Author: Fangfang Wei

Publisher:

Published: 2021

Total Pages: 207

ISBN-13:

Rhodamine derivatives have been found to sense transition metal ions selectively, and the related chemosensing behavior has been studied extensively. Drastic color changes and emission enhancements have been observed as a result of spirolactam ring-opening during the stimulation of certain transition metal ions. Because lanthanide ions are known to prefer higher coordination numbers than transition metal ions, the utilization of this preference is a potential strategy for exploring rhodamine-based chemosensors for selective lanthanide ion sensing. In addition to their application as chemosensors, rhodamine organic dyes can also be incorporated into luminescent transition metal systems and function as photosensitizers for efficient photodynamic therapy (PDT). Furthermore, introducing anti-cancer drugs into rhodamine-transition metal hybrid systems can yield synergistic effect that cause tumor cell death. In this thesis, we focus on the molecular design, characterization, properties, mechanisms, and practical application of rhodamine-based chemosensors and photosensitizers. In Chapter 1, the development of rhodamine-derivative-based chemosensors and rhodamine-containing transition metal complexes is summarized. In Chapter 2, a series of rhodamine-derivative-containing macrocycle compounds are designed, synthesized, and characterized. One macrocycle compound called MR1 was determined to exhibit selective sensing towards Tb( I) and Dy( I) ions with high sensitivity. Based on binding constants and high-resolution mass spectrometry measurement results, sensing mechanisms of MR1 for Tb( I) and Dy( I) ions are proposed. Furthermore, MR1 exhibits high stability and reusability for Ln( I) ion absorption in the solid state. This is the first example of rhodamine derivatives as fluorescent probes for Ln( I) ions. The molecular i structures of the macrocycle compounds are defined as follows: In Chapter 3, a series of rhodamine-appended Ir( I) complexes with different cyclometallating ligands are designed and synthesized, and the relationship between singlet oxygen (1O2) generation efficiency and the energy level of the Ir( I)-based triplet metal-to-ligand charge transfer (3MLCT) excited state (T1') is investigated and correlated. In addition to the direct population of the rhodamine triplet excited state (T1) through the intersystem crossing process, the T1' state acting as a relay could provide an additional pathway to generate the rhodamine T1 state, leading to enhanced 1O2 generation ability. More importantly, this study provides a novel concept for the molecular design and exploration of other photosensitizers for efficient PDT. The molecular structures of rhodamine-containing Ir( I) complexes are defined as follows: In Chapter 4, the mechanism proposed in Chapter 3 is verified to be adaptable not only in an iridium( I) system but also in a platinum( ) system. 1O2 generation ability is significantly enhanced by reducing the energy gap between the Pt( )-iv based 3MLCT state (T1') and rhodamine singlet state (S1). Furthermore, the in vitro PDT effect is significantly enhanced by introducing anti-cancer drugs into a rhodamine-tethered Pt( ) system. The molecular structures of Pt5 with high 1O2 generation ability and Pt6 with the best in vitro PDT performance are defined as follows: