Copper(I) Complexes of Dinucleating Macrocyclic Bis-Dithiadiimine Ligands

The 34- and 36-membered macrocyclic bis(dithiadiimine) Schiff bases 3,17,26,40-tetrathia-6,14,29,37-tetraazapentacyclo[40.4.1(8,12).1(31,35).0.0(19,24)]octatetraconta-6,8,10,12(47),13,19,21,23,29,31,33,35(48),36,42,44,46-hexadecaene (L-3) and 3,16,25,38-tetrathia-6,13,28,35-tetraazapentacyclo[38.4.2(8,11).2(30,33).0.0(18,23)]octatetraconta-6,8,10,12,18,20,22,28,30,32,34,40,42,44,45(46),47(48)-hexadecaene (L-2) have been synthesized in high yield by a 2 + 2 condensation of isophthalaldehyde and terephthalaldehyde with 2,2'-o-phenylenebis(methylenethio)bis(ethanamine) (L-1) in acetonitrile. Air-stable dicopper(I) complexes of L-2 and L-3 were obtained from complexation reactions with [Cu(CH3CN)(4)]ClO4 in CH3CN solution, with the structure of [Cu2L2][ClO4](2) . 0.5CH(3)OH . 2.5H(2)O confirmed by a crystal structure analysis. The complex consists of two N2S2 donor sets each tetrahedrally co-ordinated to the copper(I) ions with two para-substituted phenyl rings bridging the two N2S2 'compartments' pi-stacked parallel (separation 3.5 Angstrom), and a double helical arrangement of the ligand backbone clearly evident. Electrochemical studies of the dinuclear complexes revealed quasi-reversible Cu-I-Cu-II couples above + I V (versus NHE), with reversibility influenced by the presence of ferrocene, which acts as a surface modifier for electron transfer.