Self-Assembly through Coordination and π-Stacking: Controlled Switching of Circularly Polarized Luminescence

Multiple noncovalent interactions can drive self-assembly through different pathways. Here, by coordination-assisted changes in pi-stacking modes between chromophores in pyrene-conjugated histidine (PyHis), a self-assembly system with reversible and inversed switching of supramolecular chirality, as well as circularly polarized luminescence (CPL) is described. It was found that L-PyHis self-assembled into nanofibers showing P-chirality and right-handed CPL. Upon Zn-II coordination, the nanofibers changed into nanospheres with M-chirality, as well as left-handed CPL. The process is reversible and the M-chirality can change to P-chirality by removing the Zn-II ions. Experimental and theoretical models unequivocally revealed that the cooperation of metal coordination and pi-stacking modes are responsible the reversible switching of supramolecular chirality. This work not only provides insight into how multiple noncovalent interactions regulate self-assembly pathways.