Indian Journal of Chemistry

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

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VOLUME 49A

NUMBER 7

July 2010

CONTENTS

 

853

 

On π-electron configuration of cyclopenta-derivatives of benzenoid hydrocarbons

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ivan Gutman*, Jelena Đurđević, Dušan Bašić & Dragana Rašović

 

 

 

In prolate-rectangle-shaped benzenoids, the number of bonding molecular orbitals always exceeds the number of antibonding molecular orbitals, except if all five-membered rings lie on the same side of the benzenoid system.

 

 

 

 

 

861

 

DFT and statistical mechanics entropy calculations of diatomic and polyatomic molecules

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

G Serdaroglu* & S Durmaz

 

 

 

Statistical mechanics coupled with quantum chemical calculations can provide accurate values of the partition function and related thermodynamics properties of diatomic and polyatomic molecules described by realistic entropies at moderate- and high- temperature regimes in which the exact
sum-over-states quantum mechanical treatments is not possible.

 

 

 

867

 

Structural studies of silica modified titania and its photocatalytic activity of 4-chlorophenol oxidation in aqueous medium

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

K Joseph Antony Raj, York R Smith,
Vaidyanathan (Ravi) Subramanian &
B Viswanathan*

 

 

 

The presence of Ti-O-Si linkage is responsible for the increase in photocatalytic activity for silica modified samples over other forms of titania in both UV and visible illumination. The sample with an optimal loading of 7.5 wt.% calcined at 500 °C shows
the highest photocatalytic activity for decomposition of
4-chlorophenol.

 

 

 

 

 

 

876

 

Thermal behaviour of metal(II) isonicotinate tetrahydrates

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Monideepa Chakrabortty, Jatindra Nath Ganguli, Sanchay Jyoti Bora & Birinchi Kumar Das*

 

 

 

Thermogravimetric behaviour of six tetraaquabis(isonicotinato) metal(II) species, viz., M(C6H4O2N)2(H2O)4 (M = Mn, Fe, Co, Ni, Cu, Zn), shows that the first step involving dehydration of the coordination compounds follows the Irving-Williams order. Also, at higher temperatures their thermal decompositions follow complicated pathways.

 

 

882

 

Speciation of chromium in aqueous samples by solid phase extraction using multiwall carbon nanotubes impregnated with D2EHPA

 

 

 

 

 

 

 

 

S Vellaichamy & K Palanivelu*

 

 

 

A method for solid phase extraction of chromium(III) and chromium(VI), using multiwall carbon nanotubes impregnated with di-(2-ethyl hexyl) phosphoric acid has been developed. Under optimum conditions, the maximum adsorption capacity of this material was found to be 0.96 mg g−1 for chromium with detection limit of 0.05 mg mL−1. The adsorbent can be reused for more than 10 cycles of adsorption-desorption without any significant change in sorption of chromium metal ions (<10 %).   


Notes

 

891

 

Synthesis and characterization of a mixed cationic tetrasulfidotungstate monohydrate

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bikshandarkoil R Srinivasan*, Rathan G Mhalsikar, Christian Näther & Wolfgang Bensch

 

 

 

The organic cations, [WS4]2- anion and the lattice water in
the mixed cationic tetrasulfidotungstate monohydrate,
(dabcoH)3(NMe4)[WS4]2.H2O, are linked by several H-bonding interactions.

 

 

 

896

 

Fluorescence resonance energy transfer from proflavin hemisulphate to rose bengal in aqueous micellar solution

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

S L Bhattar, G B Kolekar & S R Patil*

 

 

 

The fluorescence of proflavine hemisulphate is quenched by rose bengal in accordance with Stern-Volmer relationship. The value of critical energy transfer distance calculated by using Foster relationship (27.2 Ĺ) is less than 50 Ĺ, indicating efficient energy transfer occurs in this donor-acceptor pair.

