Mohammed Yusuff, K K; Mayadevi, S; Preetha, G Prasad(Taylor & Francis, May 5, 2003)
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Abstract:
Two series of transition metal complexes of Schiff bases derived from
quinoxaline-2-carboxaldehyde with semicarbazide (QSC) and furfurylamine
(QFA) were synthesised and characterised by elemental analyses,
molar conductance and magnetic susceptibility measurements, IR, electronic
and EPR spectral studies. The QSC complexes have the general
formula [M(QSC)Cl2]. A tetrahedral structure has been assigned for the
Mn(II), Co(II) and Ni(II) complexes and a square-planar structure for the
Cu(II) complex. The QFA complexes have the formula [M(QFA)2Cl2].
An octahedral structure has been assigned for these complexes. All of
the complexes exhibit catalytic activity towards the oxidation of 3,5-di-tert-butylcatechol (DTBC) to 3,5-di-tert-butylquinone (DTBQ) using
atmospheric oxygen. The cobalt(II) complex of the ligand QFA was
found to be the most active catalyst.
Ramankutty, C G; Sugunan, S; Bejoy, Thomas(Elsevier, September 9, 2002)
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Abstract:
Preparation of simple and mixed ferrospinels of nickel, cobalt and copper and their sulphated analogues by the room temperature coprecipitation method yielded fine particles with high surface areas. Study of the vapour phase decomposition of cyclohexanol at 300 °C over all the ferrospinel systems showed very good conversions yielding cyclohexene by dehydration and/or cyclohexanone by dehydrogenation, as the major products. Sulphation very much enhanced the dehydration activity over all the samples. A good correlation was obtained between the dehydration activities of the simple ferrites and their weak plus medium strength acidities (usually of the Brφnsted type) determined independently by the n-butylamine adsorption and ammonia-TPD methods. Mixed ferrites containing copper showed a general decrease in acidities and a drastic decrease in dehydration activities. There was no general correlation between the basicity parameters obtained by electron donor studies and the ratio of dehydrogenation to dehydration activities. There was a leap in the dehydrogenation activities in the case of all the ferrospinel samples containing copper. Along with the basic properties, the redox properties of copper ion have been invoked to account for this added activity.
Sunajadevi, K R; Sugunan, S(Elsevier, September , 2005)
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Abstract:
Titania, sulfated titania and chromium loaded sulfated titania were prepared by sol–gel method and characterized using different technique. Phenol is nitrated regioselectively by nitric acid using chromium loaded sulfated titania catalysts. A remarkable ortho selectivity is observed in solid state nitration to yield exclusively ortho-nitrophenol. Compared to the conventional process, phenol nitration over solid acid catalyst is a clean and environment friendly process. Catalytic activity well correlates with the Brönsted acid sites of these catalysts.
Sugunan, S; Rahna, K S(Indian Journal of Chemistry, July , 2002)
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Abstract:
The incorporation of transition metal oxide pillars such as those of iron and chromium along with Al2O3, pillars within
the interlayers of a montmorillonite clay is investigated. The surface acidity of these catalysts has been evaluated for the first
time employing the equilibrium adsorption of an electron donor, perylene, and the results are compared with those obtained
by temperature programmed desorption of ammonia. The principle is based on the ability of a catalyst surface site to accept
a single electron from an electron donor like perylene to form charge transfer complexes and the amount of adsorbed species
is measured quantitatively by UV-vis spectroscopy. Fina1ly, an attempt has been made to correlate the acidity determined by
the two independcnt methods and the catalytic activity of present systems in the benzoylation of toluene with benzoyl
chloride. Incorporation of Fe and Cr has changed the properties of AI pitlared montmorillonite. Fe pillared systems have
been found to be vcry good catalysts for benzoylation reaction
Sugunan, S; Kumaree Seena, C R(Indian Journal of Chemistry, May , 1998)
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Abstract:
We have investigated the changes in surface acidity/basicity
and catalytic pro~erties of samarium oxide due to surface modification
by SO42- ion. The acidity/basicity of the catalysts is
determined by titration method using Hammett indicators.
Esterification of acetic acid by n-butanol is chosen as a test
reaction. Sm203, owing to its high basicity and low acidity, does
not catalyze the reaction. But sulphated Sm20J catalyzes the
esterification reaction effectively. Activation temperature does
not have much effect on the acidity of sulphated samaria.
Sugunan, S; Anto, Paul(Indian Journal of Chemistry, April , 1997)
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Abstract:
The surface acidity/basicity of binary oxides of Zr and La and the ternary oxides of Zr, La and Al are
reported. The data have been correlated with their catalytic activity towards liquid phase reduction of
cyclohexanone.
Sugunan, S; Bindhu, Jacob(Indian Journal of Engineering & Materials Sciences, June , 1997)
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Abstract:
The surface acidity and basicity of ternary oxides of
AI, Ce and Dy have been determined using a set of
Hammett indicators. The data have been correlated
with the catalytic activity of these oxides towards the
liquid phase reduction of cyclohexanone in 2-propanol.
The reaction is favoured by the higher basicity of
the ternary oxide.
Sugunan, S; Ampili, S; Bindhu, Jacob; Rani, Varghese(Indian Journal of Chemistry, February , 1996)
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Abstract:
The surface acidity and basicity of ternary oxides of
La, Ce and AI have been determined using a set of
Hammett indicators. The data have been correlated
with the catalytic activity of these oxides towards the
liquid phase reduction of cycIohexanone in 2-propanol.
