Synthesis, electrochemical and photochemical properties of neutral Ir(III) complex based on 3-Iodopyridine-2-carboxylate ligand

In this work, we report the synthesis and characterization of mer-[Ir(ppy)(2)(Ipic)], where ppy = 2-phenylpyridine and Ipic = 3-iodopyridine-2-carboxylate, as well as, the electrochemical and photophysical properties in solution. The electronic absorption spectra profile can be divided into two main regions: intense bands in the high energy UV-region (200-300 nm) assigned to ligand centered (IL) transition on both the cyclometalated (ppy) and the ancillary (Ipic) ligands, and lower intensity absorption bands located in the less energetic region (320-460 nm) can be experimentally assigned to the spin-allowed metal-to-ligand charge transfer (1 MLCT) transition and the spin-forbidden (MLCT)-M-3. From the electrochemical results, were obtained the oxidation peak (Ir(III)-> Ir(IV) couple) at +0.59 V resulting in a HOMO of -5.09 eV, and the reduction potentials -1.65 and -2.00 V, which can be attributed to the Ipic and ppy, respectively. Additionally, it is possible to observe that the introduction of the halogen atom promotes a significant variation in LUMO energy (2.75 eV), while the HOMO level is almost unchanged. The complex displayed broad and structureless emission spectra in acetonitrile (lambda(max) = 510 nm, phi = 0.0032 and tau = 160 ns) and dichloromethane (lambda(max) = 510 nm, 525 nm) solution at room temperature but becomes structured (lambda(max) = 490, 522 nm) in propionitrile:butyronitrile at 77 K, indicating that the emitting state at room temperature has a mixed (MLCT)-M-3-(LC)-L-3 character but at 77 K the emission has a strong (LC)-L-3 character. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study reports the synthesis and characterization of mer-[Ir(ppy)(2)(Ipic)], investigating its electronic absorption spectra and electrochemical properties. The introduction of a halogen atom significantly affects the LUMO energy, while the emission behavior varies between room temperature and 77 K.