Synthesis, protonation and Cu2+ co-ordination studies on a new family of thiophenophane receptors

The synthesis of the new thiophenophanes 2,5,8,11-tetraaza[12](2,5)thiophen ophane (L-1), 2,6,9,13-tetraaza[14](2,5)thiophenophane (L-2) and 2,5,8,11,1 4-pentaaza[15](2,5)thiophenophane (L-3) is described. The stepwise protonat ion constants of the macrocycles are determined by pH-metric titration and their protonation patterns are analysed by means of H-1 and C-13 NMR spectr oscopy. L-1 and L-2 present first protonation on the thenylic nitrogens whi le L-3 protonates first on the central nitrogens of the polyamine bridge. M olecular orbital calculations are used to locate the atomic orbitals contri buting to the HOMO of the free amines; The interaction with Cu2+ shows for L-1 and L-3 formation of binuclear complexes which readily hydrolyse to giv e very stable species, Electrochemical studies show for all three Cu2+-rece ptor systems an important stabilisation of the Cu+ oxidation state towards its disproportionation into Cu2+ and Cu-0 oxidation states.