Molecular constants for the 1Σ+ ground state of the ArH+ ion

From the near equilibrium PNO-CEPA potential and dipole moment curves the following molecular constants for the ¹⁺ ground state of the ArH⁺ ion have been calculated: r _e = 1.286Å, _e = 2723 cm^–1, _{e e} = 56 cm^–1, D ₀ = 3.89 eV and ₀ = 2.384 D. The rotationless radiative lifetimes of the five lowest vibrational states are predicted to be 2.28, 1.2, 0.85, 0.64, 0.46 for ArH⁺ and 9.09, 4.71, 3.27, 2.55 and 2.11 for ArD⁺, respectively (all values are in milliseconds and in ascending order of the vibrational levels).Dedicated to Prof. Hermann Hartmann on the occasion of his 65th birthday.     

Synthesis of 2β, 3β, 14α-trihydroxy-Δ4,7-6-ketosteroids and their derivatives

A scheme using -sitosterol as an example for synthesizing 2, 3, 14-trihydroxy-^4,7-6-ketosteroids and their derivatives from 3-hydroxy-⁵-steroids was developed.Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, 220141, Belarus, Minsk, ul, akad. Kuprevicha, 5/2. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 244–248, May–June, 2000.     

Charge control in the formation of complexes of phenol with unsaturated compounds containing organometallic substituents from group IV

The resonance donor effect of the , conjugation of R₃M and R₃MCH₂ (M = Si, Ge, Sn; R is an alklyl group) substituents with the triple bond in compounds R₃MC=CX and R₃MCH₂CCX (X = H, R) changes on passing from isolated molecules to their H-complexes. A partial ⁺ charge on the triple bond enhances , conjugation; a partial ^– charge on the triple bond has practically no effect on the resonance properties of R₃M substituents, whereas the , conjugation of R₃MCH₂ substituents diminishes owing to the effect of negative direct resonance interaction. The effect of , conjugation on the effective negative charges of the carbon atoms in the -CC- fragments was estimated quantitatively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1041–1046, June, 1994.This work was supported by the Russian Fundation for Basic Research (Grant 93-03-18372).     

Nature of low-lying electron excited states of (η5-cyclopentadienyl) (η7-cycloheptatrienyl)niobium

Electron absorption spectra of (⁵-cyclopentadienyl)(⁷-cycloheptatrienyl)niobium in solution and in the vapor phase have been measured for the first time. Possible variants of the band assignment for the spectrum of the complex in a solution have been considered. In the spectrum of the vaporous compound the bands at 29570, 31730, and 34630 cm^–1 correspond to the electron transitions from the 4d(⁺) orbital to the lowest Rydberg p- and d-levels. The values of Rydberg transition terms and symmetry of p-states have been determined.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 634–638, April, 1994.The author is grateful to I. L. Fedyushkin for the synthesis of complex 1.     

β,β-Dinitro derivatives ofN-alkyl-N′-alkoxydiazene-N-oxides

Methods of synthesis ofN-alkyl-N-alkoxydiazene-N-oxides containing a carbonyl group in the -position of alkyl or alkoxy radicals were developed. ,-Dinitro derivatives ofN-alkyl-N-alkoxydiazene-N-oxides were synthesized for the first timevia nitration of oximes obtained from the ketones.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1534–1538, August, 1995.     

Transformed steroids

A preparative method for 9a-hydroxylation of ⁵-3-hydroxysteroids using the fungi ofCircinella sp. 10Kh-1220 not capable of modifying theA ring has been developed. It is established that the yields of the main and the side products greatly depend on the transformation conditions, mycelium age, and the structure of the steroid substrate. Under the optimal transformation conditions novel 9-hydroxysubstituted derivatives of androstenolone, pregnenolone, 16-dehydro-16,17-epoxy-, and-16-methoxypregnenolone have been obtained in 36–80 % yields.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 737–743, April, 1994.     

Reactivity of pyrrole pigments,XXI: Structure and reactivity of Cu(II) and Zn(II) bilindione chelates

Summary Several Mn, Cu, and Zn chelates of etiobiliverdin-IV-, mesobiliverdin-IX, and its dimethyl ester are studied. The results show that the chemical constitution of the Cu biliverdin chelate corresponds to a formal metal oxidation state of (II) coordinated to a neutral radical of the NH trideprotonated biliverdin. The reactivity of the Cu(II) bilindione chelates in nucleophilic solvents agrees with that expected for a neutral radical structure of the ligand; in CH₃OH, they undergo oxidation towards dimethoxybilipurpurins. The magnetic behaviour of Cu(II) etiobiliverdinate-IV- in the solid state shows an intramolecular weak antiferromagnetic coupling d⁹Cu-to--radical (J=–23 cm^–1) and an intermolecular weak antiferromagnetic coupling -radical-to--radical (J=–45 cm^–1). The analogy of this magnetic behaviour to that of the cation radical of metalloporphyrins is discussed.

