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.
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