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1999

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Articles 2311 - 2340 of 2555

Full-Text Articles in Physical Sciences and Mathematics

An Investigation Of Electrical Properties Of Porous Silicon, G. Algün, M. Ç. Arikan Jan 1999

An Investigation Of Electrical Properties Of Porous Silicon, G. Algün, M. Ç. Arikan

Turkish Journal of Physics

In this work, electrical properties of porous silicon structures, formed with electrochemical anodization in HF acid solution under two different current densities, were investigated. In these experiments, Sb doped (111)-oriented n-type silicon samples with 0.006-0.015 \Omega cm resistivity was used. Samples were anodized in a solution of 38% HF and 99% C_2H_2OH at 1:1 ratio for 15 minutes. After anodization, the structures that formed at low current density (J = 5 mA/cm^2) was compared with structures that formed at high current density (J = 30 mA/cm^2). Both structures and electrical properties were investigated.

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Light Emission From Travelling Space Charge Domains, M. Hostut, N. Balkan Jan 1999

Light Emission From Travelling Space Charge Domains, M. Hostut, N. Balkan

Turkish Journal of Physics

We report light emission from n-doped GaAs epilayers associated with impact ionization when the device is biased in the negative difference resistance (NDR) regime (F > 3.5 kV cm^{-1}). Spectral distribution of the emitted light (electroluminescence) has been measured to identify the energy distribution of the recombining electron-hole pairs. Electron temperatures, calculated from the high energy tail of the electroluminescence spectra, show that the light emission is due to the recombination of the impact ionized holes with the background, channel, and the travelling space charge electrons. The range of the electron temperatures obtained indicate that the contribution to the light emission …

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Electronic Energy Spectrum In A Dqws Within A Tilted Magnetic Field, S. Elagöz, H. Sari, Y. Ergün, P. Karasu, İ. Sökmen Jan 1999

Electronic Energy Spectrum In A Dqws Within A Tilted Magnetic Field, S. Elagöz, H. Sari, Y. Ergün, P. Karasu, İ. Sökmen

Turkish Journal of Physics

The analytical solution of the Schrödinger equation for a DQWS subjected to an externally applied tilted magnetic field are obtained and the results are discussed. The dependency of energy spectrum of the system on the applied magnetic field direction is also given.

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Interference Of Charged Particles In A Vector Potential With Vanishing Magnetic Field, İsmai̇l Hakki Duru Jan 1999

Interference Of Charged Particles In A Vector Potential With Vanishing Magnetic Field, İsmai̇l Hakki Duru

Turkish Journal of Physics

An interference experiment in a magnetic field free region with non vanishing vector potential created by two perpendicularly intersecting planes carrying uniform currents is discussed. The relation of this configuration to the Aharonov-Bohm potential is examined. An experimental set up which is finite in the direction of electronic motion is studied.

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Quantum Mechanics Of The Electric Charge, Andrzej Staruszkiewicz Jan 1999

Quantum Mechanics Of The Electric Charge, Andrzej Staruszkiewicz

Turkish Journal of Physics

The Author summarizes the evidence that his quantum theory of the electric charge depends in a nontrivial way on the numerical value of the fine structure constant.

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Elementary Charges In Classical Electrodynamics, Edward Kapuscik, Maciej Widomski Jan 1999

Elementary Charges In Classical Electrodynamics, Edward Kapuscik, Maciej Widomski

Turkish Journal of Physics

In the framework of classical electrodynamics elementary particles are treated as capacitors. The electrostatic potentials satisfy equations of the Schrödinger type. An interesting "quantization condition" for elementary charges is derived.

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Two-Level Atom In A Squeezed Vacuum, Ryszard Tanas Jan 1999

Two-Level Atom In A Squeezed Vacuum, Ryszard Tanas

Turkish Journal of Physics

The master equation for a two-level atom interacting with a strong coherent field and damped into a reservoir formed by a finite bandwidth squeezed vacuum is derived. The master equation extends the Yeoman and Barnett approach to a non-zero detuning of the driving field from the atomic resonance and allows to discuss the role of squeezing bandwidth and the detuning in the level shifts, widths and intensities of spectral lines. The approach is valid for arbitrary values of the Rabi frequency and detuning but for the squeezing bandwidths larger than the natural linewidth in order to satisfy the Markov approximation.

