Solid state and solution properties of lanthanide(III) complexes of a tetraiminodiphenolate macrocyclic ligand. X-ray structure, 1H NMR and luminescence spectral studies

Bag, Pradip ; Dutta, Supriya ; Florke, Ulrich ; Nag, Kamalaksha (2008) Solid state and solution properties of lanthanide(III) complexes of a tetraiminodiphenolate macrocyclic ligand. X-ray structure, 1H NMR and luminescence spectral studies Journal of Molecular Structure, 891 (1-3). pp. 408-419. ISSN 0022-2860

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Official URL: http://linkinghub.elsevier.com/retrieve/pii/S00222...

Related URL: http://dx.doi.org/10.1016/j.molstruc.2008.04.028

Abstract

The lanthanide(III) complexes of composition [Ln(LH2)(H2O)3Cl]Cl2 (Ln = La-Lu and Y, 1-15) derived from the tetraiminodiphenolate macrocyclic ligand L2- have been prepared and characterized. In these compounds, the two uncoordinated imine nitrogens of the macrocycle are protonated and hydrogen-bonded with the metal-bound phenolate oxygens and thereby provide a zwitterionic structure to the ligand. The X-ray crystal structure of the compounds of La and Nd have been determined and they are found to be isostructural. The coordination polyhedra for the eight-coordinated metal centre in the complex cation [Ln(N2O2)(O3Cl)]2+ can be described as distorted square antiprism. Intermolecular hydrogen-bondings involving the three coordinated water molecules and the two uncoordinated chloride ions give rise to the 2-D network in which the chlorides are triply hydrogen-bridged and the water molecules are doubly hydrogen-bridged. Moreover, the aromatic rings in this network are involved in π-π interaction in two different ways. 1H NMR spectra of the complexes in (CD3)2SO have been studied. The spectral assignments for the paramagnetic complexes of Ce-Eu have been made from {1H-1H} COSY spectra and longitudinal relaxation time (T1) measurements. It is inferred that the complex species [Ln(LH2){(CD3)2SO}4]3+ that exist in solution are isostructural for the compounds of La-Eu. The contact and pseudo-contact contribution to the isotropic paramagnetic shifts in the complexes of Ce-Eu have been estimated. The luminescence spectra of the complexes of La, Sm, Eu and Tb have been studied in methanol-ethanol (1:4) glassy matrix and in the solid state at 77 K, and the quantum yields have been estimated.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Lanthanides; Macrocyclic Complexes; Crystal Structures; Paramagnetic 1H NMR; Luminescence Spectroscopy
ID Code:22747
Deposited On:24 Nov 2010 07:55
Last Modified:22 Jan 2011 10:27

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