Synthesis and Spectroscopic Characterization of Two Tetrasubstituted Cationic Porphyrin Derivatives

Abstract

An imidazolium tetrasubstituted cationic porphyrin derivative (the free base and its Zn(II) complex) with five-membered heterocyclic groups in the meso-positions were synthesized using microwave irradiation, and the compounds obtained characterized by 1H-NMR and mass spectrometry. We observed that under microwave irradiation the yield is similar to when the synthesis is performed under conventional heating, however, the time required to prepare the porphyrins decreases enormously. In order to investigate the electronic state of these compounds, we employed UV-Vis and fluorescence spectroscopy combined with quantum chemical calculations. The results reveal the presence, in both compounds, of a large number of electronic states involving the association between the Soret and a blue-shifted band. The Soret band in both compounds also shows a considerable solvent dependence. As for emission, these compounds present low quantum yield at room temperature and no solvent influence on the fluorescence spectra was observed.

Microwave Synthesis Under Solvent-Free Conditions and Spectral Studies of Some Mesoporphyrinic Complexes

“…In recent years, research specialists concerned with obtaining pharmacologically active mesoporphyrins have been focused on developing new ecological methods as an alternative method to the classical way in order to decrease the reaction times, improving the degree of purity of the final products and implicitly increasing the reaction yields [15,16,17,18,22,23,24,25,26,18,22].…”

Excited-state absorption investigation of a cationic porphyrin derivative

“…Energy gaps between the energy levels, obtained by previous TD-DFT calculations [24], suggests that light-matter interaction processes for these porphyrins occurs, at UV-Vis region, according the Jablonski diagram depicted in Fig. 1.…”

“…The acronyms S 1 and S 2 were used to designate the excited states immediately superior to the ground state. Data from TD-DFT calculation suggest that these electronic states are related to complex sets of electronic, giving to these states a multiconfigurational character [24].…”

“…Performing the calculations we obtain isc near 187 ns. These results in association with the extremely low fluorescence quantum yield (˚F = 0.0004) [24], suggests that H 2 -TDMImP should decay mainly through an internal conversion process, yielding a very low triplet state population. In fact, the results indicates that the internal conversion rate is around 12 times higher than the intersystem crossing rate and two thousands higher than radiative decay rate.…”

Synthesis and Photodynamic Activity of 5,10,15-Tris(p-chlorophenyl)-20-(2- hydroxy-3-methoxyphenyl)-21H,23H-porphyrin

“…Porphyrins, one of the most popular PSs, are aromatic macrocycles formed by four pyrrole rings joined together by interpyrrolic methine bridges; the macrocycle contains a total of 22 π electrons with 18 π electrons in direct conjugation. Porphyrins are interesting molecules that play key roles in many biological processes (oxygen transport, electron transfer and oxidation catalysis) [4][5][6].…”