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Reaktivität von Pyrrolpigmenten, 21. Mitt.: Struktur und Reaktivität von Cu(II)- und Zn(II)-Chelaten von Bilindionen

Zusammenfassung Einige Mn, Cu and Zn Chelate von Etiobiliverdin-IV-, Mesobiliverdin-IX und seinem Dimethylester werden untersucht. Im Komplex koordiniert ein Metallatom (mit der Formalladung II) mit einem Neutralradikal des dreifach NH-deprotonierten Bilindions. Die Reaktivität des Komplexes gegenüber nukleophilen Lösungmitteln entspricht erwartungsgemäß dem eines neutralen -Radikals; in CH₃OH wird er zu Dimethoxybilipurpurin oxidiert. Bei Cu(II)-Etiobiliverdinat-IV beobachtet man im festen Zustand neben schwacher, antiferromagnetischer Kupplung zwischen d⁹Cu und -Radikal (J=–23 cm^–1) auch eine schwache, intermolekulare, antiferromagnetische Wechselwirkung zwischen zwei -Radikalen (J=–45 cm^–1). Dieses magnetische Verhalten wird dem des -Kationradikals von Metalloporphyrinen gegenübergestellt.

     

The inclusion complex of piromidic acid with dimethyl-β-cyclodextrin in aqueous solution and in the solid state

Inclusion complex formation of piromidic acid (PA) with dimethyl--cyclodextrin (DM--CD) in aqueous solution and in the solid state was confirmed by the solubility method, differential scanning calorimetry (DSC) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. The apparent stability constant,K _c , of the complex was estimated to be 244 M^–1. The stoichiometry of the complex was given as the ratio 1:2 of PA to DM--CD. The dissolution rate of the PA/DM--CD complex was much greater than that of intact PA.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

Ab initio SCF and CI study of the electronic spectrum of pyridine N-oxide

Configuration interaction (CI) studies of ground, n *, * * electronically excited states are reported for pyridine N-oxide. The transition energy to the lowest * excited ¹ B ₂ state is calculated at 4.35 eV, compared to the experimental spectrum range of 3.67–4.0 eV. This state lies below the lowest n * excited ¹ A ₂ state calculated at 4.81 eV above the ground state. The only experimentally reported triplet state at 2.92 eV above the ground state is predicted to be the ³ A ₁ (*) state. The calculated energy lies at 3.27 eV. Numerous other high-lying singlet states as well as the triplet states have also been calculated. The intramolecular charge transfer character of the ground and the excited states have been studied in terms of the calculated dipole moment and other physical properties.     

Molecular structure of 1′,3′,3′-trimethyl-6-trifluoromethylsulfonyl-spiro-(indoline-2,2′-benzo[b]pyran)

Photochromic 1, 3, 3 -trimethyl-6-trifluoromethylsulfonyl-spiro(indoline-2,2-ben-zo[b]pyran) (1) was studied by X-ray diffraction analysis. In compound1, the C_spiro-O bond (1.49(1) Å (average)), broken on photoexcitation, is the longest of all the indoline spiropyrans studied.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1969–1971, November, 1994.     

Synthesis and thermal decomposition of 3-aroyl-4-aryl-2-pyrazolines

Summary 3-Aroyl-4-aryl-2-pyrazolines (21–40) have been synthesized by the reaction of ,-unsaturated ketones (1–20) with diazomethane. These 2-pyrazolines gave -methyl-,-unsaturated ketones (41–46) on thermal denitrogenation.Dedicated to Prof. Dr.F. Sauter on the occasion of his 65^th birthday     

Adiabatic corrections for thei 3Π g state of the hydrogen molecule

Summary The adiabatic corrections of thei ³_g state of H₂ are calculated for a wide range of internuclear distances using an explicitly correlated wavefunction. The vibrational structure of this state is calculated in the adiabatic approximation. It is shown that forN=1 levels of the – substate, for which the nonadiabatic corrections are negligible, the agreement between theory and experiment is excellent; the small mass independent discrepancy of the order of 0.5–3 cm^–1 is due to the convergence error in the Born-Oppenheimer calculations. For higherN the discrepancy is much larger. However, it is mass andN-dependent and it is almost entirely due to the nonadiabatic effects caused by³_g-³_g interactions. The still larger discrepancy for the + substate of thei state is evidently caused by additional interactions of thei state with close-lying states of³ _g ⁺ symmetry.Dedicated to Prof. Klaus Ruedenberg on the occasion of his 70th birthday     