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Algebraic Implementation Of Gauss' Law, Andrzej Herdegen Jan 1999

Algebraic Implementation Of Gauss' Law, Andrzej Herdegen

Turkish Journal of Physics

A C^*-algebraic model may be constructed for the description of asymptotic fields in quantum electrodynamics. In this model charged fields carry the asymptotic Coulomb field of associated charged particles.

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On The Concept Of Spin In Electrodynamics, Ivangoe Pestov Jan 1999

On The Concept Of Spin In Electrodynamics, Ivangoe Pestov

Turkish Journal of Physics

It is substantiated that spin is a notion associated with the group of internal symmetry that is tightly connected with the geometrical structure of spacetime. The wave equation for the description of a particle with spin one half is proposed. On this ground it is shown that the spin of electron is exhibited through the quantum number and accordingly the Dirac equation describes properties of particles with the projection of spin \pm \hbar/2. On the contrary, we put forward the conjecture that the spin of the quark cannot be considered as a quantum number, but only as an origin of …

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The Gauge Freedoms Of Enlarged Helmholtz Theorem And Debye Potentials; Their Use In The Multipole Expansion Of Conserved Current, Elena N. Bukina, Vladimir M. Dubovik Jan 1999

The Gauge Freedoms Of Enlarged Helmholtz Theorem And Debye Potentials; Their Use In The Multipole Expansion Of Conserved Current, Elena N. Bukina, Vladimir M. Dubovik

Turkish Journal of Physics

We discuss gauge freedom within the scope of the enlarged Helmholtz theorem and Neumann-Debye decomposition and then demonstrate its realization for the multipole expansion of a conserved electromagnetic current. The exact solution to the latter problem was obtained in 1974, but answers to some purely mathematical questions raised by I.B. French and Y. Shimamoto [1] about 40 years ago are given in this paper for the first time.

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Natural Terrestrial Electromagnetic Fields Of Extremely Low Frequencies And Detection Of Periodic Gravitational Radiation, L. V. Grunskaya, D. V. Vinogradov Jan 1999

Natural Terrestrial Electromagnetic Fields Of Extremely Low Frequencies And Detection Of Periodic Gravitational Radiation, L. V. Grunskaya, D. V. Vinogradov

Turkish Journal of Physics

The present research is connected with nontraditional ways of detecting periodic gravitational radiation. Some records of extremely low frequency variations of electromagnetic fields of Earth with extracting periodicities are realized corresponding to the source of gravitational radiation of geophysical and astrophysical origin.

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On The Experimental Search For Photon Mixing, Vsevolod Popov Jan 1999

On The Experimental Search For Photon Mixing, Vsevolod Popov

Turkish Journal of Physics

The experimental searches for photon mixing in the Okun model [1] are discussed.

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Electrical Switching In Potassium-Boro-Vanadate-Iron Glasses, H. R. Panchal, D. K. Kanchan Jan 1999

Electrical Switching In Potassium-Boro-Vanadate-Iron Glasses, H. R. Panchal, D. K. Kanchan

Turkish Journal of Physics

Electrical switching has been observed in 20K_2O : (75-y)V_2O_5 : yB_2O_3 : 5Fe_2O_3 glasses which were prepared by a splat quenching method. To investigate switching phenomenon, glass samples of the same dimension from as quenched material were examined for their I-V characteristics at various ambient temperatures. The exponential decrease of switching voltage is observed with increasing ambient temperature indicating the cause of switching due to Joule's heating. It is also observed that the switching voltage can be controlled by varying the ambient temperature and switching temperature by changing the voltage. The dependence of switching temperature on the amount of V_2O_5 …