Sugunan, S; Sunitha, Kurur; Anto, Paul(Indian Journal of Chemistry, December , 1994)
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Abstract:
The surface acidity and basicity of oxides of Sm and Zr
and their mixed oxides have been determined using a set of
Hammett indicators. The data have been correlated with
the catalytic activity of these oxides towards the liquid
phase reduction of cyclo-hexanone in 2-propanol.
Sugunan, S; Devika Rani, G; Unnikrishnan, P A(Indian Journal of Engineering & Materials Sciences, October , 1995)
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Abstract:
Acid/base strength distribution of Y2O3 and its mixed
oxides with alumina catalysts are measured on Hammett
acidity function scale and expressed in terms of H0max
value. Basicity of Y2O3 increases with increase in activation
temperature and for mixed oxides the basicity increases
with increase in concentration of Y2O3, in the catalyst.
Sugunan, S; Sherly, K B; Devika Rani, G(React. Kinet.Catal.Lett., 1993)
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Abstract:
The limit of electron transfer in electron affinity from
the oxide surface to the electron acceptor (EA) are reported
from the adsorption of EA on DY203, mixed oxides
of DY203 with alumina and mixed oxides of Y203 with y-alumina.
The extent of electron transfer is understood
from magnetic measurements.
Sugunan, S; Binsy, Varghese(Indian Journal of Chemistry, September , 1998)
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Abstract:
The electron donating properties, surface acidity/ basicity and catalytic activity of cerium - zirconium mixed
oxides at various compositions have been reported at an activation temperature of 500 degree C. The catalytic activity
for the esterification of acetic acid with n-butanol has heen correlated with electron donating properties and
surface acidity/basicity of the oxides.
The electron donating properties, surface acidity/basicity and catalytic activity of lanthana for various dopant concentrations of strontium are reported at two activation temperatures. The catalytic activity has been correlated with electron donating properties and surface acidity/basicity of the oxide.
Ferrospinels of nickel, cobalt and copper and their sulphated analogues were prepared by the room temperature coprecipitation
route to yield samples with high surface areas. The intrinsic acidity among the ferrites was found to decrease in
the order: cobalt> nickel> copper. Sulphation caused an increase in the number of weak and medium strong acid sites,
whereas the strong acid sites were left unaffected. Electron donor studies revealed that copper ferrite has both the highest
proportion of strong sites and the lowest proportion of weak basic sites. All the ferrite samples proved to be good catalysts
for the benzoy lation of toluene with benzoyl chloride. copper and cobalt ferrites being much more active than nickel ferrite.
The catalytic activity for benzoylation was not much influenced by sulphation, but it increased remarkably with calcination
temperature of the catalyst. Surface Lewis acid sites, provided by the octahedral cations on the spinel surface, are suggested
to be responsible for the catalytic activity for the benzoylation reaction.
Smitha, V K; Suja, H; Joyce, Jacob; Sugunan, S(Indian Journal of Chemistry, February , 2003)
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Abstract:
Preparation and physico-chemical characterization or
phosphate modified zirconia systems and their application to
Friedel-Crafts benzylation and benzoylation of toluene have been
reported. The influence of transition metals on the surface
properties and catalytic activity has also been discussed.
Sugunan, S; Renuka, N K(Indian Journal of Chemistry, February , 2002)
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Abstract:
Sm2O3 - vanadia catalysts have been prepared by wet
impregnation method using NH4VO3 solution. The surface
properties of the prepared catalysts have been studied using FTIR.
XRD. surface area and pore volume data. The acid-base properties
of the system have been investigated by titrimetric method using
Hammett indicators. adsorption of electron acceptors as well as
decomposition of cyclohexanol. Phenol alkylation reaction by
methanol has been carried out to investigate the catalytic activity.
It has been observed that the selectivity of the products depends
upon the composition of the supported system
Prathapachandra Kurup, M R; Sreesha, Sasi; Sithambaresan, M; Fun, H K(Elsevier, 2010)
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Abstract:
Four manganese(II) complexes Mn2(paa)2(N3)4 (1), [Mn(paa)2(NCS)2] 3/2H2O (2), Mn(papea)2(NCS)2 (3),
[Mn(dpka)2(NCS)2] 1/2H2O(4) of three neutral N,N donor bidentate Schiff bases were synthesized and physico-
chemically characterized by means of partial elemental analyses, electronic, infrared and EPR spectral
studies. Compounds 3 and 4 were obtained as single crystals suitable for X-ray diffraction. Compound 4
recrystallized as Mn(dpka)2(NCS)2. Both the compounds crystallized in the monoclinic space groups P21
for 3 and C2/c for 4. Manganese(II) is found to be in a distorted octahedral geometry in both the monomeric
complexes with thiocyanate anion as a terminal ligand coordinating through the nitrogen atom. EPR spectra
in DMF solutions at 77 K show hyperfine sextets with low intensity forbidden lines lying between each
of the two main hyperfine lines and the zero field splitting parameters (D and E) were calculated.
Sreekumar, K; Rajesh Krishnan, G(Taylor & Francis, February 22, 2010)
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Abstract:
Poly(amidoamine) dendrimers were synthesized on cross-linked aminomethyl polystyrene. Palladium
complexes of supported dendrimers prepared by ligand exchange method were reduced to dendrimernanoparticle
conjugates supported on polystyrene resin. The supported nanoparticles were used as
heterogeneous catalysts for the Suzuki coupling between aryl boronic acids and aryl halides. Various factors
affecting the catalysts performance were studied. Higher generation dendrimers gave well-defined
nanoparticles without agglomeration and these particles showed good catalytic performance