The use of organolithium reagents for the synthesis of 4-aryl-2-phenylpyridines and their corresponding iridium(iii) complexes

Abstract

A versatile palladium-free route for the synthesis of 4-aryl-substituted phenylpyridines (ppy), starting from tert-butyl 4-oxopiperidine-1-carboxylate, is reported. Reaction with an aryllithium, followed by trifluoroacetic acid dehydration/deprotection and oxidation with 2-iodoylbenzoic acid and finally phenylation, gave 4 ligands (L(1-4)H): 2,4-diphenylpyridine, 4-(4-methoxyphenyl)-2-phenylpyridine, 2-phenyl-4-(o-tolyl)pyridine and 4-mesityl-2-phenylpyridine. These ligands were coordinated to iridium to give the corresponding Ir(L)2(A) complexes (Ir1-7), where A = ancillary ligand acetylacetate or 2-picolinate. This was used to demonstrate that, through a combination of ancillary ligand choice and torsional twisting between the 4-aryl substituents of the ppy ligands, it is possible to tune the phosphorescent emission of the complexes in the range 502-560 nm.

Emission Tuning of Ir(N∧C)2(pic)-Based Complexes via Torsional Twisting of Picolinate Substituents

“…However, when the torsional angle between the aryl substituent and pic is increased, this conjugation is reduced, resulting in the complexes behaving more like the parent Ir­(X 2 ppy)­(pic) complex. Such behavior has been previously demonstrated when similar substitutions were made on the ppy ligand of an Ir­(N ∧ C) 2 (pic) system . However, changes of this extent have not been reported for such modifications to other parts of the complex.…”

“…Such behavior has been previously demonstrated when similar substitutions were made on the ppy ligand of an Ir(N ∧ C) 2 (pic) system. 19 However, changes of this extent have not been reported for such modifications to other parts of the complex.…”

Synthesis, Diastereomer Separation, and Optoelectronic and Structural Properties of Dinuclear Cyclometalated Iridium(III) Complexes with Bridging Diarylhydrazide Ligands

“…All Ir complexes were measured in degassed DCM (repeated freeze–pump–thaw cycles using a turbomolecular pump). The quantum yields of all samples were determined by the comparative method relative to Ir­(ppy) 3 as a standard (Φ = 0.46 in degassed DCM measured in-house vs quinine sulfate in 0.5 M H 2 SO 4 at Φ = 0.546) following the literature procedure . The quantum yields of complexes doped into poly­(methyl methacrylate) (PMMA) thin films were recorded on a Horiba Jobin Yvon SPEX Fluorolog 3-22 instrument using an integrating sphere and were calculated according to the literature method .…”

“…The quantum yields of all samples were determined by the comparative method relative to Ir(ppy)3 as a standard (Φ = 0.46 in degassed DCM measured in-house vs. quinine sulphate in 0.5 M H2SO4 Φ = 0.546 66 ) following the literature procedure. 88 The quantum yields of complexes doped into poly(methyl methacrylate) (PMMA) thin films were recorded on a Horiba Jobin Yvon SPEX Fluorolog 3-22 using an integrating sphere and were calculated according to the literature method. 89 Solid state PLQY data were obtained in triplicate from three samples that were prepared in parallel: the calculated standard error values were ≤10%.…”

Highly Linearized Twisted Iridium(III) Complexes

“…22 The increased reactivity of the iodo group allowed the Sonogashira reaction to proceed in reasonable yields (75%), although it was necessary to heat the reaction to 70°C to achieve this. As with the other ligands the L 5 H was produced by (λemis = 603 nm); otolyl Ir(otolppy)2(acac) (λemis = 547 nm); 24 and complex 11 (λemis = 574 nm). However, complexes with a duryl spacer showed negligible change, i.e.…”