A quantative study of the charge-transfer between conjugated thiophene rings in vibrationally excited states

Three Re(I) tricarbonyl complexes, with general formulation Re(N^L)(CO)3X (where N^L is a bidentate ligand containing a pyridine functionalized in the position 2 with a thione or a thiazol-2-ylidene group and X is either chloro or bromo) were synthesized and their reactivity explored in terms of solvent-dependent ligand substitution, both in the ground and excited states. When dissolved in acetonitrile, the complexes bound to the thione ligand underwent ligand exchange with the solvent resulting in the formation of Re(NCMe)2(CO)3X. The exchange was found to be reversible, and the starting complex was reformed upon removal of the solvent. On the other hand, the complexes appeared inert in dichloromethane or acetone. Conversely, the complex bound to the thiazole-2-ylidene ligand did not display any ligand exchange reaction in the dark, but underwent photoactivated ligand substitution when excited to its lowest metal-to-ligand charge transfer manifold. Photolysis of this complex in acetonitrile generated multiple products, including Re(I) tricarbonyl and dicarbonyl solvato-complexes as well as free thiazole-2-ylidene ligand.

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

10.26434/chemrxiv.7860023 ◽

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

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 1nOπ* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived 3ππ* 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.

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Charge Transfer Between CO22+ and Ar or Ne at Collision Energies 3-10 eV

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20030178 ◽

2003 ◽

Vol 68 (1) ◽

pp. 178-188 ◽

Cited By ~ 3

Author(s):

Libor Mrázek ◽

Ján Žabka ◽

Zdeněk Dolejšek ◽

Zdeněk Herman

Keyword(s):

Charge Transfer ◽

Excited States ◽

Ground State ◽

Scattering Method ◽

Translational Energy ◽

Centre Of Mass ◽

Energy Distributions ◽

Zener Model ◽

Beam Scattering ◽

Product Ions

The beam scattering method was used to investigate non-dissociative single-electron charge transfer between the molecular dication CO22+ and Ar or Ne at several collision energies between 3-10 eV (centre-of-mass, c.m.). Relative translational energy distributions of the product ions showed that in the reaction with Ar the CO2+ product was mainly formed in reactions of the ground state of the dication, CO22+(X3Σg-), leading to the excited states of the product CO2+(A2Πu) and CO2+(B2Σu+). In the reaction with Ne, the largest probability had the process from the reactant dication excited state CO22+(1Σg+) leading to the product ion ground state CO2+(X2Πg). Less probable were processes between the other excited states of the dication CO22+, (1∆g), (1Σu-), (3∆u), also leading to the product ion ground state CO2+(X2Πg). Using the Landau-Zener model of the reaction window, relative populations of the ground and excited states of the dication CO22+ in the reactant beam were roughly estimated as (X3Σg):(1∆g):(1Σg+):(1Σu-):(3∆u) = 1.0:0.6:0.5:0.25:0.25.

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Global double hybrids do not work for charge transfer: A comment on “Double hybrids and time‐dependent density functional theory: An implementation and benchmark on charge transfer excited states”

Journal of Computational Chemistry ◽

10.1002/jcc.26478 ◽

2021 ◽

Vol 42 (8) ◽

pp. 528-533

Author(s):

Marcos Casanova‐Páez ◽

Lars Goerigk

Keyword(s):

Density Functional Theory ◽

Charge Transfer ◽

Excited States ◽

Density Functional ◽

Time Dependent ◽

Functional Theory ◽

Dependent Density

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The Microwave Spectrum of 3,4-Dihydro-1,2-Pyran

Zeitschrift für Naturforschung A ◽

10.1515/zna-1985-0909 ◽

1985 ◽

Vol 40 (9) ◽

pp. 913-919

Author(s):

Juan Carlos López ◽

José L. Alonso

Keyword(s):

Dipole Moment ◽

Excited States ◽

Ground State ◽

Principal Axis ◽

Microwave Spectrum ◽

Average Intensity ◽

Ring Conformation ◽

Vibrationally Excited ◽

Rotational Constants ◽

Displacement Measurements

Abstract The rotational transitions of 3,4-dihydro-1,2-pyran in the ground state and six vibrationally excited states have been assigned. The rotational constants for the ground state (A = 5198.1847(24), B = 4747.8716(24) and C = 2710.9161(24) have been derived by fitting μa, μb and μc-type transitions. The dipole moment was determined from Stark displacement measurements to be 1.400(8) D with its principal axis components |μa| =1.240(2), |μb| = 0.588(10) and |μc| = 0.278(8) D. A model calculation to reproduce the ground state rotational constants indicates that the data are consistent with a twisted ring conformation. The average intensity ratio gives vibrational separations between the ground and excited states of the ring-bending and ring-twisting modes of ~ 178 and ~ 277 cm-1 respectively.

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