Control of Intramolecular 蟺鈥撓€ Stacking Interaction in Cationic Iridium Complexes via Fluorination of Pendant Phenyl Rings
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- 作者：Lei He ; Dongxin Ma ; Lian Duan ; Yongge Wei ; Juan Qiao ; Deqiang Zhang ; Guifang Dong ; Liduo Wang ; Yong Qiu
- 刊名：Inorganic Chemistry
- 出版年：2012
- 出版时间：April 16, 2012
- 年：2012
- 卷：51
- 期：8
- 页码：4502-4510
- 全文大小：432K
- 年卷期：v.51,no.8(April 16, 2012)
- ISSN：1520-510X
文摘
Intramolecular 蟺鈥撓€ stacking interaction in one kind of phosphorescent cationic iridium complexes has been controlled through fluorination of the pendant phenyl rings on the ancillary ligands. Two blue-green-emitting cationic iridium complexes, [Ir(ppy)2(F2phpzpy)]PF6 (2) and [Ir(ppy)2(F5phpzpy)]PF6 (3), with the pendant phenyl rings on the ancillary ligands substituted with two and five fluorine atoms, respectively, have been synthesized and compared to the parent complex, [Ir(ppy)2(phpzpy)]PF6 (1). Here Hppy is 2-phenylpyridine, F2phpzpy is 2-(1-(3,5-difluorophenyl)-1H-pyrazol-3-yl)pyridine, F5phpzpy is 2-(1-pentafluorophenyl-1H-pyrazol-3-yl)-pyridine, and phpzpy is 2-(1-phenyl-1H-pyrazol-3-yl)pyridine. Single crystal structures reveal that the pendant phenyl rings on the ancillary ligands stack to the phenyl rings of the ppy ligands, with dihedral angles of 21掳, 18掳, and 5.0掳 between least-squares planes for complexes 1, 2, and 3, respectively, and centroid-centroid distances of 3.75, 3.65, and 3.52 脜 for complexes 1, 2, and 3, respectively, indicating progressively reinforced intramolecular 蟺鈥撓€ stacking interactions from complexes 1 to 2 and 3. Compared to complex 1, complex 3 with a significantly reinforced intramolecular face-to-face 蟺鈥撓€ stacking interaction exhibits a significantly enhanced (by 1 order of magnitude) photoluminescent efficiency in solution. Theoretical calculations reveal that in complex 3 it is unfavorable in energy for the pentafluorophenyl ring to swing by a large degree and the intramolecular 蟺鈥撓€ stacking interaction remains on the lowest triplet state.