Rapheal,P F; Manoj, E; Prathapachandra Kurup, M R(Elsevier, 2007)
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Abstract:
Ten copper(II) complexes {[CuL1Cl] (1), [CuL1NO3]2 (2), [CuL1N3]2 · 2/3H2O (3), [CuL1]2(ClO4)2 · 2H2O (4), [CuL2Cl]2 (5), [CuL2N3] (6), [Cu(HL2)SO4]2 · 4H2O (7), [Cu(HL2)2] (ClO4)2 · 1/2EtOH (8), [CuL3Cl]2 (9), [CuL3NCS] · 1/2H2O (10)} of three NNS donor thiosemicarbazone ligands {pyridine-2-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone [HL1], pyridine-2-carbaldehyde-N(4)-2-phenethyl thiosemicarbazone [HL2] and pyridine-2-carbaldehyde N(4)-(methyl), N(4)-(phenyl) thiosemicarbazone [HL3]} were synthesized and physico-chemically characterized. The crystal structure of compound 9 has been determined by X-ray diffraction studies and is found that the dimer consists of two square pyramidal Cu(II) centers linked by two chlorine atoms.
Rare earth exchanged Na–Y zeolites,
H-mordenite, K-10 montmorillonite clay and amorphous
silica-alumina were effectively employed for the
continuous synthesis of nitriles. Dehydration of benzaldoxime
and 4-methoxybenzaldoxime were carried
out on these catalysts at 473 K. Benzonitrile (dehydration
product) was obtained in near quantitative yield
with benzaldoxime whereas; 4-methoxybenzaldoxime
produces both Beckmann rearrangement (4-methoxyphenylformamide)
as well as dehydration products
(4-methoxy benzonitrile) in quantitative yields. The
production of benzonitrile was near quantitative under
heterogeneous reaction conditions. The optimal protocol
allows nitriles to be synthesized in good yields
through the dehydration of aldoximes. Time on stream
(TOS) studies show decline in the activity of the catalysts
due to neutralization of acid sites by the basic reactant
and product molecules and water formed during the
dehydration of aldoximes.
Mohammed Yusuff, K K; Sridevi, Nadimpall; Jelaja, Padmavathy(Kluwer Academic Publishers, July 20, 2000)
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Abstract:
The nature of the diperiodatocuprate(III) (DPC) species present in aqueous alkaline medium has been investigated
by a kinetic and mechanistic study on the oxidation of iodide by DPC. The reaction kinetics were studied over the
1.0 ´ 10)3±0.1 mol dm)3 alkali range. The reaction order with respect to DPC, as well as iodide, was found to be
unity when [DPC] [I)]. In the 1.0 ´ 10)3±1.0 ´ 10)2 mol dm)3 alkali region, the rate decreased with increase in
the alkali concentration and a plot of the pseudo-®rst order rate constant, k versus 1/[OH)] was linear. Above
5.0 ´ 10)2 mol dm)3, a plot of k versus [OH)] was also linear with a non-zero intercept. An increase in ionic
strength of the reaction mixtures showed no e ect on k at low alkali concentrations, whereas at high concentrations
an increase in ionic strength leads to an increase in k. A plot of 1/k versus [periodate] was linear with an intercept in
both alkali ranges. Iodine was found to accelerate the reaction at the three di erent alkali concentrations employed.
The observed results indicated the following equilibria for DPC.
Prathapachandra Kurup, M R; Nisha, K; Sithambaresan, M(November 21, 2011)
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Abstract:
The title compound, C21H19N3O2S, exists in the thione form.
The configuration about the C N bond is E. The
hydrazinecarbothioamide unit adopts an almost planar
arrangement, with maximum deviations of 0.016 (3) and
0.016 (2) A ° for the two thiourea N atoms. An intramolecular
O—H N hydrogen bond occurs. Weak intermolecular N—
H S, C—H O and C—H interactions are observed in
the crystal structure
The effect of chromium doping on methylene
blue sensitized Poly (vinyl alcohol)/Acrylamide was carried
out by varying the ratios of Ammonium dichromate
and methylene blue. In the case of films without ammonium
dichromate, the diffraction efficiency was found to
decrease on storage. On chromium doping the storage life
was improved. Interestingly, a self-enhancement in efficiency
was observed for a particular ratio of methylene
blue and ammonium dichromate.
One-pot acetalizations of cyclohexanone. acetophenone and benzophenone were carried out using methanol over H-montmorillonite clay
(a mesoporous material). silica, alumina, and different zeolites such as HFAU-Y.HBeta, H-ZSM-5, and H-mordenite. In all the cases a single
product-the corresponding dimethylacetal-was obtained in high yields. Hemiacetal formation was not observed with any catalyst. A
comparison of catalytic activity indicated that montmorillonite K-10 is the most active catalyst for the reaction. As evidenced by the reaction
time studies, the catalyst decay is greater over the zeolite catalyst than over the clay.
