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
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
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.
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
Prathapachandra Kurup, M R; Manoj, E; Rohith, John P; Nethaji, M; Alex, Punnoose(Elsevier, July 16, 2009)
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Abstract:
An unusual copper(II) complex [Cu(L1a)2Cl2] CH3OH H2O H3O+Cl (1a) was isolated from a solution of a
novel tricopper(II) complex [Cu3(HL1)Cl2]Cl3 2H2O (1) in methanol, where L1a is 3-(2-pyridyl)triazolo
[1,5-a]-pyridine, and characterized with single crystal X-ray diffraction study. The tricopper(II) complex
of potential ligand 1,5-bis(di-2-pyridyl ketone) carbohydrazone (H2L1) was synthesized and physicochemically
characterized, while the formation of the complex 1a was followed by time-dependant monitoring
of the UV–visible spectra, which reveals degradation of ligand backbone as intensity loss of bands
corresponding to O?Cu(II) charge transfer
Manoj, Easwaran potti; Prathapachandra Kurup, M R; Fun, Hoong-Kun(Elsevier, 2007)
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Abstract:
A novel N4O coordination mode offers carbohydrazone ligands as a building block for interesting frameworks through self-assembly. Bridging mode of oxygen of bis(2-benzoylpyridine ketone) carbohydrazone (H2L) with metal centers facilitates the formation of the macrocyclic molecular square [Zn(HL)]4(BF4)4 · 10H2O, offers wide range of applications for carbohydrazones.
Prathapachandra Kurup, M R; Sheeja, S R; Neema, Ani Mangalam(Elsevier, 2010)
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Abstract:
Mn(II) complexes derived from a set of acylhydrazones were synthesised and characterized by elemental
analyzes, IR, UV–vis and X-band EPR spectral studies as well as conductivity and magnetic susceptibility
measurements. In the reported complexes, the hydrazones exist either in the keto or enolate form, as evidenced
by IR spectral data. Crystal structures of two complexes are well established using single crystal
X-ray diffraction studies. In both of these complexes two equivalent monoanionic ligands are coordinated
in a meridional fashion using cis pyridyl, trans azomethine nitrogen and cis enolate oxygen atoms positioned
very nearly perpendicular to each other. EPR spectra in DMF solutions at 77 K show hyperfine sextets
and in some of the complexes the low intensity forbidden lines lying between each of the two
hyperfine lines are also observed
Prathapachandra Kurup, M R; Jessy, Emmanuel; Sithambaresan, M(November 3, 2011)
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Abstract:
The title compound, C11H9N3O2, exists in the E conformation
with respect to the azomethane C N bond, and has the keto
form. There are two independent molecules in the asymmetric
unit and each of these features a slight slanting of the pyridine
and furan rings, which form a dihedral angle of 14.96 (10) in
one of the molecules and 5.53 (10) in the other. The crystal
structure is stabilized by N—H O and N—H N hydrogen
bonds, weak C—H O and C—H N hydrogen bonds and
C—H interactions and – interactions [shortest
centroid–centroid distance = 3.7864 (15) A ° ].
Prathapachandra Kurup, M R; Alex, Punnoose; Manoj, E(Elsevier, October 17, 2008)
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Abstract:
Ten new copper(II) complexes of five potential bisthiocarbohydrazone and biscarbohydrazone ligands
were synthesized and physico-chemically characterized. The spectral and magnetic studies of compounds
are consistent with the formation of asymmetric di-, tri- or tetranuclear copper(II) complexes of deprotonated
forms of respective ligands. The variable temperature magnetic susceptibility measurements of all
complexes showantiferromagnetic interactions between the Cu(II) centers, in agreement with very broad
powder EPR spectra. However, frozen solution EPR spectral studies are found in contradiction with the
solid-state magnetic studies and indicate that the complexes are not very stable in solutions; the possible
fragmentations of complexes are found in agreement with MALDI MS results. The EPR spectral simulation
of most of the compounds is in agreement with the presence of two uncoupled Cu(II) species in solution.
Seena, E B; Prathapachandra Kurup, M R(Elsevier, 2007)
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Abstract:
Three copper(II) complexes of salicylaldehyde N(4)-phenyl thiosemicarbazone (H2L1) and two copper(II) complexes of N(4)-cyclohexyl thiosemicarbazone (H2L2) have been synthesized and characterized by different physicochemical techniques like magnetic studies and electronic, infrared and EPR spectral studies. The complexes View the MathML source and [(CuL2)2] (4) having dimeric structure. The thiosemicarbazones bind to the metal as dianionic ONS donor ligand in all the complexes, except in the complex [Cu(HL1)2] · H2O (2). In complex 2, the ligand moieties are coordinated as monoanionic (HL−) ones. Two of the complexes [CuL1dmbipy] · H2O (3) and [CuL2dmbipy] (5) have been found to possess the stoichiometry [CuLB], where B = 4,4′-dimethyl-2,2′-bipyridine (dmbipy). The coordination geometry around copper(II) in 5 is trigonal bipyramidal distorted square based pyramidal (TBDSBP), as obtained by X-ray diffraction studies.
