39,461 research outputs found
N-Phenyl-tert-butanesulfinamide
No full textIn the racemic title compound, C10H15NOS, the packing exhibits centrosymmetric pairs of molecules linked by N—H...O=S hydrogen bonds in a head-to-tail fashion. The N—Caryl bond [1.4083 (12) Å] is considerably shorter than the N—Calkyl bonds typically found in N-alkylalkanesulfinamides (1.470–1.530 Å)
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Insights into the structures adopted by titanocalix[6 and 8]arenes and their use in the ring opening polymerization of cyclic esters
No full textInteraction of p-tert-butylcalix[6]areneH6, L1H6, with [TiCl4] afforded the complex
[Ti2Cl3(MeCN)2(OH2)(L1H)][Ti2Cl3(MeCN)3(L1H)]·4.5MeCN (1·4.5MeCN), in which two pseudo octahedral titanium centres are
bound to one calix[6]arene. A similar reaction but employing THF resulted in the THF ring-opened product [Ti4Cl2(μ3-O)2(NCMe)2(L)2(O(CH2)4Cl)2]·4MeCN (2·4MeCN), where LH4 = p-tert-butylcalix[4]areneH4. Interaction of L1H6 with TiF4 (3
equiv.) led, after work-up, to the complex [(TiF)2(μ -F)L1H]2·6.5MeCN (3·6.5MeCN). Treatment of p-tert-butylcalix[8]areneH8,
L
2H8, with [TiCl4] led to the isolation of the complex [(TiCl)2(TiClNCMe)2(μ3-O)2(L2
)]·1.5MeCN (4·1.5MeCN). From a similar
reaction, a co-crystallized complex [Ti4O2Cl4(MeCN)2(L2
)][Ti3Cl6(MeCN)5(OH2)(L2H2)]·H2O·11MeCN (5·H2O 11MeCN) was
isolated. Extension of the L2H8 chemistry to [TiBr4] afforded, depending on the stoichiometry, the complexes
[(TiBr)2(TiBrNCMe)2(μ3-O)2(L2
)]·6MeCN (6·6MeCN) or [Ti(NCMe)2Br]2[Ti(O)Br2(NCMe)](L2
)]·7.5MeCN (7·7.5MeCN), whilst use
of [TiF4] afforded complexes containing Ca2+ and Na+
, thought to originate from drying agents, namely
[Ti8CaF20(OH2)Na2(MeCN)4(L2
)2]·14MeCN (8·14MeCN), [Na(MeCN)2][Ti8CaF20NaO16(L2
)2]·7MeCN (9·7MeCN) or
[Na]6[Ti8F20Na(MeCN)2(L2
)][Ti8F20Na(MeCN)0.5(L2
)]·15.5(C2H3N) (10·15.5MeCN). In the case of TiI4, the ladder
[(TiI)2(TiINCMe)2(μ3-O)2(L2
)]·7.25CH2Cl2 (11·7.25CH2Cl2) was isolated. These complexes have been screened for their potential
to act as catalysts in the ring opening polymerization (ROP) of ε-caprolactone (ε-CL), δ-valerolactone (δ-VL) and rac-lactide
(r-LA), both in air and N2. For ε-CL and δ-VL, moderate activity at 130 oC over 24 h was observed for 1, 9 and 11; for r-LA,
only 1 exhibited reasonable activity. In the case of the co-polymerization of ε-CL with δ-VL, the complexes 1 and 11 afforded
reasonable conversions and low molecular weight polymers, whilst 4, 6, and 9 were less effective. None of the complexes
proved to be active in the co-polymerization of ε-CL and r-LA under the conditions employed herein.</p
Measurement of the ratio of prompt χ c to J / ψ production in pp collisions at √s = 7 TeV
No full textThe prompt production of charmonium χ c and J / ψ states is studied in proton-proton collisions at a centre-of-mass energy of √s = 7 TeV at the Large Hadron Collider. The χ c and J / ψ mesons are identified through their decays χ c → J / ψ γ and J / ψ → μ + μ - using 36 pb - 1 of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for χ c and J / ψ, σ (χ c → J / ψ γ) / σ (J / ψ), is determined as a function of the J / ψ transverse momentum in the range 2 < p T J / ψ < 15 GeV / c. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low p T J / ψ region
Measurement of the CP-violating phase \phi s in Bs->J/\psi\pi+\pi- decays
No full textMeasurement of the mixing-induced CP-violating phase phi_s in Bs decays is of prime importance in probing new physics. Here 7421 +/- 105 signal events from the dominantly CP-odd final state J/\psi pi+ pi- are selected in 1/fb of pp collision data collected at sqrt{s} = 7 TeV with the LHCb detector. A time-dependent fit to the data yields a value of phi_s=-0.019^{+0.173+0.004}_{-0.174-0.003} rad, consistent with the Standard Model expectation. No evidence of direct CP violation is found
Lithium calix[4]arenes: structural studies and use in the ring opening polymerization of cyclic esters
