- Polymerizable cationic iridium(III) complexes exhibiting color tunable light emission and their corresponding conducting metallopolymers
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Cyclometalated iridium(III) complexes have been synthesized for use in a variety of photophysical applications, including polymer light emitting diodes (PLEDs). A series of new complexes with one electrochemically polymerizable ligand and two phenylpyridine(ppy)-based ligands have been prepared: [Ir(ppy)2L][PF6](1), [Ir(F-mppy)2L][PF6](2), and [Ir(Br-mppy)2L][PF6](3), where L = 3,8-bis(2,2′-bithien-5-yl)-1,10-phenanthroline. The ancillary ppy ligands can be easily varied synthetically to tune emission color of the monomer from blue-green to red. The solid state structure of complex 1 has been obtained by single crystal X-ray crystallography. Conducting polymer materials have been prepared by electropolymerization of monomers and were characterized through XPS analysis and spectroscopic studies.
- Hesterberg, Travis W.,Yang, Xiaoping,Holliday, Bradley J.
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- Sensing of 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (2,4-DNT) in the solid state with photoluminescent RuII and IrIII complexes
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A series of metal-organic chromophores containing RuII or IrIII were studied for the luminometric detection of nitroaromatic compounds, including trinitrotoluene (TNT). These complexes display long-lived, intense photoluminescence in the visible region and are demonstrated to serve as luminescent sensors for nitroaromatics. The solution-based behavior of these photoluminescent molecules has been studied in detail in order to identify the mechanism responsible for metal-to-ligand charge-transfer (MLCT) excited state quenching upon addition of TNT and 2,4-dinitrotoluene (2,4-DNT). A combination of static and dynamic spectroscopic measurements unequivocally confirmed that the quenching was due to a photoinduced electron transfer (PET) process. Ultrafast transient absorption experiments confirmed the formation of the TNT radical anion product following excited state electron transfer from these metal complexes. Reported for the first time, photoluminescence quenching realized through ink-jet printing and solid-state titrations was used for the solid-state detection of TNT; achieving a limit-ofquantitation (LOQ) as low as 5.6 ngcm-2. The combined effect of a long-lived excited state and an energetically favorable driving force for the PET process makes the RuII and IrIII MLCT complexes discussed here particularly appealing for the detection of nitroaromatic volatiles and related highenergy compounds.
- Mosca, Lorenzo,Khnayzer, Rony S.,Lazorski, Megan S.,Danilov, Evgeny O.,Castellano, Felix N.,Anzenbacher, Pavel
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- Understanding Ir(III) Photocatalyst Structure-Activity Relationships: A Highly Parallelized Study of Light-Driven Metal Reduction Processes
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High-throughput synthesis and screening methods were used to measure the photochemical activity of 1440 distinct heteroleptic [Ir(C^N)2(N^N)]+ complexes for the photoreduction of Sn(II) and Zn(II) cations to their corresponding neutral metals. Kinetic data collection was carried out using home-built photoreactors and measured initial rates, obtained through an automated fitting algorithm, spanned between 0-120 μM/s for Sn(0) deposition and 0-90 μM/s for Zn(0) deposition. Photochemical reactivity was compared to photophysical properties previously measured such as deaerated excited state lifetime and emission spectral data for these same complexes; however, no clear correlations among these features were observed. A formal photochemical rate law was then developed to help elucidate the observed reactivity. Initial rates were found to be directly correlated to the product of incident photon flux with three reaction elementary efficiencies: (1) the fraction of light absorbed by the photocatalyst, (2) the fraction of excited state species that are quenched by the electron donor, and (3) the cage escape efficiency. The most active catalysts exhibit high efficiencies for all three steps, and catalyst engineering requirements to maximize these elementary efficiencies were postulated. The kinetic treatment provided the mechanistic information needed to decipher the observed structure/function trends in the high-throughput work.
- Bernhard, Stefan,Connell, Timothy U.,Diluzio, Stephen,Kowalewski, Jakub F.,Mdluli, Velabo
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p. 1431 - 1444
(2022/02/05)
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- Synthesis, separation, and circularly polarized luminescence studies of enantiomers of iridium(III) luminophores
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A family of heteroleptic (C∧N)2Ir(acac) and homoleptic fac-Ir(C∧N)3 complexes have been synthesized and their photophysical properties studied (where C∧N = a substituted 2-phenylpyridine and acac = acetylacetonate). The neutral Δ and ∧ complexes were separated with greater than 95% enantiomeric purity by chiral supercritical fluid chromatography, and the solution circular dichroism and circularly polarized luminescence spectra for each of the enantio-enriched iridium complexes were obtained. The experimentally measured emission dissymmetries (gem) for this series compared well with predicted values provided by time-dependent density functional theory calculations. The discovered trend further showed a correlation with the dissymmetries of ionic, enantiopure hemicage compounds of Ru(II) and Zn(II), thus demonstrating the applicability of the model for predicting emission dissymmetry values across a wide range of complexes.
- Coughlin, Frederick J.,Westrol, Michael S.,Oyler, Karl D.,Byrne, Neal,Kraml, Christina,Zysman-Colman, Eli,Lowry, Michael S.,Bernhard, Stefan
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p. 2039 - 2048
(2009/01/31)
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- Accelerated luminophore discovery through combinatorial synthesis
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A method for accelerating the discovery of ionic luminophores using combinatorial techniques is reported. The photophysical properties of the resulting transition-metal-based chromophores were compared against a series of analogous, traditionally prepared species. The strong overlap between these two sets confirms the identity of the parallel synthesis products and supports the truthfulness of the combinatorial results. Further support for the combinatorial method comes from the adherence of these complexes to the energy gap law. The relationship between the structure of a complex and its photophysical properties was also considered, and static DFT calculations were used to assess whether it is feasible to predict the luminescent behavior of novel materials.
- Lowry, Michael S.,Hudson, William R.,Pascal Jr., Robert A.,Bernhard, Stefan
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p. 14129 - 14135
(2007/10/03)
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