FROM SYNTHESIS TO APPLICATION:PORPHYRINS AS VERSATILE COMPOUNDS IN ENERGY, SENSING, AND CATALYSIS

Porphyrins, belonging to the class of heterocyclic tetrapyrrolic organic compounds, exhibit notable prevalence in nature. Structurally, these compounds feature a planar arrangement of four interconnected pyrrolic units, forming a flat macrocycle with an extensive conjugated system comprising 18 π-electrons. Their central cavity readily accommodates metal cations, forming stable complexes with transition metal ions. This PhD Thesis delves into the synthesis, characterization, and varied applications of porphyrins. The distinctive colour spectrum of porphyrins, spanning from red to green, originates from robust absorption within the visible spectrum. UV-VIS absorption spectroscopy plays a crucial role in examining their light-harvesting properties. When coupled with electrochemical methods and theoretical calculations, it provides insights into the involved molecular orbitals. Tailoring the chemical structure enables the precise adjustment of the HOMO-LUMO energy gap, resulting in a macrocycle with distinctive absorption and redox properties. This versatility makes it suitable for a wide range of applications, including disease treatment, sensor technology, catalysis, nonlinear optics, and molecular photovoltaics. The synthesis of porphyrins involves conventional approaches such as the Adler-Longo process and Lindsey's one-flask two-step methodology. Challenges in this process include the generation of by-products. Subsequent modifications, including metal coordination and the introduction of functional groups, further refine the porphyrinic core for specific applications. This PhD Thesis presents a comprehensive three-year research project, elucidating the synthesis, characterization, and applications of porphyrins. The exploration encompasses various applications such as Dye-Sensitized Photo-Electrochemical Cells (DSPEC), chemiresistive gas sensors, CO2 reduction catalysis, and second-order Nonlinear Optics (NLO). Each section explores design strategies, synthetic optimization, and performance evaluation, providing an in-depth understanding of the versatile realm of porphyrins.