36,000 research outputs found
Synthesis, structural and magnetic properties of TM22+[MOIV(CN)(8)]center dot nH(2)O
No full textOctacyanomolybdates (OCMs) TM2 divided by[Mo(CN)(8)]center dot nHO, where TM is Mn, Fe, Co, Ni, Cu were synthesised and characterised by IR spectroscopy and UV-VIS spectroscopy. The UV-VIS spectrum showed the intervalence charge transfer (IVCT) band between Mo-IV-CN-Cu-II and Mo-V-CN-Cu-I around 510 nm. Studied OCMs adopt tetragonal crystal structure. The H-1 NMR signals reflect the magnetic moment of the TM2- ions (mu(P)). The decay rates of free induction decay (FID) signals
increase as pp and the applied static rf-field increases. The
spin-lattice relaxation times at 27.7 MHz vary from 0.0187 ins (Mn) up to 0.45 ms (Cu). Magnetization measurements indicate long-range magnetic ordering of Mn- and Co- OCMs with the Curie temperature T-c = 4 K. The remaining OCMs (TM is Fe, Ni, Cu) are paramagnetic down to T = 1.9 K
MICROWAVE SPECTRA OF THE METHYLCYANOPOLYYNES
No full textAuthor Institution: Harvard-Smithsonian, Center for Astrophysics; Division of Engineering and Applied Sciences, Harvard University; Department of Chemistry, Wesleyan University; Harvard-Smithsonian Center for Astrophysics, Wesleyan University; Division of Engineering and Applied Sciences, Harvard UniversityThe ground state rotational spectra of four methylcyanopolyynes, and , were measured between 6 and 22 GHz by Fourier transform microwave spectroscopy. For , 8 transitions, each with nitrogen nuclear quadrupole hyperfine structure (hfs), were observed and a value of MHz was determined for the first time. Twenty-one rotational transitions of , ten rotational transitions of , and eleven rotational transitions of were detected for the first time and precise values for the rotational, leading centrifugal distortion constants of each molecule, and the nuclear quadrupole coupling constant of were determined
Reactions of 7,7,8,8-tetracyanoquinodimethane (TCNQ) with alkynyl-iron- and -ruthenium complexes: synthesis of Ru{C=CC(CN)=C(6)H(4)=C(CN)(2)}(PPh(3))(2)Cp, a new donor-acceptor molecular array
No full textReactions of 7,7,8,8-tetracyanoquinodimethane (TCNQ) with the alkynyl-iron and ruthenium complexes [M](C=CR) {[M] = Fe(dppe)Cp*, Ru(PPh3)2Cp; R = H, Ph} are described. The iron complex Fe(C=CPh)(dppe)Cp* (2a) is oxidized by TCNQ to give the kinetically stable salt [2a•+][TCNQ]•– . Displacement of [TCNQ]•– is achieved by ionic metathesis upon addition of KPF6 to produce [2a•+]PF6. In contrast, Fe(C=CH)(dppe)Cp* (2b) reacted with TCNQ to give a mixture of compounds containing Fe(=C=CH2)(dppe)Cp* (3a), {Fe(dppe)Cp*}2(µ-C=CHCH=C) (3b), and the zwitterionic complex Fe+{=C=CHC(CN)2C6H4C–(CN)2}(dppe)Cp* (3c). In contrast, the reaction of TCNQ with Ru(C=CR)(PPh3)2Cp (4a, R = Ph; 4b, R = H) gave selectively the zwitterionic vinylidenes Ru+{=C=CRC(CN)2C6H4C–(CN)2}(PPh3)2Cp (5a, R = Ph; 5b, R = H), in which the Ru centres are positively charged and the counter-anion is located on the further C(CN)2 group. On heating 5b, elimination of HCN affords Ru{C=CC(CN)=C6H4=C(CN)2}(PPh3)2Cp (1), while similar treatment of 5a gives Ru{?3-C(CN)2CPh=C6H4=C(CN)2}(PPh3)Cp (6) with loss of PPh3. X-ray structures of 1, 5a, and 6, cyclic voltammetry, and UV-vis spectroscopy of 1 provided evidence for the electronic structures of the new complexes.Michael I. Bruce, Alexandre Burgun, Guillaume Grelaud, Claude Lapinte, Brian W. Skelton, and Natasha N. Zaitsev
Thermal expansion studies on low-dimensional frustrated quantum magnets: the case of Kappa-(BEDT-TTF) 2 Cu 2 (CN) 3 and azurite
No full textThermal expansion measurements provide a sensitive tool for exploring a material's thermodynamic
properties in condensed matter physics as they provide useful information
on the electronic, magnetic and lattice properties of a material. In this thesis, thermal
expansion measurements have been carried out both at ambient-pressure and under hydrostatic
pressure conditions. From the materials point of view, the spin-liquid candidate
Kappa-(BEDT-TTF) 2 Cu 2(CN)3 has been studied extensively as a function of temperature and
magnetic field. Azurite, Cu 3 (CO 3) 2 (OH) 2 - a realization of a one-dimensional distorted
Heisenberg chain is also studied both at ambient and hydrostatic pressure to demonstrate
the proper functioning of the newly built setup "thermal expansion under pressure". ..
