SYNTHESIS OF A NOVEL 16-MEMBERED TETRAPEPTIDE MACROCYCLE, DIBENZO[C,K] 6,9,14]TETRA-AZACYCLOHEXADECANE[2,5,10,13]TETRAONE - ELECTROCHEMICALEVIDENCE FOR THE STABILITY OF -OXIDATION STATE OF COBALT AND COPPER(1)
Za. Siddiqi et Vj. Mathew, SYNTHESIS OF A NOVEL 16-MEMBERED TETRAPEPTIDE MACROCYCLE, DIBENZO[C,K] 6,9,14]TETRA-AZACYCLOHEXADECANE[2,5,10,13]TETRAONE - ELECTROCHEMICALEVIDENCE FOR THE STABILITY OF -OXIDATION STATE OF COBALT AND COPPER(1), Polyhedron, 13(5), 1994, pp. 799-805
The title ligand, a 16-membered tetrapeptide macrocycle (L), has been
obtained from the reaction of 1,2-diaminoethane and phthalic anhydride
in dioxane, and characterized by physicochemical methods. Complexes w
ith the stoichiometry [CoLCl]Cl and [CuLCl2] were obtained from the in
teraction of the macrocyclic ligand with the corresponding metal salts
. The [CoLCl]Cl complex is a low-spin square pyramid, with possible ex
istence of spin cross-over point at room temperature, whereas [CuLCl2]
contains octahedral geometry. The cyclic voltammetric studies are con
sistent with the formation of a reversible redox couple (Cu(II) half a
rrow right over half arrow left Cu(I); E0 = -0.48 V) for [CuLCl2], whe
reas irreversible reduction (Co(II)-->Co(I)) is indicated for the [CoL
Cl]Cl complex in DMSO solution. These facts are rationalized in terms
of the large cavity size of the macrocyclic ligand.