Emissive Osmium(II) Complexes with Tetradentate Bis(pyridylpyrazolate) Chelates

Abstract

A tetradentate bis(pyridylpyrazolate) chelate, L, is assembled by connecting two bidentate 3-(trifluoromethyl)-5-(2-pyridyl)pyrazole chelates at the 6 position of the pyridyl fragment with a phenylamido appendage. This chelate was then utilized in the synthesis of three osmium(II) complexes, namely, [Os(L)(CO)2] (4), [Os(L)(PPh2Me)2] (5), and [Os(L)(PPhMe2)2] (6). Single-crystal X-ray structural analyses were executed on 4 and 5 to reveal the bonding arrangement of the L chelate. Phosphine-substituted derivatives 5 and 6 are highly emissive in both solution and the solid state, and their photophysical properties were measured and discussed on the basis of computational approaches. For application, fabrication and analysis of organic light-emitting diodes (OLEDs) were also carried out. The OLEDs using 5 and 6 as dopants exhibit saturated red emission with maximum external quantum efficiencies of 9.8% and 9.4%, respectively, which are higher than that of the device using [Ir(piq)3] as a red-emitting reference sample. Moreover, for documentation, 5 and 6 also achieve a maximum brightness of 19540 cd·m(-2) at 800 mA·cm(-2) (11.6 V) and 12900 cd·m(-2) at 500 mA·cm(-2) (10.5 V), respectively.

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

“…22). This strategy has proven to enhance solubility and processability during device fabrication as demonstrated for a related Os(II) compound [98]. …”

Fluorination‐controlled Aggregation and Intermolecular Interactions in Pt(II) Complexes with Tetradentate Luminophores

“…Some features of triplet emitters derived from transition metal complexes include tunable emission color through the entire visible spectrum, microsecond‐range excited‐state lifetimes, high stability and efficiency, which renders them as suitable dopants for optoelectronic devices . Several reports describe the use of Re(I),, Ru(II), Os(II),, Ir(III), Au(III),, and Pt(II),,, complexes, due to their efficient heavy‐atom‐induced singlet‐to‐triplet intersystem crossing as well as their large enhancement of radiative decay rate from the triplet manifold which theoretically enables up to 100 % electroluminescence efficiencies ,. Pt(II) complexes have also attracted considerable attention as a result of their biological properties, such as antitumoral cytotoxicity, DNA intercalation, protein binding abilities, applications in bioimaging and phototherapy .…”

Photophysical and Cellular Imaging Studies of Brightly Luminescent Osmium(II) Pyridyltriazole Complexes

“…32,33 More commonly reported are charge-neutral complexes with anionic 1,2,4-triazolate or pyrazolate ligand systems which are frequently combined with phosphine, arsine or carbonyl donors. [34][35][36][37][38] We have recently reported a series of tris-bidentate triazole-based osmium(II) complexes and their application in light-emitting electrochemical cell devices 39,40 and the bis-tridentate complex [Os(btzpy) 2 ] 2+ (btzpy = 2,6-bis(1-phenyl-1,2,3triazol-4-yl)pyridine) which exhibits phosphorescence at 595 nm. This latter complex was shown to be readily taken up by HeLa and U2OS cancer cell lines and displays a high degree of mitochondrial localisation.…”