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A macroazoinitiator (MAI) containing a poly(ethylene oxide) (PEO) block was used with a methyl methacrylate monomer to prepare polymer particles in ethanol/H2O solutions. The effects of the monomer/MAI ratio (RMI) and H2O content in the solutions on the molecular weight, particle diameters, and chemical structure of the resulting polymer particles were investigated. The reaction mixtures showed three kinds of states, which were milky colloid solutions, macrogels and/or precipitations, and clear solutions. The colloid solutions were obtained in the solutions with an H2O content of about 50–90 vol % and a RMI of 20–400. In the colloid solutions, core–shell nanospheres consisting of PEO shells and poly(methyl methacrylate) (PMMA) cores were predominantly obtained. In the specific conditions close to the area of gel and/or precipitation formation, particles connected about 0.5–5 μm in length were obtained. Multiblock copolymers nanospheres tended to be obtained with lower RMIs, and PMMA-PEO-PMMA tri-bloc and/or PMMA-PEO di-block copolymer nanospheres were obtained with higher RMIs. The solubility of the monomer and the generated polymer in solutions may have affected the polymerization development and the state of the products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Titanium oxide (TiO2) is popular material as a white pigment, an ultraviolet rays absorbent etc. and recently TiO2 has attracted attention as a photocatalyst. We prepared mono-dispersed needle-like TiO2 particles by hydrolysis and condensation polymerization of titanium alkoxides in methanol-rich alcohol solutions with mild conditions; at atmospheric pressure and at 20-50°C. In the case of using other alcohol rich solutions, spherical particles were obtained or any particle was not obtained. H2O concentrations in solutions also affected the shapes of the particles. Using the solvent containing ≥0.2vol% H2O, the shape of the particles obtained was not needle-like but spherical. The needle-like particles were obtained only within the case where particles were prepared in methanol-rich solutions containing ≤0.1vol% H2O. The length and the aspect ratio of the particles were increased with increasing reaction period and reaction temperature. All of the particles obtained were amorphous before heating treatment. The particles possessed anatase structure after being heat-treated at 500°C for 1h. After irradiation with UV-light to the aqueous solutions of methylene blue added with the TiO2 particles, the absorbance of methylene blue decreased. The particles after heating were active as photocatalysts for decomposition of methylene blue in aqueous solutions and photocatalytic activities were dependent on the reaction conditions.

Several new pyrazolato-3,5-dicarboxylato (pzdc) bridged dinuclear chromate(III) complexes containing linear tetradentate O-N-N-O type ligands were synthesized and structurally characterized. Among them, the X-ray structure of the eddp complex Na[Cr2(eddp)(mu-pzdc)].6H2O (eddp = ethylenediamine-N,N'-dipropionate) was determined to have a (sym-cis)-(unsym-cis) geometrical configuration with intramolecular three-center hydrogen bonds, entrapping the unfavored sym-cis configuration for the Cr(eddp) moiety as well as the favored unsym-cis one. As a pair of positional disorders, there were also found to be two conformational isomers with respect to the absolute configurations of the coordinated asymmetric nitrogen atom at the G (in-plane) ring for the unsym-cis moiety. Moreover, chiral pzdc-bridged dinuclear complexes with another type of O-N-N-O ligand, 1,2-cyclohexanediamine-N,N'-diacetate (cdda), were successfully synthesized, isolated, and characterized by column chromatographic behavior, elemental analysis, and chiroptical spectra. There were two diastereomers for Na[(R,R-cdda)Cr(mu-pzdc)Cr(S,S-cdda)] and only one isomer for Na[(R,R-cdda)Cr(mu-pzdc)Cr(R,S-cdda)] and Na[(R,R-cdda)Cr(mu-pzdc)Cr(edda)] (R,R- or S,S- and R,S-cdda = R,R-trans- or S,S-trans- and R,S-cis-1,2-cyclohexanediamine-N,N'-diacetate, and edda = ethylenediamine-N,N'-diacetate). From their circular dichroism (CD) spectra, these complexes could exhibit the delta-delta absolute configuration with ((sym-cis-R,R-cdda)-(unsym-cis-edda or S,S- or R,S-cdda)) geometrical configuration, indicating the abnormal eq-eq (N-Ceq) configuration for the R,R-cdda. The comparison among the CD spectra of the ((cdda)-(cdda)) complexes revealed that two diastereomers of the ((R,R-cdda)-(S,S-cdda)) complex correspond to the conformational isomers resulting from the difference in geometrical orientations of the secondary amine protons on two coordinated asymmetric nitrogen atoms with the opposite absolute configuration in the unsym-cis-S,S-cdda moiety. In a series of the pzdc-bridged Cr(III) complexes the anomalous conformations in two different geometrical configurations could be entrapped probably owing to stereognostic coordination through the intramolecular N-H...O hydrogen bond interaction.

