Synthesis of 6-amino-6-(4-aminobenzyl)-1,4,8,11-tetra-azacyclotetradecane, a new pentadentate polyamine ligand, and crystal structure of its Co(III) complex

Article abstract of DOI:10.1016/S0020-1693(99)00031-6

The facile synthesis of the hydrochloride salt of the 6-amino-6-(4-aminobenzyl)-1,4,8,11-tetra-azacyclotetradecane L³ is reported. The Co(III) complex of this new pentadentate ligand crystallizes in the space group P2₁/n, with a=15.5901(3), b=8.9267(2), c=20.6011(4) A, β=100.5960(10)°. X-ray crystal structure analysis has shown the 6-amino group axially coordinated to the metal center, and the cyclam moiety taking a trans I configuration. Water coordinates at the sixth site. The axial Co-N distance is 1.935(3) A, and the cyclam core nitrogen-Co distances are in the range between 1.957(3) and 1.964(3) A, shorter than previously reported data for similar macrocyclic complexes. The crystal structure of the complex [Cu(L²)(NO₃)₂] (L²: 6-nitro-6-(4-nitrobenzyl)-1,4,8,11-tetraazacyclotetradecane), synthetic precursor to the L³ ligand is also reported. It crystallizes in the space group P2₁/n, with a=19.49560(10), b=8.38520(10), c=15.8518(2) A, β=111.03°.