C-Substituted Macrocycles as Candidates for Radioimmunotherapy

The reaction between aryl aldehydes, the macrocyclic ligand 6-methyl-1,4,8,11-tetraazacyclotetradecane-6-amine
(L1), and NaBH3CN produces the corresponding benzyl-substituted ligands in good yield. Copper(II) complexes
of the ligands derived from salicylaldehyde (L2), p-hydroxybenzaldehyde (L4), and p-carboxybenzaldehyde (L5)
were structurally characterized:  [CuL2](ClO4)2·3H2O (monoclinic, P21/c, a = 11.915(6) Å, b = 13.861(2) Å, c
= 17.065(8) Å, β = 102.14(2)°, Z = 4); [CuL4](ClO4)2 (monoclinic, P21/n, a = 9.550(3) Å, b = 17.977(2) Å,
c = 14.612(4) Å, β 96.76(1)°, Z = 4), and [CuL4](ClO4)2 (monoclinic, P21/n, a = 9.286(2) Å, b = 11.294(1) Å,
c = 23.609(8) Å, β 93.68(1)°, Z = 4). Conjugation of several CuII complexes to a protein (bovine serum albumin)
has been pursued with a view to the application of these macrocycles as bifunctional chelating agents in
radioimmunotherapy.