Microwave-Assisted Synthesis and Evaluation of the Optoelectronic Properties of Metallated Meso-Tetraphenylporphyrin Complex

In the present work, we report the synthesis of 5,10,15,20-tetraphenylporphyrin and the formation of its complex after insertion of a metal center with Mg+2, Co+2, Ni+2, Cu+2, or Zn+2. 1H-NMR determined the insertion with signal suppression of the internal hydrogens present in the free base of the porphyrin macrocycle. UV-vis characterization shows the absorption bands of the porphyrinic systems at 418 nm and 510-650 nm. The insertion of the metal centers generates bathochromic and hypsochromic changes in the Mg+2 and Co+2 insertions, respectively, as well as changes in the molar absorptivity coefficients. The fluorescence quantum yields for some elements were almost wholly reduced, mainly for the Co+2 and Cu+2 insertions, while Mg+2 presented a high fluorescence quantum yield. These observations agree with the results obtained by DFT and TD-DFT, in which the oscillator strength values for the Mg+2 chelate are higher even than those for the 5,10,15,20tetraphenylporphyrin free base. The electrochemical properties of the cyclic voltammetry study show four reversible oxidation and reduction peaks for the free base 5,10,15,20-tetraphenylporphyrin. Generally, the metallated meso-tetraphenylporphyrins show three reversible peaks of oxidation and reduction. All synthesized analogs' first oxidation potentials ranged from 0.346 to 0.804 V vs. SCE. In comparison, the first reduction potential ranged from-1.032 to-1.602 V vs. SCE, which gives great interest in their implementation as optoelectronic materials and even as materials for the elaboration of electrochemical sensors.