Dark matter halos in the multicomponent model. II. Density profiles of galactic halos

The multicomponent dark matter model with self-scattering and inter-conversions of species into one another is an alternative dark matter paradigm that is capable of resolving the long-standing problems of $\Lambda$CDM cosmology at small scales. In this paper, we have studied in detail the properties of dark matter halos with $M \sim 4-5 \times10^{11} M_{\odot}$ obtained in $N$-body cosmological simulations with the simplest two-component (2cDM) model. A large set of velocity-dependent cross-section prescriptions for elastic scattering and mass conversions, $\sigma_s(v)\propto v^{a_s}$ and $\sigma_c(v)\propto v^{a_c}$, has been explored and the results were compared with observational data. The results demonstrate that self-interactions with the cross-section per particle mass evaluated at $v=100$ km s$^{-1}$ being in the range of $0.01\lesssim \sigma_0/m\lesssim 1$ cm$^2$g$^{-1}$ robustly suppress central cusps, thus resolving the core-cusp problem. The core radii are controlled by the values of $\sigma_0/m$ and the DM cross-section's velocity-dependent power-law indices $(a_s,a_c)$, but are largely insensitive to the species' mass degeneracy. These values are in full agreement with those resolving the substructure and too-big-to-fail problems. We have also studied the evolution of halos in the 2cDM model with cosmic time.Comment: 17 pages, 13 figure

Cationic acyclic cucurbit[n]uril-type containers: synthesis and molecular recognition toward nucleotides

<p>We report the synthesis of <b>M2NH3</b> which is a tetracationic analogue of our prototypical acyclic CB[n]-type molecular container <b>M2</b>. Both <b>M1NH3</b> and <b>M2NH3</b> possess excellent solubility in D₂O and do not undergo intermolecular self-association processes that would impinge on their molecular recognition properties. Compounds <b>M1NH3</b> and <b>M2NH3</b> do, however, undergo an intramolecular self-complexation process driven by ion–dipole interactions between the ureidyl C=O portals and the OCH₂CH₂NH₃ arms along with inclusion of one aromatic wall in its own hydrophobic cavity. The <i>K</i>_a values for <b>M1NH3</b> and <b>M2NH3</b> towards seven nucleotides were determined by ¹H NMR titration and found to be quite modest (<i>K</i>_a in the 10²–10³ M⁻¹ range) although <b>M2NH3</b> is slightly more potent. The more highly charged guests (e.g. ATP) form stronger complexes with <b>M1NH3</b> and <b>M2NH3</b> than the less highly charged guest (e.g. ADP, AMP). The work highlights the dominant influence of the ureidyl C=O portals on the molecular recognition behaviour of acyclic CB[n]-type receptors and suggests routes (e.g. more highly charged arms) to enhance their recognition behaviour towards anions.</p

Synthesis and Recognition Properties of Cucurbit[8]uril Derivatives

A building block approach to the synthesis of Me₄CB­[8] and Cy₂CB­[8] by condensation of glycoluril hexamer <b>1</b> with bis­(cyclic ethers) <b>2</b> is reported. X-ray crystallography demonstrates that the equatorial substitution results in an ellipsoidal cavity. Me₄CB­[8] and Cy₂CB­[8] display enhanced aqueous solubility and retain the ability to bind to guests (<b>3</b>–<b>9</b>) typical of unsubstituted CB[8]. The higher inherent solubility of Me₄CB­[8] allowed it to be used as a solubilizing excipient for insoluble drugs

Catalytic Asymmetric Syntheses of Quinolizidines by Dirhodium-Catalyzed Dearomatization of Isoquinolinium/Pyridinium Methylides–The Role of Catalyst and Carbene Source

Convenient access to highly enantioenriched substituted quinolizidines has been achieved by chiral dirhodium­(II) carboxylate-catalyzed dearomatizing formal [3 + 3]-cycloaddition of isoquinolinium/pyridinium methylides and enol diazoacetates. Coordination of Lewis basic methylides to dirhodium­(II) prompts the rearrangement of the enol-carbene that is bound to dirhodium to produce a donor–acceptor cyclopropene. The donor–acceptor cyclopropene is in equilibrium with the dirhodium-bound enol-carbene and undergoes both enantioselective [3 + 3]-cycloaddition from the dirhodium-bound enol-carbene and diastereoselective [3 + 2]-cycloaddition by uncatalyzed reaction of the cyclopropene with isoquinolinium or pyridinium methylides. Increasing the mol % of catalyst loading suppresses the [3 + 2]-cycloaddition pathway

Reductive C(sp²)–N Elimination from Isolated Pd(IV) Amido Aryl Complexes Prepared Using H₂O₂ as Oxidant

Di-2-pyridyl ketone (dpk)-supported amidoarylpallada­(II)­cycles derived from various 2-(<i>N</i>-R-amino)­biphenyls (R = H, Me, CF₃CO, MeSO₂, CF₃SO₂) react with hydrogen peroxide in MeOH, THF, MeCN or AcOH to form the corresponding C–N coupled products, <i>N</i>-R-substituted carbazoles, in 82–98% yield. For R = MeSO₂ and CF₃SO₂, the corresponding reaction intermediates, amidoaryl Pd­(IV) complexes were isolated and characterized by single crystal X-ray diffraction and/or NMR spectroscopy. For the first time, the C­(sp²)–N reductive elimination from isolated amidoaryl Pd­(IV) complexes has been studied in detail

