Mono and trinuclear lanthanide complexes of 13-membered tetraaza macrocycle: Synthesis and characterization |
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Authors: | B Singh and V L Singh |
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Institution: | (1) Department of Chemistry, Banaras Hindu University, 221 005 Varanasi, India |
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Abstract: | The reaction of 1,8-diamino-3,6-diazaoctane and diethyl malonate in dry methanol yielded a 13-membered macrocycle. Complexes
of the type Ln(tatd)Cl2 (H2O)3]Cl LnIII=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy; tatd=1, 5, 8, 11-tetra-azacyclotridecane-2,4-dione] have been synthesized by template condensation.
The complex La(tatd)Cl2 (H2O)3]Cl in methanol was reacted with lanthanide chlorides to yield the trinuclear complexes of type 2{La(tatd)Cl2(H2O)3}LnCl3]Cl2 LnIII=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy]. The chemical compositions of mono and trinuclear complexes have been established on the
basis of analytical, molar conductance, electrospray (ES) and fast atom bombardment (FAB) mass data. In mononuclear complexes
the Ln3+ ion is encapsulated by four ring nitrogens and in trimetallic complexes the exo-carbonyl oxygens of two mononuclear units
coordinate to the Ln3+ ions resulting in a polyhedron around the lanthanide ions. Thus the macrocycle is bonded in a tetradentate fashion in the
former complexes and hexadentate in the latter. The coordination number nine around the encapsulated Ln3+ and seven around the exo-oxygen bonded Ln3+ ions are established. The symmetry of the ligand field around the metal ions is indicated from the emission spectra. |
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Keywords: | Tetraaza macrocyclic complexes lanthanide complexes macrocyclic lanthanide complexes |
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