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Electronic And Lattice Thermal Conductivity Of Bi_{1-X} Sb_X And Ag-Sb-Te Systems, Sabi̇r Ali̇yev, Agami̇rza Movsum-Zadeh, Sadiyar Ragimov, Eldar Zulfigarov Jan 1999

Electronic And Lattice Thermal Conductivity Of Bi_{1-X} Sb_X And Ag-Sb-Te Systems, Sabi̇r Ali̇yev, Agami̇rza Movsum-Zadeh, Sadiyar Ragimov, Eldar Zulfigarov

Turkish Journal of Physics

An investigation of the electronic (\aleph_e) and lattice (\aleph_L) parts of the thermal conductivity for samples of Bi_{1-x} Sb_x (0,02 < X < 0,12) and system of Ag-Sb-Te was carried out in the temperature interval 6-300K. Separation of \aleph_L and \aleph_e has been made by suppressing \aleph_e in magnetic field. The experimental data of \aleph_L and \aleph_e have been compared, respectively, with Gallaway's theory and with a theory which takes into account the inelastic character of scattering. It is observed that the Lorentz number L calculated by using the experimental values of \aleph_e and thermomagnetic coefficients is smaller than its Zommerfeld's value L_0 in high doping Bi_{0.88}Sb_{0.12}. A satisfactory agreement between the theory and the experiment allows to conclude that besides the normal and U-processes in Bi_{1-x}Sb_x the defects of mass also plays a considerable role in scattering. It is observed that \aleph_L of single phase samples Ag_{0.82}Sb_{1.18}Te_{2.18} is smaller than AgSbTe_2 samples. It is shown that this is due to the presence of p-Ag_2 Te in AgSbTe_2. It is established that the high concentration of intrinsic defects plays a considerable role in scattering for Ag-Sb-Te as well.

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Relative L X-Ray Fluorescene Cross-Sections In Heavy Elements In The Energy Region Of 16-122 Kev, Oğuz Doğan, Mehmet Ertuğrul, Önder Şi̇mşek, Ümi̇t Turgut, Hasan Erdoğan Jan 1999

Relative L X-Ray Fluorescene Cross-Sections In Heavy Elements In The Energy Region Of 16-122 Kev, Oğuz Doğan, Mehmet Ertuğrul, Önder Şi̇mşek, Ümi̇t Turgut, Hasan Erdoğan

Turkish Journal of Physics

Relative L1, L\alpha, L\beta and L\gamma x-ray fluorescence cross-sections were observed in Ta, W, Re, Au, Hg, T1, Pb, Bi, Th and U of 16.03, 17.78, 22.58, 25.77, 32.89, 38.18, 43.94, 50.21, 59,5 and 122 keV energies. In this study, L X-ray fluorescence cross-sections were measured at 59.5 and 122 keV and measured values of the other energies were taken from tables by Mann et. al. (1). The experimental relative fluorescene cross-sections were computed for the excitation energies 16.03, 17.78, 22.58, 25.77, 32.89, 38.18, 43.94, 50.21, 59.5 and 122 keV, compared with the theoretically calculated values by Scofield(11). The experimental …

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Supersymmetric Electroweak Radiative Corrections To E^+ E^- -> W^+W^-, S. Alam Jan 1999

Supersymmetric Electroweak Radiative Corrections To E^+ E^- -> W^+W^-, S. Alam

Turkish Journal of Physics

In this short note we summarize some of the work of our thesis, which is also reported elsewhere in detail. We have examined the one loop quantum corrections to the W pair production in the electron positron annihilation in the context of supersymmetric electroweak theory. We have adopted the On Mass Shell Renormalization scheme of Sakakibara and previously demonstrated the consistency of this scheme. The relevant analytic results are written out. A complete computer program for these corrections has been developed. This program has been checked in several ways to ensure against errors over the life of the calculation where …

