A three-dimensionally oriented π-conjugated system; synthesis and characterization of porphyrins bearing π-conjugated pendant strands

Three-dimensionally oriented π-conjugated systems were constructed by the introduction of four aniline trimer pendant strands at the meso-position of the porphyrin scaffold. The atropisomers (αααα and αβαβ) were isolated and spectroscopically characterized. The 1H NMR and UV–vis spectra revealed that the strands of the αβαβ-isomer might be in equilibrium with the conformers, in which one or more strands lean toward the porphyrin ring. In the fluorescence emission spectra, the emission from the porphyrin moiety was almost completely quenched in the αααα- and αβαβ-atropisomers.