Synthesis of Co3(CO)7(μ-η3-Allyl)(μ3-X) Complexes (X=S, Se) and Structure of the Selenium Derivative

The complexes Co₃(CO)₉( ₃-X) (X=S, Se) can be reduced to the corresponding anionic species [Co₃(CO)₉( ₃-X)]^–, which react with allyl bromide to give Co₃(CO)₇(- ³-C₃H₅)( ₃-X) (X=S, Se). These are the first two cobalt complexes containing the bridging - ³-allyl ligand. The structure of the selenium complex was determined by X-ray crystallography. Crystal data for Co₃(CO)₇(- ³-C₃H₅)( ₃-Se) are as follows: space group P2₁/c, a=9.051(2) Å, b=8.102(2) Å, c=21.27(4) Å, =93.82(3)°, Z=4, and R=0.0565 for 2491 observed reflections.     

2,2′-Diphenyl-Δ3,3′-bi-3H-indole-1,1′-dioxide: Molecular interactions and crystal structure

The Dinitrone 2,2-diphenyl-^3,3-bi-3H-indole-1,1-dioxide acts as a demethylating and dehydrogenating agent. The mechanism of interaction of the dinitrone with donors and acceptors does not involve intermediate charge-transfer complexes probably due to a self association between dinitrone molecules (as supported by X-ray determinations). The crystal structure of the dinitrone was obtained by direct methods;a=9.967 (2),b=19.817 (3),c=10.875 (2) Å, =111.2 (2)°, space group P2₁/n. The finalR andR _w were 0.089 and 0.063 for all measured reflexes.

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2,2-Diphenyl-^3,3-bi-3H-indol-1,1-dioxid: Molekulare Wechselwirkungen und Kristallstruktur

Zusammenfassung Das Dinitron 2,2-Diphenyl-^3,3-bi-3H-indol-1,1-dioxid wirkt als Demethylierungs- und Oxydationsmittel. Die Wechselwirkung des Dinitrons mit Elektronen-Acceptoren und Elektronen-Donatoren geht wegen der Selbstassoziation zwischen den Dinitron-Molekülen ohne die dazwischenliegende Bildung eines Charge-Transfer-Komplexes vor sich; das wird auch von Röntgenstrukturuntersuchungen gestützt. Die Kristallstruktur wurde mit direkten Methoden ermittelt:a=9.967 (2),b=19.817 (3),c=10.875 (2) Å; =111.2 (2)°. P2₁/n. Die endgültigen WerteR undR _w waren 0.089 und 0.063 für alle gemessenen Reflexe.

     

On the mathematical formulation and interpretation of LACO MO theory

The mathematical basis of LCAO MO theory is studied, both within the Hartree-Fock approximation and in more exact formulations. The basic LCAO expansion for molecular orbitals ¦> in terms of atomic orbitals ¦x> is conveniently written ¦> = ¦x> S ^–1 B where S is the overlap matrix for atomic orbitals and B is the matrix of atomic orbital-molecular orbital overlaps. It is suggested that matrices P and Q, defined by P=B B and Q=BnB where n is the matrix of molecular orbital occupation numbers, are appropriate to the interpretation of molecular calculations in terms of atomic orbital components, electronic populations and the degree of bonding. Implications for Hartree-Fock calculations are investigated.     

Properties of aqueous salt solutions of poly(ethylene oxide). Cloud points, θ temperatures

The determination of the properties of aqueous salt solutions of poly(ethylene oxide) has been extended to the cloud point, and temperature measurements have been made at several concentrations for various salts (flourides, iodides, acetates, formates, phosphates, bromides, thiosulfates and perchlorates). The resulting dependency of the critical temperatures (mostly between 290–350 K) on the molar concentration can be expressed as sequences showing the decreasing effect of anion species or cation species in salting out the polymer. The decreasing order of effectiveness of the anions in reducing the temperature is PO ₄ > HPO ₄ > S₂O ₃ > H₂PO ₄ ^– >F^– > HCOO^– > CH₃COO^– > Br^– > I^–. The order for cations is K⁺ Rb⁺ Na⁺ Cs⁺ > Sr⁺⁺ > Ba⁺⁺ Ca⁺⁺ > NH ₄ ⁺ > Li⁺. The changes brought about in temperatures by the salts were found to be the results of the changes taking place in the hydrophilic and hydrophobic interactions among polymer, solvent and additive salts and of the change of water structure by structure making or structure breaking ions, and of the influence of salts on the hydration sheath of the polymer.     

