T.R. Rao

The synthesis of liquid crystalline lanthanide complexes of Schiff's base ligands: N -(4- n -alkoxysalicylidene)-4′- n -alkylanilines

The reaction of N-(4-n-alkoxysalicylidene)-4′-n-alkylanilines with freshly prepared lanthanide salts leads to mesomorphic terbium and dysprosium complexes exhibiting the smectic A phase.

Fluorescent lanthanide complexes of Schiff base ligands possessing N-aryl moiety: influence of chain length on crossover (calamitic to discotic) phase behaviour

New lanthanide complexes, Tb(III), Dy(III) and Gd(III) of N-aryl based Schiff bases exhibiting mesomorphism have been synthesised and characterised. The crossover phenomena of calamitic lamellar to discotic columnar phase behaviour in these lanthanidomesogens is found to be controlled by the variation in chain length of the single alkyl substituent on the terminal N-aryl ring, hitherto the first case of a metallomesogen with only one alkyl chain length at each end of the ligand as evidenced by thermal microscopy studies and complemented by X-ray studies. It is also observed as a function of temperature in a single component. The electronic properties of these systems are dominated by the donor–acceptor substituted organic chromophore ligand, and the emission maxima revealed a large Stokes shift of 160 nm. The ligand–ligand charge transfer is reflected in emission spectra and is due to the presence of phenyl rings in the ligands.

Synthetic and spectral studies of some 4ƒ-metal complexes

Abstract Salicylaldehyde(N-benzoyl)glycyl hydrazone (SalBzGH) has been synthesized and characterized. Metal complexes of the empirical formula [Ln(SalBzGH-2H)OH(H2O)2] where Ln = Y, Pr, Nd, Sm, Eu, Gd and Dy, have been synthesized and their structures studied by infrared, far-infrared, absorption, emission and NMR spectra. 1H and 13C NMR spectra indicate the presence of dynamic equilibrium between two isomers of SalBzGH over the 298–368 K temperature range and stabilization of a single isomer upon complexation with Ln(III). The hypersensitive band profile of the Nd(III) complex indicates a change in metal coordination number due to solvation, while an increase of temperature results in a decrease of emax of the hypersensitive band. The emission spectrum of [Eu(SalBzGH-2H)OH(H2O)2] at 77 K indicates a low site symmetry. SalBzGH coordinates through imidolic oxygen, azomethine nitrogen and phenolate oxygen.

Coordinated lanthanide metal complexes ofN-benzoylglycine hydrazide

SummaryN-benzoylglycine hydrazide (BzGH) reacts with trivalent lanthanide metal ions forming complexes of the type [Ln(BzGH)2Cl(H2O)2]Cl2·nH2O, where Ln=LaIII, PrIII, NdIII, SmIII, EuIII, GdIII, TbIII, DyIII, or YIII;n=1 or 2. The structures of the complexes have been studied by conductance, magnetic, electronic, i.r.,1H n.m.r. and13C n.m.r. spectral techniques. The nephelauxetic ratio, the bonding parameter, Sinhas parameter and the covalency angular overlap parameter have been calculated from the electronic spectra of PrIII, NdIII and SmIII complexes. Seven-coordination is proposed in the NdIII complex. The i.r. and1H n.m.r. spectral data suggest bidentate BzGH in all the complexes.

Synthesis and spectral studies ofo-hydroxyacetophenone (N-benzoyl)glycyl hydrazone and some of its lanthanide(III) complexes

Summaryo-Hydroxyacetophenone (N-benzoyl)glycyl hydrazone (o-HABzGH) has been characterized by i.r.,1H n.m.r.,13C n.m.r. and mass spectral studies, and its complexes of the types [Ln(o-HABzGH)Cl2(H2O)2]Cl and [Ln(o-HABzGH−2H)OH(H2O)3], where Ln=La, Pr, Nd, Sm and Eu, have been synthesized. The structures of the complexes have been studied by conductance, magnetic, electronic, i.r.,1H n.m.r. and13C n.m.r. spectral techniques. The hypersensitive bands of the electronic spectra suggest coordination numbers six and seven around NdIII in its adduct and neutral complexes respectively. I.r. and n.m.r. spectral data suggest a neutral bidentate behaviour for the ligand in the adducts and a dinegative tridentate nature in the neutral complexes.

Synthesis and Structural Characterisation of Some Latter Lanthanide Complexes of 2-Acetylpyridineisonicotinoyl Hydrazone

Abstract 2-Acetylpyridineisonicotinoylhydrazone (2-ApINH) upon reaction with 4f metal ions, gave complexes of the formulae [M(2-ApINH)2Cl2]Cl and [M(2-ApINH-H)2OH] [M = Y(III), Gd(III), Tb(III) and Dy(III)]. The structures of the complexes have been studied by elemental analysis, molar conductance, magnetic susceptibility, electronic, IR, 1H and 13C NMR spectral techniques. The bonding parameters, viz., β, b1/2, δ(%) and χ have been calculated from the absorption spectra of the Dy(III) complexes. IR and NMR spectral data suggest non-deprotonated tridentate 2-ApINH in the eight-coordinated addition complexes and uninegative tridentate 2-ApINH in the seven-coordinated, neutral complexes.

Synthesis and Spectral Studies of Lanthanide Metal Complexes of Acetone (N-Benzoyl)Glycyl Hydrazone

Abstract Acetone (N-benzoyl)glycyl hydrazone (BzAGH) has been found to react with trivalent lanthanide metal ions to form complexes of the type [Ln(BzAGH)Cl(H2O)3]Cl2 where Ln = La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III) and Dy(III). The complexes have been characterized by elemental analyses, molar conductance, magnetic, electronic, IR, 1H NMR and 13C NMR spectral techniques. Molar conductance studies in 0.001 M MeOH solutions indicate a 2:1 electrolytic behaviour of all the complexes. The nephelauxetic ratio, the bonding parameter, the Sinhas parameter and the covalency angular overlap parameter have been calculated from the electronic spectra of the Pr(III), Nd(III) and Sm(III) complexes. The IR and 1H NMR spectral studies reveal that BzAGH acts as a neutral bidentate chelating ligand in the complexes.

Synthetic and structural studies of some trivalent lanthanide metal complexes ofo-hydroxyacetophenone (N-benzoyl)glycyl hydrazone

Abstracto-Hydroxyacetophenone (N-benzoyl)glycyl hydrazone (o-HABzGH) forms complexes of the types [M(o-HABzGH)Cl2(H2O)2]Cl and [M(o-HABzGH-2H)OH(H2O)2], where M = Y(III), Gd(III), Tb(III) and Dy(III). The complexes have been characterized by elemental analyses, molar conductance, magnetic susceptibility, infrared, electronic,1H NMR and13C NMR spectral techniques. The nephelauxetic ratio (β), covalency (δ), bonding parameter (b1/2) and angular overlap parameter (η) have been calculated from Dy(III) complexes. Infrared and NMR spectral studies show thato-HABzGH acts as a neutral bidentate ligand in the adduct complexes and as a dinegative tridentate one in the neutral complexes. A coordination number of six has been proposed for the metal ion in all the complexes.