Synthesis and luminescent properties of various organometallic complexes

Abstract

This thesis deals with luminescent materials based on metal complexes and carborane cluster. The design and synthesis of metal acomplexes and carborane clusters based new luminescent materials will be first pursued and then the characteristics of such materials can be commonly applied to the organic light emitting diodes (OLEDs). The design and synthesis of new organometallic lumophores with outstanding photoelectronic properties will be first pursued by molecular engineering approach and then the characteristics of the lumophores will be commonly applied to the photoelectronic device such as OLED. Heteroleptic tris-cyclometalated Ir(III) complexes supported by the o-carboranyl-pyridine (CBpy) as a novel C^N chelating ligand were synthesized and characterized. An X-ray diffraction study unequivocally revealed that the two C^N ligands are in a trans disposition of pyridine rings, featuring mer-like configuration in both complexes. The impact of the CBpy ligand on the photophysical and electrochemical properties of complexes was investigated. It was shown from experimental and theoretical studies that while the CBpy ligand contributes to the electronic stabilization of complexes, the photophysical properties are dominated by 2-arylpyridine ligands, such as ppy and dfppy. Heteroleptic (C^N)2Ir(acac) (C^N = 5-CBbtp (1); 4-CBbtp (2)) complexes bearing o-carborane substituted C^N-chelating ligand were prepared and characterized. While 1 exhibits a deep red phosphorescence band centered at 644 nm, 2 is non-emissive in solution at room temperature. In contrast, both complexes are emissive at 77 K and in the solid state. Electrochemical and theoretical studies suggest that while carborane substitution on the 5-position of pyridine ring lowers the 3MLCT energy by a large contribution to LUMO delocalization, which in turn assigns the lowest triplet state of 1 as [$d_{/Pi}(Ir) - {/Pi}*(C^N)$] 3MLCT in character, the substitution on the 4-position of pyridine ring lowers ...