Luminescent Osmium(II) Complexes with Functionalized 2-Phenylpyridine Chelating Ligands: Preparation, Structural Analyses, and Photophysical Properties
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(trifluoromet...
Saved in:
Published in | Inorganic chemistry Vol. 47; no. 8; pp. 3307 - 3317 |
---|---|
Main Authors | , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Chemical Society
21.04.2008
|
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | 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° 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 PPh2Me to afford the products [Os(dfppy)2(CO)(PPh2Me)] (4) and [Os(btfppy)2)(PPh2Me)] (6), in which the incoming PPh2Me 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 3ππ* 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. |
---|---|
Bibliography: | istex:905CC06AB5438A60EDC2A223ABFFA601C4037CD3 ark:/67375/TPS-92V02VGM-2 CIF files giving X-ray crystallographic data for complexes 2a,b and 4. This material is available free of charge via the Internet at http://pubs.acs.org. ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0020-1669 1520-510X |
DOI: | 10.1021/ic7023132 |