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Database, Features, and Machine Learning Model to Identify Thermally Driven Metal–Insulator Transition Compounds
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Energy Migration Processes in Re(I) MLCT Complexes Featuring a Chromophoric Ancillary Ligand
We present herein the synthesis, structural characterization, electronic structure calculations, and ultrafast and supra-nanosecond photophysical properties of a series of five Re(I) bichromophores exhibiting metal to ligand charge transfer (MLCT) excited states based on the general formula fac -[Re(N ^ N)(CO) 3 (PNI-py)]PF 6, where PNI-py is 4-piperidinyl-1,8-naphthalimidepyridine and N ^ N is a diimine ligand ( Re1 – 5 ), along with their corresponding model chromophores where 4-ethylpyridine was substituted for PNI-py ( Mod1 – 5 ). The diimine ligands used include 1,10-phenanthroline (phen, 1 ), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bcp, 2 ), 4,4'-di- tert -butyl-2,2'-bipyridine (dtbb, 3 ), 4,4'-diethyl ester-2,2'-bipyridine (deeb, 4 ), and 2,2'-biquinoline (biq, 5 ). In these metal–organic bichromophores, structural modification of the diimine ligand resulted in substantial changes to the observed energy transfer efficiencies between the two chromophores as a result of the variation in 3 MLCT excited-state energies. The photophysical properties and energetic pathways of the model chromophores were explored in parallel to accurately track the changes that arose from introduction of the organic chromophore pendant on the ancillary ligand. All relevant photophysical and energy transfer processes were probed and characterized using time-resolved photoluminescence spectroscopy, ultrafast and nanosecond transient absorption spectroscopy, and time-dependent density functional theory calculations. Of the five bichromophores in this study, four ( Re1 – 4 ) exhibited a thermal equilibrium between the 3 PNI-py and the 3 MLCT excited state, drastically extending the lifetimes of the parent model chromophores.
Next Generation Cuprous Phenanthroline MLCT Photosensitizer Featuring Cyclohexyl Substituents
A new long–lived, visible light–absorbing homoleptic Cu(I) metal–to–ligand charge transfer (MLCT) photosensitizer [Cu(dchtmp) 2 ]PF 6 (dchtmp = 2,9–dicyclohexyl–3,4,7,8–tetramethyl–1,10–phenanthroline), has been synthesized, structurally characterized, and evaluated in terms of its molecular photophysics, electrochemistry, and electronic structure. Static and time–resolved transient absorption (TA) and photoluminescence (PL) spectroscopy measured on the title compound in CH 2 Cl 2 (τ = 2.6 μs, Φ PL = 5.5%), CH 3 CN (τ = 1.5 μs, Φ PL = 2.6%), and THF (τ = 2.0 μs, Φ PL = 3.7%) yielded impressive photophysical metrics even when dissolved in Lewis basic solvents. The combined static spectroscopic data along with ultrafast TA experiments revealed that the pseudo–Jahn–Teller distortion and intersystem crossing dynamics in the MLCT excited state displayed characteristics of being sterically arrested throughout its evolution. Here, electrochemical and static PL data illustrate that [Cu(dchtmp) 2 ]PF 6 is a potent photoreductant (–1.77 V vs. Fc +/o in CH 3 CN) equal to or greater than all previously investigated homoleptic Cu(I) diimine complexes. Although we successfully prepared the cyclopentyl analog dcptmp (2,9–dicyclopentyl–3,4,7,8–tetramethyl–1,10–phenanthroline) using the same C–C radical coupling photochemistry as dchtmp, the corresponding Cu(I) complex could not be isolated due to the steric hinderance presented at the metal center. Ultimately, the successful preparation of [Cu(dchtmp) 2 ] + represents a major step forward for the design and discovery of novel earth–abundant photosensitizers made possible through a newly conceived ligand synthetic strategy.
Clustering Protein Binding Pockets and Identifying Potential Drug Interactions: A Novel Ligand-Based Featurization Method
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Near-Infrared Absorption Features of Triplet-Pair States Assigned by Photoinduced-Absorption-Detected Magnetic Resonance
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Phosphoproteome Response to Dithiothreitol Reveals Unique Versus Shared Features of Saccharomyces cerevisiae Stress Responses
To cope with sudden changes in the external environment, the budding yeast Saccharomyces cerevisiae orchestrates a multifaceted response that spans many levels of physiology. Several studies have interrogated the transcriptome response to endoplasmic reticulum (ER) stress and the role of regulators such as the Ire1 kinase and Hac1 transcription factors. However, less is known about responses to ER stress at other levels of physiology. Here, we used quantitative phosphoproteomics and computational network inference to uncover the yeast phosphoproteome response to the reducing agent dithiothreitol (DTT) and the upstream signaling network that controls it. We profiled wild-type cells and mutants lacking IRE1 or MAPK kinases MKK1 and MKK2, before and at various times after DTT treatment. In addition to revealing downstream targets of these kinases, our inference approach predicted new regulators in the DTT response, including cell-cycle regulator Cdc28 and osmotic-response kinase Rck2, which we validated computationally. Our results also revealed similarities and surprising differences in responses to different stress conditions, especially in the response of protein kinase A targets. Furthermore, these results have implications for the breadth of signaling programs that can give rise to common stress response signatures.
Monolayer-Based Single-Photon Source in a Liquid-Helium-Free Open Cavity Featuring 65% Brightness and Quantum Coherence
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Hydrogen Adsorption in Ultramicroporous Metal–Organic Frameworks Featuring Silent Open Metal Sites
In this work, we utilized an ultramicroporous metal–organic framework (MOF) named [Ni 3 (pzdc) 2 (ade) 2 (H 2 O) 4 ]·2.18H 2 O (where H 3 pzdc represents pyrazole-3,5-dicarboxylic acid and ade represents adenine) for hydrogen (H 2 ) adsorption. Upon activation, [Ni 3 (pzdc) 2 (ade) 2 ] was obtained, and in situ carbon monoxide loading by transmission infrared spectroscopy revealed the generation of open Ni(II) sites. The MOF displayed a Brunauer–Emmett–Teller (BET) surface area of 160 m 2 /g and a pore size of 0.67 nm. Hydrogen adsorption measurements conducted on this MOF at 77 K showed a steep increase in uptake (up to 1.93 mmol/g at 0.04 bar) at low pressure, reaching a H 2 uptake saturation at 2.11 mmol/g at ~0.15 bar. The affinity of this MOF for H 2 was determined to be 9.7 ± 1.0 kJ/mol. In situ H 2 loading experiments supported by molecular simulations confirmed that H 2 does not bind to the open Ni(II) sites of [Ni 3 (pzdc) 2 (ade) 2 ], and the high affinity of the MOF for H 2 is attributed to the interplay of pore size, shape, and functionality.
NO x and Hydrocarbon Trapping and Conversion in a Sequential Three-Zone Monolith: Spatiotemporal Features
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