Electronic spectra of pure uranyl(V) complexes: characteristic absorption bands due to a U(V)O2+ core in visible and near-infrared regions

To clarify the electronic spectral properties of uranyl(V) complexes systematically, we measured absorption spectra of three types of pure uranyl(V) complexes: [U(V)O2(dbm)2DMSO]-, [U(V)O2(saloph)DMSO]-, and [U(V)O2(CO3)3]5- (dbm = dibenzoylmethanate, saloph = N,N'-disalicylidene-o-phenylenediaminate, DMSO = dimethyl sulfoxide). As a result, it was found that these uranyl(V) complexes have characteristic absorption bands in the visible-near-infrared (NIR) region, i.e., at around 640, 740, 860, 1470, and 1890 nm (molar absorptivity, epsilon = 150-900 M(-1).cm(-1)) for [U(V)O2(dbm)2DMSO]-, 650, 750, 900, 1400, and 1875 nm (epsilon = 100-300 M(-1).cm(-1)) for [U(V)O2(saloph)DMSO]-, and 760, 990, 1140, 1600, and 1800 nm (epsilon = 0.2-3.6 M(-1).cm(-1)) for [U(V)O2(CO3)3]5-. These characteristic absorption bands of the uranyl(V) complexes are attributable to the electronic transitions in the U(V)O2+ core because the spectral features are similar to each other despite the differences in the ligands coordinated to the equatorial plane of the U(V)O2+ moiety. On the other hand, the epsilon values of [U(V)O2(CO3)3]5- are quite smaller than those of [U(V)O2(dbm)2DMSO]- and [U(V)O2(saloph)DMSO]-. Such differences can be explained by the different coordination geometries around the center uranium in these uranyl(V) complexes. Consequently, the absorption bands of the uranyl(V) complexes in visible-NIR region were assigned to f-f transitions in the 5f1 configuration.     

IR spectroelectrochemical study on UVO2+ complex: first evidence for weakening of U[double bond]O bond strength in uranyl moiety with reduction from U(VI) to U(V)

We have obtained the first evidence that the U[double bond]O bond strength in uranyl moiety is weakened with the reduction from U(VI)O(2)(2+) to U(V)O(2)(+) from the IR spectroelectrochemical study on U(VI)O(2)(saloph)DMSO and [U(V)O(2)(saloph)DMSO](-) (saloph = N,N'-disalicylidene-o-phenylenediaminate, DMSO = dimethyl sulfoxide) complexes with the thin layer electrode cell for IR measurements.     

Miscibility of polymer blends studied by a simplified method of data analysis using light heating modulated temperature DSC

A simple method of application of light heating modulated temperature DSC to a study of miscibility of polymer blends has been developed. In this method only the sample was measured and the standard materials were not used. The total heat flow, the complex heat capacity, the reversing and non-reversing heat flows were obtained as values measured from those quantities in hypothetical glassy state at T>T_g. The values of the hypothetical glassy state were calculated by extrapolation from T<T_g. The present method gives relative values but useful information can be obtained from the results. Some results from miscible and immiscible polymer blends are shown. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of the incorporation of amino groups in a glucose-responsive polymer complex having phenylboronic acid moieties

A novel polymer complex system sensitive to glucose was studied as a candidate material for formulating a chemically regulated insulin release system. A ternary copolymer of N-vinyl-2-pyrrolidone (NVP), 3-acrylamidophenylboronic acid (AAm-PBA) and N,N-dimethylaminopropylacrylamide (DMAPAA) (poly(NVP-co-PBA-co-DMAPAA)) was synthesized by radical copolymerization. The phenylboronic acid group in this copolymer serves as a glucose sensor moiety. Poly(NVP-co-PBA-co-DMAPAA) was soluble in water in the pH range of 3–12, in sharp contrast to a binary copolymer of NVP and AAm-PBA (poly(NVP-co-PBA)) which showed solubility only under alkaline aqueous conditions, where the boronic acid group is in a tetrahedral ionized form. The protonated amino group in poly(NVP-co-PBA-DMAPAA) contributed to increase the solubility of the polymer under physiological and acidic aqueous conditions. Furthermore, poly(NVP-co-PBA-co-DMAPAA) formed a stable polymer complex gel with poly(vinyl alcohol) (PVA) in pH 7.4 phosphate buffered solution due to the formation of a covalent linkage between the boronic acid groups in ternary copolymer and diol units in PVA. The release of myoglobin as model protein from the complex gel was increased immediately after the addition of glucose, due to the transition of gel into sol state, indicating the feasibility of this complex gel as a candidate material for a glucose-responsive delivery system for insulin.     