Interstellar CN And CH+ In Diffuse Molecular Clouds: C-12/C-13 Ratios And Cn Excitation
No full textWe present very high signal-to-noise ratio absorption-line observations of CN and CH+ along 13 lines of sight through diffuse molecular clouds. The data are examined to extract precise isotopologic ratios of (CN)-C-12/(CN)-C-13 and (CH+)-C-12/(CH+)-C-13 in order to assess predictions of diffuse cloud chemistry. Our results on (CH+)-C-12/(CH+)-C-13 confirm that this ratio does not deviate from the ambient C-12/C-13 ratio in local interstellar clouds, as expected if the formation of CH+ involves nonthermal processes. We find that (CN)-C-12/(CN)-C-13, however, can be significantly fractionated away from the ambient value. The dispersion in our sample of (CN)-C-12/(CN)-C-13 ratios is similar to that found in recent surveys of (CO)-C-12/(CO)-C-13. For sight lines where both ratios have been determined, the (CN)-C-12/(CN)-C-13 ratios are generally fractionated in the opposite sense compared to (CO)-C-12/(CO)-C-13. Chemical fractionation in CO results from competition between selective photodissociation and isotopic charge exchange (ICE). An inverse relationship between (CN)-C-12/(CN)-C-13 and (CO)-C-12/(CO)-C-13 follows from the coexistence of CN and CO in diffuse cloud cores. However, an ICE reaction with CN may mitigate the enhancements in (CN)-C-12/(CN)-C-13 for lines of sight with low (CO)-C-12/(CO)-C-13 ratios. For two sight lines with high values of (CO)-C-12/(CO)-C-13, our results indicate that about 50% of the carbon is locked up in CO, which is consistent with the notion that these sight lines probe molecular cloud envelopes where the transition from C+ to CO is expected to occur. An analysis of CN rotational excitation yields a weighted mean value for T-01((CN)-C-12) of 2.754 +/- 0.002 K, which implies an excess over the temperature of the cosmic microwave background (CMB) of only 29 +/- 3 mK. This modest excess eliminates the need for a local excitation mechanism beyond electron and neutral collisions. The rotational excitation temperatures in (CN)-C-13 show no excess over the temperature of the CMB.Robert A. Welch Foundation F-634McDonald Observator
Cn-Cer’s profile in various tissues.