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Effect Of Illumination Temperature On Thermally Stimulated Current Spectrum Of Tlins_2, Selahatti̇n Özdemi̇r, Rauf Süleymanov, Mahmut Bucurgat, Enver Bulur Jan 1999

Effect Of Illumination Temperature On Thermally Stimulated Current Spectrum Of Tlins_2, Selahatti̇n Özdemi̇r, Rauf Süleymanov, Mahmut Bucurgat, Enver Bulur

Turkish Journal of Physics

The effect of pre-illumination on both thermally stimulated current and photocurrent spectra of TlInS_2 crystal is investigated. The increase in the photosensitivity of the crystal by several orders of magnitude together with the appearance of a new peak in the thermally stimulated current spectrum are observed as a result of the pre-illumination process. The filling of the traps, especially the sensitizing centers, during the pre-illumination is found to be the most favourable physical mechanism to explain the results.

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On Symplectic Fillings Of 3-Manifolds, Paola Lisca Jan 1999

On Symplectic Fillings Of 3-Manifolds, Paola Lisca

Turkish Journal of Mathematics

No abstract provided.

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The Revovery Of Copper And Cobalt From Oxidized Copper Ore And Converter Slag, Berri̇n Zi̇yadanoğullari, Recep Zi̇yadanoğullari Jan 1999

The Revovery Of Copper And Cobalt From Oxidized Copper Ore And Converter Slag, Berri̇n Zi̇yadanoğullari, Recep Zi̇yadanoğullari

Turkish Journal of Chemistry

The aim of this study was to develop a method for obtaining copper and cobalt from oxidized copper ore and converter slag. In order to convert the copper and cobalt into sulfate compounds the main step was to roast the samples obtained by sulfurization and transfer the samples into solution. First the oxidized copper ore was roasted, followed by the mixture of converter slag and oxidized copper ore. Since the levels of copper and cobalt were low, the sulfurization process was carried out under autoclave conditions. The samples obtained were roasted. The yields of copper and cobalt passed into the …

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Electrochemical Preparation And Sensor Properties Of Conducting Polyaniline Films, M. Özden Eki̇nci̇, Ergün Eki̇nci̇, A. Ersi̇n Karagözler Jan 1999

Electrochemical Preparation And Sensor Properties Of Conducting Polyaniline Films, M. Özden Eki̇nci̇, Ergün Eki̇nci̇, A. Ersi̇n Karagözler

Turkish Journal of Chemistry

A polyaniline-glucose oxidase electrode was prepared by the electrochemical polymerization of aniline on a Pt electrode that was already pre-adsorbed by the enzyme (glucose oxidase) at a potential of 1 V vs. Ag/AgCl. Then, the amperometric responses of the enzyme electrode to the electroactive hydrogen peroxide formed by the enzyme-catalyzed reaction of the substrate (glucose) with oxygen were measured at a potential of 0.7 V in PBS solution. The effects of electrochemical polymerization (i.e., concentrations of monomer and electrolyte, film thickness) and amperometric measurement parameters (i.e. pH, temperature) on the amperometric response characteristics to glucose of the resultant enzyme electrode …

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An Investigation Of The Formation Mechanism Of Allene Or Alkyne In The 6,7-Benzobicyclo[3.2.1]Octane System By Deuterium Labeling Experiments, Yavuz Taşkesenligil, Ferhan Tümer, Cavi̇t Kazaz, Meti̇n Balci Jan 1999

An Investigation Of The Formation Mechanism Of Allene Or Alkyne In The 6,7-Benzobicyclo[3.2.1]Octane System By Deuterium Labeling Experiments, Yavuz Taşkesenligil, Ferhan Tümer, Cavi̇t Kazaz, Meti̇n Balci

Turkish Journal of Chemistry

In order to reveal the real intermediate in the base-promoted reaction of 1, 3-bromo-4,4-dideuterio-6,7-benzobicyclo[3.2.1]octa-2,6-diene 10 was synthesized and its HBr elimination reaction studied. Reaction of 10 with potassium tert-butoxide yielded butoxyl ether 18 in which proton-deuterium exchange has occured.

