Photochemistry of macrocyclic copper(II) compounds bound to polyelectrolytes

Anionic polyelectrolytes were added to aqueous solutions of copper(II) tetraazamacrocycles to modify their photochemical properties. Steady-state photolysis of solutions containing polycarboxylates, at pH 6.5, showed formation of copper(I) macrocycles with minimal degradation to free copper ions, Cu-aq(+) or Cu-aq(+). Product quantum yields indicated that: (i) the polycarboxylate surrounding helped to enhance the photochemical properties of copper(II) macrocyclic complexes, serving as sacrificial electron donors; and (ii) there was an interaction of the photogenerated carbon dioxide molecules with the copper(I) units, forming long-lived species. Moreover, the polyelectrolyte microenvironment protected the copper(I) macrocycles from prompt conversion by different reaction pathways, such as opening of the macrocycle and hydrolysis. Time resolved experiments helped to elucidate the nature of the reaction intermediates and indicated formation of an adduct between the copper moiety and carbon dioxide.