No full textResults are presented as pmol Cn-Cer/mg protein with means ± st dev. of 6x replicates. A. Brain; B. Heart; C. Kidney; D. Lung; E. Bladder; F. Spleen; G. Liver; H. Blood plasma; I. Tumor xenograft.</p
A Percyanovinylidene -Ruthenium Complex, Ru{=C=C(5)(CN)(3)[=C(CN)(2)](2)}(dppe)Cp*
No full textThe reaction between Ru(C=CC=CAg)(dppe)Cp* and tcne affords a novel percyanovinylidene complex by an unusual decyano-dimerization reaction of the cyanocarbon with the diynyl fragment. This complex is also obtained from tcne and Ru{C=CC=C[Au(PPh3)]}(dppe)Cp*, together with Ru{C=CC[=C(CN)2]C[Au(PPh3)]=C(CN)2}(dppe)Cp *, formed by the anticipated [2 + 2] cycloaddition and subsequent ring-opening reactions. © 2011 American Chemical Society.Michael I. Bruce, Jonathan C. Morris, Brian K. Nicholson, Brian W. Skelton, Allan H. White, and Natasha N. Zaitsev
BONDING AND DYNAMICS OF CNRg AND CRg COMPLEXES
No full textAuthor Institution: Department of Chemistry, Emory University, Atlanta, GA 30322The van der Waals complexes of CN and C with rare gas atoms (Rg) are of interest from the perspectives of their bonding characteristics and predissociation dynamics. Matrix isolation data indicate that that the bonding ranges from a weak van der Waals interaction for the Ne complexes to incipient chemical bonding for Xe. The low-lying vibronic states of CN and C are interleaved, which facilitates electronic energy transfer. Consequently, electronic predissociation of CNRg and CRg complexes provides a useful means to examine the detailed dynamics of electronic energy transfer. Predissociation processes for CNRg complexes have been characterized using double resonance techniques. The final state distributions exhibit symmetry preferences that yield insights concerning the topologies of the relevant potential energy surfaces. In addition, bond energies can be deduced from the predissociation dynamics. Data for the binary complexes CNRg (Rg=Ne, Ar, Kr, and Xe) and CRg will be presented, along with theoretical analyses based on potential energy surfaces
Gas-phase formation and spectroscopic characterization of the disubstituted cyclopropenylidenes c-C3(C2H)2, c-C3(CN)2, and c-C3(C2H)(CN)
No full textAims. The detection of c-C3HC2H and possible future detection of c-C3HCN provide new molecules for reaction chemistry in the dense ISM where R-C2 and R-CN species are prevalent. Determination of chemically viable c-C3HC2H and c-C3HCN derivatives and their prominent spectral features can accelerate potential astrophysical detection for this chemical family. This work will characterize three such derivatives: c-C3(C2H)2, c-C3(CN)2, and c-C3(C2H)(CN).
Methods. Interstellar reaction pathways of small carbonaceous species are well-replicated through quantum chemical means. Highly-accurate cc-pVX Z-F12/CCSD(T)-F12 (X =D,T) calculations generate the energetics of chemical formation pathways as well as the basis for quartic force field and second-order vibrational perturbation theory rovibrational analysis of the vibrational frequencies and rotational constants of the molecules under study.
Results. The formation of c-C3(C2H)2 is as thermodynamically and, likely, stepwise favorable as the formation of c-C3HC2H, rendering its detectability to be mostly dependent on the concentrations of the reactants. c-C3(C2H)2 and c-C3(C2H)(CN) will be detectable through radioastronomical observation with large dipole moments of 2.84 D and 4.26 D, respectively, while c-C3(CN)2 has an exceedingly small and likely unobservable dipole moment of 0.08 D. The most intense frequency for c-C3(C2H)2 is ν2 at 3316.9 cm−1 (3.01 µm) with an intensity of 140 km mol−1. c-C3(C2H)(CN) has one frequency with a large intensity, ν1, at 3321.0 cm−1 (3.01 µm) with an intensity of 82 km mol−1. c-C3(CN)2 lacks intense vibrational frequencies within the range that current instrumentation can readily observe.
Conclusions. c-C3(C2H)2 and c-C3(C2H)(CN) are viable candidates for astrophysical observation with favorable reaction profiles and spectral data produced herein, but c-C3(CN)2 will not be directly observable through any currently-available remote sensing means even if it forms in large abundances
Topological duality on the function space H(CN)
No full textBy a classical theorem, there is an isomorphism between the space of entire functions of exponential type on Cn,ExpCn, and the analytic functions on H(Cn),H′(Cn) [see, for example, F. Trèves, Topological vector spaces, distributions, and kernels, Academic Press, New York, 1967; MR0225131 (37 #726)]. In this note, the author extends this useful theorem to H(CN), the space of analytic functions on the countable product of complex lines. Specifically, he considers H(CN) endowed with the compact-open topology τ0 and the associated bornological topology τδ. For both τ=τ0 and τδ, the author characterizes the strong duals (H(CN),τ)′ as spaces of entire functions of exponential type on CN. {Reviewer's remark: In the meantime the author has shown (private communication) that these dual spaces are different.}Depto. de Análisis Matemático y Matemática AplicadaFac. de Ciencias MatemáticasTRUEpu
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