Self-organisation of dodeca-dendronized fullerene into supramolecular discs and helical columns containing a nanowire-like core

Twelve chiral and achiral self-assembling dendrons have been grafted onto a [60]fullerene hexa-adduct core by copper-catalyzed alkyne azide “click” cycloaddition. The structure adopted by these compounds was determined by the self-assembling peripheral dendrons. These twelve dendrons mediate the self-organisation of the dendronized [60]fullerene into a disc-shaped structure containing the [60]fullerene in the centre. The fullerene-containing discs self-organise into helical supramolecular columns with a fullerene nanowire-like core, forming a 2D columnar hexagonal periodic array. These unprecedented supramolecular structures and their assemblies are expected to provide new developments in chiral complex molecular systems and their application to organic electronics and solar cells.     

Designing multifunctional expanded pyridiniums: properties of branched and fused head-to-tail bipyridiniums

The multifaceted potentialities of expanded pyridiniums (EPs), based on one pyridinium core bearing a 4-pyridyl or 4-pyridylium as the N-pyridinio group, are established at both experimental and theoretical levels. Two classes of head-to-tail (htt) EPs were designed, and their first representative elements were synthesized and fully characterized. The branched (B) family is made up of 2,6-diphenyl-4-aryl-1,4'-bipyridin-1-ium (or 1,1'-diium) species, denoted 1B and 2B for monocationic EPs (with aryl = phenyl and biphenyl, respectively) and 1B(Me) and 2B(Me) for related quaternarized dicationic species. The series of fused (F) analogues comprises 9-aryl-benzo[c]benzo[1,2]quinolizino[3,4,5,6-ija][1,6]naphthyridin-15-ium species, denoted 1F and 2F, and their 2,15-diium derivatives referred to as 1F(Me) and 2F(Me). Electrochemistry (in MeCN vs SCE) reveals that branched EPs undergo a single reversible bielectronic reduction at ca. -0.92 V for 1B/2B and -0.59 V for 1B(Me)/2B(Me), whereas pericondensed species show two reversible monoelectronic reductions at ca. -0.83 and -1.59 V for 1F/2F and ca. -0.42 and -1.07 V for 1F(Me)/2F(Me). Regarding electronic absorption features, all htt-EP chromophores show absorptivity in the range of ca. 1-4 × 10(4) M(-1) cm(-1), with red-edge absorptions extending toward 450 and 500 nm (in MeCN) for 2B(Me) and 2F(Me), respectively. These lowest-energy pi-pi* transitions are ascribed to intramolecular charge transfer between the electron-releasing biphenyl group and the htt-bipyridinium electron-withdrawing subsystems. EPs display room-temperature photoemission quantum yields ranging from 10% to 50%, with the exception of 1B, and branched luminophores are characterized by larger Stokes shifts (8000-10?000 cm(-1)) than fused ones. Lastly, a method to predict the efficiency of photobiscyclization of branched EPs into fused ones, based on the analysis of computed difference maps in total electron density for singlet excited states, is proposed.     

Can Na(2)[B(12)H(12)] be a decomposition product of NaBH(4)?

We synthesized Na(2)[B(12)H(12)] by a solid state procedure and thermal decomposition of Na[B(3)H(8)], and calculated from a first-principles approach the thermodynamic and structural properties. In particular, the calculated enthalpy of formation of the monoclinic structure, at T = 0 K, of -1086.196 kJ mol(-1) showed that it is a very stable compound. Therefore, in case it were formed during the thermal decomposition of NaBH(4), it would be rather considered a product, which, in addition, prevents the subsequent re-hydrogenation process because of its low reactivity to hydrogen. We reported the isotherms of absorption of H(2), O(2), and H(2)O, calculated both theoretically and experimentally.     

Hawking-like radiation does not require a trapped region

We discuss the issue of quasiparticle production by "analogue black holes" with particular attention paid to the possibility of reproducing Hawking radiation in a laboratory. By constructing simple geometric acoustic models, we obtain a somewhat unexpected result: We show that, in order to obtain a stationary and Planckian emission of quasiparticles, it is not necessary to create a trapped region in the acoustic spacetime (corresponding to a supersonic regime in the fluid flow). It is sufficient to set up a dynamically changing flow asymptotically approaching a sonic regime with sufficient rapidity in laboratory time. This result is generic to curved-space quantum field theory, the "analogue spacetimes" we consider providing a guide to physical intuition, and a possible route to laboratory experiments.     

