Synthesis of Two Novel Optically Active #-Shaped Cyclic Tetramers Based on Planar Chiral [2.2]Paracyclophanes

Abstract

This study reports the synthesis of optically active cyclic tetramers comprising four stacked π-electron systems from two enantiomerically pure [2.2]paracyclophane compounds (bis-(para)-pseudo-ortho- and bis-(para)-pseudo-meta-tetrasubstituted [2.2]paracyclophane compounds). Depending on the combination of the absolute configurations of the planar chiral pseudo-ortho- and pseudo-meta-[2.2]paracyclophane units, the cyclic tetramers formed either parallel-#- or weave-#-structures. The optical and chiroptical properties of both structures were investigated experimentally and theoretically. In particular, the weave-#-shaped cyclic tetramer exhibited good chiroptical properties and emitted circularly polarized luminescence (CPL) with a high anisotropy factor (|g_lum | value of the order of 10^-3 ) and a CPL brightness (B_CPL ) higher than 100.

Keywords: [2.2]paracyclophane; circularly polarized luminescence; cyclic oligomer; planar chirality.