Electrochemical and Phosphorescent Properties of New Ir(III) Complexes Coordinated by Various Bipyridine Derivatives

Abstract

+ with electron acceptor substituents shows a large red-shift to 622 nm. It is noticed that iridium polypyridine complexes show intense emissions at various colors, such as yellow for [IrCl2(dmbpy)2] + and red for [IrCl2(bqn)2] + , which can be applied to photosensitizers. The spectroscopic and electrochemical details are also reported herein.

Synthesis, Characterization, and DFT Investigation of IrIII Tolylterpyridine Complexes

“…6 ) 2 (1-4): Syntheses of the complexes were undertaken by using a Mitsubishi Electric RR-12AF microwave oven (500 W, 2450 MHz) on medium-high power in a round-bottom flask fitted with a reflux condenser. [10,23] One target complex 3 (L = dmbpy), for example, was prepared by a sequential procedure with a ligand replacement. (NH 4 ) 3 [IrCl 6 ] (0.238 g, 0.500 mmol) and tterpy (0.161 g, 0.500 mmol) were mixed in ethylene glycol (15 mL).…”

“…[14] Similarly, the bands at 282 nm in 2 could be assigned as dpphen(π)-dpphen(π*) transitions. [10] The absorption bands at 311 nm in both 1 and 2 have been assigned as tterpy(π)-tterpy(π*) transitions. On the other hand, the absorption spectrum of 4 with a bpy ligand is very similar to that of 3 with a dmbpy ligand.…”

“…The absorption bands at 252, 278, and 306 nm in the free tterpy are the same as those in 5 ( Table 2) and have been assigned as tterpy(π)-tterpy(π*) transitions. [10] Although the free tterpy ligand does not absorb around 320-500 nm, 5 exhibits large absorption bands at 346 and 374 nm. As a consequence of complex formation, the electronic charges are delocalized, and thus the absorption bands at 346 and 306 nm in 5 can be assigned as tterpy(π)-tterpy(π*) transitions.…”

“…These processes have also been assigned as tterpy ligand-centered reductions. [10] The typical electrochemical behavior of iridium(III) polypyridine complexes are ligand-site oxidations and reductions. The highest occupied molecular orbital (HOMO) is localized on the ligand molecule, and the oxidative processes take place there.…”

“…[8,9] In our previous work, we synthesized and crystallized [IrCl 2 L 2 ]PF 6 complexes {L = bqn, phen, dpphen, bpy, and dmbpy} to reveal their long-lived excited states and good photoluminescence efficiencies. [10][11][12][13] Abbreviations of the ligands used here are bqn = 2,2Ј-biquinoline, phen = 1,10-phenanthroline, dpphen = 4,7-diphenyl-1,10-phenanthroline, bpy = 2,2Ј-bipyridine, and dmbpy = 4,4Ј-dimethyl-2,2Ј-bipyridine. Recently, we focused on Ir III complexes with a 2,2Ј:6Ј,2ЈЈ-terpyridine (terpy) and a polypyridine ligand.…”