Indian Journal of Chemistry

Sect. A: Inorganic, Bio-inorganic, Physical, Theoretical & Analytical

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CODEN: ICACEC; ISSN: 0376-4710 (Print), 0975-0975 (Online)

 

 

 

 

VOLUME 53A

NUMBER 2

FEBRUARY 2014

 

CONTENTS

 

 

135

 

The supramolecular assembly of cyanurate cobalt(II) complexes: Crystal structure, TD-DFT approach and thermal study

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Soumen Mistri, Santiago García-Granda,
Ennio Zangrando* & Subal Chandra Manna
*

 

 

 

DFT calculations of the isolated complex cation of [Co(H2CA)(H2O)5]·(H2CA)·2H2O (H3CA = cyanuric acid) show a slight deviation from the structural results obtained by X-ray diffraction. Theoretically possible spin allowed quartet-quartet electronic transitions have been assigned using TD-DFT results.

 

 

 

 

 

143

 

Ultrafast radiationless decay mechanisms through conical intersections in cytosine. A new semi-planar conical intersection

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Saadullah G Aziz, Walid I Hassan,
Shaaban K Alrouby, Abdulrahman Alyoubi &
Rifaat Hilal
*

 

 

The conical intersection seam in the ultrafast radiationless decay of cytosine is explored. A new conical intersection has been identified and characterized  at the DFT and CASSCF levels of theory.

 

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152

 

Zinc-doped biphasic calcium phosphate nanopowders synthesized via sol-gel method

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Gunawan, I Sopyan*, Suryanto & A Naqshbandi

 

 

 

Zinc-doped biphasic calcium phosphate powders are synthesized by sol-gel method. X-ray diffraction patterns show that the phases present in Zn-doped BCP are hydroxyapatite, β-TCP and parascholzite. Morphology analysis show that the size
of agglomerates tends to increase with the increasing
Zn concentration.

 

 

 

159

 

Oxidation of captopril by hexacyanoferrate(III) in aqueous hydrochloric acid medium – A kinetic and mechanistic study

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Girish G Ariga, Amruta Mutalikdesai, Deepti Jog, Manjula Kirgi, Sharanappa T Nandibewoor &
Shivamurti A Chimatadar*

 

 

 

The oxidation mechanism of captopril by hexacyanoferrate(III) in hydrochloric acid and acetic acid medium has been investigated.

 

 

 

 

 

Notes

 

167

 

Catalytic combustion of methane on Ce1-xMxO2-d (M=Si, Mg, Al) oxides

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Jian-Feng Tu, Lei-Hong Zhao, Xin Hu, Tie Li,
Yi-An Fang, Meng-Fei Luo & Jian-Jun Lin
*

 

 

The doping of Si and Mg into fluorite CeO2 phase increases the surface area and the amount of oxygen vacancies, increasing the reducibility of the catalyst. Hence, the Si and Mg doped CeO2 catalysts present high activity in catalytic combustion of methane.

 

 

 

 

 

 

174

 

Oxidation of phenylthioureas by cetyltrimethylammonium permanganate: A kinetic study

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Prangya Rani Sahoo & Bijay K Mishra*

 

 

 

On oxidation by cetyltrimethyl ammonium permanganate
in acetonitrile, substituted phenylthioureas yield the corresponding ureas.

 

 

 

 

 

 

 

 

 

179

 

Does silicon prefer to form conjugated bonds with carbon in the C6SiH8+ system?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Srihari Murthy

 

 

 

DFT calculations at the B3LYP/6-31G* level  show that the
p-silaphenylmethane cation is more stable than the phenylsilane cation by about 11 kcal mol-1.  This indicates that in the C6SiH8+ system there is at least one instance where silicon prefers to form conjugated bonds with carbon.

 

 

 

 

 

 

Authors for correspondence are indicated by (*)

 

 

Indian Journal of Chemistry

Vol. 53A, February 2014, pp. 135-142

 

 

The supramolecular assembly of cyanurate cobalt(II) complexes:
Crystal structure, TD-DFT approach and thermal study

Soumen Mistria, Santiago García-Grandab, Ennio Zangrandoc, * & Subal Chandra Mannaa, *

aDepartment of Chemistry and Chemical Technology, Vidyasagar University,
Midnapore 721 102, West Bengal, India

Email: scmanna@mail.vidyasagar.ac.in

bDepartment of Physical and Analytical Chemistry, University Oviedo–CINN,C/ Julián Clavería, 8, 33006 Oviedo, Spain

cDepartment Chemical and Pharmaceutical Sciences, University of Trieste, via Giorgieri, 1, Trieste, 34127, Italy

Received 3 September 2013; revised and accepted 20 January 2014

The synthesis, structural elucidation and TD-DFT analysis of the self-assembly of a cobalt(II) complex
with
cyanuric acid is reported. The asymmetric unit in the crystal comprises a cobalt complex cation, [Co(H2CA)(H2O)5]+ (H3CA = cyanuric acid), a cyanurate mono anion, and two lattice water molecules, which are assembled in the supramolecular network via pair-wise coupling of N-H∙∙∙O type occurring between the ion pairs and additional hydrogen bonds involving aqua ligands and lattice water molecules.