 

 

 

 

 

 

901

 

Photo-oxidative degradation of an azo dye direct
red 31 in the presence of ZnS catalyst

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A Nageswara Rao*, B Sivasankar & V Sadasivam

 

 

 

Photocatalytic degradation of direct red 31 on irradiation with
UV light in the presence of ZnS photocatalyst follows first order kinetics and may be explained on the basis of Langmuir–Hinshelwood mechanism.

 

 

 

Authors for correspondence are indicated by (*)

 

 

 

Indian Journal of Chemistry

Vol. 49A, July 2010, pp. 853-860

 

On π-electron configuration of cyclopenta-derivatives of benzenoid hydrocarbons

Ivan Gutman*, Jelena Đurđević, Dušan Bašić & Dragana Rašović

Faculty of Science, P.O. Box 60, 34000 Kragujevac, Serbia

Email: gutman@kg.ac.rs

Received 19 May 2010; accepted 15 June 2010

Within the Hückel molecular orbital model, Kekulčan benzenoid hydrocarbons have equal number of bonding and antibonding molecular orbitals, and no non-bonding molecular orbitals. In cyclopenta-derivatives of benzenoid hydrocarbons this regularity may be either preserved or violated, depending on the number and position of the five-membered rings. Some general regularities along these lines are established. In particular, the problem is completely solved in the case of prolate-rectangle-shaped benzenoids; the number of bonding molecular orbitals always exceeds the number of antibonding molecular orbitals, except if all five-membered rings lie on the same side of the benzenoid system.

Keywords: Theoretical chemistry, Graph theory, Electron configuration, Molecular orbitals, Hydrocarbons, Benzenoids

 

Indian Journal of Chemistry

Vol. 49A, July 2010, pp. 861-866

 

DFT and statistical mechanics entropy calculations of
diatomic and polyatomic molecules

G Serdaroglua, * & S Durmazb

a Faculty of Education, Cumhuriyet University, 58140 Sivas, Turkey

Email: goncagul.serdaroglu@gmail.com

b Faculty of Science and Arts, Department of Chemistry, Cumhuriyet University, 58140 Sivas, Turkey

Email: serdaroglu@cumhuriyet.edu.tr

Received 26 October 2010; revised and accepted 8 April 2010

Ab initio/DFT and statistical mechanics methods for calculation of entropy are reported for 20 molecules in which internal rotations are absent, and are compared with the experimental values. Agreement between these data and corresponding entropies calculated from spectral data is excellent, being within one entropy unit in almost all cases at 298.15 K. Entropies have also been calculated over a wide range of temperature i.e., 298.15 K and 0–400 K at 50 K intervals. It is clearly observed that all entropies increase with increasing temperature. The results show a sharp increase on going from 0 K to 50 K while the increase is slight at temperatures above 50 K. The results also suggest that such calculations may assist in studies on entropies and equilibria involving species for which vibrational frequencies can not easily be determined by experiment.

Keywords: Theoretical chemistry, Ab initio calculations, Statistical mechanics, Entropy, Diatomic molecules, Polyatomic molecules

 

Indian Journal of Chemistry

Vol. 49A, July 2010, pp. 867-875

 

Structural studies of silica modified titania and its photocatalytic activity of
4-chlorophenol oxidation in aqueous medium

K Joseph Antony Raja, York R Smitha, b, Vaidyanathan (Ravi) Subramanianb & B Viswanathana, *

aNational Centre for Catalysis Research, Indian Institute of Technology Madras, Chennai 600 036, India

Email: bvnathan@iitm.ac.in

bChemical & Materials Engineering Department, University of Nevada, Reno, 89557, USA

