Molecular Switching of Copper Complexes with Quaterpyridine

Chemically and electrochemically induced interconversion between five one‐stranded complexes of copper(II) and the respective double‐stranded helicates of copper(I) bearing the ligand 6,6′′′‐dimethyl‐2,2′:6′,2′′:6′′,2′′′‐quaterpyridine ( L ) culminated in different luminescence properties. Five new mononuclear complexes of copper(II) bearing the ligand L {[Cu II L Cl 2 ] ( 1 ), [Cu II L (ClO 4 ) 2 ] ( 2 ), [Cu II L (NO 3 ) 2 ] ( 3 ), [Cu II L (CF 3 SO 3 ) 2 ] ( 4 ), and [Cu II L (BF 4 ) 2 ] ( 5 )} have been reduced in two different ways: The first, by using metallic copper, gave [Cu I 2 L 2 ][Cu II Cl 4 ] ( 1a ), [Cu I 2 L 2 ][Cu II (ClO 4 ) 4 ] ( 2a ), and [Cu I 2 L 2 ][Cu II (NO 3 ) 4 ] ( 3a ), and the second, by using ascorbic acid, led to [Cu I 2 L 2 (CF 3 SO 3 ) 2 ] ( 4a ) and [Cu I 2 L 2 (BF 4 ) 2 ] ( 5a ). The conversion of the helicates into mononuclear complexes can be implemented by oxidation with hydrogen peroxide or by the displacement of Cu I by Cu II ions.