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Reaction Of Tribromonitromethane With Aldehydes And Ketones In The Presence Of Zn Metal In Aqueous Medium, Ali̇ Shaker Mahasneh Jan 1999

Reaction Of Tribromonitromethane With Aldehydes And Ketones In The Presence Of Zn Metal In Aqueous Medium, Ali̇ Shaker Mahasneh

Turkish Journal of Chemistry

Aldehydes and ketones react with tribromonitromethane in the presence of zinc metal dust, ammonium chloride and water to give dibromonitroalcohols in good yields.

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Studies On The Synthesis Of Some Substituted Flavonyl Thiazolidinedione Derivatives-I, Oya Bozdağ, Gülgün Ayhan Kilcigi̇l, Meral Tunçbi̇lek, Rahmi̇ye Ertan Jan 1999

Studies On The Synthesis Of Some Substituted Flavonyl Thiazolidinedione Derivatives-I, Oya Bozdağ, Gülgün Ayhan Kilcigi̇l, Meral Tunçbi̇lek, Rahmi̇ye Ertan

Turkish Journal of Chemistry

Synthesis and some physico-chemical properties of five flavonyl thiazolidinedione derivatives are described. These products were synthesized by Knoevenagel condensation from flavone-6-carboxaldehyde and 3-substituted 2,4-thiazolidinediones.

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Complexation Of Benzoate Ligand With The Divalent D^10 Acceptors At Different Temperatures, Betül Başaran, Efrai̇m Avşar Jan 1999

Complexation Of Benzoate Ligand With The Divalent D^10 Acceptors At Different Temperatures, Betül Başaran, Efrai̇m Avşar

Turkish Journal of Chemistry

The complex formation between zinc(II), cadmium(II), mercury(II) and benzoate ions was studied potentiometrically with glass electrode at different temperatures. The measurements have been performed in a perchlorate medium of the unit ionic strength at 25, 30, 35 and 40°C. The stability constants of the complexes were found in the order of increasing softness i.e. Zn(II) < -Cd(II)

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Supercritical Co_2 Extraction Of Ethanol, A. Güvenç, Ü. Mehmetoğlu, A. Çalimli Jan 1999

Supercritical Co_2 Extraction Of Ethanol, A. Güvenç, Ü. Mehmetoğlu, A. Çalimli

Turkish Journal of Chemistry

Extraction of ethanol was studied from both synthetic ethanol solution and fermentation broth using supercritical CO_2 in an extraction apparatus in ranges of 313 to 333 K and 80 to 160 atmospheres, for varying extraction times. The experimental system consists mainly of four parts: a CO_2 storage system, a high-pressure liquid pump, an extractor and a product collection unit. Samples were analyzed by gas chromatography. Effects of temperature, pressure, extraction time, initial ethanol concentration and consecutive solvent feeding on extraction yield were investigated. It was found that increasing the initial ethanol concentration and extraction pressure and decreasing the extraction temperature …

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The Characterization Of Na_2 Co_3 Activated Kütahya Bentonite, Nuray Yildiz, Yüksel Sarikaya, Ayla Çalimli Jan 1999

The Characterization Of Na_2 Co_3 Activated Kütahya Bentonite, Nuray Yildiz, Yüksel Sarikaya, Ayla Çalimli

Turkish Journal of Chemistry

A calcium bentonite from Kütahya region (Turkey) was activated with Na_2CO_3 at various ratios (1, 2, 2.5, 5, 10, 15g / 100 g bentonite). Due to ion exchange, the original Ca-bentonite was converted to Na-bentonite by Na_2CO_3 when the Na_2CO_3/bentonite ratio was 2.5\% (2.5 g Na_2CO_3/100 22g bentonite, A2.5). Na-bentonite (A2.5) obtained by soda activation was treated with 3 g CaCl_2/ 100 g bentonite and converted to Ca-bentonite again. The products were investigated by chemical analysis, X-ray diffraction and micropore analysis. It was observed that the cation exchange capacity (CEC) did not change until the soda ratio was 2.5\%. After …

