Gas phase ultraviolet photoelectron spectra of hydroxyanthraquinones

The gas phase u.v. photoelectron spectra of anthraquinone, 1,4-OH-1,8-OH-2,6-OH-1-NH₂-and 1-NH₂-4-OH-anthraquinones have been measured using HeI radiation. Semiempirical HAM/3 calculations have been employed to help in the band assignment. The lowest ionization potential of all the studied compounds is of π-type, except of anthraquinone where the n-O(CO) ionization is the lowest one. The results show that the intramolecular OH ⋯ O bonding stabilizes the n-orbital by ca 0.4 eV, and that the IP_n+−IP_n− energy difference should not exceed 0.5 eV, very close to that found in para-benzoquinone. No hydrogen bonding effects of the NH₂ group are apparent.     

Condensed phase photochemistry of acetic acid in the vacuum UV

The vacuum ultraviolet (VUV) photolysis of acetic acid (HAC) in Ar, N₂, CO and CO-doped argon matrices was performed at 10 K by systematically exciting into specific absorption bands with various VUV resonance line sources. The major overall processes which occur as a reuslt of photoexcitation are (1) CH₃COOH + hν → CH₄ + CO₂, (2) and (3) CH₃COOH + hν → CH₃ + CO₂ + H and (4) CH₃COOH + hν → CH₃OH + CO. All three of these overall processes occur to varying extents as a result of excitation into the four VUV bands of HAC. The results of experiments performed in CO and N₂ matrices suggest that reactions (2) and/or (3) dissociate from triplet states corresponding to n′ → π^* and n → σ^* (3s) transitions. Isotopic CD₃COOH experiments were performed and assisted in confirming previously proposed gas phase mechanisms.     

Condensed phase ionic polarizabilities from plane wave density functional theory calculations

A method is presented to allow the calculation of the dipole polarizabilities of ions and molecules in a condensed-phase coordination environment. These values will be useful for understanding the optical properties of materials and for developing simulation potentials which incorporate polarization effects. The reported values are derived from plane wave density functional theory calculations, though the method itself will apply to first-principles calculations on periodic systems more generally. After reporting results of test calculations on atoms to validate the procedure, values for the polarizabilities of the oxide ion and various cations in a range of materials are reported and compared with experimental information as well as previous theoretical results.     

Condensed phase aromatization during degradation of poly(vinyl chloride)

Proton NMR results for partially degraded PVC show that aromatization accompanies dehydrochlorination in the condensed phase; subsequent fragmentation leads to loss of volatile aromatics.     

The gas phase X-ray photoelectron spectrum of N,N-dimethyl-p-nitroaniline

The N1s and O1s regions of gaseous N,N-dimethyl-p-nitroaniline have been studied by X-ray photoelectron spectroscopy. The N1s (-NO₂) peak is ≈0.5 eV broader than the N1s (-NH₂) peak, indicating the presence of intense, unresolved shake-up. A shake-up peak has been observed in the O1s region at 2.1 eV higher binding energy than the main peak, with a relative intensity of 50%. The results have been compared with the corresponding features in the paranitroaniline and in the solid, and it has been found that the O1s shake-up intensity remains essentially unchanged while the N1s shake-up is enhanced in going to the solid. Comparison has also been made with a CNDO/S CI calculation which somewhat underestimates the relative intensities but is in good overall agreement with experiment.     

Gas phase high temperature photoelectron spectroscopy: The tin monoxide molecule

The HeI photoelectron spectrum of SnO (X¹Σ⁺) has been recorded. Two bands have been observed corresponding to ionization from the 6π and 13 ionization energies of 9.98 and 10.12 eV respectively. Vibrational structure associated with the first band has been analysed to give

and D_e = 3.23 ± 0.10 eV in the SnO⁺ (X²Π) state. An assessment has been made of the ability of Hartree-Fock-Slater calculations, multiple-scattering SCF-Xα calculations and ab ini energies for the group IV diatomic monoxide molecules.     

