Flexible and rigid "chirally distorted" π-systems: binaphthyl conjugates as organic CPL-active chromophores

The inclusion of high-performance dyes into chiral π-conjugated systems is an effective strategy for activating significant chiroptical properties. We report the preparation and characterization of configurationally stable, axially-chiral π-conjugated systems in which acridone or 2,5-diarylamino-terephthalate has been fused into the chiral scaffold of a 1,1'-binaphthyl moiety. The high-yielding synthesis afforded π-conjugated systems with characteristics essentially matching those of the parent dyes while introducing detectable CPL activity in solution. In the acridone conjugate, good fluorescence is maintained in solution, but in the solid state, the distortion introduced by the binaphthyl system does not substantially help in restoring emissive properties; the flexibility and the emissive properties of the 2,5-diphenylamino-terephthalate chromophore are maintained in the conjugate. The new chiral chromophoric systems show absorption in the UV-vis domain, with good fluorescence properties in the visible range (quantum yields up to 23% and g_lum values up to 4 × 10^-4).