Green to red-emitting neutral iridium complexes with phenyl-indazole type cyclometalating ligand: Synthesis, photophysical properties and DFT calculations br

A series of new heteroleptic iridium(III) complexes of the form Ir(C<^>N)2(N<^>O), Ir(2-hpiz)2(pic) (Ir1), Ir(2- hpiz)2(pyzc) (Ir2), Ir(2-hpiz)2(bop) (Ir3), Ir(2-hpiz)2(btp) (Ir4), Ir(4-fpiz)2(pic)(Ir5), Ir(4-fpiz)2(pyzc) (Ir6), Ir(4- fpiz)2(bop)(Ir7), Ir(4-fpiz)2(btp) (Ir8), Ir(2-bipiz)2(pic) (Ir9), Ir(2-bipiz)2(pyzc) (Ir10), Ir(2-bipiz)2(bop) (Ir11) and Ir(2-bipiz)2(btp) (Ir12) (2-hpiz =2-phenyl-2H-indazole, 4-fpiz =2-(4-fluorophenyl)-2H-indazole, 2-bipiz =2-([1,1 '-biphenyl]-4-yl)-2H-indazole, Hpic =2-picolinic acid, Hpyzc =2-pyrazinecarboxylic acid, Hbop =2- (benzo[d]oxazol-2-yl)phenol, Hbtp =2-(benzo[d]thiazol-2-yl)phenol)), have been synthesized and fully char-acterized. The crystal structures of Ir1, Ir5 and Ir8 have been determined by X-ray analysis and been confirmed to have intermolecular pi pi interactions and intermolecular/intramolecular C-HMIDLINE HORIZONTAL ELLIPSIS pi interactions in the crystal packings. All complexes are green-red emissive with absolute quantum yields of 0.5-2.9 % and lifetimes of 0.21-0.62 mu s in solution at room temperature. The relationship between the structures and photophysical properties of complexes Ir1-Ir12 are considered, and the DFT calculations have been used to further support the deduction. Theoretical calculations reveal that the emission of these complexes can arise from either Ir-C boolean AND N -> C boolean AND N or Ir-C boolean AND N-N boolean AND O -> C boolean AND N charge transfer, depending on the local environment of these complexes

Automated summary

A series of new heteroleptic iridium(III) complexes have been synthesized and characterized, showing green-red emissive properties with absolute quantum yields of 0.5-2.9% and lifetimes of 0.21-0.62 μs in solution at room temperature. The crystal structures of select complexes were determined to have intermolecular pi pi interactions, and theoretical calculations suggest the emission can arise from charge transfer processes.