Synthesis and Photophysical Investigation of Tetraazaporphyrin Substituted with Aggregation-Induced Emission (AIE) Active Moieties

The synthesis and characterization of free-base and Zn^II tetraazaporphyrins with tetraphenylethylene (TPE) or diphenylphenanthrene (DPP) moieties that are known to be aggregation-induced emission (AIE) active is reported. The optical spectra contain the characteristic Q and B absorption bands of Gouterman's four-orbital model and a broad envelope of weaker charge-transfer bands in the 450-600 nm region. The observed fluorescence emission lies beyond 670 nm and originates exclusively from the decay of the S₁ state of the macrocycle, regardless of the excitation wavelength used. Theoretical calculations provide further evidence of strong electronic communication between the peripheral TPE or DPP moieties and the central ring. The Zn^II complexes were found to have relatively high singlet-oxygen quantum yields. The synthesis and characterization of free-base and Zn^II tetraazaporphyrins (TAPs) with aggregation-induced emission (AIE) active moieties is reported. The TAP spectra contain the characteristic Q and B absorption bands and a broad envelope of weaker charge-transfer bands that extend from the UV to the near-infrared region. The Zn^II complexes were found to have relatively high singlet oxygen quantum yields.