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[40.4.18,12.131,35.0.019,24]octatetraconta-6,8,10,12(47),13,19,21,23,29,31,33,35(48),36,42,44,46-hexadecaene (L3) and 3,16,25,38-tetrathia-6,13,28,35-tetraazapentacyclo[38.4.28,11.230,33.0.018,23]octatetraconta-6,8,10,12,18,20,22,28,30,32,34,40,42,44,45(46),47(48)-hexadecaene (L2) have been synthesized in high yield by a 2 + 2 condensation of isophthalaldehyde and terephthalaldehyde with 2,2′-o-phenylenebis(methylenethio)bis(ethanamine) (L1) in acetonitrile. Air-stable dicopper(I) complexes of L2 and L3 were obtained from complexation reactions with [Cu(CH3CN)4]ClO4 in CH3CN solution, with the structure of [Cu2L2][ClO4]2· 0.5CH3OH·2.5H2O 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' π-stacked parallel (separation 3.5 Å), and a double helical arrangement of the ligand backbone clearly evident. Electrochemical studies of the dinuclear complexes revealed quasi-reversible CuI–CuII couples above +1 V (versus NHE), with reversibility influenced by the presence of ferrocene, which acts as a surface modifier for electron transfer.