A novel H-bonding self-assembly heteromeric molecular duplex bearing host and guest energy transfer units as high-performance electroluminescent material

Abstract

Two oligoamide strands with complementary H-bonding sequences bearing 4HB-NIM and 4HB-CzNI were synthesized. 4HB-NIM and 4HB-CzNI could be self-assembled into a heterodimeric dyad (namely 4HB-NIM-CzNI)via quadruple H-bond interactions. Photoluminescence measurements revealed that in both dilute solution and doped film states, more efficient host-guest energy transfer processes could be observed in the duplex 4HB-NIM-CzNI than the physical blends of the small molecular guest reference compound NIM and the host single strand 4HB-CzNI, which should be attributed to the shortened spatial distances in 4HB-NIM-CzNI. In addition, in comparison with NIM and the guest single strand 4HB-NIM, 4HB-NIM-CzNI shows much higher photoluminescence quantum yield [0.53 vs 0.04 (NIM) or 0.35 (4HB-NIM)] in neat-film state, indicative of the more alleviated concentration quenching of the guest fluorophore in 4HB-NIM-CzNI than 4HB-NIM and NIM. As a consequence, an organic light-emitting diode (OLED) with 4HB-NIM-CzNI as the light-emitting dopant shows much more improved electroluminescent performance than its 4HB-NIM-based reference OLED: with lower turn-on voltage (5.0 vs 5.9 V), higher maximum luminance (5260 vs 2980 cd m−2) and current efficiency (3.5 vs 3.0 cd A−1) as well as lower efficiency roll-off. All these results indicated that the integration of both host and guest fluorophores into H-bonding self-assembled material should be an effective strategy to construct high performance supramolecular electroluminescent materials.