Long-Lived Charge Separation in a Dyad of Closely-Linked Subphthalocyanine-Zinc Porphyrin Bearing Multiple Triphenylamines

Abstract

Photoinduced intramolecular events of the newly synthesized multimodular system composed of three triphenylamine (TPA) entities covalently substituted at the meso positions of the zinc porphyrin ring (ZnP), which is linked with the dodecafluorosubphthalocyanine SubPc(F)12 at its axial position with the B−O bond have been examined. Appreciable electronic interactions between the meso-substituted TPA entities and the ZnP π-system were observed, and as a consequence, ZnP(TPA)3 acts as an electron-donor, whereas the SubPc(F)12 moiety acts as an excellent electron-acceptor unit in the multimodular conjugate, ZnP(TPA)3−SubPc(F)12. The computational studies performed by the DFT-B3LYP at the 6-31G level revealed delocalization of the highest occupied molecular orbital (HOMO) over the (TPA)3 entities and the porphyrin macrocycle, while the lowest unoccupied molecular orbital (LUMO) is localized on SubPc(F)12. Free-energy calculations suggested that the light-induced processes from the excited states of ZnP(TPA)3 are exothermic in both polar benzonitrile and nonpolar toluene and benzene. The occurrence of fast and efficient charge-separation processes (∼1012 s−1) via the singlet excited state of ZnP(TPA)3 was confirmed by the femtosecond transient absorption spectral measurements in polar and nonpolar solvents. The delocalization of the π-cation radical species over the donor ZnP(TPA)3, the lower energy of the radical-ion pair, the particular characteristics of the axial B−O bond, and the triplet radical-ion pair character rationalize the charge stabilization of (ZnP(TPA)3)•+−(SubPc(F)12)•− with extremely long lifetime (370 μs) compared with the reported phthalocyanine-based compounds.

Photosynthetic Antenna–Reaction Center Mimicry by Using Boron Dipyrromethene Sensitizers

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] In this marvelous process, sunlight is harvested by the antenna complexes and the excitation energy is funneled to the reaction center (RC), where multistep electron-transfer reactions occur to generate a potential that can drive chemical reactions ( Figure 1). [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] In this marvelous process, sunlight is harvested by the antenna complexes and the excitation energy is funneled to the reaction center (RC), where multistep electron-transfer reactions occur to generate a potential that can drive chemical reactions ( Figure 1).…”

Click Reaction Synthesis and Photophysical Studies of Dendritic Metalloporphyrins

“…In the near‐UV and visible ranges, the absorption profile is due to the porphyrin core. These dendrimer spectra retain all the main features of the “parent” Zn‐tetra‐aryl‐porphyrin core (Zn‐5,10,15,20‐tetraphenyl‐porphyrin (ZnTPP)27 and Zn‐5,10,15,20‐tetrakis(2,4,6‐trimethylphenyl)‐porphyrin (ZnTMesP)22,28) (Tables 1 and 2). Nevertheless, minor changes could be seen in the spectra, which deserve to be discussed in detail.…”

Tuning the Electronic Properties of Porphyrin Dyes: Effects of meso Substitution on Their Optical and Electrochemical Behaviour

“…The synthesis of the arylamino analogues turned out to be more straightforward and higher‐yielding (Scheme ). Reaction of 4‐(diphenylamino)benzaldehyde ( 14 ),16 trimethylsilylpropynal, and pyrrole under the usual conditions gave porphyrin derivative 15 in 13 % yield. The conversion to 4 and 5 was accomplished by metallation followed by Sonogashira couplings, following the same procedure as described above, with good yields in all steps.…”