Ultraviolet photoelectron spectroscopy study of the thermochromic phase transition in urethane-substituted polydiacetylenes

Threshold solid-state ionization energies determined from ultraviolet photoelectron spectra are reported for the thermochromic polydiacetylenes (PDAs) from the bis-ethyl- and bis-n-propyl urethanes of 5,7-dodecadiyn-1,12-diol (ETCD and PUDO, respectively) and the nonthermochromic 1,6-bis-p-toluenesulfonate of 2,4-hexadiyne-1,6-diol (PTS) at temperatures above and below the thermochromic phase transition. PDA-PTS has an ionization energy of 5.66 eV which does not change significantly as the temperature is raised above 140 degrees C. At 25 degrees C, PDA-ETCD and PDA-PUDO have threshold ionization energies of 5.65 and 5.51 eV, respectively. The ionization energies of these PDAs increase by approximately 0.34 eV as temperature is raised above 140 degrees C and returns to the lower values as temperature is reduced to 25 degrees C. The magnitude of the increase in ionization energy on heating to temperatures above the thermochromic transition is very close to the shift in energy of the electronic spectrum over the same temperature range. These observations suggest that the structural changes that take place in the course of the thermochromic transition are primarily associated with the valence band and are consistent with partial relief of mechanical strains.     

高分子单链凝聚成与线团相互穿透的多链凝聚态

高分子单链凝聚态由于链内链结构单元间存在范德化吸引作用,高分子链呈打圈链构象,而多链凝聚态由于链内链单元间的吸引作用被与相互穿透的近邻链的单元间吸引作用所屏蔽,高分子链呈高斯链构象。本文简要介绍单链凝聚态试样的制备方法,单链单晶体、单链玻璃体、溶胀的单链高弹态拉伸等的实验观察,并提出从单链凝聚态到多链凝聚态的转变过程问题,即高分子线团的相互穿透过程,目前还缺少基础了解。     

Condensed Metal Clusters

The chemistry of metals in low valence states is marked by the frequent occurrence of metal clusters, which are easily recognizable when they occur as molecular units. Many metal-rich compounds of transition metals with p-elements (3rd to the 6th main groups) are closely related to the corresponding halides, since they are built up from metal clusters of the same type. The clusters are however, linked together (condensed) by metal-metal bonds. This principle of construction holds particularly well in the case of the novel reduced halides of the lanthanoids.     

Condensed pyrimidoheterocyclic systems

It is shown that reaction of 1, 2, 3, 5, 6, 7-hexahydropyrazolo[1, 5-a]pyrimidine-5, 7-dione with several amines results in the fission of the dioxopyrimidine ring. A mechanism for the ring fission is suggested.     

高分子单链凝聚态与线团相互穿透的多链凝聚态

高分子单链凝聚态由于链内链结构单元间存在范德华吸引作用,高分子链呈打圈链构象,而多链凝聚态由于链内链单元间的吸引作用被与相互穿透的近邻链的单元间吸引作用所屏蔽,高分子链呈高斯链构象.本文简要介绍单链凝聚态试样的制备方法,单链单晶体、单链玻璃体、溶胀的单链高弹态拉伸等的实验观察,并提出从单链凝聚态到多链凝聚态的转变过程问题,即高分子线团的相互穿透过程,目前还缺少基础了解.     

Condensed lamellar phase in ternary DNA-DLPC-cationic gemini surfactant system: a small-angle synchrotron X-ray diffraction study

We report on a small-angle synchrotron X-ray diffraction study of dilauroylphosphatidylcholine (DLPC) liposomes aggregated with high molecular DNA in the presence of 1,4-butanediammonium-N,N'-dilauryl-N,N,N',N'-tetramethyl gemini surfactant cations (C12GS). The aggregates prepared at the DLPC/C12GS/DNA phosphate group=2:1:1.6 molar ratio in 0.0015 mol x l(-1) NaCl aqueous solution exhibit Bragg reflections due to lamellar lipid bilayer stacking and the Bragg reflection typical of one-dimensional DNA lattice with parallel strands intercalated between lipid bilayers. In this condensed fluid lamellar L(alpha)(c) phase, the interactions between DNA and charged bilayers damp the thermally induced bilayer undulations. The diffraction data obtained with the mixture of DLPC liposomes and DNA (at DNA phosphate group/DLPC=0.8:1 molar ratio) indicate a DNA-lipid interaction in the absence of C12GS.     

