Luminescent Osmium(II) Complexes with Functionalized 2-Phenylpyridine Chelating Ligands: Preparation, Structural Analyses, and Photophysical Properties

Abstract

Cyclometalated osmium complexes with the formulas [Os(ppy) 2(CO) 2] ( 1a, b), [Os(dfppy) 2(CO) 2] ( 2a, b), and [Os(btfppy) 2(CO) 2] ( 3a, b) have been synthesized, for which the chelating chromophores ppyH, dfppyH, and btfppyH denote 2-phenylpyridine, 2-(2,4-difluorophenyl)pyridine, and 2-(2,4-bis(trifluoromethyl)phenyl)pyridine, respectively. The isomers 1a- 3a, possessing an intrinsic C 2 rotational axis as determined by single-crystal X-ray diffraction analysis, underwent slow isomerization in solution at elevated temperature, giving the respective thermodynamic products 1b- 3b, which showed a distinctive coordination arrangement produced by a 180 degrees rotation of one cyclometalated ligand around the Os(II) metal center. In contrast to the case for 1a, b and 2a, which are inert to substitution, complexes 2b and 3b (or 3a) readily react with PPh 2Me to afford the products [Os(dfppy) 2(CO)(PPh 2Me)] ( 4) and [Os(btfppy) 2)(PPh 2Me)] ( 6), in which the incoming PPh 2Me replaced the CO located trans to the carbon atom of one cyclometalated ligand. UV-vis and emission spectra were measured, revealing the lowest excited state for all complexes as a nominally ligand-centered (3)pipi* state mixed with certain MLCT character. Introduction of the electron-withdrawing substituents on the cyclometalated chelates or replacement of one CO ligand with phosphine at the metal center increased the MLCT contribution in the first excited state, giving a broad and featureless emission with greatly enhanced quantum yields.

Homoleptic Tris(Pyridyl Pyrazolate) IrIII Complexes: En Route to Highly Efficient Phosphorescent OLEDs

“…[12] Recent reports indicated that both the cyclometalated ligand (C^N)H and pyridyl azole ligand (N^N)H are capawww.chemeurj.org ble of reacting with reagents M 3 (CO) 12 , M= Ru and Os, to afford good yields of octahedral complexes [MA C H T U N G T R E N N U N G (C^N) 2 (CO) 2 ] and [MA C H T U N G T R E N N U N G (N^N) 2 (CO) 2 ], respectively. [13,14] This implies that the (N^N)H ligand could react with IrCl 3 ·nH 2 O to afford trisubstituted [IrA C H T U N G T R E N N U N G (N^N) 3 ] in a fashion akin to the previously men-…”

Os(II) Based Green to Red Phosphors: A Great Prospect for Solution‐Processed, Highly Efficient Organic Light‐Emitting Diodes

“…Computational Methodology : Calculation on electronic singlet and triplet states of complexes 1–5 was carried out following the methods described in our previous report 26. In brief, the density functional theory (DFT) with B3LYP hybrid functional was applied for the computation.…”

Synthesis, characterization and photophysical properties of quinolin-8-olato chelated osmium(II) organometallics bearing a pendant imine-phenol motif and electrogeneration of trivalent analogue

“…A representative case is shown in Figure 6. Assuming that the band has MLCT character as suggested above, the possible involvement of the 3 MLCT state [15,16,33] incorporating π * (Q) contribution is implicated in the emission process. We also note that the parent organometallics of type 1 do not display any fluorescence in the visible region.…”

“…It was also reported in the literature that a series of compounds derived from 8-hydroxyquinoline showed that they could possess strong antifungal, antiasthmatic and antiplatelet activity [10][11][12][13]. In particular the chemistry of osmium compounds is of current interest in the context of synthesis, reactivity and photophysical properties [1,9,[14][15][16].…”