Structures, stabilities, and electronic and optical properties of c(58) fullerene isomers, ions, and metallofullerenes.

The 1205 classical isomers of fullerene C58, as well as one quasi-fullerene C58 isomer with a heptagonal ring (labeled as Cs:hept) have been investigated by the quantum chemical methods PM3, HCTH/3-21G, and B3LYP/6-31G(d). Isomer C3v:0001, which has the lowest number of adjacent pentagons, is predicted to be the most stable isomer, but the quasi-fullerene isomer Cs:hept is only 2.50 kcal mol-1 higher in energy. Systematic investigations of the electronic properties of C3v:0001 and Cs:hept find that the C3v:0001 isomer has high vertical electron affinity (3.19 eV). The nucleus-independent chemical shifts (NICS) value at the center of Cs:hept (-5.1 ppm) is more negative than that of C60 (-2.8 ppm). The NICS value at the center of the heptagonal ring in Cs:hept (-2.5 ppm) indicates weakly aromatic character. In contrast, the C58(6-) and C58(8-) ions of the C3v:0001 and Cs:hept geometries possess large aromatic character, with NICS values between -14.0 and -26.2 ppm. To clarify the thermodynamic stabilities of C58 isomers at different temperatures, the entropy contributions are taken into account on the basis of the Gibbs energy at the B3LYP/6-31G(d) level. The C3v:0001 isomer prevails in a wide range of temperatures, and the Cs:hept isomer is also an important component around 2800 K. The IR spectra of C58 isomers are simulated to facilitate experimental identification of different isomers. In addition, the electronic spectra and the second-order hyperpolarizabilities are predicted by ZINDO and the sum-over-states model. The static second-order hyperpolarizability of the C3v:0001 isomer is 96.5 % larger than that of C60, and its second-order hyperpolarizabilities at external field frequencies are at least nine times larger than those of C60.     

Determination of zinc in high purity bismuth by thermal neutron activation

A neutron activation analysis for the determination of zinc in bismuth was developed. After irradiating the samples for 44 days at 4·10¹¹n/cm²/sec, zinc was separated quantitatively by hexone extraction and precipitation as quinaldate. The sensitivity of the method was estimated as 0.05 p.p.m. No zinc could be detected in the high purity bismuth samples. An addition method of analysis showed that the precision was 1.2%.     

2,6-di-tert-butyl-4-perimidylphenols and their oxidation

1,8-Naphthylenediamine was reacted with 2,6-di-tert-butyl-4-formyl-phenol to produce 2,6-di-tert-butyl-4-(1,3-dihydro-perimidyl) phenol (I). The latter was coverted into 2,6-di-tert-butyl-4-(1H-perimidyl)phenol (II) by oxidizing I with sodium pyrosulfate. When phenol II was oxidized by lead dioxide in toluene and THF, the EPR spectra revealed a 12-component multiplet with perimidyl splitting constants a¹ _N=a³ _N=a_H ^NH=0.2 mT; a_H ^6.7=0.6 mT.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 1, pp. 64–67, January, 1992.     

Synthesis of 1,2,3,4,8,9,10,11-octahydro-[1,4] diazepino[6,5,4-jk ]earbazole and related compounds

1,2,3,4,8,9,10,11-Octahydro[1,4]diazepino[6,5,4-jk]earbazole (VIa) was synthesized from 2,3,4,5-tetrahydro-1H-benzodiazepine (la) via the route shown in Scheme 1. Other compounds which were prepared similarly are 3-acetyl-6-chloro-1,2,3,4,8,9,10,11-octahydro[1,4]diazepino-[6,5,4-jk]carbazole(Vb) and 3-methyl-1,2,3,4,8,9,10,11-octahydro[1,4]diazepino[6,5,4-jk]carb-azole (VIII). Chemical transformations which were carried out with VI and 3-acetyl-1,2,3,4,8,9, 10,11-octahydro[1,4]diazepino[6,5,4-jk]carbazole (Va) are also described.     

Chemische Vitamin D<Subscript>3</Subscript>-Bestimmung in Lebertran

The different aspects of Vitamin D₃ determination and the data reported in the literature are discussed. The spectrophotometric determination of Vitamin D₃ in cod-liver oil is carried out after the alkaline saponification, extraction of unsaponified parts, precipitation of accompanying sterols and the column- and thin-layer chromatographic purification and separation of vitamin D₃ on 40 cm plates from other vitamins. The dyestuff α-naphtholbenzein is suited well as standard substance for the better location and identification of vitamin D₃ zone on the thin-layer plate. The results obtained from the chemical method were checked through the simultaneous biological determination.     

Direct determination of cadmium at parts-per-billion level in waters by derivative atomic absorption spectrometry using atom trapping technique

A method has been described for the direct determinations of trace cadmium using derivative atom trapping flame atomic absorption spectrometry with an improved water-cooled stainless steel trapping equipment. The characteristic concentration (gave a derivative absorbance of 0.0044) and detection limit (3sigma) of cadmium were 0.028 and 0.02 ng ml(-1) when collecting for a 1 min, respectively, which were 992 and 145-fold better than those of the conventional flame atomic absorption spectrometry. The detection limit and sensitivity of the proposed method for a 2 min collection time were 1 and 2 orders of magnitude higher than those of conventional flame atomic absorption spectrometry. The present method was applied to the determinations of cadmium in water samples with a recovery range of 91 approximately 111% and a relative standard deviation of 4.7 approximately 5.6%.     

