The Snthesis Of Meso-tetrakis (1-arylpyrazol-4-yl) Porphyrins And Their Quantitative Structure-Property Relationships Studies

As an important kind of photochemical and photobiological compounds, porphyrins have been receiving more and more interest. In the field of organic electroluminescen, porphyrins have been studied by many research groups because of their ideal red-emitting. However, low photoluminescent yields of fluorescent dyes prevent porphyrins for practical use. To solve this problem, a series of nitrogen heterocycle porphyrin compounds were obtained in our laboratory by introducing a pyrazole heterocyclic ring with high fluorescent quantum yield to the parent porphyrin. And six meso-tetrakis(1-arylpyrazol-4-yl)porphyrins with different substitutes have been designed and synthesized. Preparation of these porphyrins was carried out by cyclization of tetramethoxypropane with substituted phenylhydrazine, followed by formylation under Vilsmeier-Haack condition to give the corresponding aldehydes, which reacted with pyrrole under the Adler reaction condition to get the target porphyrins. The structures of all these compounds were characterized by ~1HNMR, elemental analysis, UV-Vis spectra and mass spectra. The formylation reaction of pyrazole heterocyclic and the synthetic methods of porphyrins have been studied too. At the same time, the fluorescence spectra of meso-tetrakis (1-arylpyrazol-4-yl)porphyrin were mensurated. Compared with meso-tetraphenylporphyrin, the newly synthesized meso-tetrakis(1-arylpyrazol-4-yl)porphyrins not only have ideal red-emitting, but also exhibite high fluorescent quantum yields that are two or three times than that of meso-tetraphenylporphyrin. Since the fluorescent quantum yields of porphyrins are improved consumedly, the problem of the practical use of porphyrins is ultimately circumvented.Moreover, to carry out the predictions of the fluorescent quantum yields of porphyrins, the relationship between their molecular structures and fluorescence quantum yields of the meso-tetrakis(1-arylpyrazol-4-yl)porphyrins were studied. It can be observed that the fluorescence quantum yields of the porphyrins are strongly related to the molecular front orbital energies, the total energy, the radius of gyration and the molecular density. With the decreasing of the difference of the molecular front orbital energies, the increasing of the total energy of the compound, the increasing of the molecular volume or avoiding the heavy-atom effect, the compound fluorescence quantum yields could be improved. Then, the quantitative model was established between the four factors and the fluorescence quantum yields of the porphyrins. This model could be use to predict the fluorescence quantum yields of the interested porphyrin compounds. The desirable performance exhibited by the model could achieve high accurate prediction of the fluorescence quantum yields of the meso-tetrakis(l-arylpyrazol-4-yl)porphyrins. The correlation coefficient between the calculated fluorescence quantum yields of the seven porphyrin compounds and that of the observed values is more than 0.98. In addition, a detail discussion about the four influencing factors of the compound fluorescence quantum yields was presented. For the compounds with different substitutents, the effection of the four factors are different, too. Consequently, a new approach for well and truly studying the relationship between the molecular structures and their fluorescence quantum yields was developed, which is with great promise of the research of porphyrin compounds.