title: Blue and blue-green light-emitting cationic iridium complexes: synthesis, characterization, and optoelectronic properties.
abstract: Two new cationic iridium complexes, [Ir(ppy)2(phpzpy)]PF6 (complex 1) and [Ir(dfppy)2(phpzpy)]PF6 (complex 2), bearing a 2-(3-phenyl-1H-pyrazol-1-yl)pyridine (phpzpy) ancillary ligand and either 2-phenylpyridine (Hppy) or 2-(2,4-difluorophenyl)pyridine (Hdfppy) cyclometalating ligands, were synthesized and fully characterized. The photophysical and electrochemical properties of these complexes were investigated by means of UV-visible spectroscopy, emission spectroscopy, and cyclic voltammetry. Density functional theory (DFT) and time dependent DFT (TD-DFT) calculations were performed to simulate and study the photophysical and electrochemical properties of both complexes. Light-emitting electrochemical cells (LECs) were fabricated by incorporating complexes 1 and 2, which respectively exhibit blue-green (488 and 516 nm) and blue (463 and 491 nm) emission colors, achieved through the meticulous design of the ancillary ligand. The luminance and current efficiency measurements recorded for the LEC based on complex 1 were 1246 cd m(-2) and 0.46 cd A(-1), respectively, and were higher than those measured for complex 2 because of the superior balanced carrier injection and recombination properties of the former.
authors: †Department of Polymer Science and Chemical Engineering, Pusan National University, Busan 609-735, South Korea.
authors: Chozhidakath Damodharan
authors: CD
authors: Sunesh
authors: †Department of Polymer Science and Chemical Engineering, Pusan National University, Busan 609-735, South Korea.
authors: Kanagaraj
authors: K
authors: Shanmugasundaram
authors: †Department of Polymer Science and Chemical Engineering, Pusan National University, Busan 609-735, South Korea.
authors: Madayanad Suresh
authors: MS
authors: Subeesh
authors: ‡Department of Nanomaterials Engineering, Pusan National University, Busan, 609-735, Republic of Korea.
authors: Ramesh Kumar
authors: RK
authors: Chitumalla
authors: ‡Department of Nanomaterials Engineering, Pusan National University, Busan, 609-735, Republic of Korea.
authors: Joonkyung
authors: J
authors: Jang
authors: †Department of Polymer Science and Chemical Engineering, Pusan National University, Busan 609-735, South Korea.
authors: Youngson
authors: Y
authors: Choe
keywords: electroluminescence; iridium complexes; light-emitting electrochemical cells; pyrazole; thin film