SOME PHOTOPHYSICAL PROPERTIES OF 3-CARBETHOXYPSORALEN, 8-METHOXYPSORALEN and 5-METHOXYPSORALEN TRIPLET STATES

Abstract Triplet absorption spectra, extinction coefficients (ɛ_T), decay rates ( K ₁), oxygen quenching rates (k_q) and intersystem crossing yields (φ_T) for 3-carbethoxypsoralen (3-CPs). 8-methoxypsoralcn (8-MOP) and 5-methoxypsoralen (5-MOP) in methanol are reported. For 8-MOP and 3-CPs corresponding values are also reported with water as the solvent. Some photophysical data are also reported for 5-MOP in water, but ɛ_T and φ_T were not obtained.
The phosphorescence spectra for these furocoumarin derivatives in ethanol at 77 K are reported together with the corresponding lowest triplet energy and lifetime. The values of the various photophysical properties obtained are compared with values reported by previous workers.     

Deuterium N.M.R. of the n-octyl-β-D-glucopyranoside-solvent liquid-crystalline systems

Deuterium quadrupolar splittings were measured as a function of concentration and temperature for deuteriated water, benzene-d₆, toluene-d₈ and acetonitrile-d₃, dissolved in n-octyl-β-D-glucopyranoside (OG). The splittings and temperature dependence are larger for the apolar solvents. Water forms rather rigid structures with OG as indicated by its large linewidths. OG can accommodate both water and benzene (or toluene) together and the results for such systems are also reported. Some additional results for the hydroxyl deuteriated OG and for a system containing a lower homologue of OG are reported.     

Vapor–liquid equilibria and excess volumes of the binary systems ethanol + ethyl lactate, isopropanol + isopropyl lactate and n-butanol + n-butyl lactate at 101.325 kPa

Isobaric vapor–liquid equilibrium data have been experimentally determined at 101.3 kPa for the binary systems ethanol + ethyl lactate, isopropanol + isopropyl lactate and n-butanol + n-butyl lactate. No azeotrope was found in any of the systems. All the experimental data reported were thermodynamically consistent according to the point-to-point method of Fredenslund. The activity coefficients were correlated with the NRTL and UNIQUAC liquid-phase equations and the corresponding binary interaction parameters are reported. The densities and derived excess volumes for the three mixtures are also reported at 298.15 K.     

The polarizability of LiBr

Finite field SCF MO calculations are reported for LiBr over a range of bond distance from 3.8 a_o to 15 a_o Values of the pair potential, dipole moment and polarizability tensor are reported, and the polarizability curves compared with those of LiF and LiCl.     

Ab initio molecular orbital calculations for butadiene and its ions

Ab initio calculations are reported for cis and trans butadiene and some of their ions. The calculations are compared with semi-empirical results, and used to predict coupling constants.     

RESONANCE RAMAN SPECTRA AND NORMAL MODE DESCRIPTIONS OF A BACTERIOCHLOROPHYLL a MODEL COMPLEX

Abstract— Resonance Raman (RR) spectra are reported for the bacteriochlorophyll a (BChl a) model complex, copper methylbacteriopheophorbide a (CuBPheo a). The spectra are acquired at a number of excitation wavelengths in the Q_y+ Q_x and B regions of the absorption spectrum. The RR data obtained for CuBPheo a are correlated to those previously reported for BChl a. The normal modes of the BChl structure are calculated by using the semiempirical quantum chemistry force field (QCFF/ PI) method of Warshel and Karplus [J. Am. Chem. Soc. 94 ,5612–5625 (1972)]. The vibrational data are used in conjunction with the calculations to obtain a cohesive assignment for the normal modes of BChl a with frequencies between 1100 and 1700 cm^-1. The forms of the normal modes of BChl a are predicted to be different both from those of chlorophyll a and from those of porphyrins.     

Effect of basic set quality and electron correlation on the scale factors of a harmonic force field

The completely optimized structure and harmonic force field of s-trans-buta-1,3-diene are reported at the MP2/6-31G and MP2/6-31G* levels of computation. Sets of empirical scale factors for the calculated force fields are derived and compared with the corresponding values computed at the RHF/4-31G and RHF/6-31G levels. Changes in the scale factors for this series of force fields are discussed. The vibrational frequencies are also reported for thirteen isotopomers of s-trans-buta-1,3-diene using the MP2/6-31G* force field. Some characteristics of the gauche and cis forms of buta-1,3-diene are also given.     

PLASMA POLYMERIZATION OF ACETYLENE/CO_2/H_2

A study has been made on the plasma polymerization of acetylene/CO_2/H_2 in a capacitively coupled RF plasma. The monomer mixture yielded a crosslinked film with light brown color. A kinetic study is reported for the plasma polymer ization of acetylene/CO_2/H_2. The effects of discharge power level and reactor geometry on the rate of polymer formation are reported. The structure of the plasma polymer is investigated by IR study.     

Direct determination of calcium,copper, iron,magnesium, manganese and zinc in amniotic fluid samples using inductively coupled plasma-atomic emission spectrometry

An inductively coupled plasma-atomic emission spectrometric method is reported for the determination of calcium, copper, iron, manganese, magnesium and zinc. Samples are introduced directly when a sheath gas device is used. An external calibration procedure is used. The standards are prepared in a matrix composed of 0.5% (w/v) albumin and 0.76% (w/v) sodium chloride. The procedure was evaluated with a standard reference material (NBS SRM 909 Human Serum); all the values obtained are in agreement with the certified values. Results obtained for the determination of zinc, calcium, magnesium, copper, iron and manganese in amniotic fluid samples are reported.     

