European journal of inorganic chemistry issue:16 pages:3303-3310
The conversion of 12-metallacrown-4 complexes with copper(II) in the central cavity to 15-metallacrown-5 complexes with lanthanide(iii) ions in the central cavity upon addition of trivalent lanthanide ions was analysed in solution by electrospray ionisation mass spectrometry (ESI-MS), absorption spectrophotometry, circular dichroism and proton NMR spectroscopy. In all cases, copper(II) ions were the ring metals. The lanthanide-induced shifts of the proton resonances in the NMR spectra of different lanthanide (m)-containing 15-metallacrown-5 complexes with tyrosinehydroximate ligands were studied. The dynamics of ligand exchange of alpha-aminohydroximate-based lanthanide (iii) -containing 15-metallacrown-5 complexes were studied in methanol solutions. The ring structure of the 12-metallacrown-4 complex that acts as starting compound for the formation of the 15-metallacrown-5 complexes was optimized by DFT methods using alanine-hydroximate as a model ligand.