Synthesis, Conformation and Equilibrium Study of New Piperazine and Azamacrocyclic Ligands with N-(Tetrahydro-2-oxofuran-3-yl) and N-[(Carboxy)(2-hydroxyethyl)methyl] Pendant Arms

摘要

New piperazine (1), homopiperazine (2), 1-tosyl-1,4,7-triaza-cyclononane (3), 1,4,7-triazacyclononane (4), and 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (5) derivatives 1a-5a with 2-oxotetrahydrofuran-3-yl pendant arms have been synthesized from the parent cyclic polyamines 1-5 and 2-bromobutyrolactone in acetonitrile. Their conformational properties have been studied by molecular mechanics and NMR spectroscopy, and new sets of Karplus parameters for calculation of the vicinal coupling constants of the butyrolactone moieties have been determined. Compounds 1a-5a were hydrolysed to (carboxy)(2-hydroxyethyl)methyl derivatives 1b-5b by treatment with aqueous sodium hydroxide. The protonation and complexation properties of 4b (HOET-NOTA) were studied by pH potenitiometry, photometry, and ~1H NMR titrations, and the results were compared with the corresponding values for NOTA. It was found that, although complexation of 4b with smaller metal ions was approximately tow orders of magnitude weaker, its stability constants with the lanthanides remained unchanged.