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)]þ (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 C, 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 C), 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)]þ (dmbpy = 4,40-dimethyl-2,20-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)]þ, 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.
Federico Polo [Investigation]
|Titolo:||Control of the Mutual Arrangement of Cyclometalated Ligands in Cationic Iridium(III) Complexes. Synthesis, Spectroscopy, and Electroluminescence of the Different Isomers|
|Data di pubblicazione:||2011|
|Appare nelle tipologie:||2.1 Articolo su rivista |