Browse
Submit Data
Databases
API
Help

Dataset Information

8 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Direct observation of reversible electronic energy transfer involving an iridium center.

ABSTRACT: A cyclometalated iridium complex is reported where the core complex comprises naphthylpyridine as the main ligand and the ancillary 2,2'-bipyridine ligand is attached to a pyrene unit by a short alkyl bridge. To obtain the complex with satisfactory purity, it was necessary to modify the standard synthesis (direct reaction of the ancillary ligand with the chloro-bridged iridium dimer) to a method harnessing an intermediate tetramethylheptanolate-based complex, which was subjected to acid-promoted removal of the ancillary ligand and subsequent complexation. The photophysical behavior of the bichromophoric complex and a model complex without the pendant pyrene were studied using steady-state and time-resolved spectroscopies. Reversible electronic energy transfer (REET) is demonstrated, uniquely with an emissive cyclometalated iridium center and an adjacent organic chromophore. After excited-state equilibration is established (5 ns) as a result of REET, extremely long luminescence lifetimes of up to 225 μs result, compared to 8.3 μs for the model complex, without diminishing the emission quantum yield. As a result, remarkably high oxygen sensitivity is observed in both solution and polymeric matrices.

SUBMITTER: Denisov SA

PROVIDER: S-EPMC3950932 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Direct observation of multistep energy transfer in LHCII with fifth-order 3D electronic spectroscopy.

Project description:During photosynthesis, sunlight is efficiently captured by light-harvesting complexes, and the excitation energy is then funneled towards the reaction centre. These photosynthetic excitation energy transfer (EET) pathways are complex and proceed in a multistep fashion. Ultrafast two-dimensional electronic spectroscopy (2DES) is an important tool to study EET processes in photosynthetic complexes. However, the multistep EET processes can only be indirectly inferred by correlating different cross peaks from a series of 2DES spectra. Here we directly observe multistep EET processes in LHCII using ultrafast fifth-order three-dimensional electronic spectroscopy (3DES). We measure cross peaks in 3DES spectra of LHCII that directly indicate energy transfer from excitons in the chlorophyll b (Chl b) manifold to the low-energy level chlorophyll a (Chl a) via mid-level Chl a energy states. This new spectroscopic technique allows scientists to move a step towards mapping the complete complex EET processes in photosynthetic systems.

| S-EPMC4532882 | biostudies-literature

Direct observation of coherent energy transfer in nonlinear micromechanical oscillators.

Project description:Energy dissipation is an unavoidable phenomenon of physical systems that are directly coupled to an external environmental bath. In an oscillatory system, it leads to the decay of the oscillation amplitude. In situations where stable oscillations are required, the energy dissipated by the vibrations is usually compensated by replenishment from external energy sources. Consequently, if the external energy supply is removed, the amplitude of oscillations start to decay immediately, since there is no means to restitute the energy dissipated. Here, we demonstrate a novel dissipation engineering strategy that can support stable oscillations without supplying external energy to compensate losses. The fundamental intrinsic mechanism of resonant mode coupling is used to redistribute and store mechanical energy among vibrational modes and coherently transfer it back to the principal mode when the external excitation is off. To experimentally demonstrate this phenomenon, we exploit the nonlinear dynamic response of microelectromechanical oscillators to couple two different vibrational modes through an internal resonance.

| S-EPMC5458562 | biostudies-literature

Direct observation of narrow electronic energy band formation in 2D molecular self-assembly.

Project description:Surface-supported molecular overlayers have demonstrated versatility as platforms for fundamental research and a broad range of applications, from atomic-scale quantum phenomena to potential for electronic, optoelectronic and catalytic technologies. Here, we report a structural and electronic characterisation of self-assembled magnesium phthalocyanine (MgPc) mono and bilayers on the Ag(100) surface, via low-temperature scanning tunneling microscopy and spectroscopy, angle-resolved photoelectron spectroscopy (ARPES), density functional theory (DFT) and tight-binding (TB) modeling. These crystalline close-packed molecular overlayers consist of a square lattice with a basis composed of a single, flat-adsorbed MgPc molecule. Remarkably, ARPES measurements at room temperature on the monolayer reveal a momentum-resolved, two-dimensional (2D) electronic energy band, 1.27 eV below the Fermi level, with a width of ∼20 meV. This 2D band results from in-plane hybridization of highest occupied molecular orbitals of adjacent, weakly interacting MgPc's, consistent with our TB model and with DFT-derived nearest-neighbor hopping energies. This work opens the door to quantitative characterisation - as well as control and harnessing - of subtle electronic interactions between molecules in functional organic nanofilms.

| S-EPMC9470058 | biostudies-literature

Direct observation of barrier-limited folding of BBL by single-molecule fluorescence resonance energy transfer.

Project description:One controversial area in protein folding mechanisms is whether some small, ultra-fast-folding proteins exist in distinct native and denatured state ensembles, separated by an energy barrier, or if there is a continuum of states between native and denatured. In theory, the simplest way of distinguishing between single-state barrierless or "downhill" folding and conventional separate state folding is by single-molecule spectroscopy, which can detect either distinct populations of proteins or a continuum. But, the time resolution of approximately 1 ms of most confocal fluorescence microscopes for single-molecule fluorescence resonance energy transfer (SM-FRET) is longer than that for the structural relaxation of proteins such as BBL, whose mechanism of folding is controversial. We have constructed a highly sensitive confocal fluorescence microscope and measured the distribution of FRET efficiencies of appropriately labeled BBL in time bins of 50 and 200 mus under conditions in which its structural relaxation time is 340 mus or less. The experiments are at the very limits of detection because of signal artefacts from shot noise, photo-bleaching, and other events that broaden signals of individual states so they appear to coalesce. However, with appropriate tuning of the thresholds for detection and length of data collection, we clearly observed 2 distinct states of BBL, with FRET efficiencies corresponding to native and denatured states. The population of each state varied with GdmCl or urea during chemical denaturation transitions corresponding to conventional barrier-limited folding at 279 K and pH 7 and pH 5.8. The folding of BBL is accordingly barrier limited.

| S-EPMC2742407 | biostudies-literature

Direct observation of reversible bond homolysis by 2D EXSY NMR.

