Control of the mutual arrangement of cyclometalated ligands in cationic iridium(III) complexes. Synthesis, spectroscopy, and electroluminescence of the different isomers
Articolo
Data di Pubblicazione:
2011
Citazione:
Control of the mutual arrangement of cyclometalated ligands in cationic iridium(III) complexes. Synthesis, spectroscopy, and electroluminescence of the different isomers / J.M. Fernaindez-Hernaindez, C.H. Yang, J.I. Beltrain, V. Lemaur, F. Polo, R. Frohlich, J. Cornil, L. De Cola. - In: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. - ISSN 0002-7863. - 133:27(2011), pp. 10543-10558. [10.1021/ja201691b]
Abstract:
Synthetic control of the mutual arrangement of the cyclometalated ligands (C^N) in Ir(III) dimers, [Ir(C^N)2Cl]2, and cationic bis-cyclometalated Ir(III) complexes, [Ir(C^N)2(L^L)]+ (L^L = neutral ligand), is described for the first time. Using 1-benzyl-4-(2,4-difluorophenyl)-1H-1,2,3-triazole (HdfptrBz) as a cyclometalating ligand, two different Ir(III) dimers, [Ir(dfptrBz) 2Cl]2, are synthesized depending on the reaction conditions. At 80 °, the dimer with an unusual mutual cis-C,C and cis-N,N configuration of the C^N ligands is isolated. In contrast, at higher temperature (140 °), the geometrical isomer with the common cis-C,C and trans-N,N arrangement of the C^N ligand is obtained. In both cases, an asymmetric bridge, formed by a chloro ligand and two adjacent nitrogens of the triazole ring of one of the cyclometalated ligands, is observed. The dimers are cleaved in coordinating solvents to give the solvento complexes [Ir(dfptrBz) 2Cl(S)] (S = DMSO or acetonitrile), which maintain the C^N arrangement of the parent dimers. Controlling the C^N ligand arrangement in the dimers allows for the preparation of the first example of geometrical isomers of a cationic bis-cyclometalated Ir(III) complex. Thus, N,N-trans-[Ir(dfptrBz) 2(dmbpy)]+ (dmbpy = 4,4′-dimethyl-2,2′- bipyridine), with cis-C,C and trans-N,N arrangement of the C^N ligands, as well as N,N-cis-[Ir(dfptrBz)2(dmbpy)]+, with cis-C,C and cis-N,N C^N ligand orientation, are synthesized and characterized. Interestingly, both isomers show significantly different photophysical and electroluminescent properties, depending on the mutual arrangement of the C^N ligands. Furthermore, quantum chemical calculations give insight into the observed photophysical experimental data.
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
J.M. Fernaindez-Hernaindez, C.H. Yang, J.I. Beltrain, V. Lemaur, F. Polo, R. Frohlich, J. Cornil, L. De Cola
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