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

Abstract

Multiple noncovalent interactions can drive self-assembly through different pathways. Here, by coordination-assisted changes in π-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 π-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.

Keywords: chirality; luminescence; noncovalent interactions; supramolecular chemistry; zinc.