Analysis of cyanoacrylate ultraviolet absorbers using liquid chromatography/atmospheric pressure chemical ionization mass spectrometry: influence of fragmentor voltage and solvent on ionization and fragmentation behaviors

Ionization efficiencies and fragmentation patterns of cyanoacrylate ultraviolet (UV) absorbers, Uvinul 3035 and Uvinul 3039, were studied using liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS). Solvent effect on the ionization efficiencies was investigated using methanol, ethanol, acetone, and chloroform. The fragmentation patterns were also investigated by varying the fragmentor voltage. Solvated ions, the [M+H + solvent](+) of methanol, ethanol, and acetone were detected, but the [M+H + chloroform](+) ion was not observed. For Uvinul 3039 in chloroform, the [M+CHCl(2)](+) ion was detected instead of the solvated ion. Relative abundance of the solvated ion was decreased by increasing the fragmentor voltage. Fragment ions of m/z 250, 232, and 204 were detected and their abundance increased with an increase in the fragmentor voltage. The m/z 250 ion can be accounted for by a McLafferty rearrangement. The fragment ions of m/z 232 and 204 were formed not only by subsequent fragmentations of the m/z 250 ion, but also by ion-molecule reactions of solvent ion and neutral analyte.     

Structural transformation due to Co-host inclusion in ionic clathrate hydrates

The present findings on the co-host role in restructuring the host water framework might provide important information on tuning the cage dimensions via lattice distortion and promoting the total number of cages via structural transformation. This co-host-induced structural modification can improve the physicochemical properties of ionized clathrate hydrates, particularly given that the host framework is able to function as a pathway to deliver protons or electrons.     

Intermolecular interaction-induced hierarchical transformation in 1D nanohybrids: analysis of conformational changes by 2D correlation spectroscopy

We have examined both self-assembly and confinement effect in room-temperature ionic liquid (RTIL)-aluminum hydroxide hybrids (RAHs) to attain a fundamental understanding of special phenomena in nanoscale spaces as well as to design functional nanomaterials for practical applications. Phase-controlled one-dimensional (1D) RAHs were synthesized through a simple ionothermal process. The RAHs were hierarchically transformed in terms of the molecular structures, morphologies, and phases of the materials during the ionothermal process with respect to the concentration of RTIL. In addition to the hierarchical transformation, the RTIL/aluminum hydroxide nanohybrids revealed unexpected physical behaviors, including thermal transition variation of the RTIL in confined environments and a phase transition from nanosolid to nanoliquid affected by changes of the melting points. More importantly, intermolecular interaction induced-self-assembly and confinement effect of RTILs inside an integrated hybrid system, which have not been clearly explained to date, were analyzed by 2D infrared correlation spectroscopy (2D IR COS); dynamic behaviors of RTILs, i.e., sequentially spatial reorientation and kinetically conformational changes, were attributed to the interactions between RTILs and aluminum hydroxides. 2D IR COS offers a new way to interpret highly complex, veiled systems such as the formation mechanism of nanoparticles, biomineralization, self/supramolecular assembly, and nanoconfinement.     

Single-conformation ultraviolet and infrared spectroscopy of model synthetic foldamers: beta-peptides Ac-beta3-hPhe-NHMe and Ac-beta3-hTyr-NHMe

The conformational preferences and infrared and ultraviolet spectral signatures of two model beta-peptides, Ac-beta3-hPhe-NHMe (1) and Ac-beta3-hTyr-NHMe (2), have been explored under jet-cooled, isolated molecule conditions. The mass-resolved, resonant two-photon ionization spectra of the two molecules were recorded in the region of the S0-S1 origin of the phenyl or phenol ring substituents, respectively. UV-UV hole-burning spectroscopy was used to determine that two conformations of 1 are present, with the transitions due to conformer A, with S0-S1 origin at 34431 cm(-1), being almost 20 times larger than those due to conformer B, with S0-S1 origin at 34404 cm(-1). Only one conformation of 2 was observed. Resonant ion-dip infrared spectroscopy provided single-conformation infrared spectra in the 3300-3700 cm(-1) region. The spectra of conformer A of both molecules have H-bonded and free amide NH stretch infrared transitions at 3400 and 3488 cm(-1), respectively, while conformer B of 1 possesses bands at 3417 and 3454 cm(-1). For comparison with experiment, full optimizations of all low-lying minima of 1 were carried out at the DFT B3LYP/6-31+G* and RIMP2/aug-cc-pVDZ levels of theory, and single point MP2/6-31+G* calculations at the DFT geometries. On the basis of the comparison with previous studies in solution and the calculated results, conformer A of 1 and 2 were assigned to a C6 conformer, while conformer B of 1 was assigned to a unique C8 structure with a weak intramolecular H-bond. The reasons for the preference for C6 over C8 structures and the presence of only two conformations in the jet-cooled spectrum are discussed in light of the predictions from calculations.     

