PHOTOPHYSICAL PROPERTIES OF MONONUCLEAR, DINUCLEAR AND TETRANUCLEAR COPPER(I)-POLYPYRIDINE COMPLEXES

We report results concerning the absorption spectra, luminescence spectra, luminescence lifetimes and emission quantum yields for two dinuclear copper(I) complexes [Cu(L(1))](2)(ClO4)(2), (C-1), and [Cu(L(2))](2)(ClO4)(2) (C-2), (L(1)=1,2-bis(9-methyl-1,10-phenanthrolin-2-yl)ethane and L(2)=1,2-bis(6'-methyl-2,2'-bipyridin-6-yl)ethane). For both complexes the lowest energy absorption band is metal-to-ligand charge transfer (MLCT) in nature, involving the oligopyridine ligand. The luminescence observed both at 77 K and at room temperature is due to an emitting MLCT level. Related mono-, di- and tetranuclear copper(I) complexes C-3 to C-5 were not found to emit showing that the metal is weakly protected from the surrounding medium. C-3=[Cu(L(3))](2)(ClO4)(2) (L(3)=5,5',3'',5'''-tetramethyl-2,2':6',2'':6'',2'''-quaterpyridine); C-4=[Cu(L(4))]BF4) (L(4)=bpy.bpy macrocycle); C-5=[Cu-4(L(5))(2)](ClO4)(4)(L(5)=8,21-bis[(9-methyl-1,10- phenanthrolin-2-yl)methyl]-8,21,27,28,29,30-hexaazapentacyclo [21.3.1.1(2,6),1(10,14),1(15,19)]triaxonta-1(27), 2,4,6(30),10,12,14(29),15,17,19(28),23,25-dodecaene).