A series of [(R′-C^N^C-R′′)Pt(L)] complexes with doubly deprotonated cyclometalated R′-C^N^C-R′′ ligands (R′-C^N^C-R′′=2,6-diphenylpyridine derivatives) functionalized with carbazole, fluorene, or thiophene unit(s) have been synthesized and their photophysical properties studied. The X-ray crystal structures reveal extensive intermolecular π⋅⋅⋅π and CH⋅⋅⋅π interactions between the cyclometalated C^N^C ligands. Compared to previously reported cyclometalated platinum(II) complexes [(C^N^C)Pt(L)], which are non-emissive in solution at room temperature, the carbazole-, fluorene- and thiophene-functionalized [(R′-C^N^C-R′′)Pt(L)] (L=DMSO 1–9, CNAr, 1 a–9 a) complexes are emissive in solution at room temperature with λmax at 564–619 nm and Φ=0.02–0.26. The emissions of the [(R′-C^N^C-R′′)Pt(L)] complexes are attributed to electronic excited states with mixed 3MLCT and 3IL character. The carbazole/fluorene/thiophene unit(s) allow the tuning of the electronic properties of the [(R′-C^N^C-R′′)Pt] moiety, with the emission maxima in a range of 564–619 nm. These are the first examples of organoplatinum(II) complexes bearing doubly deprotonated cyclometalated C^N^C ligands that are emissive in solution at room temperature. In non-degassed DMSO, the emission intensities of 6 a–9 a are enhanced upon exposure to ambient light. This phenomenon is caused by reacting photogenerated 1O2 with a DMSO molecule to form dimethyl sulfone, leading to the removal of dissolved oxygen in solution. Self-assembled nanowires and nanorods are obtained from precipitation of 3 a in THF/H2O and 8 a in DMSO/Et2O, respectively. The [(R′-C^N^C-R′′)Pt(L)] complexes are soluble in common organic solvents with a high thermal stability (>300 °C), rendering them as phosphorescent dopants for organic light-emitting diode (OLEDs) applications. Red OLEDs with CIE coordinates of (0.65±0.01, 0.35±0.01) were fabricated from 7 a or 8 a. A maximum external efficiency (ηExt) of 12.6 % was obtained for the device using 8 a as emitter.
If you can't find a tool you're looking for, please click the link at the top of the page to "Go to old article view". Alternatively, view our Knowledge Base articles for additional help. Your feedback is important to us, so please let us know if you have comments or ideas for improvement.