Seven bis(ligand) Co(III) complexes {[CoL21] NO3 · H2 O (1), [CoL21] Cl · 2 H2 O (2),[CoL21] ClO4 (3), [CoL22] NO3 (4), [CoL22] Cl · 2 H2 O (5), [CoL23] Br · 2 H2 O (6), [CoL23] ClO4 · H2 O (7)} of three thiosemicarbazone ligands {pyridine-2-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone [HL1], pyridine-2-carbaldehyde-N(4)-2-phenylethyl thiosemicarbazone [HL2] and pyridine-2-carbaldehyde-N(4)-(methyl),N(4)-(phenyl) thiosemicarbazone [HL3]} were synthesized and physico-chemically characterized. All complexes are assigned octahedral geometries on the basis of spectral studies. The ligands deprotonate and coordinate by means of pyridine nitrogen, azomethine nitrogen, and thiolate sulfur atoms. The single crystal X-ray structures of HL3 and two nitrate compounds are discussed. The structural studies corroborate the spectral characterization.
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.
Sreesha, Sasi; Prathapachandra Kurup, M R; Suresh, E(Springer, January 1, 2007)
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Abstract:
The cobalt(III) complex, [Co(L)2(N3)2]2(ClO4)2, L being a Schiff base N-[phenyl(pyridin-2-yl)methylene]aniline has been synthesized and the crystal structure determined using X-ray crystallography. The complex crystallizes in triclinic system, space group P-1 with unit cell parameters a=10.9367(9) , b=18.0817(17) , c=20.1629(16) , α=111.341(2), β=91.622(2), γ=107.5030(10), V=3499.1(5) 3 and Z=2. It crystallizes with two independent molecules in the asymmetric unit. The two cobalt atoms are hexa-coordinate and have a distorted octahedral geometry, satisfied by four nitrogen atoms from two molecules of the Schiff base and two nitrogen atoms from the monodentate azide group. The perchlorate ions are non-coordinating.
Prathapachandra Kurup, M R; Laly, K; Suja, Krishnan(Elsevier, November 10, 2009)
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Abstract:
Five Mn(II) complexes of bis(thiosemicarbazones) which are represented as [Mn(H2Ac4Ph)Cl2]
(1), [Mn(Ac4Ph)H2O] (2), [Mn(H2Ac4Cy)Cl2]·H2O (3), [Mn(H2Ac4Et)Cl2]·3H2O (4) and
[Mn(H2Ac4Et)(OAc)2]·3H2O (5) have been synthesized and characterized by elemental analyses,
electronic, infrared and EPR spectral techniques. In all the complexes except [Mn(Ac4Ph)H2O], the
ligands act as pentadentate neutral molecules and coordinate to Mn(II) ion through two thione sulfur
atoms, two azomethine nitrogens and the pyridine nitrogen, suggesting a heptacoordination. While in
compound [Mn(Ac4Ph)H2O], the dianionic ligand is coordinated to the metal suggesting six coordination
in this case. Magnetic studies indicate the high spin state of Mn(II). Conductivity measurements reveal
their non-electrolyte nature. EPR studies indicate five g values for [Mn(Ac4Ph)H2O] showing zero field
splitting.
