Heterodinuclear Ln-Na Complexes withan Asymmetric Macrocyclic Compartmental Schiff Base

摘要

Heterodinuclear lanthanide(III)-sodium(I) complexes [LnNa(L)(Cl)_2(CH_3O)](Ln = La-Nd, Sm-Lu), where H_2L is a [1+1] asymmetric compartmental macrocyclic ligand containing a N_3O_2 Schiff base and a O_3O_2 crown-ether-like coordination site, have been prepared and characterized by IR, ~1H, ~(13)C, and ~(23)Na NMR spectroscopy, mass spectrometry, and electron microscopy. In the solid state, the lanthanide(III) ions coordinate the Schiff-base N_3O_2 site, and the sodium ion occupies the O_3O_2 crownlike cavity, as shown by the X-ray crystal structures of the Nd, Eu, Gd, and Yb derivatives. In these complexes, the lanthanide(III) ion is coordinated by two chlorine atoms in the trans position and by three nitrogen and two negatively charged phenol oxygen atoms of the Schiff base, and the on is heptacoordinated with a pentagonal bipyramidal geometry. The sodium ion is coordinated by three etheric oxygen atoms and the two phenolic oxygens that act as a bridge. a methanol molecule is also coordinated in the apical position of the resulting pentagonal pyramidal polyhedron. A detailed ~1H and ~(13)C NMR study was carried out in CD_3OD for both diamagnetic and paramagnetic heterodinuclear complexes [LnNa(L)(Cl)_2(CH_3OH)]. The complexes are also isostructural in solution, and their structures parallel those found in the solid state. Moreover, some signification distances determined in the solid state and in solution are comparable. Finally, the potential use of these complexes as molecular probes for the selective recognition of specific metal ions has been tested. In particular, their ability to act as shift reagents and the selectivity of the O_3O_2 site towards Li~+, Ca~(2), and K~+ were investigated by ~(23)Na NMR spectroscopy.