Direct Hydroxylation of Benzene with Hydrogen Peroxide Using Fe Complexes Encapsulated into Mesoporous Y-Type Zeolite.

Mesoporous Y-type zeolite (MYZ) was prepared by an acid and base treatment of commercial Y-type zeolite (YZ). The mesopore volume of MYZ was six times higher than that of YZ. [Fe(terpy)2]2+ complexes encapsulated into MYZ and YZ with different Fe contents (Fe(X)L-MYZ and Fe(X)L-YZ; X is the amount of Fe) were prepared and characterized. The oxidation of benzene with H2O2 using Fe(X)L-MYZ and Fe(X)L-YZ catalysts was carried out; phenol was selectively produced with all Fe-containing zeolite catalysts. As a result, the oxidation activity of benzene increased with increasing iron complex content in the Fe(X)L-MYZ and Fe(X)L-YZ catalysts. The oxidation activity of benzene using Fe(X)L-MYZ catalyst was higher than that using Fe(X)L-YZ. Furthermore, adding mesopores increased the catalytic activity of the iron complex as the iron complex content increased.

Regioselective and Stereospecific Dehydrogenative Annulation Utilizing Silylium Ion-Activated Alkenes.

Treatment of dialkylbenzylsilanes (1) with trityl tetrakis(pentafluorophenyl)borate (TPFPB) afforded the corresponding silylium ions in equilibrium with their intra- or intermolecular π-complexes, which underwent dehydrogenative annulation with various alkenes to form 1,2,3,4-tetrahydro-2-silanaphthalenes (4) in up to 82% isolated yield. Sterically bulkier substituents on the silicon atom tended to increase the yield of cyclic products 4. The annulation products retained the stereochemistry in cases of the reactions using internal alkenes. The use of diisopropyl(1-naphthyl)silane (2) instead of 1 also resulted in annulation to obtain the 2,3-dihydro-1-sila-1H-phenalene derivatives 6. Electrophilic aromatic substitution at the 8-position was predominant, despite the two potentially reactive positions on the naphthyl group. The steric hindrance of the naphthyl group prevented addition of the cis-alkene to the silylium ion, which would considerably decrease yields of the desired products from 2 compared to those from 1.

Biobased polymers: synthesis of graft copolymers and comb polymers using lactic acid macromonomer and properties of the product polymers.

For developing broader application of biobased polymers, graft copolymers and comb polymers having poly(lactic acid) (PLA) side chains have been synthesized by using a macromonomer technique. PLA macromonomers (MMm) having a methacryloyl polymerizable group with different PLA chain length with an average length m = 4, 6, 8, 12, 18, and 30 were prepared via ring-opening polymerization of l-lactide using hydroxyethyl methacrylate (HEMA) initiator catalyzed by Sn(Oct)(2). Radical polymerization behaviors of these macromonomers were examined. Radical copolymerization of MMm (m = 4, 6, and 8), with vinyl monomers like n-butyl methacrylate (BMA) and n-butyl acrylate (BA) in water as the reaction medium, gave stable miniemulsions of poly[n-butyl (meth)acrylate-graft-lactic acid]s [PB(M)A-g-PLAm]. MMm with m value higher than 12, however, gave aggregate products in a minor amount besides miniemulsions in a major amount, producing not a stable emulsion system of graft copolymers. The solution copolymerization, on the other hand, produced a wider variety of the graft copolymers, where a wider range of MMm (even m ≥ 12) can be employed. In a 1,4-dioxane solution, the radical copolymerization of MMm with BMA and methyl methacrylate (MMA) gave various graft copolymers [PB(M)MA-g-PLAm]. A new type of comb polymers (PMMm) having PLAm as pendant side chains were obtained by radical homopolymerization of MMm in a 1,4-dioxane solution. The graft copolymers and comb polymers obtained here are amorphous. Physical properties of the polymers from miniemulsions suggested them to be applicable for coatings or elastic materials which are environmentally desirable as a new class of biobased polymers. In addition, the present approach provided fundamental information on relationships between the length of PLA side chain and the bulk properties of the product polymers.

[Evaluation of shortened protocol of graph plot method with ¹²³I-IMP].

