Tuning the photophysical properties of heteroleptic Ir(III) complexes through ancillary ligand substitution: Experimental and theoretical investigation

A series of new phosphorescent heteroleptic Iridium(III) complexes with 2-phenylpyridine, acetylacetone and 2-picolinic acid as ancillary ligands have been designed and synthesized. The photophysical and electrochemical properties have been investigated experimentally and theoretically. The UV-vis absorption and photoluminescence (PL) emission spectra of the complexes were carried out in solution as well as thin film. The PL study indicates that the Iridium complexes show broadband emission ranging from green to yellowish-green in solution and greenish-yellow to yellow emission in PMMA films with appropriate CIE color gamut. The PLQY of the complexes were found to be in the range of 0.12-0.29. Singlet and triplet energy levels were calculated by using time dependent DFT (TD-DFT) calculations. The excited triplet energy was estimated and correlated to structural and energetic characteristics of the reported host materials. Further, investigations have been performed to explore the optical, electronic, charge transport, and stability properties of Ir(III) complexes as charge transport and emissive materials for organic light emitting devices (OLEDs). Furthermore, all the complexes are promising luminescent and its hole transporting performance is more favorable than electron transport performances. According to theoretical calculations, it is clearly indicating that, Ben-Ir-acac complex is a more potential emitter for OLED applications. (C) 2017 Published by Elsevier B.V.