Off-off-on chiroptical property switching of a pyrene luminophore by stepwise helicate formationElectronic supplementary information (ESI) available: Experimental section; ESI mass spectrum in the entire range; 1H, 1H COSY, ROSEY, and NOESY correlations; and assignment of rotatory strength for P-(L′)3(Zn2+)2. See DOI: 10.1039/c9cc01138b

• Main Authors: Imai, Yuki, Yuasa, Junpei
• Format: Article
• ISSN: 1359-7345; 1364-548X
• DOI: 10.1039/c9cc01138b

Pyrene-based chiral ligands (L R and L S ) consisting of two chiral imidazole sidearms at the 1,8-positions first form pyrene-bridged oligomers [(L ( R  or  S ) ) 3 (Zn 2+ ) n ], which are chiroptically inactive, with a low concentration of zinc ions (Zn 2+ ). Upon addition of more Zn 2+ , chiroptically active coordination helicates ([(L ( R  or  S ) ) 3 (Zn 2+ ) 2 ]) are formed. The stepwise assembly process successfully facilitated an "off-off-on" chiroptical switching process of a pyrene luminophore controlled by the concentration of Zn 2+ . The resulting pyrene-bridged helicates exhibit high performance in terms of a dissymmetry factor of circular dichroism (| g CD | = 0.006) and circularly polarized luminescence (| g CPL | = 0.01). The stepwise formation of pyrene-bridged helicates [(L ( R  or  S ) ) 3 (Zn 2+ ) 2 ] with a large dissymmetry factor (| g CD | = 0.006 and | g CPL | = 0.01) results in off/off/on-type chiroptical property switching of the pyrene luminophore controlled by the concentration of zinc ions (Zn 2+ ).