J. Serb. Chem. Soc. 62(11) 1025-1029 (1997)
Original scientific paper
Application of line graph in physical chemistry.
Predicting the surface tension of alkenes
IVAN GUTNAM, LJILJANA POPOVIC, BIJAY K. MISHIRA*, MINATI KUANAR*, ERNESTO ESTRADA** and NICOLAIS GUEVARA**
Faculty of Science, University
of Kragujevac, R. Domanovi}a 12, P.O.Box 60, 34000 Kragujevac, Yugoslavia
*Centre of Studies of Surface Science and Technology, Department of Chemistry, Sambalpur University, Jyoti Vihar 768019, India and
**Universidad Central de Las Villas, Santa Clara 54830, Villa Clara, Cuba
Received 9 April 1997)
For a molecular graph G we construct a sequence of graphs Li(G), i = 0, 1, 2,..., such that L0(G) = G, L1(G) is the line graph of G, L2(G) is the line graph of L1(G), etc. Let mi be the number of edges of Li(G). We show that the surface tension of alkanes is well reproduced by means of linear functions of the invariants mi, i = 0, 1, ...., k. Satisfactory accuracy (correlation coefficient 0.97) is achieved already at k = 2.
Key words: line graph, surface tension, QSPR.
Mechanism of the reactions between chloro(2,2':6',2''-terpyri-dine)platinum(II) and ligands containing a thiol group
ZIVADIN D. BUGARCIC,BILJANA V. DJORDJEVIC and MILOS I. DJURAN
Faculty of Science, Department of Chemistry, University of Kragujevac, R. Domanovi}a 12, P.O.Box 60, 34000 Kragujevac, Yugoslavia
(Received 23 April 1997)
The reactions between the [Pt(terpy)Cl]+ complex and ligands with a thiol group, such as cysteine and thioglycolic acid, have been studied by 1H-NMR spectroscopy in d4-CD3OD at 22°C. The second-order rate constants at 22°C are (4.9±0.3)×10-2 mol dm-3 s-1 for cysteine and (5.2±0.2)×10-2 mol dm-3 s-1 for thioglycolic acid. However, methionine, as a thioether ligand, seems to be unreactive under the same experimental conditions. Steric effects cannot be the main reason for the difference in reactivity. This difference could be explain by deprotonation of the thiols, the final product being the thiolate complex [Pt(terpy)(SR)]+. There is no possibility for the deprotonation in the case of methionine and this could be the main reason for the difference in the reactivity of thiols (cysteine and thioglycolic acid) and thioethers (methionine) with [Pt(terpy)Cl]+.
Key words: platinum(II), terpy, complex, thiol, cysteine, methionine, mechanism.
The mechanisms of tris(4-morpholinecarbodithioato-S,S')cobalt(III) complex formation by solid state reaction from ammine cobalt(III) complexes
TIBOR J. SABO, JASNA VLAJKOVIC and VERA DONDUR*
Faculty of Chemistry and *Faculty of Physical Chemistry, University of Belgrade, Studentski Trg 16, P.O.Box 158 & 137, YU-11001 Belgrade, Yugoslavia
(Received 7 February, revised 3 July 1997)
In this paper, the solid state reaction, conducted with a mixture of pentaamminechlorocobalt(III) chloride and potassium 4-morpholinecarbodithioate was investigated under isothermal conditions. The reaction proceeds at relatively low temperatures (154-192°C). The yield of product solid-solid reaction, tris(4-morpholinecarbo-dithio-ato-S,S')cobalt(III) complex, does not exceed 65%. The kinetic of the reaction of powdered and pressed samples were investigated. The reaction proceeded according to the diffusional mechanism. Activation energies of 200 kJ/mol and 100 kJ/mol for the powdered and pressed form, respectively, were obtained.
Key words: cobalt(III) complexes, kinetic, mechanism, pentaamminechlorocobalt(III) chloride, potassium 4-morpholinecarbodithioate.
Investigations of the effect of the S-arginine chelate conformation on the optical activityof the tris(S-arginine)cobalt(III) diastereomers
PETAR N. RADIVOJŠA
Faculty of Chemistry, University of Belgrade, P.O.Box 158, YU-11001 Belgrade, Yugoslavia
(Received 16 May 1997)
The effect of the S-arginine chelate conformation on the optical activity of tris(S-arginine)cobalt(III) diastereomers was investigated by means of circular dichroism (CD). It was found that the l-conformation of the S-arginine chelate in facial diastereomers of the above complex contributes more to the negative CD of D-dia-stereomers, than does the d-conformation to the positive CD of L-diastereomers. In addition, it was established that the d-conformation of the S-arginine chelate in both diastereomers causes only a small difference of the CD of meridional diasteromers.
Key words: cobalt(III) complex, S-arginine, circular dichroism, optical activity, chelate conformation.
