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UV-Vis absorption spectra and emission peaks of indole and 7-fluoroindole are measured and it is observed that 7-fluoroindole quenches the fluorescence signals significantly compared to indole. This observation is elucidated reconstruction of the potential energy surfaces, determination of the conical intersections, and dynamical studies. It is observed that a single fluorine substitution on indole leads to the appearance of several accessible low-energy conical intersections that cause fast nonradiative decay. In this paper, we have investigated the nonradiative processes of Ind and 7F-Ind theoretically using high-level methods, such as EOM-EE-CCSD, SA-CASSCF, MS-CASPT2/6-311++G(d,p) levels of theory, to study these pathways and their feasibility.
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http://dx.doi.org/10.1039/d2cp00465h | DOI Listing |
Chem Sci
August 2025
State Key Laboratory of Chemical Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
We report time-sliced velocity map imaging studies of the methyl (CH) and electronically excited sulfur (S(D)) fragments formed following the photoexcitation of jet-cooled CHSH molecules in the 2A'' ← X̃ A' absorption band (. at wavelengths in the range 190 ≤ ≤ 210 nm). Analyses of images of CH fragments in their = 0, 1 and 2 vibrational levels confirm the perpendicular parent transition dipole moment and prompt bond fission and show that the ground state SH(X) partners are formed with an inverted vibrational population distribution, peaking at = 2 at the shortest excitation wavelengths investigated.
View Article and Find Full Text PDFChemPhotoChem
March 2025
Max Planck Research Group, Faculty of Chemistry and Pharmacy, Universidad del Atlántico, Barranquilla, 081007, Colombia.
Azocompounds are among the most important group of molecular photoswitches due to their multiple applications in various scientific areas. We studied the thermal and photochemical reactions of an azocompound with photo-induced antibiotic properties using calculations based on Kohn-Shan, Spin-Flip and time-dependent Density Functional Theory. Our primary goal is to understand the absorption spectra and isomerization pathways governing the molecule's light-controlled antibiotic activity.
View Article and Find Full Text PDFIn this Letter, we report phase-dependent excited-state relaxation pathways and fluorescence mechanisms of the 1-NH molecule using quantum chemical simulations. In the liquid phase, the synergistic coupling between excited-state intramolecular proton transfer (ESIPT) and twisted intramolecular charge transfer (TICT) facilitates nonradiative decay through a conical intersection (CI) channel, leading to the quenching of Keto* fluorescence. Conversely, in the solid phase, restricted molecular rotation blocks the CI channel and promotes barrierless ESIPT, yielding strong Keto* emission in the near-infrared (NIR) region.
View Article and Find Full Text PDFJ Chem Phys
August 2025
Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Conical intersections (CIs) play an important role in photochemistry, allowing for ultrafast radiationless decay in processes such as photodissociation. In addition to these natural CIs, an external electric field can create light-induced conical intersections (LICIs), as the dipole-field interaction shifts the coupled potential energy surfaces. This work explores the effect of LICIs on the minor molecular (NH + H2) channel of ammonia photodissociation, building on prior work that studied the major radical (NH2 + H) channel.
View Article and Find Full Text PDFJ Chem Theory Comput
August 2025
Department of Chemistry, Princeton University, Princeton, New Jersey 08540, United States.
We revisit the photodynamics of tetracyanoethylene-hexamethylbenzene (TCNE-HMB), the molecular complex studied by Hochstrasser et al. [ 100, 4797-4810, 1994] that has long challenged the applicability of Marcus's theory of electron transfer for predicting photochemical reactions. Using a novel black-box electronic structure algorithm (time-dependent density functional theory with one double, TDDFT-1D) to efficiently run molecular dynamics that can treat charge recombination, we run ab initio surface hopping molecular dynamics and confirm that, for a polar solvent, charge recombination rates can be incredibly fast (indeed faster than the solvent relaxation time); for nonpolar solvents, the rate is much slower.
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