Ground-State and Excited-State C⋮C Stretching Frequencies of Dimetallapolyyne Redox Congeners. Direct Evidence for Metal→Alkynyl π-Back-Bonding

1997 ◽  
Vol 16 (23) ◽  
pp. 4948-4950 ◽  
Author(s):  
Kevin D. John ◽  
Timothy C. Stoner ◽  
Michael D. Hopkins
Keyword(s):  
Excited State ◽  
Ground State ◽  
Direct Evidence ◽  
Back Bonding

scholarly journals Direct Visualization of Energy-transferred Excited State in Eu Complex

2014 ◽  
Vol 70 (a1) ◽  
pp. C102-C102 ◽  
Author(s):  
Kunihisa Sugimoto ◽  
Akihiko Fujiwara ◽  
Masaki Takata ◽  
Hiroshi Tanaka ◽  
Miki Hasegawa
Keyword(s):  
Energy Transfer ◽  
Excited State ◽  
Charge Density ◽  
Electrostatic Potential ◽  
Ground State ◽  
Direct Evidence ◽  
Entropy Method ◽  
Direct Visualization ◽  
Band Shape ◽  
Hexadentate Ligand

Highly luminescent lanthanide (Ln) complexes have attracted much attention because Ln3+ions show long-lived ff-emissions with narrow band shape. Their unique photo-optical properties are promising for the design of light-emitting materials and sensing devices. Although the ff-emissions are essentially weak because of Laporte forbidden, chelate ligands is effective to strengthen the intramolecular energy transfer from photo-excited organic ligands to Ln3+ions. The direct evidence of energy transfer from ligands to Ln3+and details of excited state, however, are still veiled. Here, we report direct visualization of energy-transferred excited state in Eu complex with a hexadentate ligand (L) consisting of two bipyridine moieties bridged by an ethylendiamine unit, [Eu3+(L)(NO3)2](PF6) (Eu(L))[1] by Maximum Entropy Method (MEM) charge density[2] and electrostatic potential analysis[3] based on SR X-ray diffraction. First, we confirmed that the electron numbers of Eu and ligand L in the excited state are the same as those in the ground state, which is a direct evidence of energy transfer instead of charge transfer. Next, we observed charge re-distribution in the Eu ion and the ligand L. The electrostatic potential distributions calculated using MEM charge density give an experimental evidence for the existence of polarization of ligand L both in the ground and photo-excited states. The orientation polarization in the ground state changed during pumping at 315 nm, and the charge re-distribution are qualitatively consistent with a theoretical prediction. This characteristic luminescence behavior based on the energy relaxation process have not been detected by fundamental crystal structural analysis. We have succeeded in visualization of subtle but important change due to energy transfer in the mononuclear Europium complex with hexadentate ligand at the first time.

Renilla Bioluminescence: A Morphologic Approach to the Location of Photocytes

1974 ◽  
Vol 32 ◽  
pp. 208-209
Author(s):  
Ben O. Spurlock ◽  
Milton J. Cormier
Keyword(s):  
Excited State ◽  
Ground State ◽  
Molecular Basis ◽  
Light Emission ◽  
Chemical Basis ◽  
Electronic Excited State ◽  
Colonial Form ◽  
The Common ◽  
Eighteenth And Nineteenth Centuries ◽  
Catalyzed Oxidation

The phenomenon of bioluminescence has fascinated layman and scientist alike for many centuries. During the eighteenth and nineteenth centuries a number of observations were reported on the physiology of bioluminescence in Renilla, the common sea pansy. More recently biochemists have directed their attention to the molecular basis of luminosity in this colonial form. These studies have centered primarily on defining the chemical basis for bioluminescence and its control. It is now established that bioluminescence in Renilla arises due to the luciferase-catalyzed oxidation of luciferin. This results in the creation of a product (oxyluciferin) in an electronic excited state. The transition of oxyluciferin from its excited state to the ground state leads to light emission.

Ground State and Excited State H-Atom Temperatures in a Microwave Plasma Diamond Deposition Reactor

1996 ◽  
Vol 6 (9) ◽  
pp. 1167-1180 ◽  
Author(s):  
A. Gicquel ◽  
M. Chenevier ◽  
Y. Breton ◽  
M. Petiau ◽  
J. P. Booth ◽  
...  
Keyword(s):  
Excited State ◽  
Ground State ◽  
Microwave Plasma ◽  
Diamond Deposition

Spin-Forbidden Excitation Enables Infrared Photoredox Catalysis

2020 ◽  
Author(s):  
Tomislav Rovis ◽  
Benjamin D. Ravetz ◽  
Nicholas E. S. Tay ◽  
Candice Joe ◽  
Melda Sezen-Edmonds ◽  
...  
Keyword(s):  
Excited State ◽  
Ground State ◽  
Intersystem Crossing ◽  
Photoredox Catalysis ◽  
Infrared Irradiation ◽  
Triplet Excitation ◽  
New Family ◽  
Ir Light

We describe a new family of catalysts that undergo direct ground state singlet to excited state triplet excitation with IR light, leading to photoredox catalysis without the energy waste associated with intersystem crossing. The finding allows a mole scale reaction in batch using infrared irradiation.

