Structural features of aliphatic N-nitrosamines of 7-azabicyclo[2.2.1]heptanes that facilitate N-NO bond cleavage

N-Nitrosamines can be considered as potential nitric oxide (NO)/nitrosonium ion (NO(+)) donors. However, the relation of the structures of N-nitrosamines, in particular of aliphatic N-nitrosamines, to the characteristics of release of NO or NO(+) remains unclear. Here we show that aliphatic N-nitrosoamines of 7-azabicyclo[2.2.1]heptanes can undergo heterolytic N-NO bond cleavage. On the basis of the observation of reduced rotational barriers of the N-NO bonds in solution and nitrogen-pyramidal structures of the N-nitroso group in the solid state, we postulate that N-NO bond cleavage of N-nitrosamines is enhanced by a reduction of the resonance in the N-NO group. Computational studies suggest that these structural features of the N-nitrosamines of 7-azabicyclo[2.2.1]heptane are derived from angle strain imposed on the CNC angles.     

Influence of the reaction temperature and ph on the coordination modes of the 1,4-benzenedicarboxylate (BDC) ligand: a case study of the Ni(II)(BDC)/2,2'-bipyridine system

Three new Ni(BDC)/2,2'-bipy compounds, Ni2(BDC)(HBDC)2(2,2'-bipy)2 (2), Ni3(BDC)3(2,2'-bipy)2 (3), and Ni(BDC)(2,2-bipy)2.2H2O (5), in addition to the previously reported Ni(BDC)(2,2'-bipy).0.75H2BDC (1) and Ni(BDC)(2,2'-bipy)(H2O) (4) [BDC = 1,4-benzenedicarboxylate; 2,2'-bipy = 2,2'-bipyridine], have been synthesized by hydrothermal reactions. A systematic investigation of the effect of the reaction temperature and pH resulted in a series of compounds with different compositions and dimensionality. The diverse product slate illustrates the marked sensitivity of the structural chemistry of polycarboxylate aromatic ligands to synthesis conditions. Compound 1, which has a channel structure containing guest H2BDC molecules, is formed at the lowest pH. The guest H2BDC molecules are connected by hydrogen bonds and form extended chains. At a slightly higher pH, a dimeric molecular compound 2 is formed with a lower number of protonated carboxylate groups per nickel atom and per BDC ligand. Reactions at higher temperature and the same pH lead to the transformation of 1 and 2 into the two-dimensional, layered trinuclear compound 3. As the pH is increased, a one-dimensional polymer 4 is formed with a water molecule coordinated to Ni2+. Bis-monodentate and bischelating BDC ligands alternate along the chain to give a crankshaft rather than a regular zigzag arrangement. A further increase of the pH leads to the one-dimensional chain compound 5, which has two chelating 2,2'-bipy ligands. Crystal data: 2, triclinic, space group P, a = 7.4896(9) angstroms, b = 9.912(1) angstroms, c = 13.508(2) angstroms, alpha = 86.390(2) degrees , beta = 75.825(2) degrees, gamma = 79.612(2) degrees, Z = 2; 3, orthorhombic, space group Pbca, a = 9.626(2) angstroms, b = 17.980(3) angstroms, c = 25.131(5) angstroms, Z = 4; 5, orthorhombic, space group Pbcn, a = 14.266(2) angstroms, b = 10.692(2) angstroms, c = 17.171(2) angstroms, Z = 8.     

Thermodynamic Insight into the Origin of a Calix[n]arene-[60]fullerene Interaction and its Application to a Porphyrin-[60]fullerene Energy Transfer System

The calixarene-fullerene interaction,which causes only a slight change in the absorptionspectra, has been substantiated by calorimetricmeasurements: the H° values arecomparable with those obtained from the associationconstants estimated by a spectroscopic method. Furthermore, we determined the association constantbetween homooxacalix[3]arene and [60]fullerenederivatives with a porphyrin moiety by fluorescencespectra.     

