Ultrafast excited state relaxation dynamics in a heteroleptic Ir(iii) complex, fac-Ir(ppy)2(ppz), revealed by femtosecond X-ray transient absorption spectroscopy

2021 ◽  
Author(s):  
Jungkweon Choi ◽  
Mina Ahn ◽  
Jae Hyuk Lee ◽  
Doo-Sik Ahn ◽  
Hosung Ki ◽  
...  
Keyword(s):  
Excited State ◽  
Time Constant ◽  
Absorption Spectroscopy ◽  
Internal Conversion ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Relaxation Dynamics ◽  
X Ray ◽  
Forbidden Transition ◽  
Calculation Results

The experimental and calculation results demonstrate that the 3MLppzCT state generated by the spin-forbidden transition rapidly relaxes to 3MLppyCT through internal conversion process with a time constant of ∼450 fs.

Triplet Excited State Distortions in a Pyrazolate Bridged Platinum Dimer Measured by X-ray Transient Absorption Spectroscopy

2010 ◽  
Vol 114 (48) ◽  
pp. 12780-12787 ◽  
Author(s):  
Jenny V. Lockard ◽  
Aaron A. Rachford ◽  
Grigory Smolentsev ◽  
Andrew B. Stickrath ◽  
Xianghuai Wang ◽  
...  
Keyword(s):  
Excited State ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Triplet Excited State ◽  
X Ray

Excited-state molecular structures captured by X-ray transient absorption spectroscopy: a decade and beyond

2010 ◽  
Vol 66 (2) ◽  
pp. 240-251 ◽  
Author(s):  
Lin X. Chen ◽  
Xiaoyi Zhang ◽  
Jenny V. Lockard ◽  
Andrew B. Stickrath ◽  
Klaus Attenkofer ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Metal Complexes ◽  
Absorption Spectroscopy ◽  
Chemical Reaction ◽  
Transient Absorption ◽  
Molecular Structures ◽  
Transient Absorption Spectroscopy ◽  
Reaction Pathways ◽  
X Ray

Transient molecular structures along chemical reaction pathways are important for predicting molecular reactivity, understanding reaction mechanisms, as well as controlling reaction pathways. During the past decade, X-ray transient absorption spectroscopy (XTA, or LITR-XAS, laser-initiated X-ray absorption spectroscopy), analogous to the commonly used optical transient absorption spectroscopy, has been developed. XTA uses a laser pulse to trigger a fundamental chemical process, and an X-ray pulse(s) to probe transient structures as a function of the time delay between the pump and probe pulses. Using X-ray pulses with high photon flux from synchrotron sources, transient electronic and molecular structures of metal complexes have been studied in disordered media from homogeneous solutions to heterogeneous solution–solid interfaces. Several examples from the studies at the Advanced Photon Source in Argonne National Laboratory are summarized, including excited-state metalloporphyrins, metal-to-ligand charge transfer (MLCT) states of transition metal complexes, and charge transfer states of metal complexes at the interface with semiconductor nanoparticles. Recent developments of the method are briefly described followed by a future prospective of XTA. It is envisioned that concurrent developments in X-ray free-electron lasers and synchrotron X-ray facilities as well as other table-top laser-driven femtosecond X-ray sources will make many breakthroughs and realise dreams of visualizing molecular movies and snapshots, which ultimately enable chemical reaction pathways to be controlled.

scholarly journals Excited State Dynamics of 7-Deazaguanosine and Guanosine 5’ Monophosphate

2021 ◽  
Author(s):  
Sarah E. Krul ◽  
Sean J. Hoehn ◽  
Karl Feierabend ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Ground State ◽  
Internal Conversion ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Water Mixture ◽  
Relaxation Dynamics ◽  
Similar Time ◽  
Excited State Dynamics ◽  
Computational Calculations

<p>Minor structural modifications to the DNA and RNA nucleobases have a significant effect on their excited state dynamics and electronic relaxation pathways.<b> </b>In this study, the excited state dynamics of 7-deazaguanosine and guanosine 5’-monophosphate are investigated in aqueous and in a mixture of methanol and water using femtosecond broadband transient absorption spectroscopy following excitation at 267 nm. The transient spectra are collected using photon densities that ensure no parasitic multiphoton-induced signal from solvated electrons. The data can be fit satisfactorily using a two- or three-component kinetic model. By analyzing the results from steady-state, time-resolved, computational calculations, and the methanol-water mixture, the following general relaxation mechanism is proposed for both molecules, L<sub>b</sub> ® L<sub>a</sub> ® <sup>1</sup>ps*(ICT) ® S<sub>0</sub>, where the <sup>1</sup>ps*(ICT) stands for an intramolecular charge transfer excited singlet state with significant ps* character. In general, longer lifetimes for internal conversion are obtained for 7-deazaguanosine compared to guanosine 5’-monophosphate. Internal conversion of the <sup>1</sup>ps*(ICT) state to the ground state occurs on a similar time scale of a few picoseconds in both molecules. Collectively, the results demonstrate that substitution of a single nitrogen for a methine (C-H) group at position seven of the guanine moiety stabilizes the <sup>1</sup>pp* L<sub>b</sub> and L<sub>a</sub> states and alter the topology of their potential energy surfaces in such a way that the relaxation dynamics in 7-deazaguanosine are slowed down compared to those in guanosine 5’-monophosphate but not for the internal conversion of <sup>1</sup>ps*(ICT) state to the ground state.</p>

scholarly journals Excited State Dynamics of 7-Deazaguanosine and Guanosine 5’ Monophosphate

