Taro Tsubomura

Syntheses, antitumor activity, and molecular mechanics studies of cis-PtCl2(pzH)2 (pzH=pyrazole) and related complexes. Crystal structure of a novel Magnus-type double-salt [Pt(pzH)4][PtCl4][cis-PtCl2(pzH)2]2 involving two perpendicularly aligned 1D chains

Abstract A new Magnus-type double-salt cocrystallized with a neutral complex, [Pt(pzH)4][PtCl4][cis-PtCl2(pzH)2]2 (1), has been isolated from a reaction between K2PtCl4 and pyrazole as a result of our reinvestigation of cis-PtCl2(pzH)2 (2). Interestingly, compound 1 involves two types of 1D chains respectively growing along the a- and c-axes, giving a novel intersecting framework. The former is {cis-PtCl2(pzH)2}n (PtPt=4.342(2) and 4.373(2) A), and the latter is a Magnus-type 1D chain {[Pt(pzH)4][PtCl4]}n (PtPt=3.9388(1) A). Each stacking interaction is stabilized with two hydrogen bonds formed between the chloride atoms and the NH units of pyrazoles; Cl⋯N(pyrazole)=3.21(2)–3.49(2) A. The in vitro antitumor activity of 2 toward some human cancer cell lines is found to be comparable to that of cis-PtCl2(NH3)2. Molecular mechanics investigations of some GG-adducts of cis-Pt(pzH)2 reveal the importance of hydrogen-bond formation between the NH(pzH) units and the guanine/phosphate groups for the electrostatic stabilization of the adducts.

Homogeneous catalyses of mixed-valent octanuclear platinum complexes in photochemical hydrogen production from water

Abstract An acetamidate-bridged mixed-valent octanuclear platinum complex, [Pt(2.25+) 8 (NH 3 ) 16 (CH 3 CONH) 8 ](NO 3 ) 10 ·4H 2 O, has been employed as a hydrogen-producing catalyst in a photochemical model system, containing EDTA as a sacrificial electron donor, [Ru (II)(2,2′-bpy) 3 ] 2+ as a photosensitizer and methyl viologen as an electron relay. The catalytic activity of the octanuclear compound was higher than those previously reported for the mixed-valent tetranuclear platinum complexes with α-pyridonate or α-pyrrolidonate bridging ligands, and is also higher than that observed for another mixed-valent octanuclear platinum complex with 2-fluoroacetamidate bridging ligand, [Pt(2.08+) 8 (NH 3 ) 16 (CH 2 FCONH) 8 ] (NO 3 ) 8.66 ·4H 2 O. Photochemical decomposition of the present system, caused by both hydrogenation of methyl viologen and photodecomposition of the catalyst complex, has been studied by means of HPLC. 1 H NMR studies have revealed that cleavage of the acetamidate-bridged Pt (II) 6 Pt(III) 2 octamer into Pt(II) 2 and Pt(III) 2 dimers takes place rapidly after dissolution in aqueous media. The dinuclear Pt(II) 2 complex seems to be the major species in the solution under the photolysis conditions and would be the active species as the hydrogen-producing catalyst.

Structural and spectroscopic properties of a copper(I)–bis(N-heterocyclic)carbene complex

The structural and spectroscopic properties of a Cu(I) complex bearing a methylene-linked bis(N-heterocyclic carbene) ligand, [Cu(2)(mu-Me-mbim)(2)](PF(6))(2) were investigated. X-ray single crystal structure analysis revealed that the complex is binuclear similar to the corresponding silver(I) complex. In [Cu(2)(mu-Me-mbim)(2)](PF(6))(2), cation-pi interaction between copper and the adjacent carbene carbon is observed. On the other hand, the copper-copper interaction is very weak in the crystal and almost negligible in solution. The absorption spectrum of [Cu(2)(mu-Me-mbim)(2)](PF(6))(2) in methanol shows a strong absorption band (epsilon = 23 000 dm(3) mol(-1) cm(-1)) and a weaker shoulder (epsilon = 6200 dm(3) mol(-1) cm(-1)) at 261 nm and 300 nm, respectively. From molecular orbital calculations using TD-DFT, these absorption bands are assigned to the metal-centered transitions with some contribution from the NHC orbitals. The powdered sample of [Cu(2)(mu-Me-mbim)(2)](PF(6))(2) shows bright blue-green phosphorescence with a high quantum yield (43%). The phosphorescence is of dual-emission character at room temperature with peak maxima at 374 nm and 482 nm whereas it changes to a single emission band centered around 500 nm at 77 K. Molecular orbital calculations indicate that the luminescence derives from the triplet MC and MLCT mixed excited states. A methanolic solution of [Cu(2)(mu-Me-mbim)(2)](PF(6))(2) shows yellow-green phosphorescence with a peak maximum at 542 nm. Unlike in the solid state, no dual-emission was observed. These results suggest that the dual emission is caused by differences in the contribution of metal-metal interactions at room temperature in the solid state. The differences in the absorption and emission properties between [Cu(2)(mu-Me-mbim)(2)](PF(6))(2) and the related Cu(I)-diphosphine complex, [Cu(2)(mu-dcpm)(2)](BF(4))(2) are discussed.