Structure and Classification of Superconformal Nets

We study the general structure of Fermi conformal nets of von Neumann algebras on S ¹ and consider a class of topological representations, the general representations, that we characterize as Neveu–Schwarz or Ramond representations, in particular a Jones index can be associated with each of them. We then consider a supersymmetric general representation associated with a Fermi modular net and give a formula involving the Fredholm index of the supercharge operator and the Jones index. We then consider the net associated with the super-Virasoro algebra and discuss its structure. If the central charge c belongs to the discrete series, this net is modular by the work of F. Xu and we get an example where our setting is verified by taking the Ramond irreducible representation with lowest weight c/24. We classify all the irreducible Fermi extensions of any super-Virasoro net in the discrete series, thus providing a classification of all superconformal nets with central charge less than 3/2. Sebastino Carpi: Supported by MIUR, GNAMPA-INDAM and EU network “Noncommutative Geometry” MRTN-CT-2006-0031962 Yasuyuki Kawahigashi: Supported in part by the Grants-in-Aid for Scientific Research, JSPS. Submitted: March 3, 2008. Accepted: May 5, 2008.     

A Palladium‐Catalyzed Carbonylation Approach to Eight‐Membered Lactam Derivatives with Antitumor Activity

The reactivity of 2‐(2‐alkynylphenoxy)anilines under PdI₂/KI‐catalyzed oxidative carbonylation conditions has been studied. Although a different reaction pathway could have been operating, N‐palladation followed by CO insertion was the favored pathway with all substrates tested, including those containing an internal or terminal triple bond. This led to the formation of a carbamoylpalladium species, the fate of which, as predicted by theoretical calculations, strongly depended on the nature of the substituent on the triple bond. In particular, 8‐endo‐dig cyclization preferentially occurred when the triple bond was terminal, leading to the formation of carbonylated ζ‐lactam derivatives, the structures of which have been confirmed by XRD analysis. These novel medium‐sized heterocyclic compounds showed antitumor activity against both estrogen receptor‐positive (MCF‐7) and triple negative (MDA‐MB‐231) breast cancer cell lines. In particular, ζ‐lactam 3 j′ may represent a novel and promising antitumor agent because biological tests clearly demonstrate that this compound significantly reduces cell viability and motility in both MCF‐7 and MDA‐MB‐231 breast cancer cell lines, without affecting normal breast epithelial cell viability.     

The Virasoro Algebra and Sectors with Infinite Statistical Dimension

We show that the sectors with lowest weight $ h \geq 0,\, h \neq j{^2},\, j \in {1\over2}\mathbb{Z} $ of the local net of von Neumann algebras on the circle generated by the Virasoro algebra with central charge c = 1 have infinite statistical dimension. Communicated by Klaus Fredenhagen submitted 28/11/02, accepted: 10/03/03     

A new deuterated alkylating agent for quantitative proteomics

Weakly basic molecules containing a double bond, such as 2- and 4-vinylpyridine, are able to react and selectively alkylate -SH groups in proteins, thus preventing their re-oxidation to disulphide bridges. In contrast to conventional alkylating agents such as iodoacetamide and non-charged acrylamide derivatives, such molecules achieve 100% alkylation of all -SH residues, even in complex proteins, without reacting with other functional groups. Their use is particularly effective in proteome analysis and more generally for analyzing proteins in which the -SH groups should be blocked. Additionally, the use of vinylpyridines, partially or totally deuterated and thus with a mass difference compared with their non-deuterated counterparts of 4-7 Da, allows studies of induction/repression of protein synthesis (quantitative proteomics).     

Piperazine quaternary diammonium salts as additives to background electrolytes in capillary zone electrophoresis

The differential behavior of five different quaternary mono- and diammonium salts, among the 18 investigated, in modulating the electroendoosmotic flow (EOF) and analyte separations in capillary zone electrophoresis is evaluated. It is found that quaternary diammonium salts with positive charges separated by more than four carbon atoms, while exhibiting a very strong affinity for chromatographic silica beads, to the point of exhibiting Rf values close to zero, display, on the contrary, a very poor affinity for the silica wall of capillaries. Compounds separated only by a C2 unit (i.e., 1,4-dialkyl-1,4-diazoniabicyclo[2,2,2,]octane, salts 17 and 18) show high Rf values due to strong ion pair association. The unique behavior of quaternary monoammonium salts possessing an iodinated alkyl (butyl or octyl) tail (i.e., 1, 6, and 7) is attributed to their ability to be covalently affixed to the silica wall via alkylation of ionized silanols at alkaline pH values. They thus strongly modulate and typically invert the EOF, even when not present in the background electrolyte. On the contrary, all diammonium salts, devoid of such alkyl tails, are unable to modulate the EOF and to prevent analyte binding to the silica wall, since they are rapidly removed from the wall by the voltage gradient. However, if added in small amount to the background electrolyte, they offer excellent separations of mixtures of very similar organic acids and prevent any interaction with the capillary wall.