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Mass Spectral Studies Of Some Triorganotin Derivatives Containing Carboxylates, Moazzam Hussain Bhatti, Sagib Ali, Muhammad Mazhar, Muhammad Danish, Muhammad Azi̇z Chaudhary Jan 1999

Mass Spectral Studies Of Some Triorganotin Derivatives Containing Carboxylates, Moazzam Hussain Bhatti, Sagib Ali, Muhammad Mazhar, Muhammad Danish, Muhammad Azi̇z Chaudhary

Turkish Journal of Chemistry

The mass spectra of 16 triorganotin compounds having the general formula R_3SnL where R= CH_3, C_4H_9, C_6H_5, C_6H_{11} and L=trans-3-(2-furanyl)-2-propenoate, trans-m-methyl cinnamate, 2-(2,3-dimethylphenyl)aminobenzoate and trans-3-(2-thienyl)-2- propenoate, were investigated. The possible fragmentation pattern is discussed in detail.

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Effect Of Temperature On The Electrooxidation Of Some Organic Molecules On Pt Doped Conducting Polymer Coated Electrodes, İpek Beceri̇k, Fehmi̇ Fiçicioğlu, Fi̇gen Kadirgan Jan 1999

Effect Of Temperature On The Electrooxidation Of Some Organic Molecules On Pt Doped Conducting Polymer Coated Electrodes, İpek Beceri̇k, Fehmi̇ Fiçicioğlu, Fi̇gen Kadirgan

Turkish Journal of Chemistry

Polymer modified electrodes are of importance as possible electrocatalysts for various electrode reactions, i.e., platinum incorporated into polypyrrole or polyaniline films are known to be good systems for the electrooxidation of various organic molecules. In this study, the effect of temperature on the electrooxidation of D. glucose and methanol on Pt doped films was investigated, apparent activation energies were calculated and the results were evaluated.

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Electrochemical Reduction Of Methyl Cinnamate In The Presence Of 1,3-Bis(4-Methyl Phenylsulphonyloxy)Propane, Mustafa Güllü Jan 1999

Electrochemical Reduction Of Methyl Cinnamate In The Presence Of 1,3-Bis(4-Methyl Phenylsulphonyloxy)Propane, Mustafa Güllü

Turkish Journal of Chemistry

Electrochemical reduction of methyl cinnamate in the presence of a dielectrophile, such as 1,3-bis(4-methyl phenylsulphonyloxy)propane gives two major products: trans- (\pm) methyl 2-phenylcyclopentanecarboxylate and trans- (\pm) methyl 2,3-diphenyl-5-oxo-cyclopentanecarboxylate. The ratio of products basically depends on the electrolysis conditions.

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Autocatalytic Reduction Of Dichloro 5, 10, 15, 20 Tetraphenylporphinatoplatinum(Iv) By 1-Methylimidazole, F. Ece Bulak Jan 1999

Autocatalytic Reduction Of Dichloro 5, 10, 15, 20 Tetraphenylporphinatoplatinum(Iv) By 1-Methylimidazole, F. Ece Bulak

Turkish Journal of Chemistry

It was observed that in toluene solution, excess 1-methyl-imidazole (Melm) reduces dichloro 5, 10, 15, 20 tetraphenyl-porphinatoplatinum(IV) (PtTPPCl_2) to tetraphenylporphinato-platinum(II) (PtTPP) autocatalytically (Fig. 1). There was no Pt(III) intermediate or 1-methylimidazole radical detected by Electron Resonance Spectroscopy (ESR) at 25°C. The reaction was found to be autocatalyzed by the PtTPP product when the 1-methylimidazole to PtTPPCl_2 concentration ratio is about 10^4 or more. From the data obtained it is reasonable to suppose that aggregation of the PtTPP product with PtTPPCl_2 plays an important role in this reduction process.

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