Electron impact mass spectrometry of 3-hydroxy-3,4,5,6-tetrahydro-2H-[1]benzoxocines. A comparison with the behaviour of isomeric 2-hydroxymethyl-2,3,4,5-tetrahydro-[1]-benzoxepines and 1,2-epoxy-5-(2-hydroxyphenyl)pentane

The mass spectrometric behavior of 3-methyl-3-hydroxybenzoxocines has been studied in detail by means of linked scans and mass analyzed ion kinetic energy spectrometry. The structure of the molecular ion and the fragmentation processes are strictly related to the structure of the neutral moieties. The possible isomerization of 3-hydroxy-10-methoxy-3-methyl-3,4,5,6-tetrahydro-2H-[1]benzoxocine to 2-methyl-2-[3-(3′-methoxy-2′-hydroxy)phenyl]pentyloxirane and to 2-hydroxymethyl-9-methoxy-2-methyl-2,3,4,5-tetrahydro[1]benzoxepine is investigated.     

Why downfield proton chemical shifts are not reliable aromaticity indicators

Traces of magnetizability, traces of magnetic shielding at the hydrogen nuclei, and nucleus-independent chemical shift are not reliable aromaticity quantifiers for planar conjugated hydrocarbons. A measure of aromaticity is provided by the out-of-plane tensor components, whose magnitude is influenced by the pi-ring currents. The failure of nucleus-independent chemical shift in this regard was proved for the molecule shown in the abstract graphic, sustaining a diatropic pi-current. The validity of the ring-current model is reaffirmed. [structure: see text]     

Proton controlled intramolecular communication in dinuclear ruthenium(II) polypyridine complexes

The synthesis and characterization of two dinuclear ruthenium polypyridyl complexes based on the bridging ligands 5,5'-bis(pyridin-2' '-yl)-3,3'-bis(1H-1,2,4-triazole) and 5,5'-bis(pyrazin-2' '-yl)-3,3'-bis(1H-1,2,4-triazole) and of their mononuclear precursors are reported. The dinuclear compounds have been prepared by a Ni(0) catalyzed coupling of a mononuclear ruthenium(II) polypyridyl complex containing a brominated triazole moiety. Electrochemical and photophysical studies indicate that, in these dinuclear complexes, the protonation state of the bridge may be used to tune the intercomponent interaction between the two metal centers and that these species act as proton driven three-way molecular switches that can be read by electrochemical or luminescence techniques.     

Heterodinuclear Ln[bond]Na complexes with an asymmetrical macrocyclic compartmental Schiff base

Heterodinuclear lanthanide(III)-sodium(I) complexes [LnNa(L)(Cl)(2)(CH(3)OH)] (Ln=La[bond]Nd, Sm[bond]Lu), where H(2)L is a [1+1] asymmetric compartmental macrocyclic ligand containing a N(3)O(2) Schiff base and a O(3)O(2) crown-ether-like coordination site, have been prepared and characterized by IR, (1)H, (13)C, and (23)Na NMR spectroscopy, mass spectrometry, and electron microscopy. In the solid state, the lanthanide(III) ions coordinate the Schiff-base N(3)O(2) site, and the sodium ion occupies the O(3)O(2) crownlike cavity, as shown by the X-ray crystal structures of the Nd, Eu, Gd, and Yb derivatives. In these complexes, the lanthanide(III) ion is coordinated by two chlorine atoms in the trans position and by three nitrogen and two negatively charged phenol oxygen atoms of the Schiff base, and the ion is heptacoordinated with a pentagonal bipyramidal geometry. The sodium ion is coordinated by three etheric oxygen atoms and the two phenolic oxygens that act as a bridge. A methanol molecule is also coordinated in the apical position of the resulting pentagonal pyramidal polyhedron. A detailed (1)H and (13)C NMR study was carried out in CD(3)OD for both diamagnetic and paramagnetic heterodinuclear complexes [LnNa(L)(Cl)(2)(CH(3)OH)]. The complexes are also isostructural in solution, and their structures parallel those found in the solid state. Moreover, some significative distances determined in the solid state and in solution are comparable. Finally, the potential use of these complexes as molecular probes for the selective recognition of specific metal ions has been tested. In particular, their ability to act as shift reagents and the selectivity of the O(3)O(2) site towards Li(+), Ca(2+), and K(+) were investigated by (23)Na NMR spectroscopy.     