Received 28 April 2010; accepted 16 June 2010

A series of titania samples with different loadings of silica (0.5-10 wt.%) has been prepared by wet impregnation method. The presence of Ti-O-Si linkage for all silica loadings has been confirmed by DRIFT spectra. High dispersion of silica in the titania matrix and the bonding of Ti-O-Si in silica-titania samples are found to inhibit the transformation of amorphous to anatase titania. The UV-vis/DRS show an increase in UV and visible light absorbance for 7.5 wt.% silica calcined at 500 °C. Evaluation of photocatalytic activity of the samples for the decomposition of 4-chlorophenol shows greater activity for samples modified with silica with an optimal loading of 7.5 wt.% silica calcined at 500 °C. Conversion of 90 % and 35 % of 4-chlorophenol for UV-visible and visible light respectively is observed. Photocatalytic activity of the silica-titania samples is found to decrease with increasing crystallinity.

Keywords: Catalysis, Photocatalysis, Amorphous materials, Titania, Oxidations, Oxides

IPC Code: Int. Cl.9 B01J21/00; C07B33/00

 

Indian Journal of Chemistry

Vol. 49A, July 2010, pp. 876-881

 

Thermal behaviour of metal(II) isonicotinate tetrahydrates

Monideepa Chakrabortty, Jatindra Nath Ganguli, Sanchay Jyoti Bora & Birinchi Kumar Das*

Department of Chemistry, Gauhati University, Guwahati 781 014, India

Email: Birinchi.Das@hotmail.com

Received 15 February 2010; revised and accepted 2 June 2010

Metal isonicotinate tetrahydrates with M = Mn, Fe, Co, Ni, Cu, Zn are analogous hexacoordinate complexes of the type trans-[M(NC5H4-p-CO2)2(OH2)4], which form a robust 3-D supramolecular network in the solid state. Hydrogen bonds formed between OH2 donors and CO2- acceptors strongly hold the water molecules and the isonicotinato ligands together with the metal ions to make these compounds quite stable in air at room temperature. Thermogravimetric analysis shows that these complexes lose weight in two well defined steps occurring in the 50-600 °C range. Thermogravimetric data on the compounds are found to follow metal-dependence close to expectations based on the Irving-Williams order for bivalent metal ions.

Keywords: Coordination chemistry, Hydrogen bonded network, Thermogravimetry, Thermal stability, Irving-Williams order, Metal isonicotinate tetrahydrates

 

Indian Journal of Chemistry

Vol. 49A, July 2010, pp. 882-890

 

Speciation of chromium in aqueous samples by solid phase extraction using multiwall carbon nanotubes impregnated with D2EHPA

S Vellaichamy & K Palanivelu*

Centre for Environmental Studies, Anna University Chennai, Chennai 600 025, India

Email: kpvelu@annauniv.edu

Received 12 February 2010; revised and accepted 14 June 2010

A solid phase extraction system has been developed for the speciation of chromium(III) and chromium(VI). This method is based on the adsorption of chromium(III) on D2EHPA impregnated with multiwall carbon nanotubes and has been compared with commercially available activated carbon impregnated with D2EHPA. The chromium concentration has been determined by inductively coupled plasma atomic emission spectroscopy. The effect of parameters such as pH of the aqueous solution, amount of adsorbent, contact time, initial ion concentration, sample volume, eluent type and D2EHPA concentration have been investigated. The results indicate that the maximum adsorption of chromium(III) is at pH 4.5 ± 0.1 on the multiwall carbon nanotubes. Desorption studies have been carried out with 0.25 M Br2 in 1.0 M NaOH wherein quantitative recovery of the chromium(III) has been observed. The adsorption capacity of MWCNTs- D2EHPA is found to be 0.96 mg g -1 for chromium with detection limit of chromium 0.05 mg mL-1.  The highest pre-concentration factor of 60 could be obtained for 300 mL of sample volume.  The developed method has been applied for the speciation of chromium in natural water sample and the pre-concentration method is satisfactory (recoveries > 98 %, rsd < 10 %, n = 5) for chromium species determination.

