Synthesis of phthalocyanine functionalized with carboxylic acid groups

Abstract

Phthalocyanines, which are tetrapyrrole derivatives, have a strong and bright blue-green pigment. Synthetic compounds occur with an elevated degree of chemical and physical stability with their 18-π electrons and strong conjugation. Phthalocyanine has been the focus of research since its discovery because of its unique photochemical and photophysical characteristics, as well as its capacity to be derivatized with a variety of substitution groups. They have been extensively researched owing to their wide diversity, chemical and heat stability, variable redox properties, and vivid color. These unique qualities attract attention, which is why they are employed in a variety of applications. Also, because of its biological qualities, it is utilized in the field of materials as a high-tech material and in related applications. There are various fields in which phthalocyanine takes place. Chemical and gas sensors, dye sensitized solar cells (DSSCs), electrochromic materials, nonlinear optics, organic field-effect transistors (OFET), photocatalysts for electrochemical processes, and Langmuir-Blodgett films can be given, for example. Additionally, biological applications such as photodynamic therapy (PDT), anticancer, antibacterial, peptide binding, and DNA interactions are becoming very popular, as studies have been done recently. For these applications, some disadvantages, like aggregation propensity and lack of solubility, become crucial because many Pcs possess limited solubility in regular organic solvents and have a tendency to aggregate. Thankfully, the phthalocyanine structure's substituted groups and metal atoms allow for easy modification of its chemical and physical characteristics as well as the creation of several novel characteristics. By adding several metal atoms into the macro ring center or binding different substituent groups like bulky groups, alkyl or alkoxy groups enhance the Pc's properties. Substitution at peripheral or axial positions helps to increase solubility. It is important to know what kind of groups are binding at these positions. For example, electron-withdrawing groups not only improve the solubility properties but also gain stability in the structure, which leads to a good catalyst. In this work, there were synthesized fluorinated tetra-substituted phthalocyanines in peripheral positions with derivatized carboxylic acid in para positions. The raising qualities of carboxylic groups and fluorine were used in the design of these compounds. Initially, there was chosen 4-(2',3',4',5',6'-(pentafluorobenzyloxy)phthalonitrile as a ligand and synthesized 2,9/10,16/17,23/24-tetrakis(2',3',4',5',6'-pentafluorobenzyloxy) metal phthalocyanine with three different metal atoms: zinc (2), cobalt (3), and copper (4) through this ligand. Reactions have occurred with related metal salts and took place in a solvent-free environment. Their caharcterization has been measured with FT-IR, 1H-NMR, 13C-NMR, 19F-NMR, UV-Vis, and MALDI-TOF mass spectroscopy techniques. Following the synthesis of fluorinated phthalocyanines with different metals, carboxylic acid groups were added in the para position. These synthesises benefited from a para-selective nucleophilic substitution reaction. With this reaction, carboxylic groups took the place of the para-fluoro substitution group and obtained 2,9/10,16/17,23/24-tetrakis [(2',3',5',6'-tetrafluoro-4'-carboxyethio-benzyloxy) metal phthalocyanine (2a, 3a, and 4a). Their behaviors were investigated in terms of antioxidant, antidiabetic, antimicrobial, aPDT, and anti-biofilm activities, in addition to common characterization techniques such as FT-IR, 1H-NMR, 13C-NMR, 19F-NMR, UV-Vis, and MALDI-TOF mass spectroscopy. The results demonstrated that the final compounds (2a, 3a, and 4a) have significant anti-biofilm, aPDT, antioxidant, antidiabetic, and antibacterial properties. These findings indicate the compounds' potential as therapeutic agents for many kinds of uses, such as antibacterial medicines, antidiabetic medications, and antioxidant medicines.