Macrocyclic Lanthanide(III) Complexes with a 14-Membered Tetraaza Ambivalent Ligand

Abstract

A series of complexes of the type [Ln(mac)CI₂(H₂O)₂]Cl  {Ln
= La, Pr, Nd, Sm, Eu, Gd, Th and Dy;  mac = 1,4,8,11-tetraazacyclotetradeca-
2,3-dione] have been prepared by template reaction
of the lanthanide ion. The ligand has been obtained by the reaction
of 1, 10-diamino-4, 7 -diazadecane with diethyloxalate. The complex
[La(mac)CI₂(H₂O)₂]CI reacts with lanthanide chlorides to yield the
complexes of the type [{ La(mac)CI₂(H₂O)}₂ LnCI₃(H₂O)₂]CI. The
chemical composition of both the mononuclear and trinuclear complexes
have been established from analytical, molar conductance
and FAB mass data It is observed that the macrocycle is bonded
in a tetrakis manner in the mononuclear complexes and in a hexakis
manner in the trinuclear complexes. The coordination number eight
around the encapsulated metal ions and nine around the exocyclic
oxygen bonded metal ion are established from infrared and electronic
spectral studies. The symmetry of the ligand field around the
metal ion is indicated from the emission spectra.