The H2O2 oxidation of [Co(pyt)(en)2]2+ [1, pyt=2-pyridinethiolate(1−) ion, en=ethylenediamine] afforded the orange [Co(pyse-N,S)(en)2]2+ [2, pyse=2-pyridinesulfenate(1−) ion] complex. Irradiation of this orange complex in the solid state yielded a green complex. The molecular structure of the green complex perchlorate was determined by X-ray diffraction to be [Co(pyse-N,O)(en)2](ClO4)2 (4); linkage isomerization took place upon photolysis. The crystal data and final R value for the cocrystal (3/5) are: triclinic, P 1 , a=9.374(4) A, b=11.248(4) A, c=9.238(8) A, α=95.26(4)°, β=95.14(5)°, γ=75.75(3)°, V=938(2) A3, Z=2 and R=0.040 for 2757 unique reflections. The pyse-N,O complex has an anomalous feature in the UV–vis spectrum. It has an extra band (16 400 cm−1) on the low-energy side of the first d–d absorption band (22 200 cm−1). This band can be rationalized as a splitting component of the first d–d band generated by the anisotropic interaction of the antibonding π* orbital of the coordinating oxygen with the t2g orbitals on the cobalt center. Treatment of [Co(pyt)(en)2]2+ with excess H2O2 afforded the yellow-orange sulfinato-N,S complex, [Co(pysi-N,S)(en)2]2+ [3, pysi=2-pyridinesulfinate(1−) ion]. The molecular structure of the pysi-N,S complex was determined by X-ray diffraction to be [Co(pysi-N,S)(en)2](ClO4)2 (3), which cocrystallized with the pysi-N,O complex (5). The crystal data and final R value are: monoclinic, C2, a=28.559(8) A, b=6.960(2) A, c=10.406(3) A, β=99.90(2)°, V=2038(2) A3, Z=4 and R=0.040 for 2391 unique reflections. The pysi-N,S complex was unstable and was easily converted photochemically or thermally to the linkage-isomerized orange pysi-N,O complex (5). The sulfur atom becomes chiral (R and S) upon linkage isomerization, and two kinds of racemic salt, Λ(R)Δ(S) and Λ(S)Δ(R), were separated by fractional crystallization of the complex perchlorate. The molecular structure of the less soluble isomer (Λ(S)Δ(R)-5) of the perchlorate was determined by X-ray diffraction to be Λ(S)Δ(R)-[Co(pysi-N,O)(en)2](ClO4)2. The crystal data and final R value are: triclinic, P 1 , a=9.384(4) A, b=11.807(8) A, c=8.640(5) A, α=98.54(5)°, β=94.40(4)°, γ=96.65(5)°, V=936(2) A3, Z=2 and R=0.038 for 3061 unique reflections. The two diastereomers of Λ-[Co(pysi-N,O)(en)2]2+ were separated by SP-Sephadex column chromatography, and one of them (Λ(R)-5) was structurally characterized by X-ray crystallography. Λ(R)-[Co(pysi-N,O)(en)2](ClO4)2, which crystallizes as orthorhombic in space group P212121 with Z=4, has the cell parameters a=9.896(2) A, b=20.758(6) A, c=9.494(4) A, V=1950(2) A3. The final R value was 0.041 for 1543 unique reflections. Kinetic studies of reversible isomerization (epimerization) between Λ(R)- and Λ(S)-[Co(pysi-N,O)(en)2]2+ were performed in aqueous solutions at 60 °C. The rate constants were kΛ(R)→Λ(S)=5.5×10−6 s−1 and kΛ(S)→Λ(R)=1.7×10−6 s−1. The orange-red [Co(pyso-N,O)(en)2]2+ [6, pyso=2-pyridinesulfonate(1−) ion] complex was prepared by the reaction of cis-[Co{OS(O)2CF3}2(en)2]+ with the 2-pyridinesulfonate ligand or by the oxidation of [Co(pyse-N,O)(en)2]2+ (4) with H2O2. The molecular structure of the trifluoromethanesulfonate salt of complex 6 was determined by X-ray diffraction. [Co(pyso-N,O)(en)2](CF3SO3)2 crystallizes as monoclinic in space group P21/a with Z=4. The cell parameters are a=19.079(8) A, b=16.699(6) A, c=7.462(4) A, β=100.51(4)°, V=2338(2) A3. The final R value was 0.050 for 3966 unique reflections. The pyso ligand has the strongest ligand field strength among the ligands studied here. A series of sulfur oxidation from [Co(pyt)(en)2]2+ to [Co(pyso-N,O)(en)2]2+ is established.

New pyrazole-3,5-dicarboxylato (pzdc) chromate(III) complexes containing linear tetradentate edda (ethylenediamine-N,N‘-diacetate), trdda (trimethylenediamine-N,N‘-diacetate), or eddp (ethylenediamine-N,N‘-dipropionate) were synthesized and characterized by elemental analyses, column chromatography, 2H NMR, FAB mass spectra, and X-ray analyses. Crystallographic data for Na[Cr2(edda)2(μ-pzdc)]·5H2O (1) are monoclinic with space group P21/n, a = 11.73(1) A, b = 19.475(6) A, c = 13.229(6) A, β = 111.99(5)°, Z = 4, and a final R factor of 0.056 based on 4673 reflections. Na[Cr2(trdda)2(μ-pzdc)]·3H2O (2) crystallizes in the orthorhombic space group Fdd2, with a = 16.576(4) A, b = 29.235(6) A, c = 12.544(5) A, Z = 8, and a final R factor of 0.078 based on 2456 reflections. In both complexes two Cr(III) units were bridged by a pzdc. The complex 1 and 2 has a (sym-cis)−(unsym-cis) edda and (unsym-cis)−(unsym-cis) trdda geometrical configuration, respectively. Unlike the edda and trdda ligands, the eddp ligand for...