Synthesis and reactivity of Ln- and LnNa-macrocyclic compartmental Schiff base and polyamino complexes

Abstract

The [1+1] Schiff base macrocyclic ligands H2LA and H3LB, synthesized by condensation of 3,3′-(3-oxapentane-1,5-diyldioxy)bis(2-hydroxybenzaldehyde) (H2L′) with 1,5-diamino-3-azamethylpentane (A′) and N,N-bis(2-aminoethyl)-2-hydroxybenzylamine·3HCl (HB′·3HCl), respectively, and their related polyamines H2RA and H3RB, which exhibit enhanced stability toward hydrolysis and greater flexibility, give rise to a wide series of mono-Ln and heterodinuclear-LnNa complexes. The crystal structure of [LuNa(RB)(OH)]2, determined by single-crystal X-ray diffraction, indicates the preference of the lutetium(III) ion and of the sodium(I) ion for the Schiff base and the crown-ether like chambers, respectively. To test the flexibility of reduced ligands and the possibility to encapsulate different lanthanide(III) ions in the coordinating moiety, [LuNa(RB)(CH3COO)]·2iPrOH, [LuNa(LB)(Cl)], [LaNa(RB)(Cl)] and [LaNa(LB)(Cl)] are mixed with different lanthanide(III) salts to detect metalation, demetalation, transmetalation and/or site migration processes by ESI mass spectrometry and NMR spectroscopy. In particular the role of the metals and of the coordinating moiety in directing these processes is discussed.Furthermore, the possibility to use these complexes as probe for selective recognition of alkali and alkaline earth metal ions is tested by ESI mass spectrometry on [LuNa(RB)(CH3COO)]·2iPrOH and by the 23Na NMR shift on [YbNa(RB)(CH3COO)]. The partial or total transmetalation of the sodium(I) ion represents a relevant result capable to open interesting scientific opportunities.