CO₂ Fixation and Activation by CuII Complexes of 5,5″‐Terpyridinophane Macrocycles

An aza‐terpyridinophane receptor containing the polyamine 4,7,10,13‐tetraazahexadecane‐1,16‐diamine linked through methylene groups to the 5,5″ positions of a terpyridine unit has been prepared and characterized (L). The acid‐base behaviour, Cu II speciation and ability to form ternary complexes (Cu II ‐L‐carbonate) have been explored by potentiometric titrations in 0.15 M NaClO 4 and by UV/Vis and paramagnetic NMR spectroscopy. Comparisons are made with a previously reported terpyridinophane containing the polyamine 4,7,10‐triazatridecane‐1,13‐diamine (L 1 ). For this latter receptor, reductive coupling between indigo and carbon dioxide at indigo‐modified electrodes produces carboxylated derivatives via a solid‐state reaction under electrochemical activation.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)