Palladium(II) and platinum(II)-C(3)-substituted 2,2′-bipyridines

Reaction of Pd(OAc)₂ with HL¹ and HL² (HL¹=6-iso-propyl-2,2-bipyridine; HL²=6-neo-pentyl-2,2-bipyridine), followed by treatment with LiCl or KI, gives [PdCl(L¹)]₂, (1), [PdCl(L²)]₂ (2), and [PdI(L²)]₂ (3), respectively. The chloride bridge in complexes1 and2 is split by PPh³ to give the mononuclear species PdCl(L¹)(PPh₃) (4) and PdCl(L²)(PPh₃) (5). Spectroscopic data provide evidence for coordination of the deprotonated ligands through a nitrogen and the C₍₃₎ atom of the 6-substituted pyridine. An analogous platinum complex PtCl(L³)(SMe₂) (6) (HL³=6-tert-butyl-2,2-bipyridine) was obtained from trans-PtClMe(SMe₂)₂ and HL³. The crystal structures of compounds1 and6 have been solved by X-ray diffraction analysis.Dipartimento di Chimica, Universita di Sassari, via Vienna 2, I-07100 Sassari, Italy; Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Universita di Milano, Centro CNR, I-20133 Milano, Italy; Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1127–1137, August, 1999.     

Membranology: an interdisciplinary science

The author's studies on membrane materials and the membrane technology of mixture separation are briefly reviewed. New, promising membrane materials as well as some mechanistic features of membrane-mediated separation of gases are discussed. With a view to desalting solutions by means of the reversed-osmosis technique, the role of the mass transfer process in the membrane apparatus is considered. The prospects of the membrane methodology in solving various biotechnological and environmental problems are apprised.On the occasion of the award of a D. Sc. (honoris causa) degree to Prof. E. Drioli (Università degli Studi della Calabria, Dipartimento di Chimica) for his works on chemical membranology by the Russian Academy of Sciences in 1991.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 826–839, May, 1993.     

Studies on synthesis and molecular dynamics simulation of dendrimers containing amino acids and peptides

A series of poly(ether-amide) dendrimers with amino acids and peptides as the peripheral functional groups was synthesized, and their structures were confirmed by nuclear magnetic resonance (NMR) and electrospray ionization-mass spectrometry (ESI-MS) spectrometry. Molecular dynamics simulation of the peptide dendrimers in solution was performed, indicating that, the prior conformations of the dendrimers were atom number dependent, i.e., with the increases of the atom number, the prior conformations were more spherical. Also, the amino acid α-C atom radial distribution indicated that, with larger peripheral groups, more back-folding of the dendrimers occurred. __________ Translated from Acta Chimica Sinica, 2007, 65(1): 21–26 [译自: 化学 通报]     

Electrochemically prepared glucose biosensors: kinetic and faradaic processes involving ascorbic acid and role of the electropolymerized film in preventing electrode-fouling

The influence is discussed of ascorbic acid (AA) on the response of a glucose biosensor based on glucose oxidase immobilized in electropolymerized poly(ophenylenediamine) (PPD) or overoxidized poly(pyrrole) (oxPPy) films on a Pt electrode. The kinetics of the homogeneous reaction between AA and H₂O₂ has been investigated by two independent methods and found to be too slow to influence the response of typical glucose biosensors. Therefore, the decrease in the sensor response, observable when working in batch under typical experimental conditions, can in no way be ascribed to a depletion of H₂O₂, which is produced in the biocatalytic cycle via the homogeneous reaction with AA. While the purely additive Faradaic interference can practically be nullified by both entrapping membranes, electrode fouling by electro-oxidation products of AA (responsible for the observed decrease in glucose sensitivity) might still represent a problem when working with PPD based biosensors. In this respect the permeability characteristics of the film markedly influence the magnitude of the observed phenomena. The oxPPy film achieves the goal of completely eliminating ascorbate without blocking the access of glucose to the immobilized enzyme. Permanent address: Dipartimento di Chimica, Universita' della Basilicata, Via N. Sauro 85, I-85100 Potenza, Italy     

A study of amino-protecting groups using the polarizable continuum model (PCM)

In order to better understand the performance of 1,2-dimethyl-5-acetyl barbituric acid (DMB) as an amino protecting group relative to 5,5-dimethylcyclohexane-1,3-dione (DMD), ab initio calculations were performed. pK_a calculations using the PCM model indicated that both molecules are more acidic in the enol form. Therefore, the protecting reaction of these molecules should involve the anions formed from the loss of a proton from the enol compounds. Contrary to what would be expected, the larger efficiency exhibited by the DMB molecule cannot be attributed to an extension of the electronic conjugation effect. In the absence of any other noticeable effect that could be responsible for the greater efficiency of the DMB molecule, we are inclined to believe that the difference could be accounted for by the presence of two independent centers of conjugation.This paper is dedicated to Jacopo Tomasi in recognition of his outstanding contribution to the field of computational chemistry in solution. The authors are honored to contribute to this volume; especially so for two of them (COS and MACN) who have the privilege of his friendship.Acknowledgements The authors would like to thank the Brazilian research agencies CNPq, CAPES and FAPERJ for the financial support. C. O. da Silva thanks the Dipartimento di Chimica e Chimica Industriale, University of Pisa, where the MCSCF calculations were performed.     

