Synthetic Ditopic Receptors

A small, but emerging field of topical interest in supramolecularchemistry is ion-pair recognition, in which a host simultaneously binds both cationicand anionic guests. Details of these receptors, which combine, for example, crownethers and calixarenes for cation complexation, with Lewis acid centers, pyrroles, amidesor urea groups for anion recognition, will be discussed. The predicate of this approach,successfully achieved in certain instances, is that the binding of one guest ion caninduce electrostatic and conformational changes in the host, thereby enhancing thecomplexation of the counter ion.     

In Vitro Gastric and Intestinal Digestions of Pulsed Light-Treated Shrimp Extracts

Pulsed ultraviolet light (PUV), a novel technology most commonly used for microbial inactivation, has recently been employed to effectively mitigate food allergens in peanuts, soybean, shrimp, and almond. Putative mechanisms for the efficacy of PUV in reducing allergen reactivity include photothermal, photochemical, and photophysical effects. To date, there are no published data highlighting the effects of in vitro simulated gastric and intestinal digestion on the stability of PUV reduced allergen reactivity of food. In this study, PUV-treated shrimp extracts were subjected to simulated gastric fluid containing pepsin and simulated intestinal fluid containing trypsin and chymotrypsin, and then tested for changes in allergen potency. SDS-PAGE showed no major band deviation between undigested and digested PUV-treated shrimp extracts. IgE binding to tropomyosin remained markedly decreased as seen in Western blot analysis. Total shrimp allergen reactivity remained unchanged following in vitro peptic digestion and was markedly reduced following in vitro intestinal digestion as illustrated in indirect ELISA. The PUV reduced shrimp allergens remained at a low level under the in vitro simulated digestive conditions. The results inferred that PUV could be a potential method to create less allergenic shrimp products that would remain at a low allergen level under human gastric and intestinal digestive conditions.     

Fluorinated calixpyrroles: anion-binding extractants that reduce the Hofmeister bias

Beta-octafluoro-meso-octamethylcalix[4]pyrrole (1) and beta-decafluoro-meso-decamethylcalix[5]pyrrole (2) were found to extract caesium salts of smaller anions (bromide and chloride for 1 and nitrate for 2) as effectively as that of iodide into nitrobenzene (NB) thereby overcoming the Hofmeister bias normally observed for processes of this type.     

The Study on the Stability Constant and Species Distribution of Eu (III) and Tb (III) Complexes with BDBPH

Biomimetic hydrolysis of DNA or RNA is of increasing importance in biotechnology and medicine. The ability to cleave nucleic acids efficiently, in a non-degradative manner, and with high levels of selectivity for site or structure will be required by many applications for the manipulation of genes, the design of structural probes and the development of novel therapeutics1. There has been much interest in the development of lanthanide complexes as nucleic acid cleavage agents. It has been fou…     

Protonation and protolysis of [Fe4(CO)12(CCH3)]−

The reaction of [Fe₄(CO)₁₂(CCH₃)]^? with HSO₃CF₃ in CH₂Cl₂ solution yields the compound HFe₄(CO)₁₂(CCH₃), which was characterized chemically, spectroscopically and by single crystal X-ray diffraction. This compound retains the approximately tetrahedral 4-iron framework characteristic of the parent anion and protonation appears to have occurred on an FeFe bond. In neat HSO₃CF₃, infrared and NMR spectroscopic evidence indicates that another proton adds to the metal framework producing [H₂Fe₄(CO)₁₂(CCH₃]⁺. On long standing, this solution evolves CO, and H₂, and small amounts of CH₄ and C₂H₆. On the time scale of the experiments described here the latter two gases are obtained in an approximately $\text{1}\text{3}$ ratio. Deuterated acid leads to mixtures of the various isotopomers of CH₄ but the ethane is CD₃CH₃. Possible mechanisms for hydrocarbon production are discussed.     

Thermodynamics of Inter- and Intramolecular Hydrogen Bonding in (Diphosphine)platinum(II) Diolate Complexes and Its Role in Carbohydrate Complexation Regioselectivity

Thermodynamic data are reported for intermolecular hydrogen-bonding association of 1 and 2 equiv of phenol with [1,3-bis(diphenylphosphino)propane](phenylethane-1,2-diolato)platinum(II) ((dppp)Pt(Ped)) in dichloromethane solution: = -7.0 +/- 0.1 kcal/mol, = -7.7 +/- 0.4 kcal/mol, = -11.3 +/- 0.4 eu, and = -17.8 +/- 1.2 eu. For comparison, the thermodynamics for hydrogen bonding of phenol to triphenylphosphine oxide in dichloromethane were also determined: DeltaH degrees = -5.1 +/- 0.3 kcal/mol; DeltaS degrees = -8.8 +/- 1.0 eu. Competitive coordination exchange reactions have been used to determine the apparent intramolecular hydrogen bond strengths in (dppp)Pt(1,2-O,O'-glycerolate) and (dppp)Pt(1,2-O,O'-butane-1,2,4-triolate) in both dichloromethane (DeltaG(313) = -2.05 +/- 0.05 and -2.52 +/- 0.06 kcal/mol, respectively) and pyridine (DeltaG(313) = -0.62 +/- 0.03 and -0.82 +/- 0.03 kcal/mol, respectively). Based on these findings, the role of hydrogen-bonding interactions in determining the regioselectivities of complexation of carbohydrates to diphosphine Pt(II) is discussed.     

Conductivity and Raman spectroscopy of new indium(I) and thallium(I) ionic conductors. In4CdI6, In2ZnI4, and Tl2ZnI4, and the related compound Tl4CdI6

The new compound Tl₂ZnI₄ has been prepared and characterized by Raman spectroscopy, powder X-ray diffraction, elemental analyses, and a partial binary phase diagram. The compounds In₄CdI₆, Tl₄CdI₆, and In₂ZnI₄, for which phase diagrams are available in the literature, were characterized by Raman spectroscopy and their identities were confirmed by elemental analyses and X-ray powder diffraction. Each of these materials, except Tl₄CdI₆, undergoes a sharp order-disorder phase transition at elevated temperatures that can be detected by the measurement of Raman spectra as a function of temperature. Conductivity measurements as a function of temperature, using both reversible and blocking electrodes, reveal a high ionic conductivity in the disordered, high-temperature phase. This work suggests that indium(I) and thallium(I) ionic conductors may exist, analogous to some well-known double salt conductors based on simple silver(I) and copper(I) halides. In addition, the present study demonstrates the usefulness of Raman spectroscopy in the characterization of heavy-metal ionic conductors.