Browsing by Author "T.R. Rao"

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Benzimidazole based mesogenic Schiff-bases: Synthesis and characterization
(Elsevier B.V., 2017) Ragini Dubey; Rajasekhar Yerrasani; M. Karunakar; Angad Kumar Singh; Rupali Gupta; Vellaichamy Ganesan; T.R. Rao
Two homologous series of mesogenic Schiff-bases, N-4-((alkoxy)-(phenyl-3-hydroxy-4-(4-(5-methylbenzimidazol))-2-alkoxysalicylaldimine)benzoate (7a–d) and N-4′-(5-methyl-benzimidazole)-phenyl-4-alkoxysalicylaldimine (8a–d) incorporating benzimidazole moiety have been prepared and the molecular structures studied by FT-IR, NMR and ESI-MS spectrometry. Mesogenic behaviour was investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and variable temperature powder X-ray diffraction (PXRD) techniques. Changing the spacer (ester-linked to non-ester linked) of the Schiff-base results in enhancement of thermal stability and phase transition temperature. The members of series-I show monotropic SmA while those of series-II reflect enantiotropic SmA mesomorphism. An electrochemical study of a representative Schiff base in each series (7d and 8c) showed an electrical band gap 1.26 eV and 1.22 eV respectively. © 2017 Elsevier B.V.
Complexes of 3d metal ions of the Schiff-base, 4-hydroxy-N′-(4′-octadecyloxybenzylidene)benzohydrazide: Synthesis, spectral studies, crystal structure and magnetic interactions
(Elsevier Ltd, 2009) Angad Kumar Singh; Sanyucta Kumari; K. Ravi Kumar; B. Sridhar; Miroslaw Wrzecion; Jerzy Mroziński; T.R. Rao
A novel hydrazide-based mesogenic (nematic) Schiff-base, 4-hydroxy-N′-(4′-octadecyloxybenzylidene)benzohydrazide, (Hhodbbh) (abbreviated as HL3), was prepared and its structure studied by elemental analyses, mass, NMR and IR spectra and single crystal XRD (triclinic space group Pover(1, -) with Z = 2) techniques. The Schiff-base behaves as a non-deprotonated bi-dentate species in its metal complexes of the general formula, [M(HL3)2](OAc)2 [M = Mn, Co, Ni, Cu and Zn]. The IR and NMR spectral data imply bonding of HL3 species through amidic oxygen and azomethine nitrogen atoms. The MnII and CoII complexes show gradual decrease in the χMT product with lowering of temperature and negative Weiss constants characteristic of anti-ferromagnetic interaction. The MnII complex shows magnetic hysteresis loops at 2.0 K. © 2009 Elsevier Ltd. All rights reserved.
Complexes of some 3d metal ions of the Schiff's base, N,N′-di-4- (4′-pentyloxybenzoate) salicylidene-1″, 3″-diamino-2″- propanol: Synthesis and spectral studies
(2011) Angad Kumar Singh; Sanyucta Kumari; Pawan Raj Shakya; T.R. Rao
A nematogenic Schiff's base, N,N′-di-4-(4′-pentyloxybenzoate) salicylidene-l″, 3″-diamino-2″-propanol, (abbreviated as H2L6), was synthesized and its structure studied by elemental analyses, mass, NMR and IR spectra. The Schiff's base behaves as a dinegative hexa/tetradentate species in its metal complexes of the general formula, [ML6]n where MII, Co, Ni, Cu and Zn. Their structural characterizations were made by various spectroscopic techniques. © 2011 Elsevier B.V. All rights reserved.
Complexes of some 4f metal ions of the mesogenic Schiff-base, N,N -di-(4-decyloxysalicylidene)-1,3-diaminobenzene: Synthesis and spectral studies
(2012) Pawan Raj Shakya; Angad Kumar Singh; T.R. Rao
A mesogenic Schiff-base, N,N-di-(4-decyloxysalicylidene)-1,3- diaminobenzene, H2ddsdbz (abbreviated as H2L), that exhibits a nematic mesophase was synthesized and its structure was studied by elemental analysis, mass spectrometry, NMR, and IR spectral techniques. The Schiff-base, H2L, upon condensation with hydrated lanthanide(III) nitrates yields Ln III complexes, [Ln2(LH2)3(NO3)4](NO3)2, where Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Ho. Analyses of the IR and NMR spectral data imply bidentate Schiff-base through two phenolate oxygen atoms in its zwitterionic form to Ln III, rendering the overall geometry of the complexes as a seven-coordinate polyhedron -possibly distorted mono-capped octahedron. Polarizing optical microscope and differential scanning calorimetry studies reveal that despite H2L being mesogenic, none of the Ln III complexes synthesized under this study exhibits mesomorphism. © 2012 Copyright Taylor and Francis Group, LLC.