Prathapachandra Kurup, M R; Neema, Ani Mangalam(Elsevier, July 27, 2008)
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Abstract:
Four oxovanadium and one dioxovanadium complex with 2-hydroxyacetophenone N(4)-
phenylthiosemicarbazone (H2L) which are represented as [VOLphen]·2H2O (1), [VOLbipy] (2),
[VOLdmbipy] (3), [VOL]2 (4) and [VO2HL]·CH3OH (5) have been synthesized and characterized by
elemental analyses, electronic, infrared and EPR spectral techniques. In all the complexes 1–4 the
ligand coordinates through phenolic oxygen, azomethine nitrogen and thiolate sulfur. But in complex
[VO2HL]·CH3OH, coordination takes place in thione form instead of thiolate sulfur. All the complexes
except [VO2HL]·CH3OH are EPR active due to the presence of an unpaired electron. In frozen DMF at 77 K,
all the oxovanadium(IV) complexes show axial anisotropy with two sets of eight line patterns
Prathapachandra Kurup, M R; Suma, S; Sudarsana Kumar, M R; Siji, V L(Elsevier, February 26, 2010)
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Abstract:
Eight new transition metal complexes of benzaldehyde-N(4)–phenylsemicarbazone have been synthesized
and characterized by elemental analyses, molar conductance, electronic and infrared spectral
studies. In all the complexes, the semicarbazone is coordinated as neutral bidentate ligand. 1H NMR
spectrum of [Zn(HL)2(OAc)2] shows that there is no enolisation of the ligand in the complex. The magnetic
susceptibility measurements indicate that Cr(III), Mn(II), Fe(III), Co(II) and Cu(II) complexes are
paramagnetic and Ni(II) is diamagnetic. The EPR spectrum of [Mn(HL)2(OAc)2] in DMF solution at 77K
shows hyperfine sextet with low intensity forbidden lines lying between each of the two main hyperfine
lines. The g values calculated for the [Cu(HL)2SO4] complex in frozen DMF, indicate the presence of
unpaired electron in the dx2−y2 orbital. The metal ligand bonding parameters evaluated showed strong
in-plane bonding and in-plane bonding. The ligand and complexes were screened for their possible
antimicrobial activities.
Description:
Spectrochimica Acta Part A 76 (2010) 22–28 doi:10.1016/j.saa.2010.02.035
Prathapachandra Kurup, M R; Reena, T A(Springer, May 30, 2010)
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Abstract:
A new semicarbazone, HL has been synthesized
from quinoline-2-carboxaldehyde and N4-phenyl-3-
semicarbazide and structurally and spectrochemically
characterized. 1H NMR, 13C NMR, IR and electronic
spectra of the compound are studied. The existence of keto
form in the solid state is supported by the crystal structure
and IR data. The compound crystallizes into an orthorhombic
space group P212121. Intra and intermolecular
hydrogen bonding interactions facilitates unit cell packing
in the crystal lattice
Description:
J Chem Crystallogr (2010) 40:927–932
DOI 10.1007/s10870-010-9765-z
Prathapachandra Kurup, M R; Seena, E B; Leji, Latheef(Elsevier, November 1, 2008)
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Abstract:
A novel binuclear Ni(II) complex of salicylaldehyde 3-azacyclothiosemicarbazone (H2L) has been synthesized
and characterized by elemental analysis, IR and UV–Vis spectroscopy. The single crystal X-ray structure
of the complex shows that bridging occurs through thiolato sulfur and phenolic oxygen atoms.
Nickel centers in the complex have square planar and octahedral geometries
Prathapachandra Kurup, M R; Seena, E B; Mini, Kuriakose(Springer, February 9, 2010)
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Abstract:
Oxovanadium(IV/V) complexes of 2-hydroxyacetophenone-
3-hydroxy-2-naphthoylhydrazone (H2L)
have been synthesized and characterized. The complexes
were characterized by elemental analyses, IR, electronic
and EPR spectra. The oxovanadium(V) complex [VOL
(OCH3)] is crystallized in two polymorphic forms, denoted
by 1a and 1b, with space groups Pn21a and P 1, respectively.
Both have distorted square pyramidal structures.
Description:
Struct Chem (2010) 21:599–605
DOI 10.1007/s11224-010-9589-7
Prathapachandra Kurup, M R; Binu, Varghese; Sithambaresan, M; Suja, Krishnan; Sheeja, S R; Eringathodi, Suresh(Elsevier, 2011)
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Abstract:
An interesting series of nine new copper(II) complexes [Cu2L2(OAc)2] H2O (1), [CuLNCS] ½H2O (2), [CuLNO3]
½H2O (3), [Cu(HL)Cl2] H2O (4), [Cu2(HL)2(SO4)2] 4H2O (5), [CuLClO4] ½H2O (6), [CuLBr] 2H2O (7),
[CuL2] H2O (8) and [CuLN3] CH3OH (9) of 2-benzoylpyridine-N(4)-phenyl semicarbazone (HL) have been
synthesized and physico-chemically characterized. The tridentate character of the semicarbazone is
inferred from IR spectra. Based on the EPR studies, spin Hamiltonian and bonding parameters have been
calculated. The g values, calculated for all the complexes in frozen DMF, indicate the presence of the
unpaired electron in the dx2 y2 orbital. The structure of the compound, [Cu2L2(OAc)2] (1a) has been
resolved using single crystal X-ray diffraction studies. The crystal structure revealed monoclinic space
group P21/n. The coordination geometry about the copper(II) in 1a is distorted square pyramidal with
one pyridine nitrogen atom, the imino nitrogen, enolate oxygen and acetate oxygen in the basal plane,
an acetate oxygen form adjacent moiety occupies the apical position, serving as a bridge to form a centrosymmetric
dimeric structure