Sugunan, S; Suja, H; Deepa, C S; Sreeja Rani, K; Ouseph, M V(Indian Journal of Chemistry, November , 2002)
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Abstract:
Surface acidity of phosphate modified La2O3,CeO2 and SnO2 has been estimated by titrimetric Method using Hammett Indicators.Mixed Oxides of tin and lanthanum have also been prepared and subjected to phosphate modification.Surface characterizartion of the samples has been carried out using XRD, surface area,thermal analysis and IR spectroscopy.
Phosphate content in the samples has been chemically estimated. The catalytic activity for benzylation and esterification reaction has also been investigated.
Sugunan, S; Renuka, N K(Indian Journal of Chemistry, February , 2001)
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Abstract:
Vapour phase methylation of phenol is carried out over La2O3 supported vanadia systems of various composition. The structural features and physico chemical characterisation of the catalysts are investigated. Orthovanadates are formed in addition to surface vanadyl species on the metal oxide support. No V2O5 crystallites are detected. The acid base properties of the oxides are studied by Hammett indicator method and decomposition of cyclohexanol.The data are correlated with the catalytic activity and selectivity of the products. Ring alkylation is found to be predominant over these catalysts.
Sugunan, S; Sherly, K B(Indian Journal of Chemistry, October , 1994)
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Abstract:
Lanthanum oxide, La2O3 has been found to be an effective
catalyst for the liquid phase reduction of cyclohexanone.
The catalytic activities of La2O3 activated
at 300, 500 and 800·C and its mixed oxides with
alumina for the reduction of cyclohexanone with
2-propanol have been determined and the data parallel
that of the electron donating properties of the catalysts.
The electron donating properties of the catalysts have
been determined from the adsorption of electron acceptors
of different electron affinities on the surface of
these oxides.
The catalytic activity of some of the ABO3 (A = La, Pr
and Sm, B= Cr, Mn, Fe, Co and Ni) perovskite-type oxides
for the liquid phase reduction of ketone and oxidation of
alcohol in 2-propanol medium has been studied. The data
have been correlated with the surface electron donor
properties of these oxides. The surface electron donor
properties have been determined from the adsorption of
electron acceptors of varying electron affinities on the
oxide surface.
Spinel systems with the composition of Cu 1−x Zn x Cr 2 O 4 [x = 0 CCr, x = 0.25 CZCr-1, x = 0.5 CZCr-2, x = 0.75 CZCr-3 and x = 1 ZCr] were prepared by homogeneous co-precipitation method and were characterized by X-ray diffraction (XRD) and FT-IR spectroscopy. Elemental analysis was done by EDX, and surface area measurements by the BET method. The redox behavior of these catalysts in cyclohexane oxidation at 243 K using TBHP as oxidant was examined. Cyclohexanone was the major product over all catalysts with some cyclohexanol. 69.2% selectivity to cyclohexanol and cyclohexanone at 23% conversion of cyclohexane was realized over zinc chromite spinels in 10 h.
Iron and mixed iron aluminium pillared montrnorillonites prepared by partial hydrolysis method were subjected to room temperature
exchange with transition metals of the first series. The resulting materials were characterised by different spectroscopic techniques
and surface area measurements. About 1-3% transition metals were incorporated into the porous network. The structural
stability of the porous network was not affected by exchange. XRD and AI NMR spectroscopy evidenced the presence of iron
substituted Al13 like polymers in FeAl pillared systems. Acidity and basicity benefited much as a result of metal exchange. Acidity
and basicity were quantified by model reactions, viz., cumene cracking and cyclohexanol decomposition respectively. The presence
of basic sites in otherwise acidic pillared clays, though diminutive in amount can be of much importance in acid base catalysed
reactions.
Mohammed Yusuff, K K; Sridevi, N; Pearly Sebastian, C(Wiley InterScience, January 9, 2007)
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Abstract:
Ruthenium(III) complexes of the Schiff bases
formed by the condensation of polymer bound aldehyde and
the amines, such as 1,2-phenylenediamine (PS-opd), 2-aminophenol
(PS-ap), and 2-aminobenzimidazole (PS-ab) have been
prepared. The magnetic moment, EPR and electronic spectra
suggest an octahedral structure for the complexes. The complexes
of PS-opd, PS-ap, and PS-ab have been assigned the
formula [PS-opdRuCl3(H2O)], [PS-apRuCl2(H2O)2], [PS-ab-
RuCl3(H2O)2], respectively. These complexes catalyze oxidation
of catechol using H2O2 selectively to o-benzoquinone. The catalytic activity of the complexes is in the order [PS-ab-
RuCl3(H2O)2] . [PS-opdRuCl3(H2O)] [PS-apRuCl2(H2O)2].