Complexes of some lanthanides with acetoneisonicotinoyl hydrazone: A synthetic and spectral study
(Springer India, 1991) Genda Singh; Madhu R. Srivastava; Pariti S.S.J. Sastry; T.R. Rao
Some trivalent lanthanide complexes of acetone isonicotinoylhydrazone (AINH), having the empirical formula Ln(AINH)3Cl3, where Ln=La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III) and Y(III) were prepared. Elemental analyses, molar conductance, magnetic susceptibility, IR, electronic,1H,13C and139La NMR spectra of the complexes have been examined. It has been found that AINH behaves as a neutral bidentate ligand coordinating through the carbonyl oxygen and azomethine nitrogen. Temperature-dependence of the molar absorptivity and the metal coordination number has been established by the electronic spectra of Nd(AINH)3Cl3 recorded over the 28-80°C range. © 1991 Indian Academy of Sciences.
Complexes of some rare earth metal ions of the mesogenic Schiff-base, N,N′-di-(4′-octyloxybenzoatesalicylidene)-l″, 8″-diamino-3″,6″-dioxaoctane: Synthesis and spectral studies
(2012) Sanyucta Kumari; Angad Kumar Singh; T.R. Rao
A mesogenic Schiff-base, N,N′-di-(4′- octyloxybenzoatesalicylidene)-l″,8″-diamino-3″, 6″-dioxaoctane; H 2dobsdd (H 2L 3), that nematogenic mesophase was synthesized and its structure studied by elemental analysis and FAB mass, NMR and IR spectra. The Schiff-base, H 2L 3, upon condensation with hydrated lanthanide(III) nitrates, yields Ln III complexes of the general composition [Ln 2(L 3H 2) 3(NO 3) 4](NO 3) 2, where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho. The IR and NMR spectral data imply a bi-dentate of the Schiff-base through two phenolate oxygens in its zwitterionic form (as L 3H 2) to the Ln III ions, rendering the overall geometry of the complexes to seven-coordinated polyhedron - possibly distorted mono-capped octahedron. Among the metal complexes, only that of La III and Gd III are found to be mesogenic. © 2012 Elsevier B.V. All rights reserved.
Coordinating behaviour of a tridentate Schiff-base in its normal and hemi-acetal forms towards some 3 d-metal ions
(Springer India, 1995) Pariti S.S.J. Sastry; T.R. Rao
Metal complexes of the empirical formula [M(Hpbzgh)2], where H2pbzgh=pyridoxal N-benzoylglycyl hydrazone and M=Mn(II), Co(II), Ni(II), Cu(II), Zn(II), have been synthesized and their structures studied by electronic, IR,1H and13C NMR spectra. IR and NMR spectral data indicate uninegative tridentate coordinated ligand bonding through hydrazidic carbonyl/imidolic oxygen, azomethine nitrogen and phenolate oxygen with its pyridoxal moiety in hemi-acetal as well as normal forms. Magnetic and electronic spectral data suggest distorted octahedral geometry for the Mn(II), Co(II), Ni(II) and Cu(II) complexes. © 1995 Indian Academy of Sciences.
Coordination behaviour of pyridoxalisonicotinoyl hydrazone towards some 3d-metal ions
(1992) Genda Singh; P.S.S.J. Shastry; R.K. Lonibala; T.R. Rao
The complexes of divale t manganese, cobalt, nickel, copper, zinc and the ligand pyridoxalisonicotinoyl hydrazone (PIH) are discussed in order to illustrate the behaviour of the ligand towards the metal ions in acidic and neutral media. The complexes [M(PIH-2H)(H2O)3](M = Mn, Co and Zn), [cu(pih-2h)(h2O)2]2, [cu(pih)c1(H2O)]2 2+ and [Ni(PIH)Cl2(H2O)] have distorted octahedral structures. The isostructural crystalline complexes, [m(pih)c12]2 (M= Mn, Co andZn) are isolated from hot solutions. The electronic spectral data of cobalt in conjunction with infrared, NMR and magnetic measurements enables the assignment of the formula [m(pih) 2][MC14] to these complexes. The anion is tetrahedral while the cation has an octahedral chromophore. Characterization data indicates that [Ni(PIH-2H)H2O] has a four-coordinated square-planar chromophore. The IR, and 1H 13 C NMR spectral data indicate that PIH behaves as a neutral tridentate ligand in the chloro complexes and as a dinegative, tridentate species in the deprotonated complexes. © 1992, Taylor & Francis Group, LLC. All rights reserved.