The (123)I-IMP Graph Plot is a convenient method of analyzing cerebral blood flow without blood sampling. Data acquisition requires 45 minutes after the infusion of (123)I-IMP because the method is matched to the protocol of autoradiography (conventional method). However, we think that those protocols do not have to be matched because those theories are different. Therefore, we contrived a protocol for shortening that time by beginning SPECT data acquisition earlier and shortening the acquisition time compared to the conventional method. We compared count ratios of the decreased area to an area of the healthy side, quantitative values, and results of statistical analysis of the shortened protocol and the conventional method for cases of cerebral infarction and of dementia with Lewy bodies (DLB). Some count ratios of the shortened protocol were inferior to those of the conventional method, but the degrees did not affect the clinical diagnosis. In the other areas and cases also, the differences did not affect the clinical diagnosis. In addition to the results of this study, some previous reports have described that early SPECT images after infusion show the true cerebral blood flow. Therefore, we judged that this shortened protocol can be used as a clinical protocol.

Potential hippocampal region atrophy in diabetes mellitus type 2: a voxel-based morphometry VSRAD study.

PURPOSE: Among diabetes mellitus type 2 (DM2) patients, the frequency of cognitive dysfunction is higher and the relative risk of Alzheimer's disease (AD) is approximately twice that of nondiabetics. Cognitive impairment symptoms of AD are induced by limbic system dysfunction, and an early-stage AD brain without dementia has the potential for atrophy in the hippocampal region. In this study, we estimated potential hippocampal region atrophy in DM2 and pursued the association between DM2 and cognitive impairment/AD. MATERIALS AND METHODS: Voxel-based morphometry analysis was performed in 28 diabetics (14 men, 14 women; ages 59-79 years, mean 70.7 years) and 28 sex- and agematched (+/-1 year) nondiabetics. Severity of gray matter loss in the hippocampal region and whole brain were investigated. Group analysis was performed using twotailed unpaired t-test; significance was assumed with less than 1% (P < 0.01) of the critical rate. RESULTS: There was a significant difference between diabetics and nondiabetics regarding the severity of hippocampal region atrophy and whole-brain atrophy. Only diabetics showed a positive correlation for severity of hippocampal region atrophy and whole-brain atrophy (rs = 0.69, P < 0.0001). CONCLUSION: Aged DM2 patients have the potential for hippocampal region atrophy, and its dysfunction can be related to the expression of a cognitive impairment that resembles AD.

Synthesis of a dialuminum-substituted silicotungstate and the diastereoselective cyclization of citronellal derivatives.

A novel dialuminum-substituted silicotungstate TBA(3)H[gamma-SiW(10)O(36){Al(OH(2))}(2)(mu-OH)(2)] x 4 H(2)O (1, TBA = tetra-n-butylammonium) was synthesized by the reaction of the potassium salt of [gamma-SiW(10)O(36)](8-) (SiW10) with 2 equiv of Al(NO(3))(3) in an acidic aqueous medium. It was confirmed by the X-ray crystallographic analysis that compound 1 was a monomer of the gamma-Keggin dialuminum-substituted silicotungstate with the {Al(2)(mu-OH)(2)} diamond core. The cluster framework of 1 maintained the gamma-Keggin structure in the solution states. The reaction of 1 with pyridine yielded TBA(3)[(C(5)H(5)N)H][gamma-SiW(10)O(36){Al(C(5)H(5)N)}(2)(mu-OH)(2)] x 2 H(2)O (2), and the molecular structure was successfully determined by the X-ray crystallographic analysis. In compound 2, two of three pyridine molecules coordinated to the axial positions of aluminum centers and one of them existed as a pyridinium cation, showing that compound 1 has two Lewis acid sites and one Brønsted acid site. Compound 1 showed high catalytic activity for the intramolecular cyclization of citronellal derivatives such as (+)-citronellal (3) and 3-methylcitronellal (4) without formation of byproduct resulting from etherification and dehydration. For the 1-catalyzed cyclization of 3, the diastereoselectivity toward (-)-isopulegol (3a) reached ca. 90% and the value was the highest level among those with reported systems so far. The reaction rate for the 1-catalyzed cyclization of 3 decreased by the addition of pyridine, and the cyclization hardly proceeded in the presence of 2 equiv of pyridine with respect to 1. On the other hand, the reaction rate and diastereoselectivity to 3a in the presence of 2,6-lutidine were almost the same as those in the absence. Therefore, the present cyclization is mainly promoted by the Lewis acid sites (aluminum centers) in 1. DFT calculations showed that the formation of the transition state to produce 3a is sterically and electronically more favorable than the other three transition states for the present 1-catalyzed cyclization of 3.