Mechanism of the catalytic oxidation of catechol by ruthenium(
III) complex is suggested to take place through the formation
of a ruthenium(II) complex and its subsequent oxidation
by H2O2 to the ruthenium(III) complex.
Prathapachandra Kurup, M R; Sheeja, S R; Sarika, Sivakumar; Neema, Ani Mangalam; Edward, R T Tiekink(Elsevier, June 23, 2009)
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Abstract:
Four hydrazone ligands: 2-benzoylpyridine benzoyl hydrazone (HBPB), di-2-pyridyl ketone nicotinoyl
hydrazone (HDKN), quinoline-2-carbaldehyde benzoyl hydrazone (HQCB), and quinoline-2-carbaldehyde
nicotinoyl hydrazone (HQCN) and four of their complexes with vanadyl salts have been synthesized and
characterized. Single crystals of HBPB and complexes [VO(BPB)(l2-O)]2 (1) and [VO(DKN)(l2-O)]2 ½H2O
(2) were isolated and characterized by X-ray crystallography. Each of the complexes exhibits a binuclear
structure where two vanadium(V) atoms are bridged by two oxygen atoms to form distorted octahedral
structures within cis-N2O4 donor sets. In most complexes, the uninegative anions function as tridentate
ligands, coordinating through the pyridyl- and azomethine-nitrogen atoms and enolic oxygen whereas in
complex [VO(HQCN)(SO4)]SO4 4H2O (4) the ligand is coordinated in the keto form. Complexes [VO(QCB)(
OMe)] 1.5H2O (3) and 4 are found to be EPR active and showed well-resolved axial anisotropy with
two sets of eight line pattern
Girish Kumar,K; Saji, John K; Indira, C J(Indian Journal of Chemical Technology, November 18, 2005)
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Abstract:
This paper describes the fabrication of an ion-selective electrode in which a polymeric Schiff base complex of cobalt(II) is used as the ionophore.The main advantage of the electrode is that it is mechanically stable upto 3 months..The electrode shows a linear response in the range of 2.5 × 10-5-0.5 × 10-1 mol dm-3. The response time of the electrode is 30 s.The pH range at which the electrode works is 3.8 to 6.8. The electrode was found to be selective towards chloride ion in the presence of ions like Na+, Ca2+, Mn2+, ,Fe3+, Co2+, Ni2+, Cu2+, Zn2+, CH3COO-, NO3-, SO42- ,Br- and NO2-.
Mohammed Yusuff, K K; Suja, N R(Journal of Applied Polymer Science,Wiley InterScience, August 10, 2003)
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Abstract:
Two novel polystyrene-supported Schiff
bases, PSOPD and PSHQAD, were synthesized. A polymerbound
aldehyde was condensed with o-phenylenediamine
to prepare the Schiff base PSOPD, and a polymer-bound
amine was condensed with 3-hydroxyquinoxaline-2-carboxaldehyde
to prepare the Schiff base PSHQAD. This article
addresses the study of cobalt (II), nickel (II), and copper (II)
complexes of these polymer-bound Schiff bases. All the complexes
were characterized, and the probable geometry was suggested using elemental analysis, diffuse reflectance ultraviolet,
Fourier transform infrared spectroscopy, thermal
studies, surface area studies, and magnetic measurements.
Sreekumar, K; Thomas, Mathew; Mirajkar, S P; Sugunan, S; Rao, B S(Elsevier, 2000)
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Abstract:
The catalyst compositions of the Zn1−xCOxFe2O4 (x= 0, 0.2, 0.5, 0.8 and 1.0) spiel series possessing ‘x’ values, x less than or equal to 0.5, are
unique for selective N-monomethylation of aniline using methanol as the alkylating agent. Since dimethyl carbonate (DMC)
is another potential non-toxic alkylating agent, alkylation of aniline was investigated over various Zn–Co ferrites using DMC
as the alkylating agent. The merits and demerits of the two alkylating agents are compared. Catalytic activity followed a
similar trend with respect to the composition of the ferrospinel systems. DMC is active at comparatively low temperature,
where methanol shows only mild activity. However, on the selectivity basis, DMC as an alkylating agent could not compete
with methanol, since the former gave appreciable amounts of N,N-dimethylaniline (NNDMA) even at low temperature where
methanol gave nearly 99% N-methylaniline (NMA) selectivity. As in the case of methanol, DMC also did not give any
C-alkylated products.
