Fine-Tuning the Luminescence and HOMO鈥揕UMO Energy Levels in Tetranuclear Gold(I) Fluorinated Amidinate Complexes

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• 作者：Hanan E. Abdou ; Ahmed A. Mohamed ; Jos茅 M. L贸pez-de-Luzuriaga ; Miguel Monge ; John P. Fackler ; Jr.
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：February 20, 2012
• 年：2012
• 卷：51
• 期：4
• 页码：2010-2015
• 全文大小：296K
• 年卷期：v.51,no.4(February 20, 2012)
• ISSN：1520-510X

文摘

Tetranuclear gold(I) fluorinated amidinate complexes have been synthesized and their photophysical properties and structures described. DFT calculations were carried out to illustrate how a minor change in the ligand resulted in a loss of emission in the perfluorophenyl amidinate complex compared with nonfluorinated phenyl amidinate complexes reported previously. The fluorinated complexes reported here [Au(ArN)₂C(H)]₄ (1, Ar = 4-FC₆H₄; 2, 3,5-F₂C₆H₃; 3, 2,4,6-F₃C₆H₂; 4, 2,3,5,6-F₄C₆H) emit in the blue-green region at 470, 1, 478, 2, 508, 3, and 450 nm, 4, by excitation at ca. 375 nm at room temperature with nanosecond lifetimes. The emissions observed at 77 K in the solid state show structured emission for complexes 1 and 2, with a vibrational spacing of ca. 1200 and 1500 cmp>鈥?p>, corresponding to the vibrational modes of the amidinate ligand. The pentafluorophenyl derivative 5, Ar = C₆F_5, shows no photoluminescence in the solid state nor in the solution. This result is different from results in which the pentafluorophenyl group is attached to a phenylpyridine ligand in an Ir(III) complex and other organics. This quenching appears to be related to a nonradiative de-excitation process caused by the 蟺蟺*鈭捪€蟽* crossover in the excited state of the pentafluorophenyl amidinate ligand. With increasing numbers of fluorine atoms, there is a progressive decrease in the contribution of the amidinate ligands to the corresponding HOMO orbital. There also is a slight decrease in the ligand contribution to the LUMO with increased numbers of fluorine atoms and an exchange of the character of the orbitals of the gold centers.