Luminescent mononuclear Ag(I)-bis(diphosphine) complexes: correlation between the photophysics and the structures of mononuclear Ag(I)-bis(diphosphine) complexes.

Correlation between the photophysics and the structures of three Ag(I)-bis(diphosphine) complexes ([Ag(dppbz)(2)]NO(3) (1.NO(3)), [Ag(dppe)(2)]NO(3) (2.NO(3)), and [Ag(dppp)(2)]NO(3) (3.NO(3)) (dppbz = 1,2-bis(diphenylphosphino)benzene, dppe = 1,2-bis(diphenylphosphino)ethane, dppp = 1,3-bis(diphenylphosphino)propane) has been investigated using temperature-dependent emission measurements and electrochemical and theoretical methods. All three Ag(I)-bis(diphosphine) complexes have relatively low oxidation potential, which allows metal-to-ligand charge transfer (MLCT) contribution in the lowest excited state of the tetrahedral geometry, which is difficult in other Ag(I) complexes. Both 1.NO(3) and 2.NO(3) show orange phosphorescence with moderate quantum yield in air-free methanol at room temperature, while 3.NO(3) is less emissive in solution at room temperature. In all three complexes the temperature-dependent luminescence measurements in EtOH/MeOH 4:1 (v/v) solution indicate the blue-shift of the emission maximum and the increase of the emission intensity on lowering the temperature. In particular, the sequential emission spectral change with decreasing temperature is observed in 1.NO(3) and 2.NO(3). In the glass state at 90 K, all three complexes show intense blue phosphorescence. The theoretical calculation using density functional theory (DFT) suggests that the orange and blue emissions mainly originate from the (3)MC excited state based on a square-planar geometry and the (3)IL+(3)MLCT excited state based on a tetrahedral geometry, respectively.

A chiral 2,6-bis(oxazolinyl)pyridine ligand with amide groups to form isomorphous complexes through all the lanthanoid series.

We newly synthesized the chiral pybox ligand, 2,6-bis[(4S)-tert-butylcarbamoyl-2-oxazolin-2-yl]pyridine, whose lanthanoid(III) complexes have formed isomorphous crystals through all the lanthanoid series. The luminescence properties of the Eu(III) complex have been investigated.

Growth of L929 cells on polymeric films prepared by Langmuir-Blodgett and casting methods.

The growth and spreading of fibroblast, L929 cells, on various polymeric films prepared by the Langmuir-Blodgett (LB) and casting methods were investigated. L929 cells, which were cultivated on collagen and synthetic polymeric films prepared by the LB method, adhered and spread much more than those on synthetic films prepared by the casting method. This is explained by the fact that cell growth and cell spreading are suitable for L929 cells on the films having serum proteins that contain a high α-helix content, because LB films adsorbed those serum proteins estimated from the circular dichroism measurements of the films immersed in cell culture medium. An exponential relationship was observed from the plot of the cell density vs root mean square of roughness of the films, which is estimated by atomic force microscopy, whereas a linear relationship was observed from the plot of the spreading ratio vs the root mean square of roughness. It is suggested that the correlation between the cell growth or spreading ratio and surface roughness of the films where L929 cells were cultivated is considered to be more important than the correlation between the cell growth or spreading ratio and the contact angle of the films.

First synthesis and characterization of platinum(II) complexes of amino sugars having anti-tumour activity; crystal structure of [ptcl2(methyl 2,3-dideoxy-α-D-mannopyranoside)]·H2O

Two novel platinum(II) complexes containing a diamino sugar have been prepared and characterized, including the crystal structure of [PtCl2(methyl 2,3-diamino-2,3-dideoxy-α-D-mannopyranoside)]·H2O (1), and the anti-tumour activity of the complexes has been demonstrated.