H-atom abstraction reaction for organic substrates via mononuclear copper(II)-superoxo species as a model for DbetaM and PHM.

Hydrogen atom abstraction reactions have been implicated in oxygenation reactions catalyzed by copper monooxygenases such as peptidylglycine alpha-hydroxylating monooxygenase (PHM) and dopamine beta-monooxygenase (DbetaM). We have investigated mononuclear copper(I) and copper(II) complexes with bis[(6-neopentylamino-2-pyridyl)methyl][(2-pyridyl)methyl]amine (BNPA) as functional models for these enzymes. The reaction of [Cu(II)(bnpa)]2+ with H2O2, affords a quasi-stable mononuclear copper(II)-hydroperoxo complex, [Cu(II)(bnpa)(OOH)]+ (4) which is stabilized by hydrophobic interactions and hydrogen bonds in the vicinity of the copper(II) ion. On the other hand, the reaction of [Cu(I)(bnpa)]+ (1) with O2 generates a trans-mu-1,2-peroxo dicopper(II) complex [Cu(II)2(bnpa)2(O2(2-]2+ (2). Interestingly, the same reactions carried out in the presence of exogenous substrates such as TEMPO-H, produce a mononuclear copper(II)-hydroperoxo complex 4. Under these conditions, the H-atom abstraction reaction proceeds via the mononuclear copper(II)-superoxo intermediate [Cu(II)(bnpa)(O2-)]+ (3), as confirmed from indirect observations using a spin trap reagent. Reactions with several substrates having different bond dissociation energies (BDE) indicate that, under our experimental conditions the H-atom abstraction reaction proceeds for substrates with a weak X-H bond (BDE < 72.6 kcal mol(-1)). These investigations indicate that the copper(II)-hydroperoxo complex is a useful tool for elucidation of H-atom abstraction reaction mechanisms for exogenous substrates. The useful functionality of the complex has been achieved via careful control of experimental conditions and the choice of appropriate ligands for the complex.

Synthesis and catalysis of di- and tetranuclear metal sandwich-type silicotungstates [(gamma-SiW10O36)2M2(mu-OH)2]10- and [(gamma-SiW10O36)2M4(mu4-O)(mu-OH)6]8- (M = Zr or Hf).