Electrolyte diffusion of ZnCl2 and self-diffusion of Cd2+ ions in agar gel medium at different temperatures

The values of activation energy required for the diffusion of ZnCl₂ and for Cd²⁺ ions in Cd/Ac/₂ are reported in agar gel medium at 5×10^–5 and 0.001M concentration, respectively. These values are compared with the previously reported values in the same systems at different concentrations. The decrease in activation energy with concentration of electrolyte is in agreement with the Wang's model.     

General formulations for some polycyclic hydrocarbons. Di-q-polyhexes

Di-q-polyhexes are polygonal systems consisting of two q-gons each and otherwise only hexagons. General formulations are reported for the C_nH_s chemical formulae of such systems for q = 4, 5, 6. The case of q = 4 (terphenylenoids) is treated systematically for the first time. Constant-isomer series of C_nH_s formulae, which have been known to exist for benzenoids (q = 6) and indacenoids (q = 5), are reported here for terphenylenoids.     

Modelling the crystalline deformation of native and regenerated cellulose

The molecular mechanics modelling of the deformation of a number of proposed structures for the crystalline regions of cellulose I- , I- and II are reported. The structures used are from coordinates that have recently been reported, which have made particular reference to the ability to locate the positions of hydrogen bonds. By comparison to previously reported structures of cellulose, where the emphasis on this has also been made, and in a diagnostic way, it is shown that it is possible to make some conclusions as to their validity. The effect of removing the intramolecular hydrogen bonding is also reported. All structures, with one exception, are shown to be sensitive to this operation. Two approaches to the molecular mechanics modelling are reported, wherein the structures are minimised under restraint, by altering the c-spacing, within the COMPASS^TM forcefield to obtain a simple chain stiffness value or alternatively by performing a full elastic constants determination for the unit cell.     

Synthesis of S-monofluoromethyl phosphorothioates from PⅤ-H compounds and PhSO2SCH2F

S-Monofluoromethyl phosphorothioates represent an important class of organofluorine compounds and are re ported here for the first time.A series of S-monofluoromethyl phosphorothioates are conveniently synthesized from different P^Ⅴ-H compounds and PhSO₂SCH₂F under mild conditions.The method is compatible with common functional groups and provides potential opportunities to synthesize new bioactive molecules for medicinal chemistry.     

Ab initio calculation of the heats of formation of CF3OH and CF2O

The heats of formation of the trifluoromethanol (CF₃OH) and carbonic difluoride (CF₂O) molecules are calculated with theoretical methods of demonstrated high accuracy. The results are used to assess the accuracy of the reported value of the heat of formation of CF₂O and to provide an accurate estimate for CF₃OH. The implications of these results for atmospheric chemistry are discussed.     

Rapid and sensitive electron-capture gas chromatographic method for the determination of pinazepam and its metabolites in human plasma, urine and milk.

A rapid, sensitive and specific gas-liquid chromatographic method for the measurement of pinazepam and its metabolites in biological fluids is reported. After a single extraction of the sample with toluene, the organic phase is concentrated and, after chromatography on a 3% OV-17 column, measured with an electron-capture detector. The sensitivity was 1.0 ng/ml for pinazepam and 5.0 ng/ml for its metabolites. Plasma levels and urinary excretion in human volunteers and plasma and milk levels in women suffering from anxiety during breastfeeding are reported.     

Alkane C-H activation and catalysis by an O-donor ligated iridium complex

The first examples of well-defined, O-donor ligated, late-metal complexes that are competent for alkane C-H activation are reported. These complexes exhibit thermal and protic stability and are efficient catalysts for H/D exchange reactions with alkanes.     

Miniature toroidal radio frequency ion trap mass analyzer

A miniature ion trap mass analyzer is reported. The described analyzer is a 1/5-scale version of a previously reported toroidal radio frequency (rf) ion trap mass analyzer. The toroidal ion trap operates with maximum rf trapping voltages about 1 kVp-p or less; however despite the reduced dimensions, it retains roughly the same ion trapping capacity as conventional 3D quadrupole ion traps. The curved geometry provides for a compact mass analyzer. Unit-mass resolved mass spectra for n-butylbenzene, xenon, and naphthalene are reported and preliminary sensitivity data are shown for naphthalene. The expected linear mass scale with rf amplitude scan is obtained when scanned using a conventional mass-selective instability scan mode combined with resonance ejection.     

Vibrational frequencies and structural determination of disilylcarbodiimide

The vibrational frequencies and corresponding normal mode assignments of disilylcarbodiimide are examined theoretically using the GAUSSIAN98 set of quantum chemistry codes. MP2 and DFT (B3LYP) calculations predict a non-linear structure with C₂ symmetry. All normal modes were successfully assigned to one of eight types of motion (NCN asymmetric stretch, NCN symmetric stretch, Si–H stretch, Si–N stretch, H–Si–H bend, SiH₃ wag, SiH₃ twist, and Si–NN–Si torsion) utilizing the C₂ symmetry of the molecule. Uniform scaling factors were derived for each type of motion. Predicted infrared and Raman intensities are reported. Calculated normal mode frequencies for disilylcarbodiimide-d₆ are also reported.