Pt^II(C^N)(N-donor ligand)Cl-type complexes showing highly sensitive aggregation-induced phosphorescence emission (AIPE) behavior fulfilled by long-size ligands and a distorted molecular configuration

A series of four-coordinated Pt^II(C^N)(N-donor ligand)Cl-type complexes have been synthesized through a combination of long-size C^N-type and N-donor ligands. In addition, by varying the coordinating site in the N-donor ligand, a distorted molecular configuration has been constructed in these complexes. Their photophysical features, aggregation-induced phosphorescence emission (AIPE) behaviors, electrochemical properties and electroluminescence (EL) performance have been investigated in detail. It has been found that their AIE behaviors can be enhanced by both employing long-size ligands, especially the N-donor ligand, and adopting a distorted molecular configuration, furnishing a high AIE factor (α_AIE) of ca. 13.8. Critically, benefitting from their long-size C^N-type and N-donor ligands, these Pt^II(C^N)(N-donor ligand)Cl-type complexes can exhibit very sensitive AIE behaviors in a mixture of THF-H₂O, indicated by their noticeable emission increase with a low H₂O volumetric fraction (f_w) of ca. 0.1 in their THF solution. In solution-processed organic light-emitting diodes (OLEDs), they can achieve a luminance of 6743 cd m⁻² at 13.5 V, a maximum external quantum efficiency (η_ext) of 13.8%, a maximum current efficiency (η_L) of 42.4 cd A⁻¹ and a maximum power efficiency (η_P) of 34.4 lm W⁻¹, respectively. Hence, this research can provide key information for developing phosphorescent complexes with a highly sensitive AIE response and impressive EL ability.