Dual emissive cyclometallated iridium complexes: Synthesis, structure and photophysical properties

Herein, we present a new set of dual emissive heteroleptic cationic cyclometallated iridium complexeDepartment of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal By-pass Road, Bhauri, Bhopal, 462 066, Madhya Pradesh, Indias [(L)2Ir(N N)]+ ([1]+ -[3]+) using extended pi-conjugated 1-isopentyl-2-phenyl-1H-naphtho [2,3-d] imidazole (L) as C N chelating ligand. The complexes were characterized using various analytical techniques including single crystal X-ray crystallography. The complexes exhibit dual emission behavior (560 nm, 610 and 670 nm) at ambient condition (298 K). The photophysical properties along with DFT results indicate that the origin of emission bands is not only from the lowest energy T1 state but also there is involvement of other higher energy excited triplet states. The DFT study further reveals that the lowest excited triplet state (T1) has 3MLLCT character, whereas the closely lying other higher excited triplet states are pre-dominately of 3LLCT/3ILCT character which could be responsible for such dual emission.

Automated summary

We synthesized a new set of dual emissive heteroleptic cationic cyclometallated iridium complexes using extended pi-conjugated 1-isopentyl-2-phenyl-1H-naphtho [2,3-d] imidazole as C N chelating ligand. The complexes exhibited dual emission behavior at ambient condition, and the origin of emission bands was found to be not only from the lowest energy T1 state but also there was involvement of other higher energy excited triplet states. The DFT study further revealed the characteristics of these excited states responsible for the dual emission.