Project description:Bond homolysis is one of the most fundamental bond cleavage mechanisms. Thus, understanding of bond homolysis influences the development of a wide range of chemistry. Photolytic bond homolysis and its reverse process have been observed directly using time-resolved spectroscopy. However, direct observation of reversible bond homolysis remains elusive. Here, we report the direct observation of reversible Co-Co bond homolysis using two-dimensional nuclear magnetic resonance exchange spectroscopy (2D EXSY NMR). The characterization of species involved in this homolysis is firmly supported by diffusion ordered NMR spectroscopy (DOSY NMR). The unambiguous characterization of the Co-Co bond homolysis process enabled us to study ligand steric and electronic factors that influence the strength of the Co-Co bond. Understanding of these factors will contribute to rational design of multimetallic complexes with desired physical properties or catalytic activity.

| S-EPMC9383717 | biostudies-literature

Direct Observation of Reversible Biomolecule Switching Controlled By Electrical Stimulus.

Project description: Not available

| S-EPMC4368128 | biostudies-literature

Reversible energy-transfer switching on a DNA scaffold.

Project description:We show that FRET between Pacific Blue (PB) and Alexa488 (A488) covalently attached to a DNA scaffold can be reversibly controlled by photochromic switching of a spiropyran derivative. With the spiropyran in the closed spiro isomeric form, FRET occurs freely between PB and A488. UV-induced isomerization to the open merocyanine form shuts down the FRET process by efficient quenching of the PB excited state. The process is reversed by exposure to visible light, triggering the isomerization to the spiro isomer.

| S-EPMC4353014 | biostudies-literature

Designed Long-Lived Emission from CdSe Quantum Dots through Reversible Electronic Energy Transfer with a Surface-Bound Chromophore.

Project description:The size-tunable emission of luminescent quantum dots (QDs) makes them highly interesting for applications that range from bioimaging to optoelectronics. For the same applications, engineering their luminescence lifetime, in particular, making it longer, would be as important; however, no rational approach to reach this goal is available to date. We describe a strategy to prolong the emission lifetime of QDs through electronic energy shuttling to the triplet excited state of a surface-bound molecular chromophore. To implement this idea, we made CdSe QDs of different sizes and carried out self-assembly with a pyrene derivative. We observed that the conjugates exhibit delayed luminescence, with emission decays that are prolonged by more than 3 orders of magnitude (lifetimes up to 330??s) compared to the parent CdSe QDs. The mechanism invokes unprecedented reversible quantum dot to organic chromophore electronic energy transfer.

| S-EPMC5873259 | biostudies-literature

Direct observation of reversible liquid-liquid transition in a trehalose aqueous solution.

Project description:Water forms two glassy waters, low-density and high-density amorphs, which undergo a reversible polyamorphic transition with the change in pressure. The two glassy waters transform into the different liquids, low-density liquid (LDL) and high-density liquid (HDL), at high temperatures. It is predicted that the two liquid waters also undergo a liquid-liquid transition (LLT). However, the reversible LLT, particularly the LDL-to-HDL transition, has not been observed directly due to rapid crystallization. Here, I prepared a glassy dilute trehalose aqueous solution (0.020 molar fraction) without segregation and measured the isothermal volume change at 0.01 to 1.00 GPa below 160 K. The polyamorphic transition and the glass-to-liquid transition for the high-density and low-density solutions were examined, and the liquid region where both LDL and HDL existed was determined. The results show that the reversible polyamorphic transition induced by the pressure change above 140 K is the LLT. That is, the transition from LDL to HDL is observed. Moreover, the pressure hysteresis of LLT suggests strongly that the LLT has a first-order nature. The direct observation of the reversible LLT in the trehalose aqueous solution has implications for understanding not only the liquid-liquid critical point hypothesis of pure water but also the relation between aqueous solution and water polyamorphism.

| S-EPMC8812557 | biostudies-literature

Direct observation of coherence transfer and rotational-to-vibrational energy exchange in optically centrifuged CO<sub>2</sub> super-rotors.

Project description:Optical centrifuges are laser-based molecular traps that can rotationally accelerate molecules to energies rivalling or exceeding molecular bond energies. Here we report time and frequency-resolved ultrafast coherent Raman measurements of optically centrifuged CO2 at 380 Torr spun to energies beyond its bond dissociation energy of 5.5 eV (Jmax = 364, Erot = 6.14 eV, Erot/kB = 71, 200 K). The entire rotational ladder from J = 24 to J = 364 was resolved simultaneously which enabled a more accurate measurement of the centrifugal distortion constants for CO2. Remarkably, coherence transfer was directly observed, and time-resolved, during the field-free relaxation of the trap as rotational energy flowed into bending-mode vibrational excitation. Vibrationally excited CO2 (ν2 > 3) was observed in the time-resolved spectra to populate after 3 mean collision times as a result of rotational-to-vibrational (R-V) energy transfer. Trajectory simulations show an optimal range of J for R-V energy transfer. Dephasing rates for molecules rotating up to 5.5 times during one collision were quantified. Very slow decays of the vibrational hot band rotational coherences suggest that they are sustained by coherence transfer and line mixing.

| S-EPMC10239519 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data