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Issue 19, 2000
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Studies on lanthanide complexes of the tripodal ligandbis(2-benzimidazolylmethyl)(2-pyridylmethyl)amine. Crystal structures and luminescence properties

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Abstract

A new unsymmetric tripodal ligand bis(2-benzimidazolylmethyl)(2-pyridylmethyl)amine (L) bearing two kinds of chromophores benzimidazole and pyridine has been synthesized, and two series of lanthanide(III) complexes [LnL(NO3)3]·C2H5OH (Ln = La, Sm, Eu, Gd, Tb or Tm) and [LnLCl3(H2O)]·C2H5OH (Ln = La, Sm, Eu, Tb or Ho) have been characterized by elemental analyses, FAB mass spectra, 1H NMR, conductivity measurements, and IR spectra. The crystal and molecular structures of the three complexes [SmL(NO3)3]·C2H5OH 1, [GdL(NO3)3]·C2H5OH 2, and [SmLCl3(H2O)]·C2H5OH 3 have been determined by X-ray diffraction analysis. 1 and 2 are isomorphous with the central metal ion co-ordinated by the four nitrogen atoms of the ligand and six oxygen atoms of three chelating nitrate groups. In complex 3, besides the four nitrogen atoms of the ligand and three chlorine atoms, there is one H2O molecule co-ordinated. Conductivity studies on the [LnL(NO3)3]·C2H5OH complexes in methanol showed that two of the nitrate anions dissociate to give 2∶1 electrolytes. Comparison of the emission lifetimes of the Eu3+ and Tb3+ complexes in CH3OH and CD3OD gives the average value for q, the number of co-ordinated methanol molecules, of 3.4, suggesting the formation of species [LnL(NO3)(CH3OH)3][NO3]2. The emission quantum yields of the nitrate-co-ordinated series are substantially higher than those of the chloride series, as shown by luminescence studies in MeCN.

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Article information


Submitted
04 May 2000
Accepted
27 Jul 2000
First published
05 Sep 2000

J. Chem. Soc., Dalton Trans., 2000, 3253-3260
Article type
Paper

Studies on lanthanide complexes of the tripodal ligand bis(2-benzimidazolylmethyl)(2-pyridylmethyl)amine. Crystal structures and luminescence properties

X. Yang, C. Su, B. Kang, X. Feng, W. Xiao and H. Liu, J. Chem. Soc., Dalton Trans., 2000, 3253
DOI: 10.1039/B003566L

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