Coordination of a mesogenic Schiff-base with MnII, CoII, NiII, CuII and ZnII: Synthesis, spectral studies and crystal structures
(Elsevier Ltd, 2008) Angad Kumar Singh; Sanyucta Kumari; T.N. Guru Row; Jai Prakash; K. Ravi Kumar; B. Sridhar; T.R. Rao
A novel mesogenic (nematic) Schiff-base, N,N′-di-4-(4′-pentyloxybenzoate)salicylidene diaminoethane, H2dpbsde (abbreviated as H2L5) was synthesized and its structure studied. The Schiff-base crystallizes in the non-centrosymmetric space group Pna21 with Z = 4, and the mesogenic isomorphous nickel and copper complexes, [NiL5]2 and [CuL5], in the centrosymmetric space group P21/c with Z = 4. The (L5)2- species coordinates to the metal ions through two phenolate oxygens and two azomethine nitrogens. Both the [NiL5]2 and [CuL5] complexes involve cis-MN2O2 planes; the former complex has a low-spin distorted square-pyramidal geometry with a Ni-Ni bonding of 3.337 Å and the latter, a square-planar geometry. © 2008 Elsevier Ltd. All rights reserved.
Crystal structure and ligational aspects of the mesogenic Schiff base, N,N′-di-(4-hexadecyloxysalicylidene)diaminoethane, with some rare earth metal ions
(Elsevier S.A., 2009) Sanyucta Kumari; Angad Kumar Singh; K. Ravi Kumar; B. Sridhar; T.R. Rao
A mesogenic Schiff base, N,N′-di-(4-hexadecyloxysalicylidene)diaminoethane, H2dhdsde (abbreviated as H2L1) that exhibit smectic-C (SmC) mesophase, was synthesized and its structure studied by elemental analyses, mass, NMR & IR spectra and single crystal XRD (triclinic space group P over(1, ̄) with Z = 1) techniques. Bi-dentate bonding of the Schiff base in the mesogenic LaIII complex was implied on the basis of IR & NMR spectral data. As per the spectral studies of the complexes, the Zwitterionic species of the ligand (H2L1) coordinates to LnIII ion through two phenolate oxygens rendering the overall geometry around the metal ion to distorted square antiprism (Ln = La, Pr, Nd, Sm, Eu) and monocapped octahedron (Ln = Gd, Tb, Dy, Ho). © 2009 Elsevier B.V. All rights reserved.
Homo dinuclear lanthanide(III) complexes of a mesogenic Schiff-base, N,N′-di-(4-decyloxysalicylidene)-1′,6′-diaminohexane: Synthesis and characterization
(2011) Pawan Raj Shakya; Angad Kumar Singh; T.R. Rao
A mesogenic Schiff-base, N,N′-di-(4-decyloxysalicylidene)-1′, 6′-diaminohexane, H 2ddsdh (abbreviated as H 2L 2) that exhibits smectic-B (SmB) mesophase, was synthesized and its structure studied by elemental analysis, mass spectrometry, NMR & IR spectral techniques. The Schiff-base, H 2L 2, upon condensation with hydrated lanthanide(III) nitrates, yields Ln III complexes of the general composition [Ln 2(L 2H 2) 3(NO 3) 4](NO 3) 2, where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho. IR and NMR spectral data imply a bi-dentate bonding of the Schiff-base in its zwitterionic form (as L 2H 2) to the Ln III ions through two phenolate oxygens. The POM and DSC studies reveal that none of the Ln III complexes exhibits mesomorphism. Fluorescence studies show that the Tb III complex displays characteristic metal-centered fluorescence (solution state). © 2011 Elsevier B.V. All rights reserved.