2021 ◽  
Author(s):  
Sarah E. Krul ◽  
Sean J. Hoehn ◽  
Karl Feierabend ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Ground State ◽  
Internal Conversion ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Water Mixture ◽  
Relaxation Dynamics ◽  
Similar Time ◽  
Excited State Dynamics ◽  
Computational Calculations

<p>Minor structural modifications to the DNA and RNA nucleobases have a significant effect on their excited state dynamics and electronic relaxation pathways.<b> </b>In this study, the excited state dynamics of 7-deazaguanosine and guanosine 5’-monophosphate are investigated in aqueous and in a mixture of methanol and water using femtosecond broadband transient absorption spectroscopy following excitation at 267 nm. The transient spectra are collected using photon densities that ensure no parasitic multiphoton-induced signal from solvated electrons. The data can be fit satisfactorily using a two- or three-component kinetic model. By analyzing the results from steady-state, time-resolved, computational calculations, and the methanol-water mixture, the following general relaxation mechanism is proposed for both molecules, L<sub>b</sub> ® L<sub>a</sub> ® <sup>1</sup>ps*(ICT) ® S<sub>0</sub>, where the <sup>1</sup>ps*(ICT) stands for an intramolecular charge transfer excited singlet state with significant ps* character. In general, longer lifetimes for internal conversion are obtained for 7-deazaguanosine compared to guanosine 5’-monophosphate. Internal conversion of the <sup>1</sup>ps*(ICT) state to the ground state occurs on a similar time scale of a few picoseconds in both molecules. Collectively, the results demonstrate that substitution of a single nitrogen for a methine (C-H) group at position seven of the guanine moiety stabilizes the <sup>1</sup>pp* L<sub>b</sub> and L<sub>a</sub> states and alter the topology of their potential energy surfaces in such a way that the relaxation dynamics in 7-deazaguanosine are slowed down compared to those in guanosine 5’-monophosphate but not for the internal conversion of <sup>1</sup>ps*(ICT) state to the ground state.</p>

Structure and excited-state dynamics of dimeric copper(i) photosensitizers investigated by time-resolved X-ray and optical transient absorption spectroscopy

2021 ◽  
Vol 23 (5) ◽  
pp. 3656-3667
Author(s):  
Lucía Velasco ◽  
Leonel Llanos ◽  
Pedro Levín ◽  
Andrés Vega ◽  
Jin Yu ◽  
...  
Keyword(s):  
Excited State ◽  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
Time Resolved ◽  
X Ray ◽  
Solvent Type ◽  
Optical Transient

Three homoleptic Cu(i) dimeric photosensitizers are studied through ultrafast X-ray and optical absorption spectroscopy. The complexes show distinct excited state lifetimes, due to the solvent type and spacers' flexibilities between the Cu centres.

Highly Accurate Excited-State Structure of [Os(bpy)2dcbpy]2+ Determined by X-ray Transient Absorption Spectroscopy

2014 ◽  
Vol 136 (24) ◽  
pp. 8804-8809 ◽  
Author(s):  
Xiaoyi Zhang ◽  
Sophie E. Canton ◽  
Grigory Smolentsev ◽  
Carl-Johan Wallentin ◽  
Yizhu Liu ◽  
...  
Keyword(s):  
Excited State ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
State Structure ◽  
X Ray

scholarly journals Direct Observation of S2–S1 Internal Conversion in Pyrene by Femtosecond Transient Absorption

1999 ◽  
Vol 19 (1-4) ◽  
pp. 375-379 ◽  
Author(s):  
Frederik V. R. Neuwahl ◽  
Paolo Foggi
Keyword(s):  
Time Constant ◽  
Absorption Spectroscopy ◽  
Direct Observation ◽  
Internal Conversion ◽  
Transient Absorption ◽  
Conversion Process ◽  
Transient Absorption Spectroscopy ◽  
Kinetic Measurements ◽  
State Population ◽  
Femtosecond Transient Absorption

UV pulses of 100 fs at 340 nm are utilised to excite pyrene to the vibrationally cold S2 state. Population and depopulation processes occurring in the S2 state are investigated by transient absorption spectroscopy with a white continuum probe. In the first 400 fs after excitation it is possible to measure the growth and disappearance of a band at 585 nm which is assigned to the S14←S2 transition. As a consequence of the internal conversion process from S2 to S1 state, the disappearance of the 585 nm band and the growth of the transient spectrum due to Sn←S1 transitions can be observed. Kinetic measurements of the S2 decay and S1 growing signals provide an estimate of the rate of internal conversion which occurs with a time constant of 150±50 fs.

scholarly journals Excited state electron and energy relays in supramolecular dinuclear complexes revealed by ultrafast optical and X-ray transient absorption spectroscopy

2018 ◽  
Vol 9 (4) ◽  
pp. 860-875 ◽  
Author(s):  
Dugan Hayes ◽  
Lars Kohler ◽  
Ryan G. Hadt ◽  
Xiaoyi Zhang ◽  
Cunming Liu ◽  
...  
Keyword(s):  
Excited State ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Dinuclear Complexes ◽  
X Ray ◽  
Ultrafast Optical ◽  
State Electron ◽  
Charge Hopping

Complementary ultrafast techniques provide clear observation of charge hopping between metals in dinuclear complexes.

scholarly journals The Nature of the Long-Lived Excited State in a NiII Phthalocyanine Complex Investigated by X-Ray Transient Absorption Spectroscopy

ChemSusChem ◽  
2018 ◽  
Vol 11 (14) ◽  
pp. 2421-2428 ◽  
Author(s):  
Jiyun Hong ◽  
Matthew S. Kelley ◽  
Megan L. Shelby ◽  
Dugan K. Hayes ◽  
Ryan G. Hadt ◽  
...  
Keyword(s):  
Excited State ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
X Ray ◽  
Phthalocyanine Complex
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