Crossed and Linked Histories of Tetrapyrrolic Macrocycles and Their Use for Engineering Pores within Sol-Gel Matrices

Abstract

The crossed and linked histories of tetrapyrrolic macrocycles, interwoven with new research discoveries, suggest that Nature has found in these structures a way to ensure the continuity of life. For diverse applications porphyrins or phthalocyanines must be trapped inside solid networks, but due to their nature, these compounds cannot be introduced by thermal diffusion; the sol-gel method makes possible this insertion through a soft chemical process. The methodologies for trapping or bonding macrocycles inside pristine or organo-modified silica or inside ZrO2 xerogels were developed by using phthalocyanines and porphyrins as molecular probes. The sizes of the pores formed depend on the structure, the cation nature, and the identities and positions of peripheral substituents of the macrocycle. The interactions of the macrocyclic molecule and surface Si-OH groups inhibit the efficient displaying of the macrocycle properties and to avoid this undesirable event, strategies such as situating the macrocycle far from the pore walls or to exchange the Si-OH species by alkyl or aryl groups have been proposed. Spectroscopic properties are better preserved when long unions are established between the macrocycle and the pore walls, or when oligomeric macrocyclic species are trapped inside each pore. When macrocycles are trapped inside organo-modified silica, their properties result similar to those displayed in solution and their intensities depend on the length of the alkyl chain attached to the matrix. These results support the prospect of tuning up the pore size, surface area, and polarity inside the pore cavities in order to prepare efficient catalytic, optical, sensoring, and medical systems. The most important feature is that research would confirm again that tetrapyrrolic macrocycles can help in the development of the authentic pore engineering in materials science.

Comparative Study of the Optical and Textural Properties of Tetrapyrrole Macrocycles Trapped Within ZrO2, TiO2, and SiO2 Translucent Xerogels

“…Synthetic analogues, such as porphyrins (H 2 P), phthalocyanines (H 2 Pc) (Figure 1), and naphthalocyanines (H 2 Nc), also display very important physicochemical properties. The synthesis of synthetic porphyrins could be achieved after the elucidation of the structures of chlorophyll, and hemoglobin’s heme group [9]. In all these centrosymmetric macrocyclic compounds, the π-electron system confers upon them high chemical and thermal stabilities, as well as other interesting properties that have led to a great number of applications [10,11,12,13,14,15,16].…”

Photoreduction of Carbon Dioxide to Formic Acid in Aqueous Suspension: A Comparison between Phthalocyanine/TiO2 and Porphyrin/TiO2 Catalysed Processes

“…An alternative strategy might be the use of sensitizers, in order to use visible radiation for the activation of TiO 2 . Phthalocyanine metalloderivatives (MPcs) or their supramolecular arrangements have recently attracted an increasing interest because they have been used not only as the main species for the preparation of dyes and pigments, but also as the building blocks for the construction of new molecular materials used in various technological applications [30,31,32], including some catalytic ones [33].…”

β-Formyl- and β-Vinylporphyrins: Magic Building Blocks for Novel Porphyrin Derivatives

“…The contributions of Hans Fischer to the final structure elucidation of protoporphyrin-IX and hemin reported in 1929 and of Woodward in the synthesis of chlorophyll a in 1960 are important highlights in the extraordinary evolution observed afterwards with these molecules [ 1 , 2 , 3 ]. Today, natural and synthetic porphyrin derivatives are recognized as excellent systems to be explored in the development of novel catalysts [ 4 , 5 , 6 , 7 , 8 ], electronic devices [ 9 , 10 , 11 , 12 ], sensors [ 13 , 14 , 15 , 16 ], dyes for photovoltaic solar cells [ 17 , 18 , 19 , 20 , 21 , 22 ] and as therapeutic agents [ 23 , 24 , 25 , 26 , 27 ].…”