways depending on ligand structure and binding density

In the long succession of small transition-metal compounds interacting reversibly with DNA, semirigid binuclear ruthenium complexes stand out by displaying exceptionally slow binding kinetics. To reach the final intercalated state, one of the bulky metal centers has to be threaded through the base stack, leading to a high level of structural discrimination. This makes the idea of utilizing binuclear complexes interesting in applications involving DNA sequence or conformation recognition. The finding that threading intercalation of the two structural analogues, Lambda,Lambda-[mu-(11,11'-bidppz)X4Ru2]4+, X = 2,2'-bipyridine (Lambda,Lambda-B4) and X = 1,10'-phenanthroline (Lambda,Lambda-P4), into poly(dA-dT)2 can be described by surprisingly simple rate laws encouraged more extensive studies and analysis of these two systems. Kinetic measurements at different [basepair]/[complex] ratios show that Lambda,Lambda-B4 intercalates via a pseudo-first-order mechanism independent of binding density, whereas Lambda,Lambda-P4 displays a gradual transition from apparent first- to second-order kinetics when decreasing the [basepair]/[complex] mixing ratio. By employing the probabilistic method of McGhee and von Hippel, a rate law based on a supposed mechanism has been globally fitted and numerically integrated to describe threading of Lambda,Lambda-P4. In contrast to Lambda,Lambda-B4, the first-order mechanism of this analogue appears to require a long stretch of nonthreaded DNA. The results show that ancillary ligand structures indeed affect the mechanism of DNA threading, demonstrating the potential use of semirigid binuclear ruthenium complexes to target DNA.     

An equilibrium and kinetic study of the complexation of lithium and sodium ions by the cryptand 4, 7, 13-trioxa-1, 10-diazabicyclo-[8. 5. 5]-eicosane (C21C5)

In the solid and solution state Li⁺ and Na⁺ form inclusive and exclusive cryptates respectively with C21C₅, in which Li⁺ resides inside and Na⁺ resides outside the C21C₅ cavity. Similar inclusive and exclusive structures are observed for [Li.C211]⁺ and [Na. C211]⁺. The logarithms of the stability constants in dimethylformamide for [Li.C21C₅]⁺, [Li.C211]⁺, [Na.C21C₅]⁺ and [Na.C211]⁺ are: 2.80, 6.99, 2.87 and 5.20; and^o the corresponding decomplexation rate constants are: 107, 0.013, 28800 and 12 s^–1 at 298.2 K. The relationships between cryptate structure, stability and lability are considered, as are solvent influences.     

Observation of chicJ radiative decays to light vector mesons

Using a total of 2.74 x 10(7) decays of the psi(2S) collected with the CLEO-c detector, we present a study of chi(cJ)-->gammaV, where V=rho(0), omega, phi. The transitions chi(c1)-->gammarho(0 and chi(c1)-->gammaomega are observed with B(chi(c1)-->gammarho(0))=(2.43+/-0.19+/-0.22) x 10(-4) and B(chi(c1)-->gammaomega)=(8.3+/-1.5+/-1.2) x 10(-5). In the chi(c1)-->gammarho(0) transition, the final state meson is dominantly longitudinally polarized. Upper limits on the branching fractions of other chi(cJ) states to light vector mesons are presented.     

Complexation of dodecyl‐substituted poly(acrylate) by linked β‐cyclodextrin dimers and trimers in aqueous solution

Two‐dimensional NOESY ¹H NMR, isothermal titration calorimetric (ITC), and rheological studies of host–guest complexation by β‐cyclodextrin, β‐CD, and the β‐CD groups of the linked β‐CD dimers, β‐CD₂ur and β‐CD₂su and trimers, β‐CD₃bz and β‐CDen₃bz, of the dodecyl, C12, substituents of the 3.0% substituted poly(acrylate), PAAC12, in aqueous solution are reported. Complexations by β‐CD, β‐CD₂ur, β‐CD₂su, β‐CD₃bz, and β‐CDen₃bz of the C12 substituents of PAAC12 in 0.2 wt % solution exhibit complexation constants 10^?4K₁₁ (298.2 K) = 0.83, 5.80, 4.40, 15.0, and 1.50 dm³ mol^?1, respectively. (The corresponding ΔH₁₁ and TΔS₁₁ show a linear relationship.) The rheologically determined zero‐shear viscosities of 3.3 wt % aqueous solutions of PAAC12 alone and in the presence of β‐CD, β‐CD₂ur, β‐CD₂su, β‐CD₃bz, and β‐CDen₃bz (where the β‐CD groups and C12 substituents are equimolar) are 0.016, 0.03, 0.12, 0.25, 0.12, and 0.08 Pa s (298.2 K), respectively, and show PAAC12 to form interstrand cross‐links through complexation. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1278–1286