Soluble and Planar 2,9-Diazaperopyrenes through Reductive Aromatization of Perylene Diimides: Tunable Emission and Aggregation Behaviors

Reductive aromatization of perylene diimides with acid anhydrides in the presence of Mn or Zn metals provides soluble and planar 2,9-diazaperopyrenes with ester groups at 1,3,8,10-positions. The pivaloxy groups at the peripheral positions can be transformed into a variety of aryl groups through nickel-catalyzed cross-coupling of ester groups. Emission colors of diazaperopyrenes are tunable by the peripheral substituents. The peripheral substituents also affect the aggregation behaviors of 2,9-diazaperopyrenes in the solution and solid states.     

Internucleobase-interaction-directed self-assembly of nanofibers from homo- and heteroditopic 1,omega-nucleobase bolaamphiphiles.

The complementary 1,omega-thymine, 1,omega-adenine, and 1,omega-(thymine, adenine) bolaamphiphiles, [N,N'-bis[3-(2,4-dihydroxy-5-methylpyrimidine-1-yl)propionyl]1,n-diaminoalkane [T-n-T (n = 10, 11, 12)], N, N'-bis[3-(6-aminopurine-9-yl)propionyl]1,n-diaminoalkane [A-n-A (n = 10, 11, 12)], and N-[3-(2,4-dihydroxy-5-methylpyrimidine-1-yl)propionyl], N'-[3-(6-aminopurine-9-yl)propionyl]1,n-diaminoalkane [T-n-A (n = 10, 11, 12)], respectively] have been synthesized. The spontaneous homo- and heteroassembly of these nucleobase-based bolaamphiphiles has been studied by light microscopy, energy-filtering transmission electron microscopy, FT-IR, and powder X-ray diffraction analyses. The achiral T-10-T bolaamphiphile produced in 10% ethanolic/aqueous solutions unprecedented double-helical ropes of 1-2 microm in widths and several hundred micrometers in length, whereas the complementary homologue A-10-A gave only microcrystalline solids of 1-10 microm in size. In contrast, an equimolar mixture of T-10-T and A-10-A yielded supramolecular fibers of 15-30 nm in width. (1)H NMR, CD, and UV studies of solution photoreactions of T-10-T suggested that under natural light the chiral rope formation is triggered by photodimerization of trace amounts of the thymine moieties in the T-10-T assemblies. Complementary hydrogen bond formation between the thymine-adenine heterobase pairs was found to prevent such a photoreaction and resulted in no chiral rope formation. The heteroditopic T-12-A bolaamphiphile self-assembled to form supramolecular fibers. Multilamellar organization was proposed for the homo- and heteroassemblies made of T-n-T and A-n-A.     

Octapalladium Strings Trap C60 and C70 Fullerenes Affording Metal-Chain-Wired Bucky Balls

Reactions of Pd₈ strings supported by meso-Ph₂PCH₂P(Ph)CH₂P(Ph)CH₂PPh₂ (meso-dpmppm) ligands, [Pd₈(meso-dpmppm)₄(L)₂]⁴⁺ (L=CH₃CN ( 1 ), XylNC ( 2 )) with C₆₀ resulted in the exclusive formation of unprecedented metal-chain-wired C₆₀ bucky balls, [{Pd₄(meso-dpmppm)₂(L)}₂(C₆₀)]⁴⁺ (L=CH₃CN ( 11 ), XylNC ( 12 )), in which a C₆₀ fullerene is trapped in the central Pd–Pd junction, as unambiguously established by spectroscopic, X-ray crystallographic, and theoretical techniques. The similar reaction of Pd₈ strings supported by rac-dpmppm, [Pd₈(rac-dpmppm)₄(CH₃CN)₂]⁴⁺ ( 3 ) also afforded a racemic mixture of [{Pd₄((R*,R*)-dpmppm)₂(CH₃CN)}₂(C₆₀)]⁴⁺ ( 13 ) without scrambling the Pd₄ fragments with (R,R)- and (S,S)-dpmppm ligands. Consequently, those of enantiopure chiral Pd₈ strings, [Pd₈((R*,R*)-dpmppm)₄(CH₃CN)₂]⁴⁺, certainly afforded chiral bucky balls of [{Pd₄((R*,R*)-dpmppm)₂(CH₃CN)}₂(C₆₀)]⁴⁺ ( 13 _RR and 13 _SS ), that exhibit mirror-image circular dichroism spectra. The reactions of 1 and 2 were also applied for trapping a C₇₀ fullerene to give 2 : 1 adducts of [{Pd₄(meso-dpmppm)₂(L)}₂(C₇₀)]⁴⁺ (L=CH₃CN ( 21 ), XylNC ( 22 )). These results provide useful information for creating a platform to develop dimensionally and chirality controlled metal–carbon nanocomposite materials.     

