THE FLUORESCENCE PROPERTIES OF (2-NITRO-5,10,15,20-TETRAPHENYLPORPHYRINATO)ZINC

The photophysical and redox properties of (2-substituted porphyrinato)zinc derivatives in various solvents are investigated. Zinc complexes of 2-bromo-, 2-cyano-, and 2,3-(1,4-phenylenedinitrilo)-substituted porphyrins as well as (tetraphenylporphyrinato)zinc (Zntpp(H,H)) exhibit well-resolved Q0,0 and Q0,1 fluorescence peaks, while (2-nitro-substituted porphyrinato)zincs emit a red-shifted fluorescence with a less resolved vibrational fine structure. Stokes shift of (2-nitro-5,10,15,20-tetraphenylporphyrinato)zinc (Zntpp(H,NO2)) is considerably larger than that of Zntpp(H,H), and increases with the increase in the dielectric constant of aprotic solvents. The results are ascribed to the intramolecular charge transfer from the porphyrin ring to 2-nitro group in the lowest singlet excited state of Zntpp(H,NO2).