Interleaflet interaction and asymmetry in phase separated lipid bilayers: molecular dynamics simulations

In order to investigate experimentally inaccessible, molecular-level detail regarding interleaflet interaction in membranes, we have run an extensive series of coarse-grained molecular dynamics simulations of phase separated lipid bilayers. The simulations are motivated by differences in lipid and cholesterol composition in the inner and outer leaflets of biological membranes. Over the past several years, this phenomenon has inspired a series of experiments in model membrane systems which have explored the effects of lipid compositional asymmetry in the two leaflets. The simulations are directed at understanding one potential consequence of compositional asymmetry, that being regions of bilayers where liquid-ordered (L(o)) domains in one leaflet are opposite liquid-disordered (L(d)) domains in the other leaflet (phase asymmetry). The simulated bilayers are of two sorts: 1) Compositionally symmetric leaflets where each of the two leaflets contains an identical, phase separated (L(o)/L(d)) mixture of cholesterol, saturated and unsaturated phospholipid; and 2) Compositionally asymmetric leaflets, where one leaflet contains a phase separated (L(o)/L(d)) mixture while the other contains only unsaturated lipid, which on its own would be in the L(d) phase. In addition, we have run simulations where the lengths of the saturated lipid chains as well as the mole ratios of the three lipid components are varied. Collectively, we report on three types of interleaflet coupling within a bilayer. First, we show the effects of compositional asymmetry on acyl chain tilt and order, lipid rotational dynamics, and lateral diffusion in regions of leaflets that are opposite L(o) domains. Second, we show substantial effects of compositional asymmetry on local bilayer curvature, with the conclusion that phase separated leaflets resist curvature, while inducing large degrees of curvature in an opposing L(d) leaflet. Finally, in compositionally symmetric, phase separated bilayers, we find phase asymmetry (domain antiregistration) between the two leaflets occurs as a consequence of mismatched acyl chain-lengths in the saturated and unsaturated lipids.     

Condensed Extended Hyper-Wiener Index

According to the definitions of molecular connectivity and hyper-Wiener index, a novel set of hyper-Wiener indexes （Dn, ^mDn） were defined and named as condensed extended hyper-Wiener index, the potential usefulness of which in QSAR/QSPR is evaluated by its correlation with a number of C3-C8 alkanes as well as by a favorable comparison with models based on molecular connectivity index and overall Wiener index.     

Gas phase thermolysis of pyrazolines. 5. Electronic structure and gas phase thermolysis of tetrazole derivatives studied by photoelectron spectroscopy

The photoelectron spectra of substituted tetrazoles 1–3 , 1,4-dihydro-5H-tetrazol-5-ones 4–9 , and 1,4-dihydro-5H-tetrazole-5-thiones 10–15 have been recorded. Based on PM3 and some ab initio calculations, the ionization potentials have been assigned to molecular orbitals. Gas-phase thermolyses of 1–15 have been studied by real-time gas analysis controlled by photoelectron spectroscopy. Compounds 1 and 2 lose formaldehyde and thioformaldehyde, respectively, leaving unsubstituted tetrazole (16), which decomposes mainly through extrusion of a nitrogen molecule and formation of cyanamide. Thiirane is split off from 3, and the remaining molecule decomposes into smaller products. Compounds 4–9 are cleaved by [3+2] cycloreversion to isocyanates and azides. Some of the unsymmetrically substituted compounds exhibit a marked selectivity in this reaction. For thiones 10–15 [3+2] cycloreversion is the main way of decomposition affording isothiocyanates and azides. In addition, the sulfur atom can split off and dimerize or abstract hydrogen atoms to form hydrogen sulfide. Some products like thiirene, formaldehyde, thioformaldehyde and acetaldehyde are generated solely from substituents. Photoelectron spectroscopy proved to be an excellent method for such thermolysis studies.     

Valence anions of N-acetylproline in the gas phase: computational and anion photoelectron spectroscopic studies

We report the photoelectron spectrum of anionic N-acetylproline, (N-AcPro)(-), measured with 3.49 eV photons. This spectrum, which consists of a band centered at an electron binding energy of 1.4 eV and a higher energy spectral tail, confirms that N-acetylproline forms a valence anion in the gas phase. The neutrals and anions of N-AcPro were also studied computationally at the B3LYP∕6-31++G(d,p) level. Based on the calculations, we conclude that the photoelectron spectrum is due to anions which originated from proton transfer induced by electron attachment to the π* orbital localized at the acetyl group of N-AcPro. We also characterized the energetics of reaction paths leading to pyrrolidine ring opening in the anionic N-AcPro. These data suggest that electron induced decomposition of peptides/proteins comprising proline strongly depends on the presence of proton donors in the close vicinity to the proline residue.     

Condensed and bonded quinoxalines

Arylamides of (1,2,3,4-tetrahydro-2-oxo-3-quinoxalyl)acetic acid were obtained by reaction of N-arylmaleinimides with o-phenylenediamine and were converted to the corresponding quinoxalones by dehydrogenation with chloranil. The structures of the compounds obtained were confirmed by chemical transformations and IR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 264–266, February, 1973.See [1] for communication III.Deceased.