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The synthesis of three five-coordinate nickel() complexes with pendant arm-containing macrocycles has been achieved by the reduction of C᎐ ᎐ N bonds in the Schiff base precursors derived from diacetyl-or diformyl-pyridine and a tripodal tetramine. Demetallation of the nickel() macrocycles yielded stable pentadentate ligands that were used for the preparation of the copper() complexes. The structures of three nickel() complexes and two copper() complexes were determined by X-ray crystallography. Protonation of the pendant arm (pK a = 6.3-6.6 for the nickel complexes, and 6.5-7.3 for the copper complexes) produced four-coordinate macrocycles, one of which was structurally characterized. The primary amino group of the pendant arm coordinated to the nickel() reacted with acetic anhydride or benzoyl chloride. The resulting mono-functionalized nickel() complexes and their copper() counterparts obtained by transmetallation displayed square-planar geometry in the solid state, as determined by X-ray crystallography, and remained four-coordinate in solutions below pH 11.

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