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Dynamic and Photophysics of Coinage Metal Complexes Containing Phthalazine and Cyanine Ligands

Jamjah, Ali | 2024

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 57846 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Jamali, Sirous; Ghanbari, Bahram
  7. Abstract:
  8. This dissertation focuses on the design, synthesis, and investigation of the photophysical and chemical properties of three groups of novel compounds. In the first part, dual chromophore systems based on the combination of heptamethine cyanines and naphthalimides have been designed and synthesized, which are linked directly at the meso position. This design was carried out to optimize the energy transfer process between chromophores over short distances. In these systems, naphthalimides with various substituents such as diethylamine, diphenylamine, tert-butylphenoxy, bromine, and unsubstituted forms have been utilized to evaluate their effects on the photophysical properties and energy transfer. The results indicate that one of the unique features of these compounds is the excitation energy transfer between the donor naphthalimide units and the acceptor cyanine units. When these compounds are excited at wavelengths corresponding to the local excited states or charge transfer states of the naphthalimide units (280–460 nm), a strong emission band in the near-infrared region (around 850 nm), which is a characteristic feature of conventional cyanine derivatives, is observed. The analysis of these systems has been carried out using nuclear magnetic resonance (NMR) spectroscopy, absorption and emission spectroscopy, and ultrafast transient absorption spectroscopy on the femtosecond scale (in progress). Theoretical studies have also been employed to interpret the data and align them with experimental results. In the second part, heptamethine cyanines with metal-binding groups at the meso position have been designed and synthesized. The primary focus of this part is the direct attachment of pyridine groups at the meso position without the need for carbon-carbon coupling reactions. This design transforms cyanines into integrated ligands with the capability of direct metal binding, especially with copper. The study of the complexation properties of these compounds with copper and the investigation of their structural and photophysical characteristics are the main objectives of this section. The analysis of these systems has been conducted using nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), and Mueller matrix spectroscopy.
    In the third part, A new type of aggregation-induced emission (AIE) luminogen, consisting of a dimeric metal unit and two or three phthalazine ligands, has been introduced. These systems exhibit dynamic behavior of the ligands around the metal centers in solution. Based on variable-temperature nuclear magnetic resonance (NMR) spectroscopy, EXSY experiments, X-ray crystallographic structures, and computational results, three different pathways have been proposed for this dynamic behavior: reversible exchange involving haptotropic shifts, ligand rotation around the dimeric metal unit, and localized movement of ligands on the metal centers. The restriction of these dynamic processes in the aggregated states, in water-acetonitrile solvent mixtures, enhances the AIE phenomenon. Density functional theory (DFT) calculations and NMR analyses revealed that the bright excited states of these molecules are not localized on single molecules. Instead, their emission primarily arises from π-π dimers or oligomers. The morphology and aggregation modes of these compounds in solvent mixtures were studied using transmission electron microscopy (TEM) and concentration-dependent NMR spectroscopy. Furthermore, computational results indicated the presence of a conical intersection (CI) between the ground state
    (S₀) and the
  9. Keywords:
  10. Copper ; Molecular Dynamics ; Aggregation Induced Emission (AIE) ; Conical Intersection ; Zincke Salt ; Heptamethine Cyanine ; Phthalazine

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