Complexing Power of Vitamin D3 Toward Various Metals. Potentiometric Studies of Vitamin D3 Complexes with Al3+, Cd2+, Gd3+, and Pb2+ Ions in Water–Ethanol Solution

This study reports the stability constants of complexes with vitamin D₃ and Al³⁺, Cd²⁺, Gd³⁺ and Pb²⁺ ions in a water–ethanol medium (30/70% v/v at 25.0°C). The logarithms of the overall stability constants are: ₁ = 12.4 ± 0.5, 7.6 ± 0.3, 9.33 ± 0.07, and 9.1 ± 0.5, respectively, whereas the logarithms of ₂ are 24.4 ± 0.5 (Al³⁺), 14.3 ± 0.3 (Cd²⁺), and 15.4 ± 0.5 (Pb²⁺). Gd³⁺ forms only the 1:1 complex. These values are compared to those reported previously and correlations are established between the stability constants and physical properties, such as the ionization energy.     

Multi-step regulation of anion recognition by redox-active pseudocryptand

We synthesized an artificial redox-active Fe-pseudocryptand as an anion receptor to respond to electrochemical oxidation and reduction. Spectroscopic study and X-ray crystallography showed that the assembled urea chains and the isocyanuric platform generate an anion-binding cavity through favorable multiple hydrogen bonds and anion-π interactions. As the positive charge of the Fe center increases, the anion affinity is effectively increased due to an enhanced electrostatic interaction between the Fe atom and the anionic guest. This is the first efficient multi-step regulation of Cl⁻ selective anion recognition by the redox-active pseudocryptand.     

Stability of recombinant green fluorescent protein (GFPuv) in glucose solutions at different concentrations and pH values

The stability at room temperature (25°C) of recombinant green fluorescent protein (GFPuv), expressed by Escherichia coli cells and isolated by three-phase partitioning extraction with hydrophobic interaction column, was studied. The GFPuv was diluted in buffered (each 10 mM: Tris-HCl, pH 8.0; phosphate, pH 6.0 and 7.0 and acetate, pH 5.0) and in unbuffered (water for injection [WFI]; pH 6.70 ± 0.40) glucose solutions (from 1.5 to 50%). By assaying the loss of fluorescence intensity as a measure of denaturation, the stability of GFPuv in these solutions was evaluated relative to glucose concentration, pH, osmolarity, density, conductivity, and viscosity. The extent of protein denaturation (loss of fluorescence intensity) was expressed in decimal reduction time (D-value), the time required to reduce 90% of the initial fluorescence intensity of GFPuv. The D-value between 56 and 83 h of GFPuv at 1.5–15% glucose in WFI was equivalent to 20–30% glucose in a phosphate. The stability of GFPuv in 50% glucose was similar for all buffers studied and four times higher than in WFI. By the convenient measure of fluorescence intensity, GFPuv can be used as an indicator to report the extent of denaturation rates of other proteins in glucose solutions.     

catena‐Poly[[chloro­dipyridine­manganese(II)]‐μ3‐6‐oxo‐1,6‐dihydro­pyridine‐2‐carboxyl­ato]

The title one‐dimensional chain polymer complex, [Mn(C₆H₄NO₃)Cl(C₆H₅N)₂]_n, was isolated from the reaction of MnCl₂ with 6‐oxo‐1,6‐dihydro­pyridine‐2‐carboxylic acid (HpicOH) in pyridine. The asymmetric unit contains one [Mn(HPicO)Cl(py)₂] moiety (py is pyridine), with the (HpicO)⁻ ligand acting in a tridentate manner via the two carboxyl­ate O atoms and the pyridone O atom. The operation of inversion centres generates eight‐ and 14‐membered rings and, in conjunction with an a‐axis translation, leads to an infinite chain extending along [100]. The Mn⋯Mn separations in this chain are 5.1069 (6) and 7.1869 (6) Å. The Mn^II atom has a distorted octahedral coordination, with trans‐axial pyridine ligands and with three O atoms and the Cl atom in the equatorial plane. The conformation of the 14‐membered ring is stabilized by pairs of inversion‐related N—H⋯O hydrogen bonds.     

Preparation and Function of Poly(acrylic acid)s Modified by Supramolecular Complex Composed of Porphinatoiron and a Cyclodextrin Dimer That Bind Diatomic Molecules (O2 and CO) in Aqueous Solution

