Indenyl-functionalised triethylborane adduct of N-heterocyclic carbene: stepwise coordination of indenyl and NHC ligands toward molybdenum fragment

Indenyl-functionalised BEt(3)-adduct NHCs were prepared by the reaction of imidazolium pro-ligands with LiBEt(3)H. This compound was converted into the indenyl-coordinate molybdenum complex dangling the NHC·BEt(3) moiety as a substituent. The stepwise coordination of NHC afforded a chelate-type mononuclear complex as well as a bimetallic complex.     

Size dependences of the diradical character and the second hyperpolarizabilities in dicyclopenta-fused acenes: relationships with their aromaticity/antiaromaticity

Using long-range corrected density functional theory, the relationships between the electronic, magnetic, and nonlinear optical properties are drawn for two families of organic compounds, the dicyclopenta-fused acenes (DPAs) and the polyacenes (PAs), containing up to N = 12 fused rings. First, the longitudinal second hyperpolarizability (γ) of singlet DPAs is significantly enhanced with increasing system size, in comparison to PAs. This behavior is associated with an increase in the longitudinal spin polarization between the terminal five-membered rings of DPAs and is consistent with previous studies where γ is maximized for intermediate diradical character. The size dependence of the diradical character is also found to cause a hump in the γ/N evolution for singlet DPAs around N = 8. In fact, in the case of singlet PAs, the diradical characters y(0) and y(1), the various magnetic properties and the γ/N values vary monotonically with N, whereas for singlet DPAs, the shielding, the magnetizability, and the γ/N values exhibit extrema near N = 8 due to the appearance of transversal spin polarization in the middle six-membered rings in addition to the longitudinal spin polarization between the terminal five-membered rings. Moreover, it is shown that for singlet DPAs the longitudinal spin polarization (characterized by y(0)) is associated with the antiaromaticity (N ≤ 3) and the slight- or non-aromaticity (N ≥ 4) of the terminal five-membered rings, whereas the appearance of transversal spin-polarization (characterized by y(1)) is associated with the decrease in the aromaticity in the inner six-membered rings as shown for large PAs. Therefore, the exceptional behaviors in singlet DPAs for small N (N < 9) are caused by the increase in diradical character y(0) correlated with the anti-aromaticity or the slight-/non-aromaticity of terminal rings and the corresponding emergence of a global aromatic character. Such a relationship between the aromaticity/antiaromaticity and the diradical character is useful for designing real open-shell NLO molecules through the control of their diradical characters.     

Extraction of bismuth(III) with 2-bromoalkanoic acid in nondonating solvent from highly acidic aqueous solution.

The extraction behaviors of bismuth(III) with carboxylic acid (HL), which have not yet been clearly elucidated, because of the precipitation of hydroxide, were studied using the 2-bromoalkanoic acid in benzene and in hexane systems under aqueous conditions of high acidity at I = 1.0 M ((H,Li)NO3). The extraction equilibria were analyzed based on the-initial concentration of nitric acid and the concentration of bismuth(III) extracted in the organic phase. The extracted species and the logarithmic values of the extraction constant (log Kex) were found to be a single species of BiL3(HL)3 for the systems of 2-bromooctanoic acid/benzene (log Kex = -1.66) and 2-bromohexadecanoic acid/benzene (-1.58), and to be two species of BiL3(HL)4 (-1.01) and Bi3L9HL (-1.62) for the system of 2-bromooctanoic acid/hexane, where the monomer was dominant at a higher reagent concentration.     

Review of Measurements of Fusion Neutrons and X-Rays in Muon Catalyzed d–t Fusion at RIKEN-RAL – Details of the Detection System

Precise measurements of the absolute yields and the disappearance rates were carried out for both the X-rays from the (αμ)⁺ ion formed by muon to alpha sticking after the muon catalyzed fusion and for the fusion neutrons from ³He-free liquid and solid D/T mixtures. While the αμ X-ray yield does not contradict the values predicted by the atomic-process theories, the effective sticking probability (ω _s ) obtained by neutron measurement is much smaller than that from any of the calculations published so far, suggesting, e.g., enhanced reactivation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Scattering of 11Be halo nucleus from 209Bi at the Coulomb barrier

The scattering of the radioactive, weakly bound, halo nucleus ¹¹Be from ²⁰⁹Bi has been studied at 40MeV beam energy. The measurement performed with a low-intensity and a large-emittance secondary beam could be made using an extremely compact, large solid angle (∼ 2π sr) detecting set-up, based on 8 highly segmented Si telescopes. The ^{11, 9}Be scattering angular distributions, as well as their relative reaction cross-sections, resulted to be rather similar. This may suggest that at Coulomb barrier energies the halo structure and the very small binding energy of the ¹¹Be projectile have no big influence on the reaction dynamics.     

Ion wave excitation by radiation pressure in a plasma waveguide

After turn-off of high-power pulsed microwaves, a large-amplitude ion wave is generated which has half of the wavelength of the guided wave. The electromagnetic radiation pressure is responsible for the excitation of the ion acoustic wave.     

Conformational transition of the copolymer of maleic acid and styrene in aqueous solution

The pH-induced conformational transition of maleic acid–styrene copolymer in aqueous NaCl solutions has been investigated by potentiometric titration, viscosimetry, and dilatometry. The dependence of the intrinsic viscosity on the degree of neutralization of the primary carboxyl group indicates that the transition is from a compact to a loosely coiled form. From titration data, the standard free energy change ΔG° per monomole, for the transition from the uncharged compact from to the hypothetical uncharged loosely coiled one is estimated to be about 370–280 cal/monomole for concentrations ranging from 0.0092 to 0.2739N in NaCl. The value of ΔG° decreases slightly with increasing temperature in the temperature range from 15 to 30°C. The volume change associated with the transition was found to be ?0.6 ml in 0.01N NaCl and ?0.9 ml in 0.09N NaCl per monomole, respectively. From viscosity data, changes of molecular dimensions and the long-range interaction parameter through the transition region have been discussed.