Lanthanide complexes of a mesogenic Schiff's base having 1,3,4-oxadiazole moiety: Synthesis and characterization
(Elsevier B.V., 2016) M. Karunakar; Rajasekhar Yerrasani; Ragini Dubey; Angad Kumar Singh; T.R. Rao
A liquid-crystalline Schiff's base (HL) having 1,3,4-oxadiazole moiety with an octyloxy substituent and a series of lanthanide(III) complexes [Ln(LH)3(NO3)3] (LnIII = La, Pr, Nd, Sm, Eu, Tb and Dy; HL = N-(4′-(5-(4″-octyloxyphenyl)-1,3,4-oxadiazol)-2-phenyl)-4‴-octyloxysalicylaldimine) have been synthesized and characterized by FTIR, 1H and 13C{1H} NMR, UV–Vis, fluorescence and Mass spectral techniques. HL exists in zwitter-ionic form in the complexes, binding to the metal through phenolate oxygen; Optical and thermal behavior studies (POM, powder XRD & DSC techniques) indicate SmC and SmX mesophases of HL and non-mesogenic behavior of the complexes. © 2016
Ligational aspects of the hydrazide-based Schiff-base, N-(4″-pyridylcarboxamido)-4-(4′-hexyloxybenzoato)salicylaldimine towards some 3d metal ions and crystal structures of the Schiff-base and Zn(II) complex
(Elsevier Ltd, 2008) Angad Kumar Singh; Sanyucta Kumari; K. Ravi Kumar; B. Sridhar; T.R. Rao
A novel hydrazide-based mesogenic (nematic) Schiff-base, N-(4″-pyridylcarboxamido)-4-(4′-hexyloxybenzoato)salicylaldimine, Hpychbsal (abbreviated as H2L) was prepared and its structure studied by elemental analyses, mass, NMR and IR spectra and single crystal XRD (triclinic space group P over(1, ̄) with Z = 4) techniques. The Schiff-base behaves as a uninegative bi/tridentate species in its non-mesogenic complexes of the general formula, [M(HL)2] [M = Mn, Co, Ni, Cu and Zn] and as a dinegative tridentate species with Zn(II) in the distorted square-pyramidal complex, [ZnL · 2py], for which the crystal structure was solved (triclinic space group P over(1, ̄) with Z = 2). The IR and NMR spectral data imply bonding of HL- and L2- species through phenolate oxygen and/or amidic oxygen and azomethine nitrogen atoms. © 2008 Elsevier Ltd. All rights reserved.
Ligational behavior of furfurylidene(N-benzoyl)glycyl hydrazone toward some transition metal ions
(2001) R.K. Lonibala; N.I. Devi; R.K.B. Devi; T.R. Rao
[No abstract available]
Magnetic and spectral studies on 3d-metal complexes of acetone(N-isopropylidene)tyrosyl hydrazone
(Springer India, 1985) T.R. Rao; Mamta Sahay; R.C. Aggarwal
Acetone(N-isopropylidene)tyrosyl hydrazone, HO-C6H4-CH2-CH(N=CMe2)-CONHN=CMe2 (ath), has been found to form adducts of the type M (ath) Cl2·nH2O [M = Mn (II), Co (II), Ni (II), Cu (II) and Zn (II);n = 0, 1 or 2] and deprotonated complexes of the type M′(ath-2H) · 3H2O[M′ = Co(II), Ni(II) and Cu(II)]. Molar conductance studies in 0.001 M dmso solution have indicated the non-ionic nature of the complexes. High-spin octahedral geometry for Mn(II) and Ni(II) complexes and tetrahedral geometry for Co(II) adduct have been proposed on the basis of magnetic and/or electronic spectral studies. ir spectra suggest neutral bidentate and dinegative tridentate behaviour of the ligand in the adducts and deprotonated complexes respectively, esr spectra of Cu(II) complexes indicate zero-field splitting of Cu(ath)C12 · H2O and metal-metal interaction in both the complexes. © 1985 Indian Academy of Sciences.
