Synthesis of homodinuclear macrocyclic complexes of lanthanides and phenolic schiff bases
Successful syntheses of the first examples of homodinuclear macrocyclic lanthanide complexes are reported. The complexes were obtained as compounds of the 2:2 Schiff base formed by condensing 2,6-diformyl-p-cresol and triethylenetetramine (L7) by a template procedure using lanthanide nitrates and perchlorates. When reactant methanolic solutions were concentrated the complexes were deposited as yellow or orange microcrystalline precipitates, Ln2L7(NO3)4sigma; nH2O or Ln2L7(NO3)4tau; x(OH)x, x = 1 or 2, whereas solutions diluted three times deposited complexes as flaky off-white crystalline precipitates of light lanthanides. The orange Ln2L7(NO3)2(OH)2 complexes can be converted in quantitative yield to the off-white flaky form of Ln2L7(NO3)4sigma; nH2O by refluxing them in methanolic solution containing triethylenetetramine and a three-fold excess of Ln(NO3)3. The complexes were characterized by elemental analysis, fast atom bombardment mass spectrometry, UV-Vis and infrared spectroscopy and thermogravimetry. Interesting and mostly new polyatomic oxo clusters, e.g. Ln2O3+, Ln3O4+, Ln4O6+, Ln5O7+, were dominant in the mass spectra but are treated in detail elsewhere. © 1986.