Triterpene glycosides ofScheffleropsis angkae. II. Structure of glycosides L-E1, L-E2, L-K1, and L-K2

The structures of four triterpene glycosides from leaves ofScheffleropsis angkae (Araliaceae) are established using chemical and NMR methods. The structures 3-O--D-glucopyranosyl-(1-3)-O--L-arabinopyranosides of oleanic and ursolic acids and their 28-O--L-rhamnopyranosyl-(1-4)-O--gentiobiosyl ethers are proposed for L-E₁, L-E₂, L-K₁, and L-K₂, respectively. L-K₁ and L-K₂ are new triterpene glycosides.Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 239–241, May–June, 2000.     

On-line glucose monitoring by using microdialysis sampling and amperometric detection based on ‘wired’ glucose oxidase in carbon paste

In-vitro on-line glucose monitoring is described, based on microdialysis sampling and amperometric detection operated in a flow-injection system. Samples were injected into a two-electrode microcell containing an Ag/AgCl quasi-reference electrode and a glucose enzyme electrode as the working electrode, operated at + 0.15 Vvs. Ag/AgCl. The enzyme electrode is constructed by mixing the wired glucose oxidase into carbon paste. {Poly[1-vinylimidazole osmium(4,4-dimethylbipyridine)₂Cl)]}^+/2+ was used to wire the enzyme. The non-coated electrodes, cross-linked with poly(ethylene glycol) diglycidyl ether, responded linearly to glucose concentrations up to 60 mM, and were characterized by a sensitivity of 0.23 A mM^–1 cm^–2, when operated in flow injection mode and of 5.4 AmM ^–1 cm^–2 in steady-state conditions. This sensitivity of the resulting enzyme electrode was 50% lower than that of similarly prepared but non-cross-linked electrodes. However, the cross-linked electrodes showed superior operational and storage stabilities, which were further improved by coating the electrodes with a negatively charged Eastman AQ film. An in-house designed microdialysis probe, equipped with a polysulphone cylindrical dialysis membrane, yielded a relative recovery of 50–60% at a perfusion rate of 2.5 l/min^–1 in a well stirred glucose solution. The on-line set up effectively rejected common interferences such as ascorbic acid and 4-acetaminophen when present at their physiological concentrations.     

Ab initio Study of β-lactam antibiotics

Ab initio SCF-MO-LCAO calculations have been performed with a 7s3p/3s GTO basis set for the CH₃O--lactam + OH^– reaction which is related to the mode of action of -lactam antibiotics. The comparison of the present results with the previous ones for -lactam + OH^– and 3-cephem + OH^– shows that the CH₃O substitution has a negligible effect on the amidic bond breaking of -lactam, so that this group probably influences other steps of the antibiotic reactivity of cephaloporins.     

Solid-Phase Extraction and Spectrophotometric Determination of Trace Amounts of Mercury in Natural Samples

A sensitive and selective solid phase spectrophotometric method for the determination of trace amounts of inorganic mercury is described. Hg²⁺ was sorbed on a silica gel-packed column as an Hg²⁺–N,N-bis(2-mercaptophenyl)ethanediamide (H₂L) complex. The Hg²⁺ complex was eluted from the column using 7mL of acetone. Various parameters including pH, column flow rate, and ligand concentration were optimized. The complex was found to obey Beers law from 2.3 to 73.7µgmL^–1 within the optimum range when the preconcentration factor was two. The effective molar absorption coefficient at 523nm was 1.17×10³Lmol^–1cm^–1 at 523nm. The concentration limits in Beers law dropped from 0.09 to 2.95µgmL^–1 within the optimum range when the preconcentration factor was 50. The relative standard deviation at a concentration level of 5µgmL^–1 Hg²⁺ (9 repetitive determinations) was 1.6%. The detection limits are 0.34µgmL^–1 and 0.015µgmL^–1 when the preconcentration factors are 2 and 50, respectively. The method has been used for routine determination of trace levels of Hg²⁺ in natural waters. The potential application of this method for the removal of Hg²⁺ from natural samples (sea water and lake water) spiked with 100ngmL^–1 of Hg²⁺ was studied. In order to validate the proposed method, LGC 6156 (harbour sediment – extractable metals) was analysed by this method. The results proved that excellent extraction of Hg²⁺ from both natural water samples was obtained by solid phase extraction using N,N-bis(2-mercaptophenyl) ethanediamide.