Synthesis and characterization of s-cis-bis(ethylenediamine- -N,N'-diacetato)-µ-O,O'-glycinato-µ-hydroxo-dichromium(III) monohydrate
TIBOR J. SABO, SLADJANA SAMARDZIJA*, DEJAN POLETI** and SRECKO R. TRIFUNOVIC***
Faculty of Chemistry, P.O.Box
158, YU-11001 Belgrade,
*Faculty of Veterinary Medicine, Bul. JNA 18, YU-11000 Belgrade,
**Department of General and Inorganic Chemistry, Faculty of Technology and Metallurgy, P.O.Box 494, YU-11001 Belgrade, and
***Department of Chemistry, Faculty of Science, R. Domanovica 12, YU-34000 Kragujevac, Yugoslavia
(Received 7 February, revised 14 July 1997)
The reaction between s-cis-diaqua-(ethylenediamine-N,N'-diacetato)-chromium(III) nitrate and glycine (mole ratio 1:1, pH = 6, 80°C, 2 h) results in the formation of two nonelectrolytic compounds. One of them was identified as the title complex. The infrared and electronic absorption spectra, as well as the magnetic momentum confirm a binuclear structure and the existence of hydroxo and O,O'-glycinato bridges.
Key words: chromium(III), binuclear complex, edda, glycine.
Description of anion coordination in aluminium salt solutions using polarimetry
D. C. CHAMBERLAIN
Arjo Wiggins Ltd, Butler's Court, Beaconsfield, Bucks, HP9 IRT, England
(Received 3 March, revised 14 May 1997)
Polarimetric analysis of sucrose inversion was used to study acidity changed by anions coordinating with aluminium cations in solution. The effects of aluminium concentration, temperature and anion concentraton were investigated. The method proved useful for testing non-ideal solutions. Data show polarimetry is a sensitive indicator of solution acidity but observation from other methods are required to provide conclusive details of anion coordination modes.
Key words: acidity determination, non-ideal solutions, Al3+ion - anions coordination
Spectral properties of methylene blue modified polypyrrole film
RODICA-MARIANA ION, DANA FLORENTINA BLAIR* and OCTAVIAN RADOVICI*
Zecasin S.A., Photochemistry
Department, Splaiul Independentei 202, Bucharest-79611, Romania, and
*Polytechnical University, Polizu Street 1, Bucharest, Romania
(Received 18 October 1996, revised 30 May 1997)
In this paper the UV-Vis spectra of methylene blue incorporated into a polypyrrole polymer matrix is discussed. The changes of the absorption maxima of methylene blue in the presence of polypyrrole have been fitted with Gauss type functions using a PC computer programme. In addition, the aggregation equilibrium for methylene blue alone and in the presence of polypyrrole is evaluated.
Key words: polypyrrole, methylene blue, aggregation, conducting polymers.
Investigation of the relation between the Kramers-Kronig transforms and the stability condition necessary to derive the faradaic admittance equation involving three state variablesbesides the electrode potential
XIAOJUAN WU, YONGQUAN ZHANG, HOUYI MA*, SHULAN LI* and SHENHAO CHEN*
Department of Electronic Engineering and *Department of Chemistry, Shandong University, Jinan, 250100, P.R. China
(Received 10 April 1997)
The transform between the real and imaginary parts of the Faradaic admittance equation for an irreversible electrode process involving three state variables, besides the electrode potential, was carried out using one of the Kramers-Kronig relations. The result that the condition required by the stability for the derivation process of the equation was also satisfield in the K-K transforms shows that the equation is a true mathematic model characterizing the dependance of the Faradic admittance on angular frequency. The use of the equation, together with a general equivalent circuit, proved a convenient method to determine electrochemical parameters from EIS with four time constants.
Key words: Kramers-Kronig transform, electrochemical impedance spectroscopy (EIS), irrevesible electrode process, equvivalent circuit, faradic impedance.
Binding of toxic cations to ferritin
JASMINA VIDIC, DESANKA SUZNJEVIC, MILENKO ERCEG* and DUŠAN VUCELIC**
Institute of General and
Physical Chemistry, P.O.Box 551, YU-11001 Belgrade,
*Forensic Institute, Kraljice Ane bb, P.O. Box 574, YU-11000 Belgrade and
**Faculty of Physical Chemistry, University of Belgrade, YU-11000 Belgrade, Yugoslavia
(Received 3 April 1997)
Electrochemical studies of metalloproteins have a considerable potential in the investigation of the structure of metal-protein complexes, particularly in view of the heavy metal pollution effect. In this paper, data obtained by differential pulse polarography (d.p.p.) using a dropping mercury electrode (DME) are presented, with regard to the specific interaction of ferritin with Cd2+, Al3+ and Pb2+ from citrate buffer, pH 6.3. It is possible to more clearly observe the obtained peak current of Pb2+ on the d.p.p. curve after its binding to ferritin after digestion of the protein coat by trypsin, suggesting that the Pb2+ ions are probably associated with the protein core. However, the binding affinity of Cd2+ to ferritin is not high because the bound Cd2+ ions can be easily removed as Cd-citrate or as the more stable Cd-EDTA complex. It was also found that Al3+ ions bind rather strongly to ferritin, probably due to the association with ferric ions present in the protein core.