Study of the behavior of p-bis{3-[N,N-dialkyl-N-(4-hydroxybut-2-ynyl)ammonio]prop-2-ynyl}-benzene dichlorides in relation to aqueous alkali. Double intramolecular recyclization of benzo[5,6;5′,6′-a,c]di(2,2-dialkyl-4-hydroxymethyl)isoindolinium dichlorides

p-Bis{3-[N,N-dialkyl-N-(4-hydroxybut-2-ynyl)ammonio]prop-2-ynyl}benzene dichloride in the presence of catalytic amounts of aqueous alkali is subject to a double intramolecular cyclization forming benzo[5,6;5′,6′-a,c]di(2,2-dialkyl-4-hydroxymethyl)isoindolinium dichloride in 40–42% yield. Simultaneously an intramolecular recyclization takes place with the formation of dialkyl(6-dialkylaminomethyl-7,9,10,12-tetrahydro-8,11-dioxadicyclopenta[c,g]phenanthren-1-ylmethyl)amines in 7–9% yield. The same compounds are obtained in 70–72% yield by the recyclization of benzo[5,6;5′,6′-a,c]di(2,2-dialkyl-4-hydroxymethyl)isoindolinium dichlorides under conditions of aqueous alkaline degradation. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1329–1335, September, 2006.     

Synthesis, characterization and photosensitivity of tetrakis-α-(2-methyl-8-quinolinoxy) metallophthalocyanines

Four amphipathic cobalt(II), nickel(II), copper (II), and zinc(II) coordination compounds of tetrakis-α-(2-methyl-8-quinolinoxy)phthalocyanine are synthesized using “DBU catalytic method”. The titled complexes are characterized by elemental analysis, mass spectra, UV-Vis, and IR spectra. In addition, the rates of photo-generated singlet oxygen and the rate constants of photo-dynamic oxidation of amino-acid substrate by the complexes are measured under the optical excitation at 670 nm, and the relations between their structures and their photosensitivities are discussed. __________ Translated from Acta Chimica Sinica, 2007, 65(16): 1605–1611 [译自: 化学学报]     

Deutsche Bunsengesellschaft für Physikalische Chemie

Joint Meeting 2000 of Deutsche Bunsen–Gesellschaft für Physikalische Chemie, Koninklijke Nederlandse Chemische Vereniging The Royal Society of Chemistry‐ Faraday Division, Società Chimica Italiana ‐ Divisione di Chimica Fisica, Société Française de Chimie ‐Division de Chimie Physique, ‐ International Bunsen Discussion Meeting ‐„Physical Chemistry in Confining Geometries: From Single Molecules to Mesoscopic Systems”︁ 20. ‐ 22. September, Berlin, Germany.     

Synthesis and properties of di(polyfluoroalkyl) peroxydicarbonates

Synthesis of di(polyfluoroalkyl)peroxydicarbonates [X(CF₂) _n CH₂OC(O)O]₂, where X = H, F; n = 1, 2, 4, 6 (yield 80%) involves the step of the chloroformate formation (yield up to 93%) via the phosgenation of polyfluorinated alcohols followed by the reaction with sodium peroxide. The rate constant of monomolecular decomposition k _term was found to decrease as the polyfluoroalkyl groups were incorporated into the peroxide: it equaled 3.30 and 3.10 s⁻¹ for X = H, n = 2 and 4, respectively, and 7.36 s⁻¹ for di-n-butylperoxydicarbonate. The new peroxides are a source of the polyfluoroalkoxy radicals and nano-modifiers of the polymers to improve their heat resistance and light stability.     

Primary photoprocesses in molecules of carbocyanine dyes in binary solvent mixtures

The effect of the composition of the dimethyl sulfoxide (DMSO)-toluene mixture on the photophysical processes of thia-, indo-, and imidacarbocyanine dyes was studied. In the mixtures with the DMSO content of more than 20 vol %, the dyes representing solvated cations are characterized by high efficiency of trans → cis photoisomerization and fluorescence, in contrast to the extremely low efficiency of intersystem crossing to the triplet state. With growing the toluene content in the mixture, ion pairs between the dye cation and Cl⁻, Br⁻, I⁻, or BF⁴⁻ anion are formed. In the cases when the dye counterions are Br⁻ or I⁻, a sharp increase in the yield of the triplet molecules and a decrease in their lifetime take place. The results are discussed in terms of “the external heavy atom effect” in ion pairs.     