The di- and tetranuclear metal sandwich-type silicotungstates of Cs10[(gamma-SiW10O36)2{Zr(H2O)}2(mu-OH)2] x 18 H2O (Zr2, monoclinic, C2/c (No. 15), a = 25.3315(8) A, b = 22.6699(7) A, c = 18.5533(6) A, beta = 123.9000(12) degrees, V = 8843.3(5) A(3), Z = 4), Cs10[(gamma-SiW10O36)2{Hf(H2O)}2(mu-OH)2] x 17 H2O (Hf2, monoclinic, space group C2/c (No. 15), a = 25.3847(16) A, b = 22.6121(14) A, c = 18.8703(11) A, beta = 124.046(3) degrees, V = 8974.9(9) A(3), Z = 4), Cs8[(gamma-SiW10O36)2{Zr(H2O)}4(mu4-O)(mu-OH)6] x 26 H2O (Zr4, tetragonal, P4(1)2(1)2 (No. 92), a = 12.67370(10) A, c = 61.6213(8) A, V = 9897.78(17) A(3), Z = 4), and Cs8[(gamma-SiW10O36)2{Hf(H2O)}4(mu4-O)(mu-OH)6] x 23 H2O (Hf4, tetragonal, P4(1)2(1)2 (No. 92), a = 12.68130(10) A, c = 61.5483(9) A, V = 9897.91(18) A(3), Z = 4) were obtained as single crystals suitable for X-ray crystallographic analyses by the reaction of a dilacunary gamma-Keggin silicotungstate K8[gamma-SiW10O36] with ZrOCl2 x 8 H2O or HfOCl2 x 8 H2O. These dimeric polyoxometalates consisted of two [gamma-SiW10O36](8-) units sandwiching metal-oxygen clusters such as [M2(mu-OH)2](6+) and [M4(mu4-O)(mu-OH)6](8+) (M = Zr or Hf). The dinuclear zirconium and hafnium complexes Zr2 and Hf2 were isostructural. The equatorially placed two metal atoms in Zr2 and Hf2 were linked by two mu-OH ligands and each metal was bound to four oxygen atoms of two [gamma-SiW10O36](8-) units. The tertanuclear zirconium and hafnium complexes Zr4 and Hf4 were isostructural and consisted of the adamantanoid cages with a tetracoordinated oxygen atom in the middle, [M4(mu4-O)(mu-OH)6](8+) (M = Zr or Hf). Each metal atom in Zr4 and Hf4 was linked by three mu-OH ligands and bound to two oxygen atoms of the [gamma-SiW10O36](8-) unit. The tetra-nuclear zirconium and hafnium complexes showed catalytic activity for the intramolecular cyclization of (+)-citronellal to isopulegols without formation of byproducts resulting from etherification and dehydration. A lacunary silicotungstate [gamma-SiW10O34(H2O)2](4-) was inactive, and the isomer ratio of isopulegols in the presence of MOCl2 x 8 H2O (M = Zr or Hf) were much different from that in the presence of tetranuclear complexes, suggesting that the [M4(mu4-O)(mu-OH)6](8+) core incorporated into the POM frameworks acts as an active site for the present cyclization. On the other hand, the reaction hardly proceeded in the presence of dinuclear zirconium and hafnium complexes under the same conditions. The much less activity is possibly explained by the steric repulsion from the POM frameworks in the dinuclear complexes.

Co(III) complexes with N2(SO)2-type equatorial planar ligands similar to the active center of nitrile hydratase: role of the sulfenate group in the enzymatic reaction.

In order to gain an understanding of the role of the sulfenyl group of nitrile hydratase (NHase), a new Co(III) complex with a sulfenyl-type ligand (LC=O:N2(SO)2), Na[CoIII(LC=O:N2(SO)2)(tBuNC)2] (2), was synthesized. The compound includes two amide groups, two sulfenate sulfurs in the equatorial plane, and two tBuNC molecules in the axial positions. Characterization of the compound was performed by UV-vis spectroscopic, IR spectral, thermogravimetric (TG), and X-ray structure analytical methods. The results are discussed in the context of Co(III) complexes containing the corresponding sulfur-type (LC=O:N2S2) (1) and sulfinyl-type ligands (LC=O:N2(SO2)2) (3). Complex 2 crystallized with the formula Na[CoIII(LC=O:N2(SO)2)(tBuNC)2].urea.2H2O.0.5EtOH. The X-ray structure revealed that the Co(III) complex has an octahedral geometry with Co-S=av. 2.221 A, Co-N=av. 1.998 A, and Co-C=av. 1.87 A. The sulfenyl oxygen and amidate carbonyl oxygen are linked to urea, water, EtOH, and Na+ and participate in a hydrogen-bond and an electrostatic interaction. IR and TG measurements demonstrated that the coordination strength of tBuNC to the Co atom increases as follows: 1<2<3. Complex 2 has almost the same stability as 3 in all solutions tested, although 1 exhibits a release of axial ligands in nonaqueous solutions. DFT calculations for 1, 2, and 3 demonstrated that Milliken atomic charges of the Co(III) centers are +1.466, +1.536, and +1.542, respectively, indicating that the extent of oxidation of the sulfur atoms increases the Lewis acidity of the Co(III) centers. Interestingly, the solution-state IR spectrum of 2 exhibits a solvent-dependent S-O stretching frequency. The frequency decreases with an increase in the electrophilicity (acceptor number) of the solvent. This solvent dependence was not observed for 3, which has a sulfinate (SO2) group, suggesting that the sulfenyl oxygen atom has nucleophilic character and promotes strong binding of the tBuNC molecule to lower the reaction barrier. These findings may suggest that the sulfenate oxygen in native NHase acts as a base (proton acceptor) and contributes to the activation of a water molecule and/or nitrile molecule.

