Cyclometalated Ir( iii ) complexes [Ir(tpy)(bbibH 2 )Cl][PF 6 ] and [Ir(tpy)(bmbib)Cl][PF 6 ]: intramolecular π⋯π interactions leading to facile synthesis and enhanced luminescence

• Published in: Dalton transactions : an international journal of inorganic chemistry 2018, Vol.47 (29), p.9779-9786
• Main Authors: Qu, Zhong-Ze, Gao, Tai-Bao, Wen, Jing, Rui, Kai, Ma, Haibo, Cao, Deng-Ke
• Format: Article
• Language: English
• Subjects: Chemical synthesis; Crystal structure; Iridium; Ligands; Luminescence; Molecular chains; NMR; Nuclear magnetic resonance
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/C8DT01922C

Cyclometalated Ir( iii ) complexes [Ir(tpy)(bbibH 2 )Cl][PF 6 ] ( 1·PF6 ) and [Ir(tpy)(bmbib)Cl][PF 6 ] ( 2·PF6 ), and the control complex [Ir(tpy)(mbib)Cl][PF 6 ] ( 3·PF6 ) were synthesized at 135 °C for 10 hours for the former two complexes, while at 190 °C for 24 hours for the latter complex, in which the cyclometalated ligands bbibH 2 − , bmbib − and mbib − incorporate one or two N -methylbenzoimidazole/benzimidazole units in order to explore the influence of the molecular structures of these complexes on their synthesis conditions and luminescence behaviors. The 1 H NMR and crystal structure measurements indicate that both 1·PF6 and 2·PF6 contain intramolecular π⋯π stacking interactions between the non-coordinated N -methylbenzoimidazole/benzimidazole unit and the tpy ligand, but there are no such π⋯π interactions in 3·PF6 . At room temperature, these complexes in CH 3 CN reveal an emission with a combination of 3 MLCT and 3 LC characteristics, occurring at 534 nm with a quantum yield Φ = 39.5% and a lifetime τ = 2.39 μs for 1·PF6 , 536 nm with Φ = 66.4% and τ = 2.94 μs for 2·PF6 , and 558 nm with Φ = 27.0% and τ = 1.75 μs for 3·PF6 . Moreover, both 1·PF6 and 2·PF6 exhibit a TFA-induced luminescence decrease. Based on the comparison among 1·PF6 , 2·PF6 and 3·PF6 , we discuss the influence of intramolecular π⋯π interactions and N imidazole –H/N imidazole –CH 3 units in 1·PF6 and 2·PF6 on their syntheses and luminescence.