Liu Bingqing, Lystrom Levi, Brown Samuel L, Hobbie Erik K, Kilina Svetlana, Sun Wenfang
Department of Chemistry and Biochemistry , North Dakota State University , Fargo , North Dakota 58108-6050 , United States.
Materials and Nanotechnology Program , North Dakota State University , Fargo , North Dakota 58108-6050 , United States.
Inorg Chem. 2019 May 6;58(9):5483-5493. doi: 10.1021/acs.inorgchem.8b03162. Epub 2019 Apr 23.
Ten biscyclometalated monocationic Ir(III) complexes were synthesized and studied to elucidate the effects of extending π-conjugation of the diimine ligand (N^N = 2,2'-bipyridine in Ir1, 2-(pyridin-2-yl)quinoline in Ir2, 2-(pyridin-2-yl)[6,7]benzoquinoline in Ir3, 2-(pyridin-2-yl)-[7,8]benzoquinoline in Ir4, phenanthroline in Ir5, benzo[ f][1,10]phenanthroline in Ir6, naphtho[2,3- f][1,10]phenanthroline in Ir7, 2,2'-bisquinoline in Ir8, 3,3'-biisoquinoline in Ir9, and 1,1'-biisoquinoline in Ir10) via benzannulation at 2,2'-bipyridine on the excited-state properties and reverse saturable absorption (RSA) of these complexes. Either a bathochromic or a hypsochromic shift of the charge-transfer absorption band and emission spectrum was observed depending on the benzannulation site at the 2,2'-bipyridine ligand. Benzannulation at the 3,4-/3',4'-position or 5,6-/5',6'-position of 2,2'-bipyridine ligand or at the 6,7-position of the quinoline ring on the N^N ligand caused red-shifted charge-transfer absorption band and emission band for complexes Ir2, Ir8, Ir10 vs Ir1 and Ir3 vs Ir2, while benzannulation at the 4,5-/4',5'-position of 2,2'-bipyridine ligand or at the 7,8-position of the quinoline ring on the N^N ligand induced a blue shift of the charge-transfer absorption and emission bands for complex Ir9 vs Ir1 and Ir4 vs Ir2. However, benzannulation at the 2,2',3,3'-position of 2,2'-bipyridine or 5,6-position of phenanthroline ligand had no impact on the energy of the charge-transfer absorption band and emission band of complexes Ir5-Ir7 compared with those of Ir1. The observed phenomenon was explained by the frontier molecular orbital (FMO) symmetry analysis. Site-dependent benzannulation also impacted the spectral feature and intensity of the triplet transient absorption spectra and lifetimes drastically. Consequently, the RSA strength of these complexes varied with a trend of Ir7 > Ir5 ≈ Ir6 ≈ Ir1 > Ir3 > Ir2 > Ir10 > Ir4 > Ir8 > Ir9 at 532 nm for 4.1 ns laser pulses.
合成并研究了十种双环金属化单阳离子 Ir(III) 配合物，以阐明通过在 2,2'-联吡啶上进行苯并环化来扩展二亚胺配体（在 Ir1 中 N^N = 2,2'-联吡啶，在 Ir2 中为 2-(吡啶-2-基)喹啉，在 Ir3 中为 2-(吡啶-2-基)[6,7]苯并喹啉，在 Ir4 中为 2-(吡啶-2-基)-[7,8]苯并喹啉，在 Ir5 中为菲咯啉，在 Ir6 中为苯并[f][1,10]菲咯啉，在 Ir7 中为萘并[2,3-f][1,10]菲咯啉，在 Ir8 中为 2,2'-双喹啉，在 Ir9 中为 3,3'-联异喹啉，在 Ir10 中为 1,1'-联异喹啉）的 π 共轭对这些配合物的激发态性质和反饱和吸收 (RSA) 的影响。根据 2,2'-联吡啶配体上的苯并环化位点，观察到电荷转移吸收带和发射光谱的红移或蓝移。在 2,2'-联吡啶配体的 3,4-/3',4'-位或 5,6-/5',6'-位或 N^N 配体上喹啉环的 6,7-位进行苯并环化，导致配合物 Ir2、Ir8、Ir10 相对于 Ir1 以及 Ir3 相对于 Ir2 的电荷转移吸收带和发射带发生红移，而在 2,2'-联吡啶配体的 4,5-/4',5'-位或 N^N 配体上喹啉环的 7,8-位进行苯并环化，导致配合物 Ir9 相对于 Ir1 以及 Ir4 相对于 Ir2 的电荷转移吸收和发射带发生蓝移。然而，与 Ir1 相比，在 2,2'-联吡啶的 2,2',3,3'-位或菲咯啉配体的 5,6-位进行苯并环化对配合物 Ir5 - Ir7 的电荷转移吸收带和发射带的能量没有影响。通过前沿分子轨道 (FMO) 对称性分析解释了观察到的现象。位点依赖性苯并环化还极大地影响了三重态瞬态吸收光谱的光谱特征和强度以及寿命。因此，对于 4.1 ns 的激光脉冲，这些配合物在 532 nm 处的 RSA 强度变化趋势为 Ir7 > Ir5 ≈ Ir6 ≈ Ir1 > Ir3 > Ir2 > Ir10 > Ir4 > Ir8 > Ir9。
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