Mesogenic lanthanoid metal complexes of a non-mesogenic Schiff-base, N,N′-di-(4-hexadecyloxysalicylidene)-l′,8′-diamino-3′,6′-dioxaoctane
(2009) Sanyucta Kumari; Angad Kumar Singh; T.R. Rao
A non-mesogenic Schiff-base, N,N′-di-(4-hexadecyloxysalicylidene)-l′,8′-diamino-3′,6′-dioxaoctane, H2dhdsdd (H2L2), was synthesized, structure studied by elemental analyses and mass, NMR and IR spectra and ligated to some LnIII metal ions that yielded mesogenic (SmA/N) LnIII complexes of the general composition, [Ln2(L2H2)3(NO3)4](NO3)2, where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho. IR and NMR spectral data imply a bi-dentate bonding of the Schiff-base in its zwitterionic form (as L2H2) to the LnIII ions through two phenolate oxygens, rendering the overall geometry around LnIII to distorted mono-capped octahedron. © 2009 Elsevier B.V. All rights reserved.
N-(4-Butylphenyl)salicylaldimine at 160 K
(2003) S. Thamotharan; V. Parthasarathi; S.M. Anitha; Archana Prasad; T.R. Rao; Anthony Linden
In the title compound, C17H19NO, which is a Schiff base, an intramolecular O - H⋯N hydrogen bond involving the hydroxy group forms a six-membered ring with a graph-set motif of S(6). Several intermolecular C - H⋯π interactions occur between adjacent molecules which are arranged perpendicular to one another. © 2003 International Union of Crystallography Printed in Great Britain - all rights reserved.
Protonation constant of salicylidene (N-benzoyl)glycyl hydrazone and its coordination behaviour towards some bivalent metal ions
(2006) R.K. Lonibala; T.R. Rao; R.K. Babita Devi
Protonation constant of an unsymmetrical Schiff base, salicylidene(N-benzoyl)glycyl hydrazone (SalBzGH), and formation constants of its complexes have been determined potentiometrically at different temperatures in aqueous dioxane medium. Complexes of SalBzGH with VO(IV), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) have been prepared. Elemental analyses, pH-metric, molar conductance, magnetic susceptibility, electronic, IR, ESR, XRD (powder) and NMR studies have been carried out to study the coordination behaviour of SalBzGH toward these metal ions. pH-metric and 1H NMR studies show the presence of two dissociable protons in the ligand. IR and NMR spectra suggest the tridentate nature of the ligand, coordinating as a uninegative species in the Mn(II) complex and as a dinegative species in all the other complexes. Presence of two different conformers of the ligand at room temperature and stabilization of a single conformer upon complex formation have been established from 1H NMR spectra of the metal-free ligand, Zn(II) and Hg(II) complexes recorded at 296 K. Electronic and ESR spectra indicate highly distorted tetragonal geometry for VO(IV) and Cu(II) complexes. XRD powder patterns of the Zn(II) complexes are indexed for an orthorhombic crystal system. © Indian Academy of Sciences .
Rare earth metal complexes of a mesogenic schiff-base, N,N′-di-(4- decyloxysalicylidene)-1′, 4′-diaminobutane: Synthesis and characterization
(Taylor and Francis Inc., 2014) Pawan Raj Shakya; Angad Kumar Singh; T.R. Rao
A mesogenic Schiff-base, N,N′-di-(4-decyloxysalicylidene)-1′, 4′-diaminobutane, (H2L) that exhibits smectic-B and nematic mesophases, was synthesized and its structure studied by elemental analysis, mass spectrometry, NMR & IR techniques. H2L, upon condensation with hydrated lanthanide(III) nitrates yields LnIII complexes of the composition [Ln2(LH2)3(NO3)4](NO3)2, where LnIII = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Ho. The PrIII complex shows smectic-A and nematic phases. The IR and NMR spectral data imply a bidentate bonding of H2L in zwitterionic form (as LH2) to the LnIII ions through two phenolate oxygen atoms, rendering the overall geometry of the complexes possibly to distorted mono-capped octahedra. © 2014 Copyright Taylor and Francis Group, LLC.
Some lanthanide metal complexes of n-isonicotinamidosalicylaldimine
(Springer India, 1986) T.R. Rao; I.A. Khan; R.C. Aggarwal
Trivalent lanthanide complexes of the type K[ML 2] where M=La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III) and Dy(III) and H2 L=N-isonicotinamidosalicyladimine, have been prepared and characterised. The nephelauxetic ratio (β), covalency (δ) and bonding parameter (b 2) of K[Nd L 2] have been calculated. Infrared spectral studies reveal that N-isonicotinamidosalicylaldimine acts as a dibasic tridentate ligand. A coordination number six has been proposed for the lanthanide metal ions. © 1986 Indian Academy of Sciences.