Synthesis, Separation, and Circularly Polarized Luminescence Studies of Enantiomers of Iridium(III) Luminophores

Coughlin, Frederick J.; Westrol, Michael S.; Oyler, Karl D.; Byrne, Neal; Kraml, Christina M.; Zysman‐Colman, Eli; Lowry, Michael S.; Bernhard, Stefan

doi:10.1021/ic701747j

Cited by 139 publications

(92 citation statements)

References 40 publications

(88 reference statements)

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“…TD-DFT calculated spectra 70,79 of complex 4c in an Ir V =O state predict the pattern of broad and sharp absorption at 670 and 460 nm observed following 8 additions of 20 cerium(IV) equivalents (Figure 8, Calculated spectra of additional conceivable intermediates and in Supporting Information). Notably absent are spectral features consistent with the loss of the Cp* moiety ( Figure S5).…”

Section: Methodsmentioning

confidence: 83%

“…Time dependent calculations were performed at the optimized ground-state geometry via Gaussian 03 software. The unrestricted B3LYP functional was used and the LANL2DZ basis set was applied to all atoms since that basis set has previously resulted in superior agreement of TD-DFT spectra with experimental data 79 . The energy, oscillator strength, and rotatory strength were computed for each of the 70 lowest singlet excitations.…”

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confidence: 99%

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Carbene iridium complexes for efficient water oxidation: scope and mechanistic insights

Woods

Lalrempuia

Petronilho

et al. 2014

Energy Environ. Sci.

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107

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Iridium complexes of Cp* and mesoionic carbene ligands were synthesized and evaluated as potential water oxidation catalysts using cerium ammonium nitrate as a chemical oxidant. Performance was evaluated by turnover frequency at 50% conversion and by absolute turnover number, and the most promising precatalysts were subjected to further study. Molecular turnover frequencies varied from 190 to 451 per hour with a maximum turnover number of 38,000. While the rate of oxygen evolution depends linearly on iridium concentration, 10 concurrent spectroscopic and manometric monitoring of stoichiometric additions of oxidant suggests oxygen evolution occurs as two sequential first order reactions. Under the conditions herein, the oxygen evolving species appears to be well defined and molecular based on the kinetic effects of careful ligand design, reproducibility, and the absence of persistent dynamic light scattering signals. Outside of these conditions, the complex mechanism is highly dependent on reaction conditions. While confident characterization of the catalytically active species is difficult, especially under high-turnover conditions, this work indicates IrOx is not essential for the 15 formation of catalytically active water oxidation species.

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Section: Methodsmentioning

confidence: 83%

mentioning

confidence: 99%

Carbene iridium complexes for efficient water oxidation: scope and mechanistic insights

Woods

Lalrempuia

Petronilho

et al. 2014

Energy Environ. Sci.

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107

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“…CPL calculations based on vertical excitations have been performed in the past using a semiempirical approach restricted to p orbitals, [6] and more recently with density functional theory (DFT). [8] Expressions for CPL intensity have also been derived for chiral aggregates. [9] Computations of vibrationally resolved electronic absorption and CD spectra have been previously performed using various methods, often resulting in very good agreement with experiment.…”

Section: Introductionmentioning

confidence: 99%

Calculation of the Vibrationally Resolved, Circularly Polarized Luminescence of d‐Camphorquinone and (S,S)‐trans‐β‐Hydrindanone

Pritchard

Autschbach

2010

ChemPhysChem

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Circularly polarized luminescence (CPL), the differential emission of left- and right-handed circularly polarized light from a molecule, is modeled by using time-dependent density functional theory. Calculations of the CPL spectra for the first electronic excited states of d-camphorquinone and (S,S)-trans-beta-hydrindanone under the Franck-Condon approximation and using various functionals are presented, as well as calculations of absorption, emission, and circular dichroism spectra. The functionals B3LYP, BHLYP, and CAM-B3LYP are employed, along with the TZVP and aug-cc-pVDZ Gaussian-type basis sets. For the lowest-energy transitions, all functionals and basis sets perform comparably, with the long-range-corrected CAM-B3LYP better reproducing the excitation energy of camphorquinone but leading to a blue shift with respect to experiment for hydrindanone. The vibrationally resolved spectra of camphorquinone are very well reproduced in terms of peak location, widths, shapes, and intensities. The spectra of hydrindanone are well reproduced in terms of overall envelope shape and width, as well as the lack of prominent vibrational structure in the emission and CPL spectra. Overall the simulated spectra compare well with experiment, and reproduce the band shapes, emission red shifts, and presence or absence of visible vibrational fine structure.

