Soluble polyimides containing trans-diaminotetraphenylporphyrin: Synthesis and photoinduced electron transfer

5,15-Bis(4-aminophenyl)-10,20-diphenylporphyrin (trans-DATPP) was synthesized via the condensation of meso-(4-nitrophenyl)dipyrromethane and benzaldehyde. The further reaction with zinc acetylacetonate hydrate afforded zinc 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin (trans-ZnDATPP). A series of soluble polyimides based on trans-DATPP or trans-ZnDATPP, 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (PFMB) and 4,4′-hexafluoroisopropylidenediphthalic anhydride (6FDA) at various ratios was then prepared. Some physical properties of these polyimides were measured. It was found that every polyimide containing either trans-DATPP or trans-ZnDATPP had higher viscosity than the polyimide without porphyrin unit. Furthermore, the polyimides with trans-ZnDATPP showed lower viscosity than the ones without trans-ZnDATPP at approximately the same porphyrin content. Glass transition temperatures (Tgs) of polyimides containing trans-ZnDATPP were higher than polyimides containing trans-DATPP, and both were higher than polyimide without porphyrin. Steady state fluorescence spectroscopy of these polymers revealed that the quantum yield of polymers increased with higher content of free base porphyrin in the polymer chain. Time-correlated single photon counting experiments indicated these polyimides could be used in photonic applications.