The 14-membered tetraazamacrocyclic Ni2+ and Cuz+ complexes of 4 (1,4,8-trimethyl-ll-[(2-methylthio)ethyl]-1,4,8,11 -tetraazacyclotetradecane), 5 (I ,4-dimethyl-8,11 -bis[2-(methylthio)ethyl]-1,4,8,11 -tetraazacyclotetradecane), and 7 (1,4,8,1 1-tetrakis[2-(methylthio)ethyl]-1,4,8,ll-tetraazacyclotetrad~ane), with one, two, and four methylthio-substituted pendant chains, respectively, and the Ni2+ complex of 6 (1,4-dimethyl-8,1 1-bis (2-methoxyethyl)-l,4,8,1 1-tetraazacyclotetradecane), with two methoxy-substituted pendant chains, were synthesized and their chemistry studied with regard to modelling F430. Solution spectra in H,O, MeCN, and DMF indicate participation of the side chain in metal coordination when the donor group is a thioether, whereas no coordination with the metal ion is observed with the ether group. Similarly the X-ray structures of the thioethercontaining compounds Ni(S), , Cu(5), , and Cu( ), show a coordination number of 5, whereas that of Ni(6), with ether pendant chains, shows a coordination number of 4. Cyclic voltammetry of these complexes in MeCN reveals that NiZ+ is reversibly reduced to Ni+ between -0.64 and -0.77 V vs. SCE, the potential being influenced by the nature and number of the pendant chains. At more negative potentials, the thioether is cleaved, whereby a thiol is formed; the thiol IS then oxidized at ca. + 0.8 V vs. SCE, when a glassy carbon electrode is used, or at ca. 0 V vs. SCE at a dropping Hg electrode. No cleavage of the ether bond in Ni( ), is observed under similar conditions.