Synthesis and structural characterization of a gamma-Keggin-type dimeric silicotungstate with a bis(mu-hydroxo) dizirconium core [(gamma-SiW10O36)2Zr2(mu-OH)2]10-.

A novel dinuclear zirconium sandwich-type silicotungstate cluster of [(gamma-SiW(10)O(36))(2)Zr(2)(mu-OH)(2)](10-) (1) was synthesized by the reaction of a divacant lacunary gamma-Keggin silicotungstate [gamma-SiW(10)O(36)](8-) with ZrOCl(2).8H(2)O. The anion consisted of two [gamma-SiW(10)O(36)](8-) units sandwiching a diamond Zr(2)(mu-OH)(2) core, and each zirconium atom in 1 was six-coordinated to two mu-OH ligands and four oxygen atoms of two [gamma-SiW(10)O(36)](8-) units. The Zr(2)(mu-OH)(2) core in 1 reacted with methanol to give the corresponding monomethoxo derivative [(gamma-SiW(10)O(36))(2)Zr(2)(mu-OH)(mu-OCH(3))](10-) (2).

Mu-eta1:eta1-peroxo-bridged dinuclear peroxotungstate catalytically active for epoxidation of olefins.

The reaction of the dinuclear peroxotungstate, [(n-C4H9)4N]2[{WO(O2)2}2(mu-O)] (II), with H2O2 gives the novel mu-eta1:eta1-peroxo-bridging dinuclear tungsten species, [(n-C4H9)4N]2[{WO(O2)2}2(mu-O2)] (I), which has been characterized by X-ray crystallography, elemental analysis, IR, Raman, UV-vis, and 183W NMR. Only I is active for the epoxidation of cyclic, internal, and terminal olefins, whereas II is inactive for each. The low XSO (XSO=(nucleophilic oxidation)/(total oxidation)) value of I (0.18+/-0.02) in comparison with that of II (0.39+/-0.01) for the stoichiometric oxidation of thianthrene 5-oxide, which is a mechanistic probe for determining the electronic character of an oxidant, reveals that I is more electrophilic than II. On the basis of the kinetic and spectroscopic results, the catalytic epoxidation proceeds by the reaction of I with an olefin to form II and the corresponding epoxide followed by the regeneration of I by the reaction of II with H2O2.

Mononuclear copper(II)-hydroperoxo complex derived from reaction of copper(I) complex with dioxygen as a model of DbetaM and PHM.

A mononuclear copper(II)-hydroperoxo species has been generated by the reaction of Cu(I)-H2BPPA complex with dioxygen, which illustrates the enzymatic reaction process of the CuB site in the DbetaM and PHM.

Preparation, structure characterization, and oxidation activity of ruthenium complexes with tripodal ligands bearing noncovalent interaction sites.

Ruthenium(II/III) complexes with tripodal tris(pyridylmethyl)amine ligands bearing one, two, or three pivalamide groups (MPPA, BPPA, TPPA: amide-series ligands) or neopentylamine ones (MNPA, BNPA, TNPA: amine-series ligands) at the 6-position of the pyridine ring have been synthesized and structurally characterized. The X-ray structure analyses of the single crystals of these complexes reveal that they complete an octahedral geometry with the tripodal ligand and some monodentate ligands. The amide-series ligands prefer to form a Ru(II) complex, while the amine-series ones give a Ru(III) complex. In the presence of PhIO oxidant, the catalytic activities for epoxidation of olefins, hydroxylation of alkane, and dehydrogenation of alcohol have been investigated using the six ruthenium complexes [Ru(II)(tppa)Cl(2)] (1), [Ru(III)(tnpa)Cl(2)]PF(6) (2), [Ru(II)(bppa)Cl]PF(6) (3), [Ru(III)(bnpa)Cl(2)]PF(6) (4), [Ru(II)(mppa)Cl]PF(6) (5), and [Ru(III)(mnpa)Cl(2)]PF(6) (6). Among them, the amide-series complexes, 1, 3, and 5, showed a higher epoxidation activity in comparison with the amine-series ones, 2, 4, and 6. On the other hand, the latter showed a higher reactivity for hydroxylation, allylic oxidation, and C=C bond cleavage reactions compared with the former. Such a complementary reactivity is interpreted by the character of the ruthenium-oxo species involving electronically equivalent formulas, Ru(V)=O and Ru(IV)-O.

