Time-dependent density functional theory calculations of the photoabsorption of fluorinated alkanes

Time-dependent density functional theory (TD-DFT) calculations of the transition energies and oscillator strengths of fluorinated alkanes have been performed. The TD-DFT method with the non-local B3LYP potential yields transition energies for the methanes, which are smaller by about 10% as compared to the experimental values. An empirical linear correlation was found between the calculated and experimental transition energies both at the B3LYP/DZ+Ryd(C, F) and B3LYP/cc-pVTZ+Ryd(C, F, H) levels for a total of 19 transitions of the fluorinated methanes with linear correlation coefficients of 0.987 for the former and 0.988 for the latter. This empirical correlation for fluorinated methane molecules is found to agree well with the previously obtained empirical correlations between calculated and experimental values for non-fluorinated molecules. The results show that a single empirical-correlation relationship can be used for both non-fluorinated and fluorinated molecules to predict transition energies. This linear relationship is then used to predict the photoabsorption spectra of ethane, propane, butane, and partially and fully fluorinated derivatives. A key result of these calculations is the dominance of Rydberg transitions in the spectral region of interest.     

Selective extraction of gallium from aluminum and indium using tripod phenolic ligands

Solvent extraction of trivalent group 13 metal cations such as aluminum, gallium and indium with tripod quadridentate phenolic ligand, tris(2-hydroxy-3,5-dimethylbenzyl)amine (H(3)tdmba), was investigated as fundamental study for their mutual separation. Gallium was extracted almost quantitatively as Ga(tdmba) (logK(ex)=-6.66+/-0.06 on using chloroform as extraction solvent), whereas aluminum and indium were hardly extracted due to steric hindrance on complexation of them with the ligand. The extracted Ga species was estimated as trigonal bipyramidal complex with one H(2)O molecule. Furthermore, extractability of Ga was increased by changing the ligand to more acidic tris(5-chloro-2-hydroxy-3-methylbenzyl)amine (H(3)tcmba) (logK(ex)=-6.18+/-0.18 on using dichloroethane as extraction solvent).     

Regioselectivity of Friedel-Crafts acylation of aromatic compounds with several cyclic anhydrides

The Friedel-Crafts acylations of various aromatic compounds with cyclic anhydrides such as 2-(p-substituted phenyl)butanedioic, 3-phenylpentanedioic and homophathlic anhydrides were carried out under various conditions in order to obtain informations about the regioselectivity of the ring opening of the cyclic anhydrides and about the possible reaction pathways in the acylations.     

Direct alkenylation of arylamines at the ortho-position with magnesium alkylidene carbenoids and some theoretical studies of the reactions

1-Chlorovinyl p-tolyl sulfoxides were synthesized from ketones and chloromethyl p-tolyl sulfoxide in high yields. Treatment of the sulfoxides with isopropylmagnesium chloride at −78 °C in toluene gave magnesium alkylidene carbenoids (α-chloro alkenylmagnesium chlorides), which were treated with N-lithio arylamines to afford ortho-alkenylated arylamines in moderate yields. The reaction, in some cases, proceeded in a highly stereospecific manner at the carbon bearing the chlorine and the sulfinyl group. The structures of the α-chloro alkenylmagnesium chlorides and the reactivity of the N-lithio meta-substituted anilines were studied at the B3LYP and MP2 levels of theory with the 6-31(+)G* basis set. This reaction offers a quite novel and direct alkenylation of arylamines at the ortho-position of the aromatic ring.     

Carbon-Fluorine Bondings of Fluorinated Fullerene and Graphite

Carbon-fluorine bondings of fluorinated fullerenes and fluorine-graphite intercalation compound C_xF were investigated in detail on the basis of XPS data and the potential model using the charge distribution calculated by semiempirical method. It has been confirmed by the present study that two peaks in the C_1s spectra observed for fluorinated fullerenes are assigned to carbon atoms bonded to fluorine atoms and those unbound to fluorine atoms, and the small difference in charges and Madelung potentials of fluorine atoms in different circumstances well explains the single peak in F_1s spectra of fluorinated fullerenes. In the calculated structures of 1,3-C₆₀F₂ and 1,2-C₆₀F_x (x = 2?6) used as the models of C_xF, three kinds of carbon-fluorine bondings were observed corresponding to nearly ionic, semicovalent and covalent C? F bondings. The calculated result supports that the bi-intercalation structure of stage 1 C_xF consists of nearly ionic and semi-covalent fluorines.     