Sugunan, S; Renuka, N K(Indian Journal of Chemistry, April , 2002)
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Abstract:
Physico-chemical characterization of DY203/V2O5 systems prepared through wet impregnation method has been carried
out using various techniques like EDX, XRD, FTIR. thermal studies, BET surface area, pore volume and pore size
distribution analysis. The amount of vanadia incorporated has been found to influence the surface properties of dysprosia.
The spectroscopic results combining with X-ray analysis reveal that vanadia species exist predominantly as isolated
amorphous vanadyl units along with crystalline dysprosium orthovanadate. Basicity studies have been conducted by
adsorption of electron acceptors and acidity and acid strength distribution by temperature programmed desorption of
ammonia. Cyclohexanol decomposition has been employed as a chemical probe reaction to examine the effect of vanadia on
the acid base property of Dy2O3. Incorporation of vanadia titrates thc Lewis acid and base sites of Dy2O3, while an
enhancement of Bronsted acid sites has been noticed. Data have been correlated with the catalytic activity of these oxides
towards the vapour phase methylation of phenol
Dipyrromethene-Cu(II) derivatives possessing two dodecane alkyl chains have been used for the modification of gold
electrodes. Electroactive host molecules have been incorporated into a lipophilic dodecanethiol SAM deposited onto
gold electrodes through hydrophobic and van der Waals interactions (embedment technique). The presence of
dipyrromethene-Cu(II) redox centers on the electrode surface was proved by cyclic voltammetry and Osteryoung
square-wave voltammetry. The Au electrodes incorporating redox active Cu(II)-dipyrromethene SAMs were used for
the direct voltammetric determination of paracetamol in human plasma.
Girish Kumar,K; Joseph, Renjini(Taylor & Francis, June 1, 2009)
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Abstract:
A metalloporphyrin incorporated carbon paste sensor has been developed
for the determination of metronidazole benzoate (MTZB). Zn(II) complex
of 5,10,15,20-tetrakis (3-methoxy-4-hydroxy phenyl) porphyrin (TMHPP) was
used as the active material. The MTZB gave a well-defined reduction peak at
- 0.713V in 0.1 mol l -1 phosphate buffer solution of pH around 7. Compared
with bare carbon paste electrode (CPE), the TMHPP Zn(II) modified electrode
significantly enhanced the reduction peak current of MTZB as well as lowered
its reduction potential. Under optimum conditions the reduction peak current
was proportional to MTZB concentration over the range 1×10-3 mol1-1 to 1×10-5mol1-1. The detection limit was found to be 4.36×10-6mol1-1
. This
sensor has been successfully applied for the determination of MTZB in pharmaceutical
formulations and urine samples.
Girish Kumar,K; Thomas, D; Joseph, R; Issac, S; Lonappan, L(The Institution of Engineering and Technology, October 10, 2011)
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Abstract:
A differential pulse voltammetric sensor for the determination of tamsulosin hydrochloride (TAM) using multiwalled carbon nanotubes
(MWNTs)–Nafion-modified glassy carbon electrode (GCE) has been developed. MWNTs were dispersed in water with the help of Nafion
and were used to modify the surface of GCE via solvent evaporation. At MWNT-modified electrode, TAM gave a well-defined oxidation
peak at a potential of 1084 mV in 0.1 M acetate buffer solution of pH 5. Compared to the bare electrode, the peak current of TAM
showed a marked increase and the peak potential showed a negative deviation. The determination conditions, such as the amount of
MWNT–Nafion suspension, pH of the supporting electrolyte and scan rate, were optimised. Under optimum conditions, the oxidation
peak current was proportional to the concentration of TAM in the range 1 × 1023 M–3 × 1027 M with a detection limit of
9.8 × 1028 M. The developed sensor showed good stability, selectivity and was successfully used for the determination of TAM in pharmaceutical
formulations and urine samples
The electron-donor properties of Sm2O3 activated at 300, 500, and 800°C are reported from studies on the adsorption of electron acceptors of various electron affinities (electron affinity values in eV are given in parentheses): 7,7,8,8-tetracyanoquino-dimethane (2.84), 2,3,5,6-tetrachloro-1,4-benzoquinone (2.40), p-dinitrobenzene (1.77), and m-dinitrobenzene (1.26) in acetonitrile and 1,4-dioxane. The extent of electron transfer during the adsorption was determined from magnetic measurements. The acid-base properties of Sm2O3 at different activation temperatures are reported using a set of Hammett indicators. Electron donor-acceptor interactions at interfaces are important in elucidating the adhesion forces.
Sugunan, S; Jalaja, J M(Indian Journal of Chemistry, March , 1995)
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Abstract:
The electron donating properties of Ce02 and its mixed
oxides with alumina have been determined from the studies
of adsorption of electron acceptors of various electron
affinities on the surface of these oxides. The catalytic
activity of these oxides towards some reactions such as
oxidation of alcohols and reduction of ketones have been
Correlated with their surface electrondonor properties. The
surface acidity/basicity of these oxides have also been
determined by titration method using a set of Hammett
indicators.
