Photophysics of Pt(II) 4,6-diphenyl-2,2′-bipyridyl complexes in solution and in LB film

Two amphiphilic platinum(II) 4,6-diphenyl-2,2′-bipyridyl complexes (1 and 2) were synthesized and characterized. LB films of these two complexes were prepared and characterized by AFM technique. Electronic absorption and emission characteristics of these complexes in solutions at room temperature, in glassy solutions at 77 K, and in LB films were studied. The emission energies of the complexes in LB films are similar to those in acetonitrile solutions at room temperature. However, the lifetimes of 1 and 2 in LB films are 4–7 times as long as those in CH3CN solutions. The triplet transient difference absorption spectra of these complexes exhibit broad absorption in the visible region to the near-IR region. Introducing a hydroxyl substituent on the 4,6-diphenyl-2,2′-bipyridyl ligand favors the formation of intermolecular hydrogen bonding and thus helps the deposition of uniform and stable LB films and increases the self-quenching rate constant for emission of 2 in CH3CN solution.