Steric and hydrogen-bonding effects on the stability of copper complexes with small molecules.

A series of the copper(II) complexes with tripodal tetradentate tris(pyridyl 2-methyl)amine-based ligands possessing the hydrogen-bonding 6-aminopyridine units (tapa, three amino groups; bapa, two amino groups; mapa, one amino group) have been synthesized, and their copper(II) complexes with a small molecule such as dioxygen and azide have been studied spectroscopically and structurally. The reaction of their Cu(II) complexes with NaN(3) have given the mononuclear copper complexes with azide in an end-on mode, [Cu(tapa)(N(3))]ClO(4) (1a), [Cu(bapa)(N(3))]ClO(4) (2a), [Cu(mapa)(N(3))]ClO(4) (3a), and [Cu(tpa)(N(3))]ClO(4) (4a) (tpa, no amino group). The crystal structures have revealed that the coordination geometries around the metal centers are almost a trigonal-bipyramidal rather than a square-planar except for 1a with an intermediate between them. The UV-vis and ESR spectral data indicate that the increase of NH(2) groups of ligands causes the structural change from trigonal-bipyramidal to square-pyramidal geometry, which is regulated by a combination of steric repulsion and hydrogen bond. The steric repulsion of amino groups with the azide nitrogen gives rise to elongation of the Cu-N(py) bonds, which leads to the positive shift of the redox potentials of the complexes. The hydrogen bonds between the coordinated azide and amino nitrogens (2.84-3.05 A) contribute clearly to the fixation of azide. The Cu(I) complexes with bapa and mapa ligands have been obtained as a precipitate, although that with tapa was not isolated. The reactions of the Cu(I) complexes with dioxygen in MeOH at -75 degrees C have given the trans-micro-1,2 peroxo dinuclear Cu(II) complexes formulated as [((tapa)Cu)(2)(O(2))](2+) (1c), [((bapa)Cu)(2)(O(2))](2+) (2c), and [((mapa)Cu)(2)(O(2))](2+) (3c), whose characterizations were confirmed by UV-vis, ESR, and resonance Raman spectroscopies. UV-vis spectra of 1c, 2c, and 3c exhibited intense bands assignable to pi(O(2)(2)(-))-to-d(Cu) charge transfer (CT) transitions at lambda(max)/nm (epsilon/M(-1)cm(-1)) = 449 (4620), 474 (6860), and 500 (9680), respectively. The series of the peroxo adducts generated was ESR silent. The resonance Raman spectra exhibited the enhanced features assignable to two stretching vibrations nu((16)O-(16)O/(18)O-(18)O)/cm(-1) and nu(Cu-(16)O/Cu-(18)O)/cm(-1) at 853/807 (1c), 858/812 (2c), 847/800 (3c), and at 547/522 (2c), 544/518 (3c), respectively. The thermal stability of the peroxo-copper species has increased with increase in the number of the hydrogen-bonding interactions between the peroxide and amino groups.

Construction of a square-planar hydroperoxo-copper(II) complex inducing a higher catalytic reactivity.

A novel hydroperoxo-copper(II) complex with a square-planar geometry has been prepared, which has exhibited a higher selectivity and catalytic reactivity for dimethyl sulfide, in contrast to that with a trigonal-bipyramidal one.

An accurately-constructed structural model for an active site of Fe-containing superoxide dismutases (Fe-SODs).

A novel structural model, [Fe(bpga)(N(3))(OCH(3))] (1) (BPGA: bis(6-pivalamido-2-pyridylmethyl)(carboxy-methyl)amine), for an active site of Fe-containing SOD enzyme with N(3)(-) has been accurately designed and prepared, which has been characterized by X-ray structure analysis and UV-vis, ESR, and IR spectroscopies. Reaction of 1 with acid/base in methanol has shown that the superoxide-accessible site is the N(3)(-)-coordination site in the equatorial plane.