STUDY OF CONFORMERS OF 6,6'-DIMETHYL-2,2'-BIPYRIDINE IN THE GROUND AND EXCITED-STATES

UV absorption, luminescence, and luminescence-excitation spectra of th e trans and metal-free cis conformers of 6,6'-dimethyl-2,2'-bipyridine (6,6'-Me(2)bpy) and its Zn2+ complex have been observed in 2-propanol and 2-propanol-water mixtures at 77 K. The stable conformation of 6,6 '-Me(2)bpy in the ground state depends on the composition of the mixtu re at 77 K and the conformation remains unchanged upon photoexcitation . The lowest excited singlet energy is sensitive to the coordination t o Zn2+, while the fluorescence lifetime is sensitive to both the confo rmational change of 6,6'-Me(2)bpy and to the coordination to Zn2+.