Reactions of aliphatic fluoro-alcohols with CHClF2 at atmospheric pressure

The reactions of aliphatic fluoro-alcohols with chlorodifluoromethane (CHClF₂) at atmospheric pressure were examined. In the reaction of CF₃CF₂CH₂OH, the difluoromethylated ether was obtained in moderate yield by using ethers such as 1,4-dioxane, diglyme and THF, or their mixtures with water as a reaction solvent. While acetal and orthoformate were also produced, the selectivity of the difluoromethylated ether could be improved by adding water to the reaction. The effect of water could be explained by the reaction mechanism.     

Static and dynamic behavior of 2:1 inclusion complexes of cyclodextrins and charged porphyrins in aqueous organic media

Two heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TMe-beta-CD) molecules strongly include the peripheral substituents at the 5- and 15-positions of the charged meso-tetrasubstituted porphyrins, PorSub(4) [TPPS(4) (Sub = p-C(6)H(4)-SO(3)(-)), TPPOC3PS (p-C(6)H(4)-O-(CH(2))(3)-p-C(6)H(4)-SO(3)(-)), TCPP (Sub = p-C(6)H(4)-CO(2)(-)), and TPPOC3Py (p-C(6)H(4)-O-(CH(2))(3)-Py(+)Br(-)), where Py(+) = N-alkylpyridinium] in aqueous ethylene glycol. The binding constants (K(1) and K(2)) and the rate constants (k(1) and k(2)) for formation of the 1:1 and 2:1 complexes of TMe-beta-CD and PorSub(4) were determined. Both the binding constants and the rate constants for anionic TPPS(4), TCPP, and TPPOC3PS were much larger than those for cationic TPPOC3Py. The smaller k(1) and k(2) values for TPPOC3Py indicate a higher barrier for penetration of a cationic guest into the TMe-beta-CD cavity. The methyl groups at the rims and the cavity wall of the host are positively polarized due to the inductive effect of the ethereal oxygens. The positively polarized rims and interior of the host cavity should prevent the penetration of the cationic substituent of TPPOC3Py into the TMe-beta-CD cavity. The 2:1 TMe-beta-CD-PorSub(4) complexes are extraordinary stable in aqueous solutions, even in the case of cationic TPPOC3Py. Formation of both 1:1 and 2:1 complexes is promoted by negative and large enthalpy changes, suggesting a strong van der Waals interaction as the main binding force.     

Dispersity of stratum corneum in the mixed aqueous solutions of binary mixtures between N,N-dimethyldodecylamine oxide and sodium dodecyl sulfate or two terpenes

Solubilization of cholesterol, differential scanning calorimetric (DSC), nuclear magnetic resonance (NMR) and dynamic light scattering (DLS) measurements were performed in order to reveal the dispersion mechanisms of stratum corneum (SC) into each intact corneocytes in the following systems: (1) in the aqueous mixed solutions of sodium dodecyl sulfate (SDS) and N,N-dimethyldodecylamine oxide (C₁₂DMAO); (2) in the aqueous micellar solutions of C₁₂DMAO containing solubilized α-terpineol (α-T); and (3) in the aqueous micellar solutions of C₁₂DMAO containing solubilized limonene. The intercellular lamellar structure of SC was revealed to be disrupted and/or removed in all these solutions. However, considering the micellar sizes and the interaction among molecules in micelle, the dispersion mechanisms in these three systems were different each other. The three dispersion mechanisms of SC were estimated and discussed on the basis of the results of solubilization, DSC, NMR and DLS, respectively.