Synthesis, structure and photophysical properties of cationic Ir(III) complexes with functionalized 1,10-phenanthroline ancillary ligands

A series of substituted phenanthroline ancillary ligands with different degrees of steric hindrance, namely, 4,7-di(1H-pyrrol-1-yl)-1,10-phenanthroline (L1), 4,7-di(1H-indol-1-yl)-1,10-phenanthroline (L2) and 4,7-di(9H-carbazol-9-yl)-1,10-phenanthroline (L3), were synthesized in order to prepare cationic Ir(III) complexes. The results of photophysical studies revealed that functionalization with higher degree of steric hindrance L3 led to significant improvement of photoluminescence quantum yields (PLQYs) in neat film for these Ir(III) complexes, which may be attributed to the decrease of the intermolecular interactions. The mechanism of photophysical properties were rationalized with the help of quantum chemical calculations. Moreover, the complexes with L3 as ancillary ligands possessed good thermal stability, indicating their potential application as candidate for light-emitting electrochemical cells (LECs).

Graphical abstractA series of cationic Ir(III) complexes with different degrees of steric hindrance ancillary ligands were prepared. The results showed that introduction of L3 ligand into complexes was superior in reducing the intermolecular interaction and inhibiting the quenching process to endow corresponding Ir(III) complexes with much higher PLQYs.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Three functionalized 1,10-phenanthroline ancillary ligands were synthesized. ► A serials of cationic Ir(III) complexes based on them have been prepared. ► Introduction of L3 into complexes was superior in enhancing the PLQY. ► Experimental results were rationalized by our theoretical calculations.