| Photodynamic therapy（PDT）has emerged as an important therapeutic strategy for cancer treatment due to its noninvasive property and precise spatial and temporal control ability.The intelligent design of photosensitizers（PSs）is critical to the PDT effect.Transition-metal Ir（Ⅲ）complexes have been widely used as PDT agents for their efficient intersystem crossing（ISC）ability,excellent photochemical stability and variable photophysical properties.The previous reports mainly focused on mononuclear Ir（Ⅲ）complexes with low molar absorption coefficient and weak 1O2 generation ability,which largely restrict the PDT effect.Additional metal centers are introduced by changing or modifying the structure of different ligands to obtain multinuclear Ir（Ⅲ）complexes,resulting in enhanced 1O2 generation ability.Conventional Ir（Ⅲ）complexes possess high dark toxicity and poor water solubility.Current research mainly focuses on the fabrication of nanoparticles（NPs）with negligible dark toxicity and good water solubility by introducing amphiphilic polymers or nanocarriers.However,these reported systems suffer from sophisticated synthesis,high cost and potential biotoxicity.In addition,the absorption of Ir（Ⅲ）complexes is often located at the visible region,leading to the unnecessary light damage to biological tissues.Therefore,it is significance to construct carrier-free multinuclear Ir（Ⅲ）complex NPs with long-wavelength absorption as PSs for PDT.In this thesis,a series of cationic multinuclear Ir（Ⅲ）complex NPs with near-infrared emission were constructed as PSs based on a facile self-assembly method by selecting and modifying of auxiliary ligands reasonably.The relationship between the structure and properties of Ir（Ⅲ）complexes was studied by analyzing their photophysical properties.The specific research contents are as follows:（1）The rigid 1,3,5-triphenyl benzene was chosen as a bridge auxiliary ligand to obtain mono-and trinuclear aggregation-induced emission（AIE）cationic Ir（Ⅲ）complexes with near-infrared emission.The corresponding carrier-free NPs with good water solubility were obtained by self-assembly methods in the absence of any pre-modification step or auxiliary agent.The absorption of PSs at the long wavelength was significantly enhanced due to the introduction of multiple metal centers and extendedπ-conjugated backbone,resulting in the increased 1O2 generation ability.The formation of NPs also further improved the generation ability of 1O2.Cell-based assays corroborate that the trinuclear PS3 NPs possess superior cellular uptake,good biocompatibility and excellent phototoxicity.This work offers a new tactic to develop high-efficiency PSs for PDT.（2）The porphyrin structure was selected as bridging auxiliary ligand to construct mono-and tetra-nuclear Ir（Ⅲ）complexes and their corresponding self-assembled carrier-free NPs with near-infrared emission.The introduction of porphyrin units successfully broadened the spectral absorption range of Ir（Ⅲ）complexes,overcame the inherent short wavelength absorption defect of Ir（Ⅲ）complexes,which is advantageous for matching long-wavelength excitation and reducing the light damage to normal tissues.The 1O2generation ability was further enhanced by introducing the multiple metal Ir（Ⅲ）centers.The strategy of introducing units with long-wavelength absorption into multinuclear Ir（Ⅲ）complexes by covalent linkage successfully combines the respective advantages of organic and transition metal complexes PSs,opens a new space for the development of efficient PSs with long wavelength absorption,and provides a foundation for the wide application of transition metal complexes PSs. |
