Synthesis And Properties Of Dinuclear Imidazoline NCN Pincer Platinum Compounds

Platinum(II) complexes have been widely studied in the past few decades due to their rich spectroscopic properties, in which their absorption and emission energies are found to be readily tuned by manipulating the electronic properties of the auxiliary ligands. Square planar platinum complexes have attracted considerable attention for their potential use in a wide range of applications, such as optical chemosensors, photocatalysis, luminescent probes, vapochromism, cation sensors, and molecular photochemical devices for solar energy conversion. Platinum complexes have also been applied successfully as phosphorescent emitters in organic light-emitting diodes(OLEDs).In this work, three dinuclear pincer platinum(II) 1,3-bis(2’-imidazolinyl)phenyl(abbreviated as Phebim) complexes with a rigid bridging ligand p-phenylene oligomers were synthesized(Scheme 1) and their electronic absorption and luminescent behaviors were studied in dichloromethane solution at room temperature. All of the complexes exhibited intense π-π* absorption in the UVregion at 210-250 nm,a broad, moderate absorption band in the visible region at 300-380 nm, and weak absorptions in the range of 400-450 nm, the weak absorption at low energy can be attributed to MLCT transition(metal-to-ligand charge transfer). The solution emissions of the complexes at λmax 594-595 nm are attributed to 3MLCT states. Concentration-dependent emission data show that no aggregation occurred in dichloromethane solution for all of the complexes. The luminescence quantum yields in degassed CH2Cl2 solution are in the range of 0.84%-1.3%, which were obtained from measurements using quinine sulfate in 1M H2SO4(Ф = 0.546) as standard. For the more the structures and frontier orbitals of the three dinuclear Pt(II) complexes were investigated theoretically using the density functional theory(DFT) method.