Keywords: Cobalt, Cyanuric acid, N-H∙∙∙O hydrogen bond, DFT analysis

 

Indian Journal of Chemistry

Vol. 53A, February 2014, pp. 143-151

 

 

Ultrafast radiationless decay mechanisms through conical intersections
in cytosine. A new semi-planar conical intersection

Saadullah G Aziza, Walid I Hassanb, Shaaban K Alroubya, c, Abdulrahman Alyoubia & Rifaat Hilala, b, *

aChemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, SA

bChemistry Department, Faculty of Science Cairo University, Giza, Egypt

cChemistry Department, Faculty of Science Beni-Suief University, Beni-Suief, Egypt

Email: rhilal@kau.edu.sa

Received 26 November 2013; revised and accepted 27 January 2014

Geometry, energetics and dipole moment of all possible conformers of cytosine in the ground state are calculated using density functional theory B3LYP method and the 6-311++G(3df,3pd) basis set. The most stable conformer is keto-amino conformer. The amino group hydrogen atoms are slightly out of plane by about 6.3° and 9.9° each. Ultrafast radiationless decay mechanism has been theoretically investigated using Complete Active Space Multiconfiguration SCF calculations. Effective pathways of ultrafast radiationless transitions from the optically allowed π π* state to the ground state S0 of cytosine are explored. The nπ*, nσ*, and the ππ* states have been taken into account as states involved in the radiationless process. Optimized geometry and conical intersections have been searched in the full dimensional space for the vibrational degrees of freedom. Three competing direct decay mechanisms through three possible conical intersections have been found to exist. The first pathway is through the bending of molecule in a sofa-like structure leading to conical intersection with ground state at 4.23 eV. The second pathway occurs through a twisted structure that has hydrogen twisted and the cytosine ring slightly deformed leading to conical intersection at 4.08 eV. The third mechanism takes place via semi-planar conical intersection with main deformations inside the cytosine ring and C=O bond that have 3.97 eV at the intersection with ground state. The three mechanisms contribute to the stability of cytosine. The g-vector and h-vector for semi-planar conical intersection are calculated and discussed along with their geometrical parameters.

Keywords: Theoretical chemistry, Density functional calculations, Ultrafast radiationless decay, Cytosine,
Conical intersection, Ultrastability

 

Indian Journal of Chemistry

Vol. 53A, February 2014, pp. 152-158

 

 

Zinc-doped biphasic calcium phosphate nanopowders synthesized

via sol-gel method

 

Gunawana, b, I Sopyana, *, Suryantoa & A Naqshbandia

aDepartment of Manufacturing and Materials Engineering, Faculty of Engineering

International Islamic University Malaysia, 50728 Kuala Lumpur, Malaysia

Email: sopyan@iium.edu.my

bDepartment of Mechanical Engineering, Faculty of Engineering,

Sriwijaya University, Inderalaya 30662, Indonesia

Received 5 August 2013; revised and accepted 28 January 2014

Zinc-doped biphasic calcium phosphate (BCP) powders have been synthesized via sol-gel method. The dopant concentration ions were adjusted at 1, 2, 3, 5, 10 and 15 mol%. The powders have been calcined at varying temperatures ranging from 500-900 °C and then characterized by XRD, FTIR, TG/DTA, TEM and FESEM data. X-ray diffraction patterns show that the phases present in Zn-doped BCP are hydroxyapatite, β-TCP and parascholzite. FTIR analysis reveal that the separation of three PO43- stretching peaks is obscure and OH bending peak at 630 cm-1 broaden with an increase in Zn concentration, whereas the PO43- band of TCP at 1085 cm-1 is sharper at higher calcination temperatures. Morphology analysis show that the size of agglomerates tends to increase with the increasing Zn concentration. These findings indicate that an increase in Zn level doped to the BCP affects the phase composition, crystallization and microstructure of the samples.

Keywords: Doping, Zinc doping, Biphasic calcium phosphate, Calcium phosphate, Sol-gel method

 

 

Indian Journal of Chemistry

Vol. 53A, February 2014, pp. 159-166

 

Oxidation of captopril by hexacyanoferrate(III) in aqueous hydrochloric

acid medium – A kinetic and mechanistic study

 

* Girish G Ariga, Amruta Mutalikdesai, Deepti Jog, Manjula Kirgi, Sharanappa T Nandibewoor &
Shivamurti A Chimatadar

PG Department of Studies in Chemistry, Karnatak University, Dharwad 580 003, India

Email: schimatadar@gmail.com

Received 20 May 2013; revised and accepted 27 January 2014.