Poly(acrylic acid) (PAA) is modified by 5‐(4‐β‐alanylaminophenyl)‐10,15,20‐tris(4‐sulfonatophenyl) porphinatoiron(III) to yield iron porphyrin‐bearing PAAs (FeP(n)s) through a condensation reaction. FeP(n)s were further functionalized by Py3CD, which is a per‐O‐methylated β‐cyclodextrin (CD) dimer with a pyridine linker and includes the porphyrin pendants to form ferric hemoCD‐P(n)s. Ferrous hemoCD‐P(3), having three porphyrin chromophores in a polymer chain, is shown to bind molecular oxygen (P_1/2=7.9±1.4 Torr) in aqueous solution at pH 7.0 and 25 °C, affording oxy‐hemoCD‐P(3). Oxy‐hemoCD‐P(3) is biphasically autoxidized to ferric hemoCD‐P(3), with 27 % of the dioxygen adducts being rapidly oxidized. The rate of autoxidation of oxy‐hemoCD‐P(15), having 15 porphyrin chromophores in a polymer chain, was much faster than that of oxy‐hemoCD‐P(3), thus suggesting self‐catalyzed autoxidation of oxy‐hemoCD‐P(n)s. Oxy‐hemoCD‐P(n)s are markedly stabilized by catalase, thereby indicating that hydrogen peroxide generated from oxy‐hemoCD‐P(n) accelerates the autoxidation. Most of the hemoCD‐P(3) molecules injected into the femoral vein of a rat remained in the body, though about 16 % of the hemoCD‐P(3) molecules were excreted in the urine as a carbon monoxide adduct.     

Intermolecular vibrational mode of the benzoic acid dimer in solution observed by terahertz time-domain spectroscopy

The low-frequency modes of the benzoic acid (BA) dimer and its analogues in carbon tetrachloride (CCl(4)) have been investigated by terahertz time-domain spectroscopy. The solute spectrum is obtained by subtracting the solvent contribution from that of the solution. The difference spectrum of BA in CCl(4) has a broad band with a peak at 68 cm(-1). To assign the observed band, the spectrum is compared with spectra of other aromatic molecules, such as benzene and phenol in addition to p-methyl BA and deuterated BA species (BA-d(OH) and BA-d(5)) in CCl(4). The band at 68 cm(-1) is assigned to the cogwheel mode of the BA dimer. Density functional theory calculations also support this assignment. Finally, spectral lineshape analysis based on the multimode Brownian oscillator model is applied to the THz spectra for all the samples.     

Low-frequency modes of the benzoic acid dimer in chloroform observed by the optical Kerr effect

The low frequency Raman spectral density associated with the intermolecular hydrogen-bonding interaction of benzoic acid in chloroform was investigated through the ultrafast optically-heterodyne-detected optical Kerr effect. The low-frequency solute Raman spectrum was obtained by Fourier transform analysis and subtraction of the solvent spectrum from the solution spectrum. The resulting difference spectrum has a broad band below 150 cm(-1) with a peak at around 80 cm(-1). Previous studies of aromatic liquids suggest that the origin of such a low-frequency band is librational motion, although intermolecular hydrogen-bonding modes in benzoic acid may also contribute. To clarify these contributions to the low-frequency band, methyl benzoate was used to estimate the librational component; its structure is similar to benzoic acid, but it forms no intermolecular hydrogen bonds. Both librational and intermolecular modes were found to contribute to the low-frequency Raman spectrum of the dimer and thus can be separated. These experimental results were compared with the results of density functional theory calculations. In addition, the effect of deuteration on the Raman spectrum was also investigated.     

1,2,3-Triazol-5-ylidene-palladium complex catalyzed Mizoroki-Heck and Sonogashira coupling reactions

The bis-1,4-dimesityl-1,2,3-triazol-5-ylidene-palladium complex (1a) successfully catalyzes the Mizoroki-Heck and Sonogashira coupling reactions with aryl bromides to give the corresponding alkenes and alkynes, respectively, in good to excellent yields. In the Mizoroki-Heck reaction, electron-rich, electron-poor, and functionalized aryl bromides and alkenes are tolerated, while the substrates are limited to electron-poor aryl halides in the Sonogashira coupling reaction. The palladium complex also catalyzes cross-coupling reactions with aryl chlorides to give higher yields of products than does the bis-IMes-Pd complex analogue (2), under specific conditions.     

Oxidation of disulfides with electrophilic halogenating reagents: concise methods for preparation of thiosulfonates and sulfonyl halides

The reaction of aromatic or benzylic disulfides with 2.5 equiv of Selectfluor™ in acetonitrile/water (10:1) at room temperature efficiently produced the corresponding thiosulfonates. Conversely, the reaction of disulfides with 6.5 equiv of Selectfluor™ or thiosulfonates with 4.5 equiv of Selectfluor™ in refluxing acetonitrile/water (10:1) provided sulfonyl fluorides in high yields. Accufluor™ and FP-T300™ are also effective in preparing sulfonyl fluorides from disulfides under the similar reaction conditions. Sulfonyl chlorides or sulfonyl bromides were effectively obtained from the reaction of disulfides with 6 equiv of either N-chlorosuccinimide or N-bromosuccinimide in acetonitrile/water (10:1) at room temperature. Some other electrophilic chlorinating or brominating reagents are also able to be used instead of N-chlorosuccinimide or N-bromosuccinimide for the syntheses of sulfonyl halides from disulfides. These reactions of disulfides with electrophilic halogenating reagents are convenient methods to prepare thiosulfonates and sulfonyl halides.