Plasma chromatography of heroin and cocaine with mass-identified mobility spectra.

Plasma chromatography detects and identifies compounds in trace quantities at atmospheric pressure through characteristic positive and negative mobility spectra. To facilitate use of the technique to detect gas chromatographic effluents, a number of reference mobility spectra for different classes of compounds have been reported. Reference spectra for two more compounds, heroin and cocaine, are presented in this study. The primary ions found in these mobility spectra were determined to be M+, (M - H2)+, and (M - CH3CO2)+ for heroin and M+, (M - C6H5CO2)+ and (M - C6H5CO2 - CO2CH3)+ for cocaine using a directly interfaced plasma chromatograph-mass spectrometer. The identified ions agree closely with those predicted in the ion mobility spectra using mass-mobility correlation data coupled with chemical ionization mass spectrometry data. Also, an independent check demonstrating the reliability of reduced mobility values reported in earlier reference spectra was made.     

Direct determination of brucine by square wave voltammetry on 4-amino-2-mercaptopyrimidine self-assembled monolayer gold electrode

4-Amino-2-mercaptopyrimidine self-assembled monolayer (AMP SAMs/Au) was prepared on a gold electrode. The AMP SAMs/Au was characterized by using attenuated total reflection-fourier transform infrared (ATR-FTIR) and A.C. Impedance. The electrochemical behavior of brucine on AMP SAMs/Au was studied by cyclic voltammetry (CV) and square wave adsorptive stripping voltammetry (SWASV). The modified electrode showed an excellent electrocatalytic activity for the redox of brucine. The catalytic current increased linearly with the concentration of brucine in the range of 4.0 x 10(-7) to 2.0 x 10(-4) mol l(-1) by square wave voltammetry response. The detection limit was 6.0 x 10(-8) mol l(-1).     

Determination of gentamycin by synchronous derivative fluorimetry

Use of synchronous first-derivative fluorimetry for determination of gentamycin is described. Gentamycin reacts with acetylacetone and formaldehyde in pH 5.6 HOAc/NaOAc buffer solution to form N-gentamyl-2,6-dimethyl-3,5-diacethyl-1,4-dihydropyridine[I] which is a fluorescent substance. Spectra of [I] and the reagent blank can be separated with synchronous derivative fluorimetry, and gentamycin can be determined directly. The synchronous spectral peaks of [I] and the reagent blank are at 434 and 411 nm, respectively. The first-derivative peak of [I] is at 425 nm. Effects of pH, foreign ions, buffer system, and heating time on the determination of gentamycin have been examined. The linear regression equation of the calibration graph is C=0.0513H-0.0416, with a correlation coefficient of linear regression of 0.9978. C means total potency of gentamycin: U ml(-1); H means peak height in the linear regression equation calibration graph. The linear range for the determination of gentamycin is from 0.00 to 3.00 U ml(-1). Recovery is from 95.06 to 112.0%, R.S.D. of 3.8%. The results determined by the fluorimetric method agreed roughly with those by the microbiological method. The method is simple and has low detection limit.     

Molecular characteristics of the inhibition of human neutrophil elastase by nonsteroidal antiinflammatory drugs

Nonsteroidal antiinflammatory drugs(NSAIDs) are known as clinically effective agents for treatment of inflammatory diseases. Inhibition of cyclooxygenase has been thought to be a major facet of the pharmacological mechanism of NSAIDs. However, it is difficult to ascribe the antiinflammatory effects of NSAIDs solely to the inhibition of prostaglandin synthesis. Human neutrophil elastase (HNElastase; HNE, EC 3.4.21.37) has been known as a causative factor in inflammatory diseases. To investigate the specific relationship between HNElastase inhibition and specificity of molecular structure of several NSAIDs, HNElastase was purified by Ultrogel AcA54 gel filtration, CM-Sephadex ion exchange, and HPLC (with TSK 250 column) chromatography. HNElastase was inhibited by aspirin and salicylate in a competitive manner and by naproxen, ketoprofen, phenylbutazone, and oxyphenbutazone in a partial competative manner, but not by ibuprofen and tolmetin. HNElastase-phenylbutazone-complex showed strong Raman shifts at 200, 440, 1124, 1194, 1384, 1506, and 1768 cm(-1). The Raman bands 1194, 1384, and 1768 cm(-1) may represent evidences of the conformational change at -N=N-phi radical, pyrazol ring, and -C=O radical of the elastase-drug complex, respectively. Phenylbutazone might be bound to HNElastase by ionic and hydrophobic interaction, and masked the active site. Inhibition of HNElastase could be another mechanism of action of NSAIDs besides cyclooxygenase inhibition in the treatment of inflammatory diseases. Different inhibition characteristics of HNE-lastase by NSAIDs such as aspirin, phenylbutazone-like drugs and ineffective drugs could be important points for drawing the criteria for appropriate drugs in clinical application.