Porfirin, orto-karboran ve BODIPY konjuge sistemi: Sentez ve fotolüminesans özellikleri

In the last decades, scientists are highly insterested in the energy transfer process and mimicing this natural process by the way of design, synthesis, characteriation and application of novel artificial molecules. To mimic efficient energy transfer systems like chlorophylls, many model compounds have been synthesized and studied. For this purpose, new molecules bearing donor (D)-acceptor (A) moities are prepared. In this thesis, energy transfer process is investigated via three functional groups such as; porphyrin ring (zinc tetraphenylporphyrin), BODIPY (ethynyl BODIPY) and ortho-carborane. Porphyrins are heterocyclic compounds which include four pyrrole rings joined together through methine bridges. They show strong absorption and emission in the visible region and tunable redox properties which lead to promising applications. They can be readily modified by the substitution on the aromatic ring, either by electron-withdrawing or electron-donating groups, to gain unique optical or electronic properties. Porphyrin systems, as energy acceptors, have been covalently linked to donor units, such as organic compounds that have fluorescent properties, to mimic photosynthetic devices and to develop new efficient molecular systems. The porphyrin core easily allows attaching donor units near the periphery, directly or via spacers, and such a light-harvesting system has a great potential as a suitable system for the functioning of antennae. Among the well-known fluorophores, compounds based on the BODIPY core are preferred because they show significant characteristics, such as a high excitation coefficient, high quantum yield, good solubility in most organic solvents, and excellent stability. Small modifications to BODIPY structures, facilitate tuning of their fluorescence properties, and these types of structures are widely used to label proteins, sensor applications and energy transfer cassettes. ortho-carborane (1,2-dicarba-closo-dodecaborane), a subclass of boron cluster compounds, has unique features based on its icosahedral structure and high polarisable sigma-aromatic character. The cluster has a significantly unsymmetrical electron density distribution, which shows electron-withdrawing character when it is bonded through C vertices. It has been reported that structural parameters obtained by X-ray diffraction studies from numerous carboranes and metallacarboranes indicate that the C1-C2 distances vary considerably if substituents with lone pairs are bonded exo-cluster to the C1 or C2. Computational methods suggested that the cause of the elongation is the transfer of electron density from the available lone pairs on the substituents to the antibonding orbitals on carbon, producing a decrease in the C1-C2 bond order and, thereby, an increase in the C1-C2 distance. In the last decade, several research groups have been interested in combining organic π-conjugated systems with carborane derivatives, to modulate either one or more of their electronic, optical, and photophysical properties. o-Carborane derivatives linked to the π-conjugated groups at the C1 (and/or C2) position have shown aggregation-induced emission (AIE) or aggregation-enhanced emission (AEE) properties. Intramolecular charge transfer from the π-conjugated groups to the C1−C2 bond of o-carborane quenches the emission in solution, but the reduction in emission can be reversed by freezing the C1−C2 bond vibration in the aggregates. In this study, dyad molecule is synthesized through Sonogashira coupling reaction of ZnTPP and BODIPY units. Selective exciation of BODIPY showed an efficient energy transfer from BODIPY unit to ZnTPP. Therefore, ZnTPP acts as energy acceptor (A) and BODIPY acts as energy donor (D). In the case of target triad molecule, a V-shaped ZnTPP- o-carborane- BODIPY structure, o-carborane serves as an photo-induced charge transfer compound unit and quenches the energy transfer. The precursor molecules and target structures are all characterized by UV, FT-IR, NMR and MALDI-TOF-MS. Additionally, X-Ray crystal structure of triad molecule is solved and electrochemical methods such as CV and SWV are used to determine their redox properties.