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“…However, unlike [Ru(bipy) 3 ] 2+ the resolution of Ir(III) complexes is still in its infancy and very few reports have been published so far. [2][3][4][5][6] Separation by HPLC of the enantiomers of [Ir(ppy) 3 ] (Hppy = phenylpyridine) was reported in 2007, 3 and of [Ir(ppy-R) 2 (acac)] (R = F, OMe, Ph) in 2008. 4 Single 20 diastereomers have been isolated e.g.…”

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confidence: 99%

“…[2][3][4][5][6] Separation by HPLC of the enantiomers of [Ir(ppy) 3 ] (Hppy = phenylpyridine) was reported in 2007, 3 and of [Ir(ppy-R) 2 (acac)] (R = F, OMe, Ph) in 2008. 4 Single 20 diastereomers have been isolated e.g. [Ir(C^N*)] 3 and [Ir(C^N*) 2 (acac)] with enantiopure cyclometallating ligands, 7 or [Ir(C^N) 2 (X^Y*)] (X^Y* = amino acidate 5,8,9 , phenol oxazoline 6 ) with enantiopure X^Y ligands.…”

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Atropisomerism in a thermally switchable, cyclometallated iridium complex

et al. 2012

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5,8,9 , phenol oxazoline 6 ) with enantiopure X^Y ligands. However, these complexes have chirality at the ligand as well as the metal; hence, 25 the aim of this work was to prepare, on a synthetically useful scale, homochiral cyclometallated Ir(III) complexes which are only chiral at the metal.Our strategy was to prepare diastereomeric complexes [Ir(C^N) 2 (X^Y*)], separate the diastereomers, then remove the 30 chiral auxiliary by protonation and replace it with another bidentate ligand. A similar strategy has recently been applied by Meggers for the synthesis of homochiral trisbidentate ruthenium complexes, 10 and in 2012 was applied to iridium complexes for the first time. 5 35 The dimer [Ir(ppz) 2 Cl] 2 (a, Hppz = phenylpyrazole) was reacted with 2.2 equiv of (S)-Na(L1) 11,12 in a mixture of DCM/ methanol (2:1) at room temperature for 2-4 hrs, to give 1a as a (1:1) mixture of diastereomers, ∆S and ΛS, in good combined 45 yields (>75%) (Scheme 1). The reaction was repeated with only 0.8 equiv of (S)-Na(L1) per dimer and the 1 H NMR spectrum of the product showed a 1:1 ratio of the two diastereomers along with the unreacted excess dimer. This suggests that there is no diastereoselectivity in the synthesis and there is an equal 50 probability for the formation of the two diastereomers. The diastereomers of 1a could be separated by crystallisation from different solvents and they do not interconvert in solution, suggesting the chirality at the metal is stable at room temperature. The absolute configuration of both diastereomers was determined 55 by X-ray crystallography 13 and the structures of S-and S-1a are shown in Fig. 2. 14 The structures show that both isomers have cis carbon atoms and trans nitrogen atoms for the C^N ligands and S configuration at the chiral carbon atom of the oxazoline ligand; one isomer has a Λ configuration at the Ir centre (Fig. 2 60 left), whereas the other isomer shows a ∆ configuration (Fig. 2 right). The change in chirality at the metal leads to different orientations of L1 with respect to the [Ir(C^N) 2 ] fragment. In the ΛS isomer the pyrazole [N(4)-C(12)] pointing towards the oxazoline nitrogen is on the unsubstituted side of the oxazoline 65 and there is no steric conflict. In contrast, in the ∆S isomer, the pyrazole [N(2)-C(3)] pointing towards the oxazoline nitrogen is on the same side as the isopropyl which leads to steric congestion which is clearly evident in the planarity of L1 (Fig. 2 right). Thus, in the ΛS isomer the angle between the planes of the 70 phenol and the oxazoline is less than 3 whilst in the ∆S isomer the corresponding angle is > 20.The structures are retained in solution as determined by key NOEs between the X^Y ligand and the [Ir(C^N) 2 ] fragment (see ESI Fig S1). In ΛS-1a the isopropyl group lies above a ppz ligand

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Synthesis, Separation, and Circularly Polarized Luminescence Studies of Enantiomers of Iridium(III) Luminophores

Cited by 139 publications

References 40 publications

Carbene iridium complexes for efficient water oxidation: scope and mechanistic insights

Carbene iridium complexes for efficient water oxidation: scope and mechanistic insights

Calculation of the Vibrationally Resolved, Circularly Polarized Luminescence of d‐Camphorquinone and (S,S)‐trans‐β‐Hydrindanone

Atropisomerism in a thermally switchable, cyclometallated iridium complex

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