Ring-Opened Hemiporphyrazines: Helical Molecules Exhibiting Circularly Polarized Luminescence

We designed and synthesized a new type of small helical molecule exhibiting intense circularly polarized luminescence (CPL) (1(2H)) by modifying a 20 pi-electron hemiporphyrazine with a large transition magnetic dipole moment. The hemiporphyrazine ring was opened and one additional pyridine unit was introduced, resulting in an overlap of two pyridine rings. X-ray structure analysis confirmed that 1(2H) and its zinc complex (1(Zn)) adopt a helical geometry. A racemic mixture of 1(Zn) was resolved into two enantiomers ((P)- and (M)-1(Zn)), which exhibited CPL with a high luminescence dissymmetry factor (g(lum)) value of +/- 2.1x10(-2). The origin of the large g(lum) value was rationalized by means of DFT calculations. Helical structures could be formed in a diastereoselective manner by covalently attaching chiral units to the skeleton (1'(2H) and 1'(Zn)). 1(Zn) was found to possess chiral recognition ability for amines.