Excited-state deactivation of 5-vinyluracil: Effects of π-π conjugation and intramolecular hydrogen bond C H⋯O C

Liu, Yan; Yang, Songqiu

doi:10.1016/j.jphotochem.2016.07.012

Cited by 8 publications

(4 citation statements)

References 48 publications

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“…With consideration for previous theoretical studies related to the MECI, ,− we optimized the S 0 EQ, S 1 EQ, and S 0 /S 1 MECI geometries on the basis of spin-restricted DFT, spin-restricted TDDFT, and spin-flip TDDFT, respectively. Single-point spin-restricted TDDFT calculations were then performed for all the obtained geometries to evaluate the excitation energy components.…”

Section: Methodsmentioning

confidence: 99%

Unveiling Controlling Factors of the S₀/S₁ Minimum Energy Conical Intersection: A Theoretical Study

et al. 2018

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The minimum energy conical intersection (MECI) geometries play an important role in photophysics and photochemistry. Although a number of MECI geometries can be identified using quantum chemical methods, their chemical interpretation remains unclear. In this study, a systematic analysis was performed on the MECIs between the singlet (S0) and lowest singlet excited (S1) states of organic molecules. The frozen orbital analysis (FZOA), which approximates the excited states with minimal main configurations, was adopted to analyze the excitation energy components at the S0/S1 MECI geometries as well as the S0 and S1 equilibrium geometries. At the S0/S1 MECI geometries, the HOMO–LUMO gaps decreased as expected but did not disappear. The remaining gaps were balanced with the HOMO–LUMO Coulomb integrals. Furthermore, we discovered that the HOMO–LUMO exchange integrals became approximately zero. On the basis of this fact, a systematic interpretation of the S0/S1 MECI geometries has been described.

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Section: Methodsmentioning

confidence: 99%

Unveiling Controlling Factors of the S₀/S₁ Minimum Energy Conical Intersection: A Theoretical Study

et al. 2018

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“…Methyl sinapate (MS) is the simplest sinapate ester and composed of a phenyl ring and an acrylate, as shown in Figure . Upon photoexcitation to a bright ππ* state, excited-state trans-MS molecules evolve along the alkene double bond twisting coordinate (α in Figure ) to a conical intersection (CI) where internal conversion (IC) to the ground state (S 0 ) occurs, and then the forming hot S 0 molecules can either go back to trans-form or forward to cis-product, akin to sinapoyl malate. ,, In this work, in order to further explore the para -substitution effect on the excited-state dynamics of sinapates, we have synthesized MS, p- OMeMS, and p- HMS, as shown in Figure . In particular for p- HMS, no para -substitution results in an interaction between V(ππ*) and a relative dark V′(ππ*) state, leading to different photodynamics behaviors in the excited state.…”

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confidence: 99%

“…Transient absorption spectra (TAS) were measured by femtosecond pump–probe transient absorption spectroscopy. This setup was described in our previous studies. , Briefly, the pump pulses for MS, p- OMeMS, and p- HMS were 320, 320, and 285 nm, respectively. The probe pulse (360–750 nm) was generated by focusing a weak 800 nm pulse on a 2 mm thick CaF 2 crystal.…”

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confidence: 99%

Substitution Dependent Ultrafast Ultraviolet Energy Dissipation Mechanisms of Plant Sunscreens

Zhao

Luo

Liu

et al. 2019

J. Phys. Chem. Lett.

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An ultraviolet energy dissipation mechanism plays a critical role in the photoprotection effect of sunscreens. In this work, we discovered substitution dependent UV energy dissipation mechanisms of model plant sunscreen methyl sinapate (MS). We found that the initially populated V(ππ*) states of MS and p-OMeMS relax to the ground state nonradiatively along an ultrafast trans–cis photoisomerization in tens of picoseconds. However, for p-HMS, an internal conversion from V(ππ*) to a relative dark V′(ππ*) state occurs in less than 1 ps, leading to a branching of the excited-state relaxations. The V (ππ*) state still relaxes nonradiatively as in the case of MS and p-OMeMS. In contrast, the V′(ππ*) state decays to the ground state mainly by emitting photons, exhibiting a lifetime as long as 5 ns. It is the first time to definitely distinguish the dynamics between V(ππ*) and V′(ππ*) states in the study of sinapates and cinnamates. These results indicate the anticipation of the V′(ππ*) state should be avoided when designing sunscreens.