Thermal decomposition mechanisms of sequential bipolyesters based on propeneglycol and hydroxybenzoic/phthalic diacid derivatives

Some bipolyesters consisting of 1,2-propene glycol residue (P) and symmetric aromatic diacid residue constituted by two p-oxybenzoyl groups coupled by a terephthaloyl (HTH), phthaloyl (HOH) and isophthaloyl (HIH) group, and a nonsymmetric diacid residue constituted by a p-oxybenzoyl and a terephthaloyl group (HT), have been investigated by direct pyrolysis–mass spectrometry. The results show that intramolecular exchange reactions occurring at the pyrolysis stage cause a reorganization of the copolymer sequences. Sequential bipolyesters I–IV are ideal materials for the investigation of the extent of thermal reorganization induced in the bipolymer sequences by the pyrolytic process.     

Preparation and crystal structure of a copper(II) uranyl(VI) binuclear chelate

Summary The structure of the heterobinuclear complex of Cu²⁺ and [UO₂]²⁺ with the tetraanionic ligand derived from the condensation of 1,2-diaminoethane witho-acetoacetylphenol has been determined from diffractometer data and refined to R = 5.2%. The crystals are monoclinic,P2₁/a, witha = 26.22(2),b = 14.79(2),c = 8.10(1) Å and = 104.65(5)°; Z = 4. The ligand employed has two different coordination sets of atoms, N₂O₂ and O₂O₂, two oxygen atoms being common to both donor sets. In the complex the copper atom, which is retained in the inner N₂O₂ chamber, is five coordinate being axially bonded to a solvent molecule, whilst the uranyl ion is incorporated in the outer O₂O₂ chamber. Another molecule of solvent is retained to preserve the preferred seven coordination of uranium.     

Preparation of block copolymers by use of peroxide-terminated prepolymer

Block copolymers containing poly(tetramethylene oxide) and poly(methyl methacrylate) segments were prepared. A commercially available poly(tetramethylene oxide) terminated with tolylene diisocyanate was capped with tert-butyl hydroxymethyl peroxide and the resulting prepolymer peroxide was used as a free-radical initiator of vinyl polymerization. Block copolymers formed in temperature-programmed vinyl polymerizations possessed improved impact strengths over poly(methyl methacrylate) from 0.35 to 1.18 for a fixed (nonoptimized) block length of poly(tetramethylene oxide).     

Molecular orbital theory of the properties of inorganic and organometallic compounds. 3. STO-3G basis sets for first- and second-row transition metals

STO -3G minimal basis sets for first- and second-row transition metals have been formulated and applied to the calculation of equilibrium geometries for a variety of inorganic systems, metal carbonyls, and organometallic compounds. While the overall level of agreement with experiment is not as good as that previously noted for main-group compounds, most trends and many subtle features in geometries are reproduced.     

Mass displacements in quadrupolar field analysers

The influence of different instrumental parameters on the mass displacements observed in an ion trap and a quadrupole mass filter was investigated. In ion trap measurements it was observed that isolated ions (obtained by both ‘apex’ and ‘two-step’ isolation methods) show the same mass displacements determined in the usual mass spectra; isobaric ions of different structure irradiated with supplementary a.c. fields are ejected at different a.c. voltages, and different cooling times do not affect the mass value. In the quadrupole mass filter, differences in mass were found among isobaric ions of different structure, although to a smaller extent than those observed in the ion trap. All the data obtained are in agreement with the hypothesis of ion–r.f. field interactions originating from the polarizability of the ion.     

Reaction of ketenes with N,N-disubstituted 2-aminomethylenecycloalkanones. V. Synthesis of N,N-disubstituted 4′-aminospiro [1,3-dithiane-2,3′-(5′,6′-polymethylene-3′,4′-dihydro-α-pyrones)]

The reaction of 2-carbonyl-1,3-dithiane, a sulfene prepared in situ from 2-chloroearbonyl-1,3-dithiane and triethylamine, with N,N-disubstituted 2-aminomethylvnecycloalkanones gave the 1,4-cycloadducts, namely N,N-disubstituted 4′-aminospiro[1,3-dithiane-2,3′-(5′,6′-poly-methylene-3′,4′-dihydro-α-pyrones)].