Features of the synthesis of thiobarbituric acid arylidene derivatives in the presence of triethylamine

The synthesis of thiobarbituric acid arylidene derivatives proceeds in two steps, which include 5-(2-hydroxy-2-phenyl)ethyl derivative formation and dehydration. The triethylamine promotes increase in the negative charge on the 5th carbon atom (from −0.399 to −0.638) and positive charge on the aldehyde CH=O group carbon atom (from 0.288 to 0.300) in the transition state due to associative interaction (analysis by quantum-chemical method AM1), and it also promotes dehydration by “pushing out” the hydroxy group. The yield of thiobarbituric acid arylidene derivatives reaches 92–99%.     

Synthesis and structure of di(NON-azoxy)formals and some relatedN-alkyl-N′-alkoxydiazeneN-oxides

A series of di(NON-azoxy)formals and some relatedN-alkyl-N′-alkoxydiazeneN-oxides were prepared by the reaction ofN-nitrosohydroxylamine salts with dihaloalkanes. The dependence of the yield of di(methyl-NON-azoxy)formal on the reaction conditions and the nature of the cation was studied. The structure of di(methyl-NON-azoxy)formal and di(phenyl-NON-azoxy) formal as well as of the coppertert-butylnitrosohydroxylaminate was established by X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1486–1493, August, 1997.     

Thiolato-technetium complexes. 4(1): Synthesis,characterization and electrochemical properties of bis(1,2-bis(dimethylphosphino)-ethane)technetium(III) complexes with arene-thiolato ligands

Summary The reaction of trans-[Tc^v(OH)(O)(DMPE)₂]²⁺ (DMPE = 1,2-bis(dimethylphosphino)ethane) with a series of arenethiols in base produces the novel complexes cis-[Tc^III-(SC₆H₄X-p)₂ (DMPE)₂]⁺ for X = H, Cl, Me, OMe, t-Bu. One of the complexes has been characterized by X-ray crystallography: cis-[Tc(SPh)₂(DMPE)₂]PF₆, chemical formula Tc₁S₂P₅F₆C₂₄H₄₂, crystallizes in the orthorhombic space group P2₁nb with Z = 4 and lattice parameters a = 9.311(1) Å, b=11.190(2) Å, c = 31.936(4) Å, Vol = 3327.3(8) ų. The final weighted R-value was 0.033. Averaged structural parameters are Tc—S = 2.29(2) Å, Tc—P (trans to P) = 2.42(1) Å, Tc—P (trans to S) = 2.49(3) Å, Tc—S—C = 118.5(5)°. The complexes have been characterized by FAB mass spectrometry and u.v.-vis. spectroscopy. The visible region charge transfer bands are diagnostic for cis geometry in the [Tc(SR)₂(DMPE)₂]⁺ complexes. Electrochemical and spectroelectrochemical measurements show reversible Tc^III/II redox couples in the range -0.19V to -0.38V versus Ag/AgCl (3 M NaCl). Irreversible couples are exhibited at ca. -1.1 V to -1.2 V for Tc^II/I and +0.7V to +0.9V for Tc^IV/III. Variation in redox potential is discussed in terms of sulphur nucleophilicity.On leave from the Department of Chemistry, The University of Tsukuba, Tsukuba, Ibaraki 305, Japan.On leave from Dipartimento di Chimica dell'Universita' di Sassari, Via Vienna, 2-Sassari, Italy.     

Kinetics and possible mechanisms of alkaline hydrolysis of alkoxy-<Emphasis Type="Italic">NNO</Emphasis>-azoxy compounds

Hydrolysis rate of alkoxy-NNO-azoxy compounds like di(methoxy-NNO-azoxy)methane I, di-(methyl-NON-azoxy)formal II, di(methoxy-NNO-azoxy)methane III, and 2,2-di(methoxy-NNO-azoxy)propane IV in 5 M KOH solution was measured by manometric method at 80°C; rates relation is 1:40:540:10. Reversible deprotonation to form C-anions followed by their rapid decomposition is a presumable mechanism for compounds I–III. Nucleophilic attack of OH-anion on the carbon atom of CH₃ON=N(O) group is the most probable first stage of hydrolysis in the case of compound IV.     

