1,4,7,10,13,16,19,22‐Octaazacyclotetracosane‐1,4,7,10,13,16,19,22‐octaacetic Acid (H8OTEC) and 1,4,7,10,14,17,20,23‐Octaazacyclohexacosane‐ 1,4,7,10,14,17,20,23‐octaacetic Acid (H8OHEC): Synthesis and Characterization of Two Large Macrocyclic Polyamine Polycarboxylic Ligands and Some of Their Copper(II) and Lanthanide(III) Complexes

The optimized synthesis of two new macrocyclic polyamine polycarboxylic ligands, 1,4,7,10,14,17,20,23-octaazacyclohexacosane-1,4,7,10,14,17,20,23-octaacetic acid (H8OHEC) (10) and 1,4,7, 10,13,16,19,22-octaazacyclotetracosane-1,4,7,10, 13,16,19,22-octaacetic acid (H8OTEC) (12), is presented. The key step in the synthesis of both is the high yield carboxymethylation of the corresponding macrocyclic amines using tert-butyl bromoacetate followed by acidic hydrolysis of the acetate protecting groups. The molecular structures of the intermediates 1,4,7,10,14,17,20,23-octaazacyclohexacosane (OHEC-amine) (8), and octa-tert-butyl 1,4,7,10,13,16,19,22- octaazacyclotetracosane-1,4,7,10,13,16,19,22-octaacetate (OTEC-ester) (11) are determined by X-ray crystal structure analysis. OHEC-amine 8 reacts with 2 equiv. of CuSO4 yielding the dinuclear complex [Cu2(OHEC-amine)](SO4)2 (13). Complex 13 crystallizes with 16 molecules of water. 13 · 16 H2O contains two copper atoms, which are coordinated in a strongly distorted octahedral fashion by four nitrogen atoms, one oxygen atom from the sulfate dianion and one oxygen atom from a water molecule. The new ligands 10 and 12 are fully characterized by 1D- and 2D-NMR spectroscopy. Both ligands form dinuclear lanthanide(III) chelates (LnY, Sm, Eu, Gd, Yb, Lu), which are stable and highly water soluble. With lanthanum(III) only mononuclear complexes are formed.