Jyothi, T M; Sugunan, S; Rao, B S(Catalysis Letters, 2000)
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Abstract:
A comparative study on the anisole methylation with methanol over lanthanum-promoted Sn02 catalyst and its sulfate-doped analogue
is presented. A maximum 2.6-xylenol selectivity of 82% was achieved at 400 degreeC under optimized conditions at an anisole
conversion of 65% over lanthanum-promoted Sn02 catalyst. The sulfate modification resulted in the dealkylation of anisole to phenol
followed by several unselective side reactions due to the creation of strong acid sites. The activity of lanthanum-modified tin oxide
catalysts in the selective formation of 2.6-xylenol is ascribed to the presence of weak Lewis acid sites and comparatively stronger basic
sites.
Girish Kumar,K; Saji John,Konnully(Department of Applied Chemistry, April 15, 2006)
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Abstract:
This paper reports the synthesis of a series of six new polystyrene anchored metal complexes of Co(II), Fe(III), Ni(II),
Cu(II), Zn(II), and dioxouanium(VI) using the polystyrene anchored Schiff base of 2-nitrobenzaldehyde and the corresponding
metal salts. The metal salts used were anhydrous FeCl3, CoCl2 Æ 6H2O, Ni(CH3COO)2 Æ 4H2O, Cu(CH3-
COO)2 Æ H2O, Zn(CH3COO)2 Æ 2H2O, and UO2(CH3COO) Æ 2H2O. Physico chemical characterizations have been made
from diffuse reflectance and vibrational spectra, elemental analysis, magnetic measurements, and TG studies. The elemental
analysis suggest a 1:2 metal:ligand ratio when the complexation has carried out at 70 C for about 12 h reflux. The
ligand is monodentate and coordinates through the azomethine nitrogen. The Fe(III), Co(II), Ni(II), and Cu(II) complexes
are all paramagnetic whereas Zn(II) and U(VI) are diamagnetic. Zn(II) is assigned a tetrahedral structure, Cu(II) and
Co(II) are assigned a square planar structure and Fe(III), Ni(II), and U(VI) are all assigned an octahedral structure.
The polystyrene anchored ligand has been developed as an excellent reagent for the removal of Cu(II). Optimum conditions
have been developed for the removal of metal ion from solutions by studying the effect of change of concentration of
metal ion, ligand, effect of pH, time of reflux, and interference effect of other ions. It was found that within a span of 20 min
it is possible to remove 90% of the metal ion from a 30 ppm metal ion solution in the pH range 4–5.5.
Sreekumar, K(Japaneese society of Applied physics, November 8, 2006)
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Abstract:
Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)–acrylamide films were fabricated to improve the
storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride
concentration was optimized as 3:18 10 3 mol/l for a dye concentration of 6:2 10 4 mol/l. The gratings recorded on the
optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or
thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.
Prathapachandra Kurup, M R; Reena, T A(Elsevier, March 15, 2010)
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Abstract:
Five copper(II) complexes [CuLCl]2·CuCl2·4H2O (1), [CuLOAc] (2), [CuLNO3]2 (3), [CuLN3] (4) and
[CuLNCS]·3/2H2O (5) of di-2-pyridyl ketone-N4-phenyl-3-semicarbazone (HL) were synthesized and
characterized by elemental analyses and electronic, infrared and EPR spectral techniques. In all these
complexes the semicarbazone undergoes deprotonation and coordinates through enolate oxygen, azomethine
and pyridyl nitrogen atoms. All the complexes are EPR active due to the presence of an unpaired
electron. EPR spectra of all the complexes in DMF at 77K suggest axial symmetry and the presence of
half field signals for the complexes 1 and 3 indicates dimeric structures
Description:
Spectrochimica Acta Part A 76 (2010) 322–327 doi:10.1016/j.saa.2010.03.011
Mohammed Yusuff, K K; Rani, Abraham(Elsevier,Journal of Molecular Catalysis A: Chemical 198 (2003) 175–183, December 2, 2002)
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Abstract:
Copper(II) complexes of two biologically important ligands, viz., embelin (2,5-dihydroxy-3-undecyl-2,5-cyclohexadien
1,4-dione) and 2-aminobenzimidazole were entrapped in the cages of zeolite Y by the flexible ligand method. The capability
of these compounds in catalyzing the reduction of oxygen (industrially known as deoxo reaction) was explored and the
results indicate an enhancement of the catalytic properties from that of the simple copper ion exchanged zeolite. These
point to the ability of the ligands in enhancing the oxygen binding capability of the metal ion. Elemental analyses, Fourier
transform infrared (FTIR), diffuse reflectance and EPR spectral studies, magnetic susceptibility measurements, TG, surface
area analyses and powder X-ray diffraction studies were used in understanding the presence, composition and structure of
the complexes inside the cages. The study also reveals the increased thermal and mechanical stability of the complexes as a
result of encapsulation.
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.