Structures of three molybdenum(0)–tetracarbonyl–Schiff base compounds

The structures of three molybdenum(0)–tetracarbonyl–Schiff base compounds, determined by X-ray diffraction techniques, are reported. The Schiff bases are those derived from 2-acetylpyridine and 4-methoxyaniline, 4-trifluoromethoxyaniline, or 3-fluoro-4-methylaniline. The structure of the Schiff base ligand has also been determined for the ligand derived from 4-trifluoromethoxyaniline. Comparisons are made between metal–nitrogen bond distances, and carbon–nitrogen and carbon–carbon bond distances in the chelate rings, for these and a number of related molybdenum(0)–tetracarbonyl-diimine compounds. Comparisons are also made between ligand geometry in the free and coordinated states.     

Spectroscopic characterization of environmentally relevant C10-chloroterpenes from a photochemically modified toxaphene standard

Twenty-five pure environmentally relevant toxaphene components have been isolated from photochemically modified technical toxaphene by means of a combination of column chromatography on silica gel and preparative high resolution liquid chromatography. These compounds are 6 chlorinated camphenes (1–3, 5, 7, and 11) and 19 chlorinated bornanes (4, 6, 8–10, 12–16, 18–24, 26, and 27 according to Table 1). Two further chlorobornanes (17 and 25) have been isolated from a highly chlorinated mixture obtained by the excess chlorination of 2-exo,10-dichlorobornane. The structural elucidation of the isolated compounds has been carried out with spectroscopical methods.     

Interaction of [acacRh(CO) n ]+ ions (n=0–2) with aromatic nitro compounds in the gas phase

Summary The mass-spectrometry method has been applied to a study of the interaction of [acacRh(CO)₂]⁺ with aromatic nitro compounds in the gas phase and the reactivity order of these compounds has been determined. The coordination mechanism has been found to depend upon the nature of the nitro compound and its ability to replace carbonyl ligands increases with increasing electron-donor ability of substituents. Specific reactions leading to dissociation of C–H, N–O, and O–H bonds are discussed.     

Copper(II)–8-mercaptoquinoline,copper(II)–5,8-dimercaptoquinoline and copper(II)–5-thiomethyl-8-mercaptoquinoline complexing in a copper(II)hexacyanoferrate(II) gelatin-immobilized matrix

Novel complexing processes in the Cu^II–8-mercaptoquinoline, Cu^II–5,8-dimercaptoquinoline and Cu^II–5-thiomethyl-8-mercaptoquinoline systems proceeding in the copper(II)hexacyanoferrate(II) gelatin-immobilized matrix in contact with aqueous solutions of the ligands indicated, have been studied. Under the conditions specified for complexing in the Cu^II–8-mercaptoquinoline system, only a monomeric water-insoluble coordination compound was formed. In the Cu^II–5,8-dimercaptoquinoline system, three coordination compounds were formed and, in the Cu^II–5-thiomethyl-8-mercaptoquinoline system, two such compounds were formed. Conversely, complexing in solution or solid phase results in the formation only coordination compounds in each of the system studied.     

An application of the DFT-based scaled quantum mechanical force field method to a weakly bonded system: N2O4

The adequacy of the density functional derived scaled quantum mechanical force field method of Rauhut and Pulay has been tested for a weakly bound dimer, N₂O₄. The Becke3–Lee–Yang–Parr/6-31G^* harmonic force field has been scaled with the transferable scale factors of Rauhut and Pulay (developed originally for `common' organic compounds without any reference to the N–O bond) resulting in 20.7 and 38 cm⁻¹ for the mean and the maximal individual deviations, respectively, as compared with experimental spectra. Consequently, the force field method of Rauhut and Pulay may give reliable results for non-common compounds as well.     

