Aggregation-induced enhanced fluorescence emission of chiral Zn(II) complexes coordinated by Schiff-base type binaphthyl ligands

A pair of novel chiral Zn(II) complexes coordinated by Schiff-base type ligands derived from BINOL (1,1 '-bi-2-naphthol), R-/S-Zn, were synthesized. X-ray crystallography revealed the presence of two crystallographically independent complexes; one has a distorted trigonal-bipyramidal structure coordinated by two binaphthyl ligands and one disordered methanol molecule (molecule A), while the other has a distorted tetrahedral structure coordinated by two binaphthyl ligands (molecule B). Numerous CH & ctdot;pi and CH & ctdot;O interactions were identified, contributing to the formation of a 3-dimensional rigid network structure. Both R-/S-Zn exhibited fluorescence in both CH2Cl2 solutions and powder samples, with the photoluminescence quantum yields (PLQYs) of powder samples being twice as large as those in solutions, indicating aggregation-induced enhanced emission (AIEE). The AIEE properties were attributed to the restraint of the molecular motion arising from the 3-dimensional intermolecular interactions. CD and CPL spectra were observed for R-/S-Zn in both solutions and powders. The dissymmetry factors, g(abs) and g(CPL) values, were within the order of 10(-3) to 10(-4) magnitudes, comparable to those reported for chiral Zn(II) complexes in previous studies.