Synthesis of Donor‐Acceptor π‐Conjugated Macrocycles by Post‐Functionalization †

Main observation and conclusion In this paper, two novel donor‐acceptor (D‐A) macrocyclic compounds 5 and 7 were successfully synthesized by post‐functionalization of a planar dimer macrocycle (1) and a highly twisted trimer macrocycle (2), respectively, via controllable oxidation of methoxy groups and condensation between diketones and phenylenediamine in succession. Compared with unembellished 9,10‐dimethoxyphenanthrene, the resultant dibenzo[a,c]phenazine motif is electron‐deficient rather than electron‐rich, yielding two D‐A π‐conjugated macrocycles with more contractive energy gaps. Density functional theory (DFT) calculations further support the unequivocal evidence of the D‐A properties of macrocycles 5 and 7. The difference of their photophysical properties was investigated by the aid of ultraviolet‐visible absorption and fluorescence spectrophotometers. Furthermore, the stacking patterns of 7 and its contrast π‐conjugated macrocycle trimer (2) were compared via the analysis of X‐ray single crystal, in which the electron‐deficient dibenzo[a,c]phenazine unit provides extra interaction sites, resulting in orderly arrangement of 7 in the solid state.