Coordination Modes of a Series of Xylylene-Bridged Bis(1,4,7-triazacyclonon-1-yl) Ligands: Synthesis, Structure, and Properties of Nickel(II) and Copper(II) Complexes

Abstract

Three bis(1,4,7-triazacyclonon-1-yl) ligands, 1,2-bis(1,4,7-triazacyclonon-1-ylmethyl)benzene (L1), 1,3-bis(1,4,7-triazacyclonon-1-ylmethyl)benzene (L2), and 1,4-bis(1,4,7-triazacyclonon-1-ylmethyl)benzene (L3), have been synthesized and their nickel(II) and copper(II) coordination chemistry investigated. Reaction of L1 with excess Ni2+ ions affords a mixture of mononuclear and binuclear complexes, which are readily separated by cation exchange chromatography and crystallized as their perchlorate salts, [NiL1](ClO4)2 (1) and [Ni2L1(H2O)6](ClO4)4· 4H2O (2). Similar treatment of L2 and L3 with excess Ni2+ ions affords exclusively the binuclear complexes [Ni2L2(H2O)6](ClO4)4 (3) and [Ni2L3(H2O)6](ClO4)4·3H2O (4), respectively. Reaction of all three ligands with excess Cu2+ ions also yields binuclear complexes, which may be isolated as neutral species, [Cu2LBr4]·xDMF (5, L = L1, x = 1; 6, L = L2, x = 0; 7, L = L3, x = 0), or as perchlorate salts, [Cu2L(H2O)4](ClO4)4·xH2O (8, L = L1, x = 5; 9, L = L2, x = 4; 1...