Photoinduced ligand dissociation follows reverse energy gap law: nitrile photodissociation from low energy 3MLCT excited states

2020 ◽  
Vol 56 (29) ◽  
pp. 4070-4073
Author(s):  
Lauren M. Loftus ◽  
Jeffrey J. Rack ◽  
Claudia Turro
Keyword(s):  
Excited State ◽  
Excited States ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Energy Gap ◽  
Low Energy ◽  
Transient Absorption Spectroscopy ◽  
Ligand Dissociation ◽  
Energy Gap Law

Transient absorption spectroscopy is used to show that stabilization of the 3MLCT excited state in a series of Ru(ii) complexes leads to decreased population of the 3LF state, but does not reduce the efficiency of photoinduced nitrile dissociation.

Investigation of ultrafast excited state dynamics of 2,2′,4,4′,6,6′-hexanitrostilbene using femtosecond transient absorption spectroscopy

RSC Advances ◽  
2014 ◽  
Vol 4 (104) ◽  
pp. 60382-60385 ◽  
Author(s):  
Genbai Chu ◽  
Min Shui ◽  
Ying Xiong ◽  
Jing Yi ◽  
Kemei Cheng ◽  
...  
Keyword(s):  
Excited State ◽  
Excited States ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Excited State Dynamics ◽  
Femtosecond Transient Absorption ◽  
Femtosecond Transient Absorption Spectroscopy

A study on the dynamics and structures of the excited states of 2,2′,4,4′,6,6′-hexanitrostilbene shows equilibrium between vibrationally hot S1 (S*1) and S1 states with lifetimes of 0.8 and 6 ps, respectively.

Excited state dynamics of symmetric and asymmetric Cr3(dpa)4Cl2 measured using femtosecond transient absorption spectroscopy

2017 ◽  
Vol 19 (37) ◽  
pp. 25471-25477 ◽  
Author(s):  
Chao-Han Cheng ◽  
Wen-Zhen Wang ◽  
Shie-Ming Peng ◽  
I-Chia Chen
Keyword(s):  
Excited State ◽  
Excited States ◽  
Metal Atom ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Chain Complex ◽  
Transient Absorption Spectroscopy ◽  
Femtosecond Transient Absorption ◽  
Femtosecond Transient Absorption Spectroscopy ◽  
Atom Chain

Relaxation pathway of excited states in extended metal atom chain complex Cr3(dpa)4Cl2.

Nonthermalized excited states in Ru(II) polypyridyl complexes probed by ultrafast transient absorption spectroscopy with high photon energy excitation

2008 ◽  
Vol 86 (12) ◽  
pp. 1118-1125 ◽  
Author(s):  
Sherri A McFarland ◽  
Karen AWY Cheng ◽  
Felix S Lee ◽  
Frances L Cozens ◽  
Norman P Schepp
Keyword(s):  
Excited State ◽  
Excited States ◽  
Photon Energy ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Singular Value ◽  
Transient Absorption Spectroscopy ◽  
Energy Excitation ◽  
Polypyridyl Complexes ◽  
Value Decomposition

The picosecond excited state dynamics of a series of homoleptic Ru(II) polypyridyl complexes (where LL = bpy, dmb, dmeob, dfmb, or dttb) have been investigated in aqueous solution at room temperature using femtosecond transient absorption spectroscopy with high photon energy excitation. All of the complexes studied produced similar spectroscopic signatures: a near-instantaneous bleach centered at 470–500 nm corresponding to the static absorption spectrum, as well as an intense absorption (475–650 nm) that decayed within the instrument response function (IRF) to form a broad, low-level absorption extending from 500–650 nm. Detailed analyses of both kinetic and spectral parameters by singular value decomposition (SVD) indicate that the excited state difference spectra contain contributions from at least three distinguishable species that have been assigned as ligand-based π* ← π* and ligand-to-metal-charge-transfer (LMCT) transitions concomitant with the loss of the ground state metal-to-ligand-charge-transfer (MLCT) transition. Kinetic information extracted at 530 nm (an optical marker for the fully intraligand-delocalized 3MLCT state) or 660 nm (LMCT transitions) appear to be biphasic in some cases with the amplitude of the IRF-limited component becoming larger with shorter wavelength excitation. Further, rise dynamics were observed at redder probe wavelengths for Ru(bpy)32+ and Ru(dttb)32+. These observations are different from those obtained using lower photon energy excitation and show that excitation wavelength strongly influences the early photophysical events in these Ru(II) complexes.Key words: ruthenium, photophysics, lasers, transient absorption spectroscopy, excited states, singular value decomposition (SVD).

Exploring Differences in Excited-State Properties of Styryl-BODIPY Chromophores upon Change from α- to β-Substitution

2020 ◽  
Vol 234 (11-12) ◽  
pp. 1735-1758
Author(s):  
Mirko Scholz ◽  
Caroline Hoffmann ◽  
Johannes R. Klein ◽  
Marcel Wirtz ◽  
Gregor Jung ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Energy Gap ◽  
Stokes Shift ◽  
Transient Absorption Spectroscopy ◽  
Slight Reduction ◽  
Polar Solvents ◽  
Absorption And Emission

AbstractWe present a femtosecond pump-probe UV-Vis broadband transient absorption spectroscopy study of two styryl-substituted BODIPY chromophores with different position of the substituent. The α-substituted isomer shows typical BODIPY-type spectral features, such as sharp absorption and emission bands, a small Stokes shift and an excited-state lifetime in the 4 ns range, which only weakly depends on the solvent. In contrast, β-styryl-BODIPY features much broader steady-state absorption and emission spectra and a larger Stokes shift, particularly in polar solvents. Transient absorption spectroscopy including a complete global kinetic analysis reports a substantial decrease in S1 lifetime to 300 ps for polar solvents upon change from α- to β-substitution. In the case of the α-isomer, TD-DFT calculations identify a typical “cyanine-type” electron rearrangement upon S0 → S1 excitation accompanied by a slight reduction in dipole moment. In contrast, the same transition in the β-isomer shows strong intramolecular charge transfer (ICT) character involving a substantial increase in dipole moment. Assuming a simple energy-gap-law argument, the accelerated nonradiative decay of the β-isomer in polar solvents may be linked to the decrease of the S1(ICT)-S0 energy difference. BODIPY dyes with a conjugated substituent in β-position therefore suffer a substantial loss in fluorescence brightness in polar environments compared with their α-substituted counterparts. This might limit their applicability in fluorescence imaging.

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>

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