Cross-couplings in the elaboration of luminescent bis-terpyridyl iridium complexes: the effect of extended or inhibited conjugation on emission
作者:Wendy Leslie、Andrei S. Batsanov、Judith A. K. Howard、J. A. Gareth Williams
DOI:10.1039/b313638h
日期:——
The utility of Suzuki cross-coupling methodology for the in situ elaboration of bromo-functionalised bis-terpyridyl iridium(III) complexes has been explored. The complex [Ir(tpy)(tpy-ϕ-Br)]3+ tpy-ϕ-Br = 4′-(4-bromophenyl)-2,2′:6′,2″-terpyridine} undergoes palladium-catalysed cross-coupling with aryl boronic acids to yield biaryl-substituted complexes directly. The biphenyl and 4-cyanobiphenyl-substituted products display relatively intense, long-lived (τ > 100 µs) yellow emission in degassed aqueous solution at room temperature, assigned to a 3π–π* state. A 4-aminobiphenyl-substituted analogue displays an additional low energy absorbance band, attributed to an intraligand charge-transfer (ILCT) excited state, and is scarcely emissive under the same conditions. The iridium(III) complex of 4′-mesityl-terpyridine is also reported. Its emission is much shorter-lived, with a spectral profile resembling that of unsubstituted [Ir(tpy)2]3+, confirming the need for the attainment of a roughly coplanar geometry for stabilisation of the 3π–π* excited state.
已探索铃木交叉耦合方法在原位构建溴功能化双四吡啶铱(III) 配合物的实用性。配合物 [Ir(tpy)(tpy-ϕ-Br)]3+ tpy-ϕ-Br = 4′-(4-溴苯基)-2,2′:6′,2″-四吡啶} 通过钯催化与芳基硼酸发生交叉耦合,直接生成二芳基取代的配合物。在去气的水溶液中,双苯基和 4-氰基双苯基取代的产物在室温下表现出相对强烈、长寿命(τ > 100 µs)的黄色发射,归因于 3π–π* 状态。一个 4-氨基双苯基取代的类似物显示出额外的低能吸收带,归因于配体内电荷转移(ILCT)激发态,并在相同条件下发射极少。还报告了 4′-美克酰基-四吡啶的铱(III) 配合物。它的发射寿命较短,其光谱特征类似于未取代的 [Ir(tpy)2]3+,确认了为稳定 3π–π* 激发态而需达到大致共面几何形状的必要性。