Aerobic C–H Acetoxylation of 8‑Methylquinoline in Pd^II–Pyridinecarboxylic Acid Systems: Some Structure–Reactivity Relationships

Catalytic oxidative C–H acetoxylation of 8-methylquinoline as a model substrate with O₂ as oxidant was performed using palladium­(II) carboxylate catalysts derived from four different pyridinecarboxylic acids able to form palladium­(II) chelates of different size. A comparison of the rates of the substrate C–H activation and the O₂ activation steps shows that the C–H activation step is rate-limiting, whereas the O₂ activation occurs at a much faster rate already at 20 °C. The chelate ring size and the chelate ring strain of the catalytically active species are proposed to be the key factors affecting the rate of the C–H activation

Catalytic Asymmetric Syntheses of Quinolizidines by Dirhodium-Catalyzed Dearomatization of Isoquinolinium/Pyridinium Methylides–The Role of Catalyst and Carbene Source

Convenient access to highly enantioenriched substituted quinolizidines has been achieved by chiral dirhodium­(II) carboxylate-catalyzed dearomatizing formal [3 + 3]-cycloaddition of isoquinolinium/pyridinium methylides and enol diazoacetates. Coordination of Lewis basic methylides to dirhodium­(II) prompts the rearrangement of the enol-carbene that is bound to dirhodium to produce a donor–acceptor cyclopropene. The donor–acceptor cyclopropene is in equilibrium with the dirhodium-bound enol-carbene and undergoes both enantioselective [3 + 3]-cycloaddition from the dirhodium-bound enol-carbene and diastereoselective [3 + 2]-cycloaddition by uncatalyzed reaction of the cyclopropene with isoquinolinium or pyridinium methylides. Increasing the mol % of catalyst loading suppresses the [3 + 2]-cycloaddition pathway

Aerobic C–H Acetoxylation of 8‑Methylquinoline in Pd^II–Pyridinecarboxylic Acid Systems: Some Structure–Reactivity Relationships

Catalytic oxidative C–H acetoxylation of 8-methylquinoline as a model substrate with O₂ as oxidant was performed using palladium­(II) carboxylate catalysts derived from four different pyridinecarboxylic acids able to form palladium­(II) chelates of different size. A comparison of the rates of the substrate C–H activation and the O₂ activation steps shows that the C–H activation step is rate-limiting, whereas the O₂ activation occurs at a much faster rate already at 20 °C. The chelate ring size and the chelate ring strain of the catalytically active species are proposed to be the key factors affecting the rate of the C–H activation

N–N Bond Cleavage of Mid-Valent Ta(IV) Hydrazido and Hydrazidium Complexes Relevant to the Schrock Cycle for Dinitrogen Fixation

Chemical reduction of the Ta­(V) hydrazido chloride <b>1</b> generates the open-shell, mononuclear Ta­(IV) hydrazido complex <b>2</b>, which upon N-methylation yields the corresponding structurally characterized Ta­(IV) hydrazidium <b>6</b>. Chemical reduction of <b>6</b> results in N–N bond cleavage to generate a cis/trans mixture of the [Ta­(V),Ta­(V)] bis­(μ-nitrido) product <b>7</b> in tetrahydrofuran and the mononuclear Ta­(V) parent imide <b>8</b> in toluene. These results serve to establish an important foundation for the pursuit of a group-5 metal variant of the Schrock cycle for dinitrogen fixation

Oxidation of a Monomethylpalladium(II) Complex with O₂ in Water: Tuning Reaction Selectivity to Form Ethane, Methanol, or Methylhydroperoxide

Photochemical aerobic oxidation of <i>n</i>-Pr₄N­[(dpms)­Pd^IIMe­(OH)] (<b>5</b>) and (dpms)­Pd^IIMe­(OH₂) (<b>8</b>) (dpms = di­(2-pyridyl)­methanesulfonate) in water in the pH range of 6–14 at 21 °C was studied and found to produce, in combined high yield, a mixture of MeOH, C₂H₆, and MeOOH along with water-soluble <i>n</i>-Pr₄N­[(dpms)­Pd^II(OH)₂] (<b>9</b>). By changing the reaction pH and concentration of the substrate, the oxidation reaction can be directed toward selective production of ethane (up to 94% selectivity) or methanol (up to 54% selective); the yield of MeOOH can be varied in the range of 0–40%. The source of ethane was found to be an unstable dimethyl Pd^IV complex (dpms)­Pd^IVMe₂(OH) (<b>7</b>), which could be generated from <b>5</b> and MeI. For shedding light on the role of MeOOH in the aerobic reaction, oxidation of <b>5</b> and <b>8</b> with a range of hydroperoxo compounds, including MeOOH, <i>t</i>-BuOOH, and H₂O₂, was carried out. The proposed mechanism of aerobic oxidation of <b>5</b> or <b>8</b> involves predominant direct reaction of excited methylpalladium­(II) species with O₂ to produce a highly electrophilic monomethyl Pd^IV transient that is involved in subsequent transfer of its methyl group to <b>5</b> or <b>8</b>, H₂O, and other nucleophilic components of the reaction mixture