Enhancement of the intrinsic fluorescence of acridine and its induced circularly polarized luminescence (CPL) in ionic two-coordinate coinage metal complexes

The intrinsic pi-pi* fluorescence of acridine is weak due to the deactivation via coupling with a close-lying non-emissive 1n-pi* state. By employing the lone pair of acridine to establish coordination bonds in a series of two-coordinate Cu(i) and Ag(i) complexes, significantly enhanced intrinsic fluorescence of acridinyl is observed with a photoluminescent quantum yield (Phi PL) approaching 50%. Using chiral camphorsulfonate counterions, the cationic complex was induced to emit circularly polarized fluorescence with a reasonable glum of 5 x 10-3. Enhanced blue fluorescence of acridine is achieved in carbene-M-acridine ionic complexes, where M is Cu(i) and Ag(i), approaching 50%. With the help of chiral counter ions, circularly polarized fluorescence of acridine is induced in crystalline state.