A cytotoxic and apoptosis-inducing sesquiterpenoid isolated from the aerial parts of Artemisia princeps PAMPANINI (Sajabalssuk)

Repeated silica gel and octadecyl silica gel (ODS) column chromatography of the aerial parts of Artemisia princeps PAMPANINI (Sajabalssuk) led to the isolation of a new sesquiterpenoid, 3-((S)-2-methylbutyryloxy)-costu-1(10),4(5)-dien-12,6 alpha-olide (2), along with two previously reported sesquiterpenoids: 8 alpha-angeloyloxy-3beta,4 beta-epoxy-6 beta H,7 alpha H,8 beta H-guaia-1(10),11(13)-dien-12,6 alpha-olide (1, carlaolide B) and 3beta,4 beta-epoxy-8 alpha-isobutyryloxy-6 beta H,7 alpha H,8 beta H-guaia-1(10),11(13)-dien-12,6 alpha-olide (3, carlaolide A). The structure of compound 2 was elucidated by spectroscopic data analysis, including one dimensional (1D) and two dimensional (2D) nuclear magnetic resonance (NMR) experiments. Of the isolates, compound 2 exhibited potent cytotoxicity against human cervix adenocarcinoma cells and induced apoptosis.     

Chemical constituents from the leaves of Manglietia phuthoensis and their effects on osteoblastic MC3T3-E1 cells

Two new phenyl glycosides, mangliesides A and B (1, 2), a new ionol glycoside, manglieside C (3), two new lignan glycosides, mangliesides D and E (4, 5), were isolated from the leaves of Manglietia phuthoensis, along with two known lignans, 3-methoxymagnolol (6) and obovatol (7). Their structures were established by means of 1D and 2D NMR, electrospray ionization (ESI)-MS and HR-ESI-MS experiments. Among them, compounds 2 and 5 significantly (p<0.05) increased the growth and differentiation of osteoblastic MC3T3-E1 cells in vitro.     

Benzofurans and sterol from the seeds of <Emphasis Type="Italic">styrax obassia</Emphasis>

Two benzofurans (1, 2) along with five known compounds (3.7) were isolated from the seeds of S. obassia. Their structures were elucidated as methyl 3-[7-methoxy-2-(3′,4′-methylenedioxyphenyl)-5-benzofuranyl]-propionate (1), methyl 3-[2-(3′,4′-methylenedioxyphenyl)-5-benzofuranyl]-propionate (2), egonol (3), egonolacetate (4), egonol-2-methylbutanoate (5), 7-demethoxyegonol-2-methylbutanoate (6), and stigmasterol (7) on the basis of their comprehensive spectroscopic analysis including 2D NMR data. Compounds 1, 2 are obtained for the first time from nature, while this is the first record of compound 7 from the Styrax species. Published in Khimiya Prirodnykh Soedinenii, No. 4, pp. 350-353, July-August, 2008. Original article submitted May 4, 2007.     

Coordination asymmetry in divanadium(V) compounds containing a V2O3 core: synthesis, characterization, and redox properties

A general protocol for the synthesis of micro-oxo divanadium(V) compounds [LOV(micro-O)VO(Salen)] (1-5) incorporating coordination asymmetry has been developed for the first time. One of the vanadium centers in these compounds has an octahedral environment, completed by tetradentate Salen ligand, while the remaining center has square pyramidal geometry, made up of tridentate biprotic Schiff-base ligands (L2-) with ONO (1-3) and ONS (4, 5) type donor combinations. Single crystal X-ray diffraction analysis, ESI-MS, and NMR (both 1H and 51V) spectroscopy have been used extensively to establish their identities. The V(1)-O(6)-V(2) bridge angle in these compounds, save 3, lie in a narrow range (166.20(9)-157.79(16) degrees) with the V2O3 core having a rare type of twist-angular structure, somewhat intermediate between the regular anti-linear and the syn-angular modes. For 3, however, the bridge angle is sufficiently smaller 117.92(8) degrees that it forces the V2O3 core to adopt an anti-angular geometry. The V(1)...V(2) separations in these molecules (3.7921(7)-3.3084(6) A) are by far the largest compared to their peers containing a V2O3 core. The molecules retain the binuclear structures also in solution as confirmed by NMR spectroscopy. Their redox behaviors appear quite interesting, each undergoing a one-electron reduction in the positive potential range (E1/2, 0.42-0.45 V vs Ag/AgCl) to generate a trapped-valence mixed-oxidation products [LVVO-(micro-O)-OVIV(salen)]1-, confirmed by combined coulometry-EPR experiments. The bent V-O-V bridge in these molecules probably prevents the symmetry-constrained vanadium d xy orbitals, containing the unpaired electron, to overlap effectively via the ppi orbitals of the bridging oxygen atom, thus accounting for the trapped-valence situation in this case.     

Effect of electrode spacing on image flicker in fringe-field-switching liquid crystal display

Low-frequency driving of a liquid crystal display (LCD) panel to minimise power consumption has drawn much attention recently. In case an LCD panel is driven by a low-frequency fringe field, image flickering phenomenon is detected by the naked human eye when the sign of the applied electric field is reversed. We investigated the effect of electrode spacing on the image flickering phenomenon induced by the flexoelectric effect in a fringe-field-switching (FFS) liquid crystal cell. We found that the image flicker in an FFS cell under low-frequency driving can be eliminated in a simple manner by changing the electrode spacing.