Effective account of 2p–2h excitations in molecular calculations by the equation-of-motion method

The excitation energies and oscillator strengths of transitions in the helium atom (as a test system) and carbon dioxide and ethylene molecules are calculated by a modified equation-of-motion method with effective account of the most important polarization effects, including the 2p−2h (two particles-two holes) interactions, in the quasiparticle approximation of the density functional. Two different types of the effective potential of the partile-hole polarization interaction are used. The accuracy of the calculations is sensitive to the type of the potential. It is shown that the account of the polarization corrections for the 2p−2h effects is of fundamental importance since it contributes up to 30% to the values of the excitation energies and oscillator strengths. Odessa Institute of Hydrometeorology. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 4, pp. 615–622, July–August, 1995. Translated by I. Izvekova     

Functionalization of <Emphasis Type="Italic">N-tert</Emphasis>-butoxycarbonyl-7-and <Emphasis Type="Italic">N-tert</Emphasis>-butoxycarbonyl-8-bromo-10-azabicyclo[4.3.1]deca-3,7-dienes. A route to a ferruginine homolog

N-tert-Butoxycarbonyl-7-and N-tert-butoxycarbonyl-8-bromo-10-azabicyclo[4.3.1]deca-3,7-dienes are convenient substrates for further modification using replacement of the Br atom by a cyano group or a Li atom. Treatment of lithium derivatives with dimethylformamide and N-methoxy-N-methylacetamide gave the corresponding α,β-unsaturated aldehydes (67–84%) and ketones (∼70%). Ketone 4b is a direct precursor of a homolog of the alkaloid ferruginine. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1794–1796, September, 2007.     

Study on spectroscopy of two flavonyl glycosides from Andrographis paniculata

To study the bioactive constituents from Andrographis paniculata, two compounds were isolated and purified by column chromatography on AB-8 macro-porous adsorption resin and polyamide. Their structures were determined by various spectroscopic methods, including UV, FABMS, ¹H-NMR, ¹³C-NMR, DQFCOSY, TOCSY, HMQC, HMBC, and NOESY. The ¹H-NMR and ¹³C-NMR signals of the two compounds were assigned. The structures of the two compounds were elucidated as 5,4′-dihydroxy-7-methoxyflavone-6-yl-β-D-glucopyranoside and 5,4′-dihydroxy-7-methoxyflavone-8-yl-β-Dglucopyranoside, respectively. __________ Translated from Acta Chimica Sinica, 2007, 65(14): 1399–1402 [译自: 化学学报]     

Thermodynamic analysis of fluorescence enhancement and Quenching theory equations

The action of the three kinds of new third generation cephalosporin-class drugs, cefepime hydrochroride, cefpiramide and ceftizoxime with HSA and BSA was studied at different temperatures through the fluorescence method. First, the binding constants were calculated by using fluorescence quenching and enhancement theoretical equations. Their thermodynamic functions were also calculated. Because the K _A corresponding to the different theoretical equations are not completely the same, the thermodynamic parameters calculated are also different. In this paper, the differences among these thermodynamic data obtained from the different theoretical equations were analyzed and the results show that the thermodynamic data deduced from fluorescence enhancement are more reasonable. Thus, we propose that even when the fluorescence quenching action of the acceptorsubstrate is studied, more realistic data can be obtained by using the fluorescence enhancement equation. __________ Translated from Acta Chimica Sinica, 2007, 65(19): 2109–2116 [译自: 化学学报]     

New approach to cyclic sulfites and sulfates through reactions of sulfur oxychlorides with glycidols

Reactions of 2,3-epoxyalcohols (glycidols) with thionyl chloride or sulfuryl chloride afford cyclic sulfites or sulfates, respectively. These reactions yield predominantly 4-chloroalkyl-1,3,2-dioxathiolane oxides. The configuration of the C(4) atom in the latter compounds exactly corresponds to that of the C(2) atom of the parent glycidol, whereas the configuration of the exocyclic atom is almost completely reversed with respect to that of the C(3) atom of the precursor. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1586–1593, September, 2000.     

C→N migration of methoxycarbonyl and acetyl groups in reactions of functionally substituted carbanions with aryl isocyanates. Kinetics and mechanism of the reactions

The kinetics and mechanism of C→N migrations of methoxycarbonyl and acetyl groups in the reactions of the sodium derivative of methyl (2-cyano-2-phenyl)acetate and 1,1-diacetyl-2-phenyl-2-tributylphosphonioethanide with aryl isocyanates were studied by spectrophotometry. The reactions afford a prereaction complex via a concerted mechanism, according to which the nucleophilic attack of the carbanionic center to the carbon atom of the isocyanate group and the subsequent nucleophilic attack of the nitrogen atom to the carbonyl carbon atom, resulting in the C-C bond cleavage, occur almost simultaneously in the framework of the same transition state. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 850–853, May, 2006.