Color Tunable Circularly Polarized Luminescence Properties of Chiral Platinum(II) Complexes with Salen Ligands

A series of novel chiral platinum complexes 1–8 (R = 4-NEt2 (1), 4-F (2), 5-CF3 (3), 5-Cl (4), 5-OCF3 (5), 4-CF3 (6), 5-F (7), 5-MeO (8)) was prepared and their circularly polarized luminescence (CPL) properties were compared with those of the non-substituted analogue 9 (R = H). The complexes showed multi-color (green, yellow, and red) phosphorescence in the solution state, depending on the substitution position of the functional group of the ligands. The chiral complexes exhibited CPL with absolute luminescence dissymmetry factor (glum) of up to the 1.3 × 10−3 in the dilute solution state. Acid-induced CPL was also achieved by the protonation of the diethylamino group of complex 1 with CH3SO3H. Density functional theory (DFT) calculations were conducted to further understand the structure dependence of the chromogenic behavior of these complexes. A series of novel circularly polarized luminescent chiral Schiff-base platinum(II) complexes with tetradentate salen ligands have been synthesized. Obtained complexes exhibited intense green to red circularly polarized luminescence in dilute solution state under UV irradiation, and theoretical study using density functional theory (DFT) and time dependent (TD)-DFT calculations revealed correlation between their structures and photophysical properties.