Keywords: Solid phase extraction, Speciation studies, Chromium, Carbon nanotubes, Nanotubes, ICP-AES

 

Indian Journal of Chemistry

Vol. 49A, July 2010, pp. 891-895

 

Synthesis and characterization of a mixed cationic
tetrasulfidotungstate monohydrate

Bikshandarkoil R Srinivasana, *, Rathan G Mhalsikara, Christian Nätherb & Wolfgang Benschb

aDepartment of Chemistry, Goa University, Goa 403 206, India

Email:srini@unigoa.ac.in

bInstitut für Anorganische Chemie, Christian-Albrechts-Universität Kiel, Max-Eyth Strasse 2, D-24118 Kiel, Germany

Received 9 Febraury 2010; revised and accepted 17 June 2010

Synthesis and structural characterization of a mixed cationic tetrasulfidotungstate monohydrate (dabcoH)3(NMe4)[WS4]2. H2O (dabco = 1,4-diazabicyclo[2.2.2]octane; NMe4 = tetramethylammo-nium) is described. The compound crystallizes in the centrosymmetric monoclinic space group P21/c and its structure consists of three crystallographically independent monoprotonated (dabcoH)+ cations, a tetramethylammonium cation, two unique tetrasulfidotungstate anions, and a lattice water. The organic cations, [WS4]2- anion and lattice water are linked by several weak H-bonding interactions.

Keywords: Coordination chemistry, Crystal structure, Tetramethylammonium, Tetrasulfidotungstate

IPC Code: Int. Cl.9 C07F11/00

 

Indian Journal of Chemistry

Vol. 49A, July 2010, pp. 896-900

 

Fluorescence resonance energy transfer from proflavin hemisulphate to
rose bengal in aqueous micellar solution

S L Bhattar, G B Kolekar & S R Patil*

Fluorescence Spectroscopy Research Laboratory, Department of Chemistry, Shivaji University,
Kolhapur 416 004, Maharashtra, India

Email: srp_fsl@rediffmail.com

Received 20 July 2009; revised and accepted 10 June 2010

The fluorescence resonance energy transfer from proflavine hemisulphate to rose bengal in aqueous sodium dodecyl sulfate has been investigated at room temperature using steady-state fluorescence spectroscopy technique. The fluorescence of proflavine hemisulphate is quenched by rose bengal and the quenching is in accordance with Stern-Volmer relationship. The efficiency of energy transfer is found to depend upon concentration of rose bengal. The value of critical energy transfer distance calculated by using Foster relationship (27.2 Ĺ) is less than 50 Ĺ, indicating efficient energy transfer occurs in this donor-acceptor pair.

Keywords: Fluorescence resonance, Fluorescence quenching, Proflavine hemisulphate, Energy transfer, Dyes, Rose bengal

 

Indian Journal of Chemistry

Vol. 49A, July 2010, pp. 901-905

 

Photo-oxidative degradation of an azo dye direct red 31 in
the presence of ZnS catalyst

A Nageswara Raoa, *,  B Sivasankarb & V Sadasivamb

aDepartment of Chemistry, Sathyabama University, Chennai 600 119, Tamil Nadu, India

Email: raoankem@rediffmail.com

bDepartment of Chemistry, Anna University, Chennai 600 025, Tamil Nadu, India

Received 4 August 2009; revised and accepted 8 June 2010

The photocatalytic degradation of direct red 31 on irradiation with UV light in the presence of ZnS photocatalyst has been reported. Effect of pH, weight of catalyst and concentration of dye on the degradation has been studied. A higher removal of dye is observed under mildly acidic conditions. The optimum weight of catalyst loading is found to be 3.0 g/L. The dye degradation obeys first order kinetics and is explained on the basis of Langmuir-Hinshelwood mechanism.

Keywords: Photochemistry, Photooxidation, Dyes, Azodyes, Direct red 31

IPC Code: Int. Cl.9 B01J23/06; B01J27/04; C07B33/00; C09B