A facile synthesis of 1-cycloalkenyl isothiocyanates with silicon tetraisothiocyanate

The reaction of cycloalkanones with silicon tetraisothiocyanate in the presence of (Me₃SiO)₂SO₂^?nBu₃SnF or Zn(NCS)₂ provides 1-cycloalkenyl isothiocyanates in good yields under mild conditions.     

Conformation of poly(S-(2-N-carbazolylethyl)-L-cysteine) in the solid state

The β-forming characteristics of poly(S-(2-N-carbazolylethyl)-L -cysteine), (CELC)_n, were examined by infrared (IR) spectroscopy. The film of (CELC)₃₉ cast from tetrahydrofuran (THF) showed the typical spectrum of the antiparallel β-form with the amide I band at 1630 cm^?1, whereas that of (CELC)₂₀₀ from dimethylformamide (DMF) or pyridine exhibited the amide I band at 1640 cm^?1 which shifted to 1630 cm^?1 on heating at 100°C for 5 min. As a result of the examination of the spectral variation due to the degree of polymerization, casting solvents, casting temperatures, and heat treatment, together with the evaluation of interaction constants for intermolecular hydrogen bonds, the band at 1640 cm^?1 was attributed to the antiparallel-chain pleated sheet (designated as β′-form) with weaker hydrogen bond strength than that of the usual antiparallel β-form. The β′-β-transformation is discussed in terms of the rigidity of the side-chain region.     

Comprehensive two-dimensional high-performance liquid chromatography for the separation of polycyclic aromatic hydrocarbons

A comprehensive two-dimensional HPLC system for the separation of polycyclic aromatic hydrocarbons was developed using a pentabromobenzyl column as the first dimension and two short monolithic C18 columns as the second dimension. The primary column and two secondary columns were coupled by a 10-port 2-position valve. The effluent from the first dimension was repetitively injected into the second dimension every 12 s. Due to its resolution, this technique is a powerful tool for the separation of polycyclic aromatic hydrocarbons in a complex matrix such as environmental samples.     

ZINC TETRAPHENYLPORPHYRIN-SENSITIZED PHOTOREDUCTION OF ANTHRAQUINONESULFONATE IN AQUEOUS MICELLAR SOLUTIONS*

Abstract— Zn-tetraphenylporphyrin (ZnTPP), solubilized in non-ionic surfactant micelles, was found to sensitize photoreductions of some sodium anthraquinonesulfonatesz in the presence of ascorbic acid under anaerobic conditions. The reaction rate was increased by the addition of an anionic surfactant, while retardation was observed with a cationic surfactant. The pH-reaction rate profiles showed maxima located in the order corresponding to pK_a-values for the semiquinone of each anthraquinone-sulfonate. A reaction scheme involving the formation of ZnTPP⁺ at the primary step, followed by back-reduction with ascorbic acid, is proposed. The reaction scheme is in good agreement with the results of flash photolysis. The surfactant micelles are suggested to aid the charge-separation between the ionic species just after the redox reaction involving the photoexcited ZnTPP and anthraquinonesulfonates.     

Structures and stabilities of 3d-transition metal-benzene organometallic clusters

In the gas phase, we have successfully synthesized organometallic clusters, M_n(benzene)_m (M=3d transition metal atoms), by using a laser vaporization method. The measurements of mass spectra and ionization energies (E_i) have revealed that the organometallic clusters can take two types of structures; layered sandwich structures (m = n + 1) and metal clusters saturatedly covered with benzenes. For early transition metals of Sc, Ti, and V, only the multiple decker sandwich structure clusters were preferentially produced, in which benzene and metal atoms are alternately piled up. For late transition metals of Co and Ni, the metal clusters saturatedly surrounded by benzenes were also produced as well as the sandwich clusters. Furthermore, the E_is of M₁(benzene)₂ (M = Sc-Ni) were systematically measured and their electronic properties will be discussed.