No full textWe have structurally characterized a number of lithiated calix[4]arenes, where the bridge in the calix[4]arene is thia (–S–, LS H4), sulfinyl (–SO–, LSOH4), sulfonyl (–SO2–, LSO2H4), dimethyleneoxa (–CH2OCH2–, LCOCH4) or methylene (–CH2–, LH4). In the case of L4SH4, interaction with LiOtBu led to the isolation of the complex [Li8(L4S)2(THF)4]5THF (15THF), whilst similar interaction of L4SOH4 led to the isolation of [Li6(L4SOH)2(THF)2]5(THF) (22THF) and [Li6(LCOC)2(HOtBu)2]0.78THF1.22hexane (60.78THF1.22hexane), respectively. In the case of LH4, reaction with LiOtBu in THF afforded a monoclinic polymorph [LH2Li2(thf)(OH2)2]3THF (73THF) of a known triclinic form of the complex, whilst reaction of the de-butylated analogue of LH4, namely de-BuLH4, afforded a polymeric chain structure {[Li5(de-BuL)(OH)(NCMe)3]2MeCN}n (82MeCN). For comparative catalytic studies, the complex [Li6(LPr)2(H2O)2]hexane (9 hexane), where LPr2H2 ¼ 1,3-di-n-propyloxycalix[4]areneH2, was also prepared. The molecular crystal structures of 1–9 are reported, and their ability to act as catalysts for the ring opening (co-)/polymerization (ROP) of the cyclic esters 3-caprolactone, d-valerolactone, and rac-lactide has been investigated. In most of the cases, complex 6 outperformed the other systems, allowing for higher conversions and/or greated polymer Mn
Scandium calix[n]arenes (n= 4, 6, 8): structural, cytotoxicity and ring opening polymerization studies
No full textInteraction of [Sc(OR)3] (R = iPr or triflate) with p-tert-butylcalix[n]arenes, where n = 4, 6, or 8, affords a number of intriguing structural motifs, which are relatively non-toxic (cytotoxicity evaluated against cell lines HCT116 and HT-29) and a number were capable of the ring opening polymerization (ROP) of cyclohexene oxide
Use of titanocalix[4]arenes in the ring opening polymerization of cyclic esters
No full textThe known dichloride complexes [TiCl2L(O)2(OR)2] (type I: R = Me (1), n-Pr (2) and n-pentyl (3); L(OH)2(OR)2 = 1,3-dialkyloxy-p-tert-butylcalix[4]arene), together with the new complexes {[TiL(O)3(OR)]2(μ-Cl)2}·6MeCN (R = n-decyl (4·6MeCN)), and [Ti(NCMe)Cl(L(O)3(OR))]·MeCN (type II: R = Me, 5·MeCN) are reported. Attempts to prepare type II for R = n-Pr and n-pentyl using [TiCl4] resulted in the complexes {[TiL(O)3(On-propyl)]2(μ-Cl)(μ-OH)} 6·7MeCN and {[TiL(O)3(On-pentyl)]2(μ-Cl)(μ-OH)}·7.5MeCN (7·7.5MeCN), respectively; use of [TiCl4(THF)2] resulted in a co-crystallized THF ring-opened product [Ti(NCMe)(μ3-O)L(O)4TiCl(O(CH2)4Cl)]2-2[TiCl(NCMe)(L(O)3(On-Pr))]·11MeCN (8·11MeCN). The molecular structures of 2·2MeCN, 4·6MeCN, and 5·MeCN together with the hydrolysis products {[TiL(O)3(OR)]2(μ-Cl)(μ-OH)} (R = n-Pr 6·7MeCN; n-pentyl, 7·7.5MeCN, 9·9MeCN); R = n-decyl 10·8.5MeCN) and that of the ring opened product 8·11MeCN and the co-crystallized species [Ti2(OH)Cl(L(O)3(OR))][L(OH)2(OR)2]·2.85(C2H3N)·0.43(H2O) (R = n-pentyl, 11·2.85(C2H3N)·0.43(H2O)) are reported. Type I and II complexes have been screened for their ability to act as catalysts in the ring opening polymerization (ROP) of ϵ-caprolactone (ϵ-CL), δ-valerolactone (δ-VL), ω-pentadecalactone (ω-PDL) and rac-lactide (r-LA), both with and without benzyl alcohol present and either under N2 or in air. The copolymerization of ϵ-CL with δ-VL and with r-LA has also been investigated. For the ROP of ϵ-CL, all performed efficiently (>99% conversion) at 130 °C over 24 h both under N2 and in air, whilst over 1 h, for the type I complexes the trend was 3 > 2 > 1 but all were poor (≤12% conversion). By contrast, 5 over 1 h at 130 °C was highly active (85% conversion). At 80 °C, the activity trend followed the order 5 ≈ 4 > 3 > 2 > 1. For δ-VL, at 80 °C the activity trend 5 ≈ 4 > 1 > 2 > 3 was observed. ROP of the larger ω-PDL was only possible using 5 at 130 °C over 24 h with moderate activity (48% conversion). For r-LA, only low molecular weight products were obtained, whilst for the co-polymerization of ϵ-CL with δ-VL using 5, high activity was observed at 80 °C affording a polymer of molecular weight >23,000 Da and with equal incorporation of each monomer. In the case of ϵ-CL/r-LA co-polymerization using 5 either under N2 or air, the polymerization was more sluggish and only 65% conversion of CL was observed and the resultant co-polymer had 65:35 incorporation. Complex 5 could also be supported on silica, however this system was not as active as its homogeneous counterpart. Finally, the activity of these complexes is compared with that of three benchmark species: a di-phenolate Ti compound {TiCl2(2,2′-CH3CH[4,6-(t-Bu)2C6H2O]2)} (12) and a previously reported NO2-containing titanocalix[4]arene catalyst, namely cone-5,17-bis-tert-butyl-11,23-dinitro-25,27-dipropyloxy-26,28-dioxo-calix[4]arene titanium dichloride (13), as well as [Ti(Oi-Pr)4]; the parent calixarenes were also screened
Synthesis, structure and magnetism of a unique dodecanuclearcopper(II) 'picture frame' held in a 4 x 4 grid-like assembly
No full textThe synthesis, structure and preliminary magnetic studies of a novel dodecanuclearcopper(II) grid-like assembly are reported
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