Synthesis and examination of optical and electrochemical properties of quinoline-substituted phthalocyanines

Macrocyclic compounds represent a class of compounds containing nine or more and at least three heteroatoms. The most significant development in macrocycles was Pedersen's work on ethers, which earned him the Nobel Prize in Chemistry. Complexes of natural compounds like cytochromes and chlorophyll, which include macrocyclic complexes such as porphyrins, are intriguing. As a result, there is a considerable body of literature on porphyrins and phthalocyanines. Phthalocyanine, first discovered as a byproduct of synthesizing cyanobenzamide from phthalimide and acetic anhydride in 1907 by Braun and Tcherniac at the Southern Metropolitan Gas Company in London, became a green byproduct in 1907. It was later used as a blue-green dye after the elucidation of its structure in 1934. Phthalocyanines are used as inks to color plastics, metal surfaces, textile products, and in various industrial applications. In recent years, the number of researchers studying the chemical properties of phthalocyanines has significantly increased. New soluble and asymmetric phthalocyanines remain a focal point due to their electrochemical and redox properties, electro and photocatalytic reactivities, and the development of new methods for synthesizing polymeric materials. The central metal ion and peripheral substituents are two major variables. The possibility of placing various metal ions at the center, combined with an infinite variety of substituents, leads to a vast diversity of potentially new and interesting products. Applications of asymmetrically substituted phthalocyanines include polymer and oligomer synthesis, Langmuir-Blodgett (LB) film fabrication, and the use of zinc and aluminum derivatives in photodynamic cancer treatment. These compounds possess liquid crystal properties. The word "phthalocyanine" (Pc) is derived from the Greek words "nafta" (mineral oil) and "siyanin" (dark blue). Phthalocyanines are 16-membered (8 nitrogen and 8 carbon) macrocyclic transition compounds with highly conjugated 18-π electrons. Phthalocyanines are generally considered as condensation products of tetrabenzotetraazeporphyrin or four isoindolin units. Non-metal phthalocyanines are denoted as H2Pc, while metal-containing phthalocyanines are abbreviated as MPc. Many ortho-disubstituted benzene derivatives serve as raw materials for the production of non-metal phthalocyanines. Non-metal phthalocyanines are created through the solvent or solventless cyclotetramerization of phthalonitriles. Solvents like pentanol or 2-(dimethylamino)ethanol are used. Basic catalysts like anhydrous ammonia (NH3) are effective reagents for the cyclotetramerization of phthalonitriles in molten or solvent phases. Phthalocyanine compounds have been used as pigments for many years, characterized by their very fine blue and green colors, particularly after they were first illuminated in 1934. Phthalocyanines have various properties that make them suitable for applications such as photoconductive elements in photocopiers, photodynamic elements in cancer treatment and other medical applications, catalysts for controlling sulfur-containing gas emissions, and the oxidation of saturated hydrocarbons at low temperatures. In 1834, quinoline was obtained from coal tar, and in 1885, isoquinoline was obtained from coal tar. The substance obtained by the pyrolysis of cinchona alkaloid is called quinoline because it resembles quinine compounds. It can fuse a benzene ring with a pyridine ring to form an aromatic polycyclic structure. The most important examples are quinoline, which is a heteroaromatic compound with a boiling point of 239°C, and isoquinoline, which is a heteroaromatic solid with a melting point of 240°C. Quinoline is primarily used as a raw material for various specialty chemicals. Its most important use is as a starting material for 8-hydroxyquinoline, a multifunctional chelating agent and a precursor to pesticides. The 2- and 4-methyl derivatives of quinoline are also used as raw materials for cyanine dyes. Quinoline sulfonamides are used to treat tuberculosis, cancer, and malaria. Various coumarin derivatives have chemotherapeutic and antiallergic effects. Quinoline is mainly used as an intermediate in the production of other products. Quinolines are