The oxidation of captopril by hexacynoferrate(III) in hydrochloric acid and 50% acetic acid-water(v/v) at a constant ionic strength (I = 3.10 mol dm-3) has been studied spectrophometrically at 25 °C. The reactions are initiated by mixing previously thermostated solutions of hexacyanoferrate(III) and captopril containing the required amounts of hydrochloric acid and sodium perchlorate. The kinetics have been followed under pseudo-first order conditions with captopril in excess. The stoichiometry is found to be 2:2, i. e., two moles of hexacyanoferrate(III) react with two moles of captopril. The reaction products have been identified as [Fe(CN6)]4- and captopril disulfide. The product, captopril disulfide, has been confirmed by IR and GC-MS analysis. The reaction is of first order with respect to hexacyanoferrate(III) and fractional order with respect to captopril concentration. Increase in hydrochloric acid concentration accelerates the rate of reaction at constant ionic strength and at other conditions constant. The order with respect to acid concentration is nearly two. The added product, [Fe(CN6)]4-, does not show any significant effect on the rate of the reaction. The effects of ionic strength and dielectric constant on the rate of reaction have also been studied. Based on the experimental results, a suitable mechanism is proposed and the rate law is derived. The reaction constants involved in the different steps of mechanism are calculated. The activation parameters with respect to limiting step of the mechanism and also the thermodynamic quantities are determined and discussed.

Keywords: Kinetics, Reaction mechanism, Oxidation, Hexacynoferrate(III), Captopril

 

 

Indian Journal of Chemistry

Vol. 53A, February 2014 pp. 167-173

 

 

Catalytic combustion of methane on Ce1-xMxO2-d (M=Si, Mg, Al) oxides

Jian-Feng Tua, Lei-Hong Zhaob, Xin Hua, Tie Lib, Yi-An Fangb, Meng-Fei Luob & Jian-Jun Lina, *

aCollege of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, PR China

Email: linjj@zjnu.cn

bZhejiang Key Laboratory for Reactive Chemistry on Solid Surfaces, Institute of Physical Chemistry, Zhejiang Normal
University, Jinhua 321004, China

Received 12 September 2013; revised and accepted 30 January 2014

A series of mixed oxides of cerium, viz., Ce1-xMxO2-& (M=Si, Mg, Al) has been prepared by sol-gel method. X-ray diffraction technique, BET surface area measurements, scanning electron microscopy images and Raman spectroscopy ascertain their structures, while hydrogen temperature-programmed reduction determine the redox properties. Catalytic methane combustion tests with catalytic amounts of this series of compounds show that the activity of CeO2 is highly improved when Ce is substituted with Si or Mg. Among the studied catalysts, Ce0.95Si0.05O2 has the highest catalytic activity with T90 at 600 oC. Doping of Si or Mg into CeO2 results in higher catalytic activity than pure CeO2 due to higher surface area, smaller particle size, increased amount of oxygen vacancies and enhanced reducibility.

Keywords: Catalysts, Catalytic combustion, Methane combustion, Ceria, Doped catalyst, Solid solutions

 

 

Indian Journal of Chemistry

Vol. 53A, February 2014, pp. 174-178

 

 

Oxidation of phenylthioureas by cetyltrimethylammonium permanganate:
A kinetic study

Prangya Rani Sahoo & Bijay K Mishra*

Centre of Studies in Surface Science and Technology,
School of Chemistry, Sambalpur University,
Jyoti Vihar 768 019, India

Email: bijaym@hotmail.com

Received 9 July 2013; revised and accepted 22 January 2014

Phenylthioureas have been subjected to oxidation in acetonitrile medium in neutral condition to investigate the oxidation behaviour of cetyltrimethylammonium permanganate on multifunctional groups. The oxidation product in each reaction is found to be the corresponding phenylurea. The rate of reaction is dependent on [CTAP], [phenylthiourea], [surfactant] and reaction temperature. A Michaelis-Menten type kinetics is observed with respect to the substrate. A reaction mechanism involving the formation of a cyclic intermediate in the slow step is proposed for the oxidation reaction.

Keywords: Kinetics, Reaction mechanism, Oxidation, Phenylthioureas, Cetyltrimethylammonium permanganate

 

Indian Journal of Chemistry

Vol. 53A, February 2014, pp. 179-180

 

 

Does silicon prefer to form conjugated bonds with carbon in the
C6SiH
8+ system?

Srihari Murthy

Sri Venkateswara College of Engineering, Post Bag No. 1 Pennalur, Irungattukotai 602 117, India

Email: smurthy@svce.ac.in

Received 9 September 2013; revised and accepted 6 January 2014

Quantum chemical calculations based on geometry optimization using density functional theory at the B3LYP/6-31G* level are used to determine the relative stabilities of neutral and cationic C6SiH8 species, namely, the p-silaphenylmethane, phenylsilane and the silacycloheptatriene species.  It is found that for the cations, silicon substitution in the phenyl ring leads to increased stability, thereby, causing the p-silaphenylmethane cation to be more stable than the phenylsilane cation by about 11 kcal mol-1.  However, the situation is reversed in the case of the neutrals.  The silacycloheptatriene species is the least stable of the three, both in neutral and cationic form.

Keywords: Theoretical chemistry, Organosilicon chemisty, Density functional calculations, Quantum chemistry,
p-Silaphenylmethane cation, Phenylsilane, Gas phase ion chemistry