Fine-tuning the luminescence and HOMO-LUMO energy levels in tetranuclear gold(I) fluorinated amidinate complexes
- Abdou, H.E. 3
- Mohamed, A.A. 2
- López-De-Luzuriaga, J.M. 1
- Monge, M. 1
- Fackler Jr. 3
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1
Universidad de La Rioja
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2
Delaware State University
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3
Texas A&M International University
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ISSN: 0020-1669
Any de publicació: 2012
Volum: 51
Número: 4
Pàgines: 2010-2015
Tipus: Article
beta Ver similares en nube de resultadosAltres publicacions en: Inorganic Chemistry
Resum
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-FC 6H 4; 2, 3,5-F 2C 6H 3; 3, 2,4,6-F 3C 6H 2; 4, 2,3,5,6-F 4C 6H) 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 cm -1, corresponding to the vibrational modes of the amidinate ligand. The pentafluorophenyl derivative 5, Ar = C 6F 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 ππ*-πσ* 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. © 2012 American Chemical Society.