Characteristic and spectroscopic properties of the Schiff-base model compounds

Two series of conjugated aromatic imines (Schiff-base model compounds) with different central groups and various side-group substitutions have been synthesized and characterized by elemental analysis, differential scanning calorimetry (DSC) technique, hydrogen nuclear magnetic resonance (¹H NMR), Fourier transform infrared (FTIR) and ultra-violet and visible light (UV–vis) spectroscopy measurements. The UV–vis absorption of solutions of these compounds in dimethylacetamid (DMA), chloroform and methanol was investigated in the optical range from 240 to 450 nm, where two distinct absorption bands: at 250–280 and 315–360 nm with the different level of absorption have been observed. The influence of compound molecular structure and polarity of solvent on the absorption spectra and the possible optical transitions have been discussed. Structure of diamines in the azomethine models fundamentally affected their spectroscopic properties and conjugation of π-electrons.     

Phenolic compounds ofGeranium sanguineum

The chemical composition of the phenolic compounds of the epigeal part of blood-red geranium has been studied. The structure of the main substance of the polyphenolic complex of the plant has been established — bis(hexahydroxydiphenoyl)trigalloylglucose. The high antiviral and antitumoral activity of the total phenolic compounds of the geranium has been shown.A. A. Sadykov Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax 627071. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 40–44, January–February, 1994.     

New architectures in hydrogen bond catalysis

New achiral sulfamide, phosphoric triamide, and thiophosphoric triamide compounds have been synthesized. Their activity as hydrogen bond catalysts for the Friedel–Crafts and Baylis–Hillman reactions compares favorably with that of a known and an active thiourea catalyst. The new compounds were also studied by X-ray crystallography and their solid state structures are described.     

Integral intensities of the IR bands of the stretching vibrations of the NH,C=O,and C=C groups in theVinca alkaloids

Summary 1. The frequencies and integral intensities of the bands of the stretching vibrations of the NH, C=O, and C=C groups in some indoline, indole, and hydroxyindole alkaloids and certain other compounds have been investigated.2. From the changes in the intensities of the NH bands in vincanine, akuammicine, vinervine O-methyl ether, and their dihydro derivatives, it has been concluded that the first-mentioned compounds contain chelate bonds.3. On the basis of the results of the measurements of the intensities for vincanine and dihydrovincanine, the bands in the 1500–1700 cm^–1 region have been identified.4. The bands in the 1600–1700 cm^–1 region of a number of natural alkaloids are due to the complex vibrations of the whole grouping.Khimiya Prirodnykh Soedinenii, Vol. 2, No. 3, pp. 185–192, 1966     

Liquid chromatography with triple-quadrupole or quadrupole-time of flight mass spectrometry for screening and confirmation of residues of pharmaceuticals in water

LC–MS–MS has been performed with triple-quadrupole (QqQ) and quadrupole-time of flight (Q-ToF) instruments and has been used for screening and confirmation of pharmaceuticals in surface, drinking, and ground water. Screening was based on monitoring of one specific MS–MS ion of the target compounds. Confirmation of the identity of the pharmaceuticals was based either on the monitoring of two specific MS–MS ions and calculation of the ratio of their intensities, or on the exact masses of MS–MS product ions obtained for a molecular ion by use of LC–Q-ToF MS. The set of pharmaceuticals included four analgesics (acetylsalicylic acid, diclofenac, ibuprofen, and paracetamol), three antibiotics (sulfamethoxazole, erythromycin, and chloramphenicol), five blood-lipid regulators and beta-blockers (fenofibrate, bezafibrate, clofibric acid, bisoprolol, and metoprolol), and the anti-epileptic drug carbamazepine. Limits of quantification ranged from 5 to 25 ng L^–1. Fifty-six samples were analysed and residues of the pharmaceuticals were detected in almost all surface and groundwater and in some drinking water samples. The identity of the compounds could be confirmed by use of both QqQ- and Q-ToF-based LC–MS–MS. However, the latter technique has the distinct advantage that a large number of pharmaceuticals can be screened and confirmed at low concentrations (1–100 ng L^–1) in one run.