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“…A redshift of λ Max found in C -methyl- N -phenyl tetrazoles of 1 a and 2 a ( 1 a : 238 nm → 2 a : 250 nm) is resulted from the non-planar structure of 1 a . Although there exist hyperconjugative effects between methyl and tetrazole rings in the four tetrazoles (σ–π for 1 a , 2 a and σ–p for 1 b , 2 b ), the additional effects of π–π conjugative donations in N -methyl- C -phenyl tetrazoles of 1 b and 2 b are also involved in the substituent group of phenyl with the tetrazole ring . These can be diagrammatically seen in Scheme .…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Understanding and Reactivity Analyses for the Photochemistry of Disubstituted Tetrazoles

Yang

Liang

et al. 2023

J. Phys. Chem. A

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The photolysis of tetrazoles has undergone extensive research. However, there are still some problems to be solved in terms of mechanistic understanding and reactivity analyses, which leaves room for theoretical calculations. Herein, multiconfiguration perturbation theory at the CASPT2//CASSCF level was employed to account for electron correction effects involved in the photolysis of four disubstituted tetrazoles. Based on calculations of vertical excitation properties and evaluations of intersystem crossing (ISC) efficiencies in the Frank–Condon region, the combination of space and electronic effects is found in maximum-absorption excitation. Two types of ISC (1ππ* → 3nπ*, 1ππ* → 3ππ*) are determined in disubstituted tetrazoles, and the obtained rates follow the El-Sayed rule. Through mapping three representative types of minimum energy profiles for the photolysis of 1,5-, and 2,5-disubstituted tetrazoles, a conclusion can be drawn that the photolysis of tetrazoles exhibits reactivity characteristic of bond-breaking selectivity. Kinetic evaluations show that the photogeneration of singlet imidoylnitrene operates predominately over that in the triplet state, which can be confirmed by a double-well model in the triplet potential energy surface of 1,5-disubstituted tetrazole. Similar mechanistic explorations and reactivity analyses were also applied to the photolysis of 2,5-disubstituted tetrazole to unveil fragmentation patterns of nitrile imine generation. All computational efforts allow us to better understand the photoreactions of disubstituted tetrazoles and to provide useful strategies for regulating their unique reactivity.

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Excited-state deactivation of 5-vinyluracil: Effects of π-π conjugation and intramolecular hydrogen bond C H⋯O C

Cited by 8 publications

References 48 publications

Unveiling Controlling Factors of the S₀/S₁ Minimum Energy Conical Intersection: A Theoretical Study

Unveiling Controlling Factors of the S₀/S₁ Minimum Energy Conical Intersection: A Theoretical Study

Substitution Dependent Ultrafast Ultraviolet Energy Dissipation Mechanisms of Plant Sunscreens

Mechanistic Understanding and Reactivity Analyses for the Photochemistry of Disubstituted Tetrazoles

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Excited-state deactivation of 5-vinyluracil: Effects of π-π conjugation and intramolecular hydrogen bond C H⋯O C

Cited by 8 publications

References 48 publications

Unveiling Controlling Factors of the S0/S1 Minimum Energy Conical Intersection: A Theoretical Study

Unveiling Controlling Factors of the S0/S1 Minimum Energy Conical Intersection: A Theoretical Study

Substitution Dependent Ultrafast Ultraviolet Energy Dissipation Mechanisms of Plant Sunscreens

Mechanistic Understanding and Reactivity Analyses for the Photochemistry of Disubstituted Tetrazoles

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Unveiling Controlling Factors of the S₀/S₁ Minimum Energy Conical Intersection: A Theoretical Study

Unveiling Controlling Factors of the S₀/S₁ Minimum Energy Conical Intersection: A Theoretical Study