Excimer-origin CPL vs monomer-origin magnetic CPL in photoexcited chiral binaphthyl-ester-pyrenes: Critical role of ester direction

Two chiral binaphthyl (BNp) derivatives bearing oppositely oriented ester linkers to two pyrene (Py) moieties [(R)/(S)-1 and (R)/(S)-2)] enabled Py-origin circularly polarized luminescence (CPL), magnetic CPL (MCPL), and circular dichroism (CD). (R)-1 that exhibited negative CD showed positive Py-excimer CPL but did not exhibit MCPL. Conversely, (R)-2, with negative CD, did not show excimer-origin CPL, but exhibited clear Py-monomer MCPL.