In order to enhance the photoluminescence of cyclometalated iridium(III) complexes, which are potentially useful for biolabeling and bioimaging, a series of benzyl ether branched dendritic moieties with carbazolyl termini were introduced to the cyclometalating CâN ligands of the heteroleptic Ir(III) complexes. The complexes also contain a bidentate bipyridine ligand with a carboxyl group for further bioconjugation or functionalization. The dendritic benzyl ether moieties with carbazolyl peripheral groups have demonstrated a dual function as both a Förster resonance energy transfer (FRET) donor and an oxygen shield to the Ir(III) complex core. The peripheral carbazolyl groups absorb UV light more intensively and transfer energy efficiently to the Ir(III) complex core via the FRET effect, and thus the photoluminescence of the Ir(III) complex at around 560 nm is significantly enhanced. Furthermore, the benzyl ether dendrimers containing carbazolyl termini can shield the Ir(III) complex core to weaken the oxygen quenching effect, which leads to a further enhancement of the PL of the Ir(III) complex.
为了增强环
金属化
铱(III)络合物的光致发光性能,该络合物在
生物标记和
生物成像中具有潜在应用,研究人员在异
配体铱(III)络合物的环
金属化CâN
配体上引入了一系列带有
咔唑末端的
苄醚支链树状单元。这些络合物还包含一个带有羧基的双齿联
吡啶配体,便于进一步的
生物共轭或功能化。这些带有
咔唑侧基的
苄醚树枝状单元展现了双重功能,既作为福尔斯特共振能量转移(FRET)的供体,又能为Ir(III)络合物核心提供氧屏蔽。外围的
咔唑基团更强烈地吸收紫外光,并通过FRET效应有效地将能量转移到Ir(III)络合物核心,从而显著增强了Ir(III)络合物在约560 nm处的光致发光。此外,含有
咔唑末端的
苄醚树枝状聚合物能够屏蔽Ir(III)络合物核心,从而减弱氧的猝灭效应,进一步增强了Ir(III)络合物的光致发光。