Direct numerical simulation of stable and unstable turbulent thermal boundary layers

This paper presents direct numerical simulations (DNS) of stable and unstable turbulent thermal boundary layers. Since a buoyancy-affected boundary layer is often encountered in an urban environmental space where stable and unstable stratifications exist, exploring a buoyancy-affected boundary layer is very important to know the transport phenomena of the flow in an urban space. Although actual observation may qualitatively provide the characteristics of these flows, the relevant quantitative turbulent quantities are very difficult to measure. Thus, in order to quantitatively investigate a buoyancy-affected boundary layer in detail, we have here carried out for the first time time- and space-developing DNS of slightly stable and unstable turbulent thermal boundary layers. The DNS results show the quantitative turbulent statistics and structures of stable and unstable thermal boundary layers, in which the characteristic transport phenomena of thermally stratified boundary layers are demonstrated by indicating the budgets of turbulent shear stress and turbulent heat flux. Even though the input of buoyant force is not large, the influence of buoyancy is clearly revealed in both stable and unstable turbulent boundary layers. In particular, it is found that both stable and unstable thermal stratifications caused by the weak buoyant force remarkably alter the structure of near-wall turbulence.     

Iridium‐Catalyzed Coupling Reaction of Primary Alcohols with 2‐Alkynes Leading to Hydroacylation Products

A novel iridium‐catalyzed intermolecular coupling reaction of primary alcohols or aldehydes with 2‐alkynes was successfully achieved with high regioselectivity to give hydroacylation products such as α,β‐unsaturated ketones in good yields. The mechanistic investigation of the reaction strongly indicated that the coupling proceeds through the initial formation of homoallylic alcohols followed by dehydrogenation to β,γ‐unsatutated ketones and then isomerisation, which leads to the hydroacylation products.     

Evaluation of CH3-DTPA-Gd (NMS60) as a new MR contrast agent: early phase II study in brain tumors and dual dynamic contrast-enhanced imaging

PURPOSE: A newly developed contrast material, CH3-DTPA-Gd (NMS60), a trimer containing 3 Gd(3+) atoms per molecule, has been shown to offer greater enhancement and longer vascular retention than gadopentetate dimeglumine (Gd-DTPA) in animals. We report on our early phase II study on NMS60 in brain tumor patients together with supplementary investigations. METHODS AND MATERIALS: The longitudinal relaxation rate (R(1)=1/T(1)) and the transverse relaxation rate (R(2)*=1/T(2)*) of NMS60 and Gd-DTPA were determined at 20 degrees C in water at 1.5 T. An NMS60 dose of 0.1 or 0.2 mmol (Gd)/kg was randomly assigned and administered to 10 patients (five women, five men; mean age: 49 years) with brain tumors. Safety and contrast-enhancing ability of NMS60 were evaluated. Dual dynamic contrast-enhanced T(1) and R(2)* studies (DUCE imaging) were also carried out in two patients. RESULTS: Regarding the relaxivity per Gd, R(1) and R(2)* of NMS60 were 9.5 and 11.0 (mmol/L x s)(-1), respectively, compared to 4.8 and 7.2 (mmol/L x s)(-1) for Gd-DTPA. Although a transient slight increase of alanine aminotransferase was observed in one case, no other adverse reactions were observed after administration of NMS60. Contrast enhancement by NMS60 was excellent at both concentrations, and when tumor detectability was assessed with a five-point scale, the diagnostic usefulness was 4 or higher in all cases. In DUCE imaging, NMS60 appeared to show high signal intensity, when compared with the data obtained separately for Gd-DTPA. CONCLUSION: NMS60 had a high contrasting effect and little toxicity, and is expected to be clinically useful.     

Preparation of Self-Organized Porous Polymer Masks for Si Dry Etching

Summary: Self-organized honeycomb-patterned polymer films were prepared by using condensed water droplet arrays as templates. Porous polymer masks for dry etching were easily prepared on Si substrates by peeling off the honeycomb-patterned films. After dry etching, hexagonally-arranged micro-pores were formed on the surface of Si substrates.