Amidate Iridium(III) Bis(2-pyridyl)phenyl Complexes: Application Examples of Amidate Ancillary Ligands in Iridium(III)-Cyclometalated Complexes

Abstract

The syntheses, structures, and photophysical properties of a series of iridium(III) bis(2-pyridyl)phenyl complexes, (ppy)2Ir(LX) (LX = amide ligands), are described. The complex (ppy)2Ir(N-phenylmethacrylamide) (5), bearing an acrylamidate ligand, has been further employed for polymerization to generate the metal-containing homopolymer poly((ppy)2Ir(N-phenylmethacrylamide)) (6). In addition, the complexes (ppy)2Ir(acetylaniline) (2) and (ppy)2Ir(N-phenylbenzamide) (3) have been structurally characterized by X-ray crystallography. It was found that the amidate ligand binds to the Ir center in an imine/alkoxide mode via a four-membered, nearly planar ring (N−Ir−O−C); the limited delocalization is supported by the lengthened C−O bond compared to the C−N bond length in the amidate backbone and no strong absorption around 1650 cm−1 in the infrared spectra. The photophysical and electrochemical properties of these complexes were then studied. The maximum emission wavelengths ranging from 510 to 548 nm as well as the ΔE p values varying from 2.55 to 2.77 V can be attributed to the different effects of ancillary amide ligands tolerating different electronic characters. The HOMO and LUMO energy levels and compositions of the iridium complexes were investigated by DFT calculations. The amidate ancillary ligands affect the absorption and emission energies of these complexes by tuning the HOMO energies.

Synthesis, characterization and photophysical properties of two heteroleptic 2-(4,6-difluorophenyl)pyridyl iridium(III) complexes with amidate ancillary ligands

“…This orientation has been previously reported for analogous heteroleptic complexes containing Ir-bis(ppy) and Ir-bis with other complexes containing Ir-(dfppy) fragment [26][27][28][29][30]32]. The Ir1\N3 and Ir1\O1 bond lengths are 2.154 and 2.207 Å, in agreement with those of other Ir(III) amidate complexes reported by us previously [24,25]. Complexes 2 and 3 show similar absorption spectra, as reflected by the shape of Fig.…”

“…Chemical shifts and splittings of signals in 1 H, 13 [26][27][28][29][30] and Ir(III) amidate complexes reported by us [24,25]. The typical chemical shift at 179.19 in 13 C NMR spectrum is characteristic of the amidate carbon atom in the four-membered metallocycle.…”

“…As a result of our continuing effort, we have shown that amides are able to bind to iridium center via κ 2 mode and thus form a four-membered metallocycle. Consequently, a number of photoluminescent Ir(III) complexes with several amidate ancillary ligands have been synthesized and characterized, and have been demonstrated to exhibit high photoluminescent efficiencies and quite wide color bands [24,25]. On the other hand, iridium complexes containing 2-(4,6-difluorophenyl) pyridyl (dfppy) cyclometalating ligand have been shown to exhibit distinct photopysical properties from classical iridium phenylpyridyl complexes due to the involvement of small, strongly electronegative fluorine atoms that can effectively alter the energy level of the HOMO and LUMO orbitals of the complexes [26][27][28][29][30].…”

Ancillary Ligand Effects on Red‐Emitting Cyclometalated Iridium Complexes

“…All the reactions and purification steps were conducted inside the glovebox to exclude air. The four‐membered chelate amidate complexes were synthesized according to the procedure described in the literature . Two different amidate substituent patterns were used, each with one alkyl and one phenyl substituent.…”

Electrochemiluminescence of iridium complexes with ammonia in dimethylformamide and its analytical application for ammonia detection

“…1. The iridium complexes 1 and 2 [1 = (phenylpyridine) 2 Ir(acetylaniline); 2 = (phenylpyridine) 2 Ir(N-phenylmethacrylamide)] were synthesized by our group [30]. The iridium complexes 3 and 4 [3 = Ir(ppy) 3 ; 4 = (pq) 2 Ir(acac)] were purchased from Beijing Aglaia Technology Development Co. Ltd. Tetra-n-butylammonium hexafluorophosphate (TBAPF 6 , 99%, used as supporting electrolyte) and DMF (99.9%) were purchased from J&K Scientific Ltd.…”