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.
Mohammed Yusuff, K K; Arun, Vasudevan; Robinson, P P; Manju, Sebastian; Leeju, P; Varsha, Gopalakrishnan; Digna, Vasudevan(Elsevier, Dyes and Pigments 82 (2009) 268–275, January 18, 2009)
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Abstract:
A novel bisazomethine Schiff base was synthesised by the condensation of 3-hydroxyquinoxaline-2-
carboxaldehyde and 2,3-diaminomaleonitrile. 1H NMR, 13C NMR, HPLC and FT-IR studies revealed that
the compound exists in two major tautomeric forms. The Schiff base exhibits positive absorption and
fluorescent solvatochromism and displays dual fluorescence with large stoke shifts. Cyclic voltammetric
analysis of the compound in 1:1 methanol–THF was influenced by scan rate. Thermal analysis of the
compound was undertaken using TG–DTA and DSC
Mohammed Yusuff, K K; Pearly Sebastian, Chittilappilly; Sridevi, N(Elsevier,Journal of Molecular Catalysis A: Chemical 286 (2008) 92–97, February 5, 2008)
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Abstract:
Zeolite Y-encapsulated ruthenium(III) complexes of Schiff bases derived from 3-hydroxyquinoxaline-2-carboxaldehyde and 1,2-
phenylenediamine, 2-aminophenol, or 2-aminobenzimidazole (RuYqpd, RuYqap and RuYqab, respectively) and the Schiff bases derived from
salicylaldehyde and 1,2-phenylenediamine, 2-aminophenol, or 2-aminobenzimidazole (RuYsalpd, RuYsalap and RuYsalab, respectively) have
been prepared and characterized. These complexes, except RuYqpd, catalyze catechol oxidation by H2O2 selectively to 1,2,4-trihydroxybenzene.
RuYqpd is inactive. A comparative study of the initial rates and percentage conversion of the reaction was done in all cases. Turn over frequency
of the catalysts was also calculated. The catalytic activity of the complexes is in the order RuYqap > RuYqab for quinoxaline-based complexes and
RuYsalap > RuYsalpd > RuYsalab for salicylidene-based complexes. The reaction is believed to proceed through the formation of a Ru(V) species.
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.
Mohammed Yusuff, K K; Mayadevi, S(Taylor & Francis, 1997)
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Abstract:
Some new transition metal complexes of the Schiff base
quinoxaline-2-car boxalidene-2-aminophenol (HQAP) have been
synthesized and characterized by elemental analyses, conductance
and magnetic measurements and IR and UV-Visible spectral studies.
The complexes have the following empirical formulae: [Mn(QAP121,
[Fe(QAPl2C1I, [Co(QAPl21, [Ni(QAP121 and [Cu(QAP121. A tetrahedral
structure has been assigned for the manganese(=), cobalt(II1,
nickel(II1 and copper(II1 complexes. For the iron(IIIl complex an
octahedral dimeric structure has been suggested
Mohammed Yusuff, K K; Manju, Sebastian; Arun, Vasudevan; Robinson, P P; Leeju, Pally; Digna, Varghese; Varsha, Gopalakrishnan(Taylor & Francis, Journal of Coordination Chemistry, October 15, 2009)
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Abstract:
The mononuclear cobalt(II) complex [CoL2] H2O (where HL is quinoxaline-2-carboxalidine-
2-amino-5-methylphenol) has been prepared and characterized by elemental analysis, conductivity
measurement, IR, UV-Vis spectroscopy, TG-DTA, and X-ray structure determination.
The crystallographic study shows that cobalt(II) is distorted octahedral with each tridentate
NNO Schiff base in a cis arrangement. The crystal exhibits a 2-D polymeric structure parallel to
[010] plane, formed by O-H...N and O-H... O intermolecular hydrogen bonds and pye
stacking interactions, as a racemic mixture of optical enantiomers. The ligand is a Schiff base
derived from quinoxaline-2-carboxaldehyde
Mohammed Yusuff, K K; Nampoori, V P N; Arun,V; Mathew, S; Robinson, P P; Jose,M(Elsevier, Journal of Dyes and Pigments, March 20, 2010)
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Abstract:
The Schiff base, 3-hydroxyquinoxaline-2-carboxalidine-4-aminoantipyrine, was synthesized by the
condensation of 3-hydroxyquinoxaline-2-carboxaldehyde with 4-aminoantipyrine. HPLC, FT-IR and NMR
spectral data revealed that the compound exists predominantly in the amide tautomeric form and
exhibits both absorption and fluorescence solvatochromism, large stokes shift, two electron quasireversible
redox behaviour and good thermal stability, with a glass transition temperature of 104 oC. The
third-order non-linear optical character was studied using open aperture Z-scan methodology employing
7 ns pulses at 532 nm. The third-order non-linear absorption coefficient, b, was 1.48 x 10-6 cm W-1 and
the imaginary part of the third-order non-linear optical susceptibility, Im c(3), was 3.36x10-10 esu. The
optical limiting threshold for the compound was found to be 340 MW cm-2.
Mohammed Yusuff, K K; Digna, Varghese; Arun, Vasudevan; Robinson, P P; Manju, Sebastian; Leeju, P; Varsha, Gopalakrishnan(International Union of Crystallography, Acta Crystallographica Section C ,Crystal Structure Communications, November 11, 2009)
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Abstract:
The Schiff base compounds N,N0-bis[(E)-quinoxalin-2-ylmethylidene]
propane-1,3-diamine, C21H18N6, (I), and N,N0-bis[(E)-
quinoxalin-2-ylmethylidene]butane-1,4-diamine, C22H20N6,
(II), crystallize in the monoclinic crystal system. These
molecules have crystallographically imposed symmetry.
Compound (I) is located on a crystallographic twofold axis
and (II) is located on an inversion centre. The molecular
conformations of these crystal structures are stabilized by
aromatic pye stacking interactions.