Key words: ferritin, differential pulse polarography, aluminum, lead, cadmium
The dependence of the mechanical properties of materials on their electronic structure
A. M. MARICIC, M. V. NIKOLIC, S. M. RADIC, B. D. STOJANOVIC and M. M. RISTIC
Joint Laboratory for Advanced Materials of the Serbian Academy of Sciences and Art, Knez Mihailova 35, YU-11000 Belgrade, Yugoslavia
(Received 1 April 1997)
In this paper problems of mechanical properties of materials from the viewpoint of their electronic structure have been investigated. Special attention was paid to the importance of the statistical weight of stable atomic configurations (SWASK) for basic explanation of the interdependence of mechanical properties and electronic structure.
Key words: mechanical properties, electronic structure, SWASK.
The role of the liquid phase in
the structural changes of ZrO2 within the
SNEZANA BOŠKOVIC, FEODOR SIGULINSKI and EMILIJA KOSTIC
Vinca Institute of Nuclear Sciences, Materials Science Laboratory, P.O.Box 522, YU-11001 Belgrade, Yugoslavia
(Received 23 April 1997)
The structural changes of ZrO2 were followed in the Si3N4-ZrO2-CeO2 system at temperatures between 1500°C and 1780°C, in an argon atmosphere. The dominant crystalline phase of ZrO2 in this system is the monoclinic form, with Si ions incorporated in the lattice. Ce ions do not stabilize the ZrO2 c+t modification because CeO2 preferentially takes part in the formation of the liquid phase.
Key words: composites Si3N4-ZrO2-CeO2, structure, liquid phase.
Transparent ferroelectric glass
ceramics of the ABO3 type
MILICA TODOROVIC and LJILJANA RADONJIC*
Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, YU-11000 Belgrade, and
*Faculty of Technology, University of Novi Sad, Bulevar Cara Lazara 1, YU-21000 Novi Sad, Yugoslavia
(Received 20 September 1996, revised 11 June 1997)
Ferroelectric glass ceramics based on ABO3 crystals, obtained by the direct crystallization of the glasses, were investigated. The glass samples, of composition within the system (Li or Na or K)2 O - (Nb or Ta)2O5 - SiO2 - Al2O3 were prepared by the melting process, after which they were subjected to crystallization by heat treatment at appropriate temperatures for appropriate times. It was found that stable glasses could only be obtained over a very narrow composition range. The Layton mole ratio B/N has a significant influence on the nucleation rate of the crystal phase. The Kokubo alumina content is also an important parameter for the transparency of the glass ceramics. It was found that, besides these two parameters, the type and content of the alkali metal oxides are also very important for the crystallization mechanism of the glasses. Lithium ions facilitate the rapidity of nucleation and the crystal growth of the glasses much more than either sodium or potassium ions. The mechanism of crystallization of ABO3 crystals is based on phase separation of the glasses, followed by nucleation of the crystal phase. The measured values of the dielectric constant and the refractive index show that these change in a very complex way, depending on the development of the microstructure.
Key words: ferroelectric glass-ceramics, glass crystallization, phase separaton, alkali niobate and tantalate glass ceramics.
Low temperature processes during the synthesis of lanthanum lead borosilicate glasses
NIKOLA S. BLAGOJEVIC, SNEZANA R. GRUJIC, ROZALIJA R. NINKOVIC and LJILJANA C. KARANOVIC*
Faculty of Technology and
Metallurgy, Karnegijeva 4, YU-11000 Belgrade and
*Faculty of Geology and Mining, Djušina 7, YU-11000 Belgrade, Yugoslavia
(Received 14 March, revised 19 June 1997)
Low temperature processes during the synthesis of PbO-B2O3-SiO2-La2O3 glasses were studied by thermal analysis of the batch mixture of glasses and X-ray powder diffraction analysis of samples that crystallized during invesrtigations of the crystallization ability of the synthesized glasses. The obtained results and available thermodynamic data indicate the formation of PbO.B2O3, PbO.2B2O3 and La2O3.B2O3.SiO2 in the temperature interval 400-700°C.
Key words: lanthanum lead borosilicate glasses, low temperature processes, thermal analysis, X-ray analysis.
Optimal plasma process routes in the Al-H-N system for aluminum nitride powder production
ZIVOTA G. KOSTIC, PREDRAG Lj.
STEFANOVIC, PAVLE B. PAVLOVIC and
SLOBODAN DJ. ŠIKMANOVIC
Vinca Institute of Nuclear
Sciences, Laboratory for Thermal Engineering and Energy,
P.O.Box 522, YU-11001 Belgrade, Yugoslavia
(Received 15 October 1996, revised 21 April 1997)
The results of equilibrium composition and total enthalpy computation, in the temperature range of 1000 K to 6000 K and under a pressure of 1 bar, for Al - H - N system are presented in this paper. These data enable mass, temperature and enthalpy parameter determination, and optimization of the process for ultrafine aluminum nitride powder production, where aluminum evaporation in a nitrogen plasma is followed by cooling with ammonia.
Key words: aluminum nitride powder, plasma synthesis.