also used in metallurgical processes, dye production, catalysts, and corrosion inhibitors. Phthalocyanines can exist as oligomers or dimers depending on their structures, the nature of the solvents they dissolve in, and other factors. Two or more phthalocyanine rings are brought together by intermolecular interactions called aggregation. Factors affecting phthalocyanine aggregation include solvent effects, concentration effects, phase state (solid, liquid, gas), an increase in the atomic weight of the central ion, temperature, bidentate ligands, and the combination of the axial position of the central ion. The melting points of the synthesized compounds were determined using a Schorpp MPM-H1 device. 1H NMR and 13C NMR analyses were performed using a VARIAN Infinity Plus model 300 MHz NMR device. FT-IR spectra were recorded with a Perkin Elmer Spectrum Two device, and optical UV measurements were conducted with a Shimadzu UV 2600 device. LC-MS analysis was carried out with a Shimadzu LCMS 9030 device, and MALDI-TOF analysis with a Shimadzu AXIMA Performance device. Alternative voltammetry measurements were performed using a potentiostat/galvanostat (PARSTAT 2273, Princeton Applied Research). Intensive research continues. Phthalocyanines and their metal owners own commercial enterprises as dyes. Phthalocyanines show intense colors and high chemical and thermal stability. The high stability of metallic phthalocyanines makes them suitable for sensorial applications, dyes, catalysis, etc. It provides opportunities for applications in various fields such as Metal complexes of phthalocyanines and porphyrins are used in photodynamic cancer therapy, semiconductor therapy, liquid crystals, and Langmuir-Blodgett films. The potential use of photodynamic cancer therapy (PDT) has been gaining ground recently due to its use in treating certain cancers. In PDT, it is activated using photosynthetic agents for light duration at specific wavelengths with selective elasticities. Metalophthalocyanines, as photosynthetic agents with strong absorption appearing in the region, were used as harvested stabilizers for photodynamic therapy (PDT). Their biggest disadvantage is that phthalocyanines are generally insoluble in organic solvents. However, this creates some difficulties in many applications such as PDT. It has been observed that this difficulty increases its solubility in aqueous media by enabling the formation of quaternary ammonium salts with ammonium, methyl iodide and sulfo groups [80]. Cloxiquinol (5-chloro-8-quinolinol, chloroxyquinoline, kloxiquinin, dermofongin A) and quinolinol derivatives (cliquinol, 5-chloro-7-iodo-8-quinolinol, quinoform quinn ambiicide, vioform) are anti-disinfectant formulations and potent for dermatological diseases. It shows antioxidant properties. Both are members of a group of drugs called 8-quinolinols that inhibit DNA replication, and both are actively used against protozoan and viral infections. Clioquinol is used for the treatment of gastrointestinal disorders, skin infections and fungi, diarrhea, eczema, some bacteria, jock itch, fungi, yeasts, protozoan parasites, and recently tuberculosis. As known, phthalocyanines, with their high molar absorptivity coefficients and absorption in the visible and near-infrared regions, are ideal compounds for applications such as photodynamic therapy, photovoltaics, fluorescence sensors, dyes, and photoelectronic devices. However, for these applications, it is essential that they do not aggregate in solution or film phase. Therefore, in this thesis work, two new phthalocyanine compounds (ZnPc and MnPc) with symmetric quinoline substitutions were synthesized to examine their electrochemical properties using cyclic voltammetry. This was done to determine whether they are suitable for photovoltaic studies. The analysis revealed that the LUMO levels of both compounds are more negative than the conduction band of TiO2, and their HOMO levels are more positive than the Nernst potential of the I-/I3- redox electrolyte (0.4 V vs. NHE). These results indicate that both compounds can efficiently perform electron injection and regeneration in a solar cell. Synthetic dyes like phthalocyanines stand out in terms of ease of synthesis (or production) and cost-effectiveness when compared to poly or single crystal silicon used in commercial photovoltaic cells.