Synthesis and characterization of metal complexes with various luminescent properties

Abstract

The heteroleptic Ir(III) ($\textbf{1}$) and Pt(II) ($\textbf{2}$) complexes containing the short conjugation length ligand of 2-benzylpyridine and 2,4-pentanedione were synthesized and their luminescent properties were studied. They showed green (530 nm) and blue (430 nm) phosphorescence, respectively. The platinum complex is 56 nm blue-shifted than Pt(ppy)(acac). In the devices of ITO / CuPC / α-NPD / 6% $\textbf{2}$ : mCP / BCP / Alq3 / Cathode, the EL efficiency is comparatively low due to probably the inefficient carrier transfer from host (mCP) to dopant. A novel iridium-platinum heterodinuclear complex $[Ir(ppyFF)_2](\mu_2- \textbf{L})[Pt(ppy)]$ ($\textbf{5}$) [ppyFF = 2-(2,4-difluorophenyl)-pyridine, ppy = 2-phenylpyridine, $\textbf{L}$ = 1,3-bis(3-phenyl-3-oxopropanoyl)benzene dianion] was prepared to investigate the photophysical, electrochemical, and photoinduced energy transfer properties. The properties of iridium mononuclear complex $Ir(ppyFF)_2(H\textbf{L})$ ($\textbf{3}$), homodinuclear complex $[Ir(ppyFF)_2]_2(\mu_2- \textbf{L})$ (4) and reference mononuclear complexes bearing DBM ligand (DBM = dibenzoylmethane), $Ir(ppyFF)_2(DBM)$ ($\textbf{1}$) and Pt(ppy)(DBM) ($\textbf{2}$), were also compared. The absorption spectrum of 5 is found to be the sum of the independent spectra of $\textbf{1}$ and $\textbf{2}$, indicating independent light absorption in each metal-centered moiety in $\textbf{5}$. Complex $\textbf{5}$ exhibits orange-red emission at room temperature and 77 K, which turned out to be originated from $^3LC$ states of the $\textbf{L}$ bridging ligand. It is revealed that both the high energy $Ir(ppyFF)_2$ and Pt(ppy) moieties act as energy donors when linked to the lower energy $\textbf{L}$ bridging ligand, affording an effective energy transfer to the bridging ligand. The electrochemical properties of $\textbf{5}$ indicate that reductions occur on the outside ligand of each metal moiety and the inner bridging ligand, whereas oxidat...