Substituent effects on the kinetics for the chemiluminescence reaction of 6-arylimidazo[1,2-a]pyrazin-3(7H)-ones (Cypridina luciferin analogues): support for the single electron transfer (SET)-oxygenation mechanism with triplet molecular oxygen

Kinetics of chemiluminescence reactions of 2-methyl-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one (1c, Cypridina luciferin analogue) and substituent effects of the 6-aryl group of derivatives 1 strongly suggest that the rate-determining step is a single electron transfer from an anion derived from 1 to a triplet molecular oxygen (O₂) in the oxygenation process.     

Chloroprene as a source of fine chemicals: palladium-catalyzed synthesis of terminal allenes

[reaction: see text] Several functionalized terminal allenes were prepared in moderate to excellent yield by a palladium-catalyzed reaction of chloroprene (2-chloro-1,3-butadiene) with soft nucleophiles.     

On the Theory of Gravitational Field in Finsler Spaces

Some structural considerations are made on the Finslerian gravitational field: A Finslerian metrical structure such as g_λχ(x, y) = γ_λχ(x) + h_λχ(x, y) is proposed, where γ_λχ denotes the Riemann metric of Einstein's gravitational field, while hλχ the Finsler metric induced by the Riemann metric h_ij(y) of the internal field; The intrinsic behaviour of the internal variable y, which is expressed as ?ⁱ = K(x, y) y^j in the internal field, is grasped by the Finslerian parallelism δyⁱ (=0), which is reflected in the spatial structure of the external gravitational field by the mapping relation δy^χ = e(x) δyⁱ. The whole metrical Finsler connection D for g_λχ(i.e., Dg_λχ = 0) is determined by taking account of the intrinsic behaviour δy^χ.     

Study of a high-dimensional chaotic attractor

The nature of a very high-dimensional chaotic attractor in an infinite-dimensional phase space is examined for the purpose of studying the relationships between the physical processes occurring in the real space and the characteristics of high-dimensional attractor in the phase space. We introduce two complementary bases from which the attractor is observed, one the Lyapunov basis composed of the Lyapunov vectors and the another the Fourier basis composed of the Fourier modes. We introduce the exterior subspaces on the basis of the Lyapunov vectors and observe the chaotic motion projected onto these exteriors. It is shown that a certain statistical property of the projected motion changes markedly as the exterior subspace goes out of the attractor. The origin of such a phenomenon is attributed to more fundamental features of our attractor, which become manifest when the attractor is observed from the Lyapunov basis. A counterpart of the phenomenon can be observed also on the Fourier basis because there is a statistical one-to-one correspondence between the Lyapunov vectors and the Fourier modes. In particular, a statistical property of the high-pass filtered time series reflects clearly the difference between the interior and the exterior of the attractor.     

Novel synthesis of macrocycles with 1,1′-binaphthalene-2,2′-diol using intramolecular oxidative coupling

A new series of BINOL-based macrocycles with two phenolic protons have been synthesized via oxidative coupling reaction using CuCl(OH)-TMEDA.     

Do solid surface potential barriers retard convoy peak electrons?

Using a coaxial cylindric electron spectrometer and an electrostatic ion energy analyzer in tandem, a direct measurement of the difference of the energy of convoy peak electron and the electron equivalent ion energy of protons emerging from the downstream surface of C, Au and Al foils is performed in the proton energy range from 60 to 250 keV. This measurement is made possible using the accepted evidence that for a gas target these energies are equal. It is found that also for the beam foil convoy peak electrons, within an experimental average uncertainty of about ±0.1 eV, there is no difference between these energies. If one accepts that the origin of convoy electrons is from inside the solid, the conclusion is that no retardation by the solid surface potential barrier, which is of the order of a few eV, is observed. This is attributed to the strong electron-ion Coulomb interaction which almost completely overshadows the force exerted on the electron by the field of the surface barrier.