Wide tuning of emission color of iridium (III) complexes from green to deep red via dicyanovinyl substituent effect on 2-phenylpyridine ligands

The synthesis, photophysical and electrochemical characteristics of new iridium complexes with electron-withdrawing dicyanovinyl group bound to phenylpyridine ligands are reported. The emission energy of these materials strongly depends on the position and substituent nature. A 154 nm wide tuning range of photoluminescence from the green (λ = 522 nm) of iridium (III) bis(5-dicyanovinylphenylpyridinato)picolinate to the deep red emission (λ = 676 nm) of iridium (III) bis(4-dicyanovinyl phenylpyridinato)picolinate has been achieved in solution. An unusually strong absorption capacity from 350 to 510 nm has been observed for the complex, iridium (III) bis(5-dicyanovinyl phenylpyridinato) picolinate, which also shows significantly different emission energy in solution and solid film. The performed DFT/TD-DFT calculations elucidated the substituent effects.