The catalytic activity of Perovskite-type mixed oxides (LaCo03 . PrCo03 and SmCo03 ) for the
reduction of cyclohexanone to cyclohexanol with 2-propanol (Meerwein-Ponndorf-Verley reduction)
has been studied. The data have been correlated with the surface electron donor properties
of these mixed oxides.
Sugunan, S; Devika Rani, G(Indian Journal of Chemistry, November , 1993)
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Abstract:
The adsorption of electron acceptors, viz.,7,7,8,8-tetracyanoquinodimethane(TCNQ), 2,3,5,6-tetrachloro-p-
benzoquinone (chloranil) and p-dinitrobenzene
(PDNB) on the surface of three rare earth oxides Y2O3,
Nd203 and Pr6O11 has been studied in acetonitrile and
dioxan. From the radical concentration on the surface
determined using ESR spectral data, the electron donor
strength of the rare earth oxides are reported.
Invertase was adsorbed onto micro-porous acid-activated montmorillonite clay (K-10) by two procedures, namely adsorption and covalent binding. The immobilized enzymes were characterized by XRD, surface area measurements and 27Al NMR. XRD measurements revealed an expansion of clay layers due to immobilization which suggests that intercalation had taken place. Surface area measurements also support this observation. 27Al NMR showed that interaction of enzyme with tetrahedral and octahedral Al changes with the immobilization procedure. Sucrose hydrolysis was performed in a batch reactor. The immobilized enzymes showed enhanced pH and thermal stabilities. Optimum pH and temperature were found to increase upon immobilization. The effectiveness factor (η) and Michaelis constant (Km) suggest that diffusional resistances play a major role in the reaction. The immobilized invertase could be stored in buffer of pH 5 and 6 at 5 °C without any significant loss in activity for 20 days.
The differaction efficiency,sensitivity and storage life of Methylene blue sensitized poly(vinyl chloride) film was improved by the addition of an electron donor in the matrix. The
addition of pyridine enhanced the diffraction efficiency by two times and storage life of the
gratings was increased to 2-3 days.
Thomas Lee, S; Suresh, Kumar P; Unnikrishnan, K P; Nampoori, V P N; Girijavallabhan, C P; Sugunan, S; Radhakrishnan, P(Department of Applied Chemistry, May 15, 2003)
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Abstract:
In this communication, we discuss the details of fabricating an off-line fibre
optic sensor (FOS) based on evanescent wave absorption for detecting trace
amounts of Fe3+ in water. Two types of FOS are developed; one type uses
the unclad portion of a multimode silica fibre as the sensing region whereas
the other employs the microbent portion of a multimode plastic fibre as the
sensing region. Sensing is performed by measuring the absorption of the
evanescent wave in a reagent medium surrounding the sensing region. To
evaluate the relative merits of the two types of FOS in Fe3+ sensing, a
comparative study of the sensors is made, which reveals the superiority of
the latter in many respects, such as smaller sensing length, use of a double
detection scheme (for detecting both core and cladding modes) and higher
sensitivity of cladding mode detection at an intermediate range of
concentration along with the added advantage that plastic fibres are
inexpensive. A detection limit of 1 ppb is observed in both types of fibre and
the range of detection can be as large as 1 ppb–50 ppm. All the
measurements are carried out using a LabVIEW set-up.
Sreekumar, K(Optical society of America, June 20, 2004)
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Abstract:
A methylene-blue-sensitized polymer blend of polyvinyl alcohol and polyacrylic acid is fabricated and
tested for holographic recording. It was found to have good characteristics such as high sensitivity,
storage stability, ease of fabrication, and environmental stability. Optimization of the ratio of polyvinyl
alcohol polyacrylic acid, the sensitizer concentration, pH, energy, diffraction efficiency measurements,
etc., have been done. pH is found to have a great influence on the recovery of the dye in this matrix.
The results of experimental investigations into the properties of this new material are reported.
The fabrication and analytical applications of two types of potentiometric
sensors for the determination of ketoconazole (KET) are described. The
sensors are based on the use of KET-molybdophosphoric acid (MPA) ion pair
as electroactive material. The fabricated sensors include both polymer membrane
and carbon paste electrodes. Both sensors showed a linear, stable and near
Nernstian slope of 57.8mV=decade and 55.2mV=decade for PVC membrane
and carbon paste sensors respectively over a relatively wide range of KET concentration
(1×10-2-5×10-5 and 1×10-2-1×10-6). The sensors showed a fast
response time of <30 sec and <45 sec. A useful pH range of 3–6 was obtained
for both types of sensors. A detection limit of 2.96 10 5M was obtained for
PVC membrane sensor and 6.91 10 6M was obtained for carbon paste sensor.
The proposed sensors proved to have a good selectivity for KET with respect to a
large number of ions. The proposed sensors were successfully applied for the
determination of KET in pharmaceutical formulations. The results obtained
are in good agreement with the values obtained by the standard method.