Synthesis and molecular structure of [RuCl{C(CHPh)OC(O)CH2CH3}(CO)(PPh3)2]: a real intermediate in ruthenium complex-catalyzed selective synthesis of a (Z)-enol ester

Abstract Reaction of [RuCl(η2-O2CCH2CH3)(CO)(PPh3)2] (1) and phenylacetylene gives [RuCl{C(CHPh)OC(O)CH2CH3}(CO)(PPh3)2] (2a). The X-ray structure analysis of 2a reveals that it includes a (Z)-enol ester-like 1-propanoyloxy-2-phenylethenyl-C1,O ligand. In the catalytic addition of propanoic acid to phenylacetylene, the complex 2a acts as a real intermediate that gives (Z)-2-phenylethenyl propanoate, selectively. The presence of the free PPh3 in the reaction mixture depresses formation of some dicarbonylruthenium species that catalytically produce (E)- and Markovnikov-type enol esters.

PHOTOCHEMICAL REACTIONS OF PALLADIUM(0) AND PLATINUM(0) PHOSPHINE COMPLEXES

Abstract Photochemical reactions of the binuclear palladium(0) complex [Pd2(dppm)3] with organic halides yield palladium(I) dihalogeno complexes with irradiation of visible light. Photooxidation of alcohols was observed for ethanol and 2-propanol with the palladium complex. Photophysical and quenching properties of a chiral [Pt(BINAP)2] complex (BINAP = RR- or SS-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) were studied. The emitting MLCT excited state has a long lifetime. Photochemical reactions of [Pt(BINAP)2] with organic halides cause halogen abstraction. Atom and electron transfer may be candidates for the initial stage of the photoreaction. The mechanism of the photoreaction is discussed with the quenching data.

TWO NOVEL TYPES OF METAL COMPLEXES DERIVED FROM TRIPOD AMINES AND ACETYLACETONE

Abstract Condensations of tris(2-aminoethyl)amine (tren) with acetylacetone (acac) give two different types of complexes, depending upon the coexisting metal ions; one contains two tridentate ligands which have β-ketoimine moieties at all primary amino groups of tren, and the other has a pentadentate ligand having a β-ketoimine moiety at one of the three amino groups of tren. The Sr2+, Ca2+, Mg2+, and Mn2+ ion give the former type complexes and Cu+, Co3+, and Zn2+ give the latter. The crystal structures of all the complexes have been characterized by X-ray analyses. Crystal data for the Sr2+ complexes: SrC90H106N8O6B2, a = 12.32(1), b = 17.65(2), c = 10.98(1)A, α = 99.04(9), β = 104.53(9), γ = 104.47(9)°, V = 2176(4) A3, triclinic, P 1 , Z= 1 . For the Ca2+ complex: CaC90H106N8O6B2, a = 12.882(2), b = 15.904(4), c = 11.314(4) A , α = 102.37(2), β = 94.70(2), γ = 110.16(1)°, V = 2094(1) A 3 , triclinic, P 1 , Z = 1 . For the Mg2+ complex: MgC90H106N8O6B2, a = 12.839(4), b = 15.773(6), c = 11.199(3) A , α = 101.50(3), β = 95.35(3), γ = I10.24(2)°, V = 2052(1) A3, triclinic, P 1 , Z = 1 . For the Mn2+ complex: MnC90H106N8O6B2, a = 12.858(3), b = 15.818(6), c = 11.210(3) A , α = 101.80(2), β = 95.06(2), γ = 110.20(2)°, V = 2063(l) A3, triclinic, P 1 , Z = 1 . For the Cu2+ complex: CuC35H43N4OB, a = 11.060(5), b = 15.874(4), c = 17.886(4) A, β = 91.89(3)°, V = 3138(I) A3, monoclinic, P2 1 n , Z = 4 . For the Zn2+ complex: ZnC35H43N4OB, a = 11.084(4), b = 15.955(3), c = 17.838(2) A , β = 92.11(2)°, V = 3152(1) A 3 , monoclinic, P2 1 n , Z = 4 . For the C03+ complex: CoC35H43N4OBCl, a =1 7.996(2), b = 10.150(5), c = 19.741(2) A , β = 113.460(7)°, V = 3307(1) A 3 , monoclinic, P2 1 c , Z = 4. The selectivity of the products is discussed in terms of the ionic size and the affinity between the metal ion and the donor atoms. The reaction of acac with tris(3-aminopropyl)amine in the presence of the Ca2+ ion was also performed, the first type of the structure was found. The structure is also confirmed by X-ray analysis. Crystal data: CaC96H124N8O6B2, a = 12.364(4), b = 16.502(6), c = 12.008(5) A , α = 103.62(3), β = 91.14(3), γ = 110.09(2)°, V = 2222(1) A 3 , triclinic, P 1 , Z= 1 .