Excited-State Dynamics in the RNA Nucleotide Uridine 5’-Monophosphate Investigated by Femtosecond Broadband Transient Absorption Spectroscopy

2019 ◽  
Author(s):  
Matthew M. Brister ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Transient Absorption ◽  
Electronic Energy ◽  
Transient Absorption Spectroscopy ◽  
Electronic Relaxation ◽  
Vibrationally Excited ◽  
Excited State Dynamics ◽  
Π State

<p></p><p> Damage to RNA from ultraviolet radiation induce chemical modifications to the nucleobases. Unraveling the excited states involved in these reactions is essential, but investigations aimed at understanding the electronic-energy relaxation pathways of the RNA nucleotide uridine 5’-monophosphate (UMP) have not received enough attention. In this Letter, the excited-state dynamics of UMP is investigated in aqueous solution. Excitation at 267 nm results in a trifurcation event that leads to the simultaneous population of the vibrationally-excited ground state, a longlived <sup>1</sup>n<sub>O</sub>π* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived <sup>3</sup>ππ* state in an ultrafast time scale. The results elucidate the electronic relaxation pathways and clarify earlier transient absorption experiments performed for uracil derivatives in solution. This mechanistic information is important because long-lived nπ* and ππ* excited states of both singlet and triplet multiplicities are thought to lead to the formation of harmful photoproducts.</p><p></p>

Mechanistic analysis of light-driven overcrowded alkene-based molecular motors by multiscale molecular simulations

2021 ◽  
Vol 23 (14) ◽  
pp. 8525-8540
Author(s):  
Mudong Feng ◽  
Michael K. Gilson
Keyword(s):  
Molecular Dynamics ◽  
Excited State ◽  
Molecular Dynamics Simulations ◽  
Ground State ◽  
Molecular Motors ◽  
Motor Performance ◽  
Molecular Simulations ◽  
Mechanistic Analysis ◽  
Dynamics Simulations ◽  
Shed Light

Ground-state and excited-state molecular dynamics simulations shed light on the rotation mechanism of small, light-driven molecular motors and predict motor performance. How fast can they rotate; how much torque and power can they generate?

Ground-state and excited-state absorption in rare-earth doped optical fibres

1990 ◽  
Vol 26 (5) ◽  
pp. 320 ◽  
Author(s):  
M. Monerie ◽  
T. Georges ◽  
P.L. Francois ◽  
J.Y. Allain ◽  
D. Neveux
Keyword(s):  
Rare Earth ◽  
Excited State ◽  
Ground State ◽  
Excited State Absorption ◽  
Optical Fibres ◽  
Rare Earth Doped

A meta-analysis and review examining a possible role for oxidative stress and singlet oxygen in diverse diseases

2017 ◽  
Vol 474 (16) ◽  
pp. 2713-2731 ◽  
Author(s):  
Athinoula L. Petrou ◽  
Athina Terzidaki
Keyword(s):  
Oxidative Stress ◽  
Excited State ◽  
Singlet Oxygen ◽  
Ground State ◽  
Meta Analysis ◽  
Common Mechanism ◽  
High Electron ◽  
A Value ◽  
First Excited State

From kinetic data (k, T) we calculated the thermodynamic parameters for various processes (nucleation, elongation, fibrillization, etc.) of proteinaceous diseases that are related to the β-amyloid protein (Alzheimer's), to tau protein (Alzheimer's, Pick's), to α-synuclein (Parkinson's), prion, amylin (type II diabetes), and to α-crystallin (cataract). Our calculations led to ΔG≠ values that vary in the range 92.8–127 kJ mol−1 at 310 K. A value of ∼10–30 kJ mol−1 is the activation energy for the diffusion of reactants, depending on the reaction and the medium. The energy needed for the excitation of O2 from the ground to the first excited state (1Δg, singlet oxygen) is equal to 92 kJ mol−1. So, the ΔG≠ is equal to the energy needed for the excitation of ground state oxygen to the singlet oxygen (1Δg first excited) state. The similarity of the ΔG≠ values is an indication that a common mechanism in the above disorders may be taking place. We attribute this common mechanism to the (same) role of the oxidative stress and specifically of singlet oxygen, (1Δg), to the above-mentioned processes: excitation of ground state oxygen to the singlet oxygen, 1Δg, state (92 kJ mol−1), and reaction of the empty π* orbital with high electron density regions of biomolecules (∼10–30 kJ mol−1 for their diffusion). The ΔG≠ for cases of heat-induced cell killing (cancer) lie also in the above range at 310 K. The present paper is a review and meta-analysis of literature data referring to neurodegenerative and other disorders.

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