TY - JOUR
T1 - Luminescent Osmium(II) Complexes with Functionalized 2-Phenylpyridine Chelating Ligands
T2 - Preparation, Structural Analyses, and Photophysical Properties
AU - Hwang, Kwun-Chi
AU - Chen, Jing-Lin
AU - Chi, Yun
AU - Lin, Chun-Wei
AU - Cheng, Yi-Ming
AU - Lee, Gene-Hsiang
AU - Chou, Pi-Tai
AU - Lin, Sue-Yi
AU - Shu, Ching-Fong
PY - 2008/4/1
Y1 - 2008/4/1
N2 - 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 C2 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.
AB - 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 C2 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.
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U2 - 10.1021/ic7023132
DO - 10.1021/ic7023132
M3 - RGC 21 - Publication in refereed journal
SN - 0020-1669
VL - 47
SP - 3307
EP - 3317
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 8
ER -
