Tracking a Paternò–Büchi Reaction in Real Time Using Transient Electronic and Vibrational Spectroscopies

Harris, Stephanie J.; Murdock, Daniel; Grubb, Michael P.; Clark, Ian P.; Greetham, Gregory M.; Towrie, Michael; Ashfold, Michael N. R.

doi:10.1021/jp507958y

Cited by 8 publications

(3 citation statements)

References 33 publications

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“…The photochemical addition of carbonyl compounds to alkenes to form an oxetane ring is known as the Paternò−Büchi reaction, 31 whose mechanism, although is normally accepted to proceed via the triplet 3 (nπ*) excited state of the carbonyl compound, 32 still constitutes a matter of debate in the scientific community. [33][34][35] Figure 1. Scheme of the reaction leading to the thymine-thymine (6-4) adduct.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced formation mechanism of the thymine–thymine (6–4) adduct in DNA; a QM(CASPT2//CASSCF):MM(AMBER) study

et al. 2018

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The UVB-induced photomechanism leading the carbonyl group of a thymine nucleobase to react with the carbon-carbon double bond of a consecutive thymine nucleobase in a DNA strand to form the thymine-thymine (6-4) photodamage adduct remains poorly understood. Key questions remain unanswered, concerning both the intrinsic features of the photoreaction (such as the contribution (or not) of triplet states, the nature of the involved states and the time-scale of the photoprocess) and the role played by the non-reactive surroundings of the two reactive pyrimidine nucleobases (such as the nature of the flanked nucleobases and the flexibility of the whole DNA molecule). A small number of theoretical studies have been carried out on the title photoreaction, most of which have used reduced model systems of DNA, consequently neglecting potential key parameters for the photoreaction such as the constraints due to the double strain structure and the presence of paired and stacked nucleobases. In the present contribution the photoactivation step of the title reaction has been studied in a DNA system, and in particular for a specific DNA hairpin for which the quantum yield of photodamage formation has been recently experimentally measured. The reaction has been characterized by carrying out high-level QM/MM computations, combining the CASPT2//CASSCF approach for the study of the reactive part (i.e. the two thymine molecules) with an MM-Amber treatment of the surrounding environment. The possibility of a reaction path along both the singlet and triplet manifolds has been characterized, the nature of the reactive states has been analyzed, and the role played by the flexibility of the whole system, which in turn determines the initial accessible geometrical conformations, has been evaluated, thus substantially contributing towards the elucidation of the photoreaction mechanism. On the basis of the obtained results, it can be observed that a charge-transfer state can decay from a pro-reactive initial structure towards a region of energy degeneracy with the ground state, from which the subsequent decay along the ground state hypersurface can lead to the photoreaction.

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Section: Introductionmentioning

confidence: 99%

Photoinduced formation mechanism of the thymine–thymine (6–4) adduct in DNA; a QM(CASPT2//CASSCF):MM(AMBER) study

et al. 2018

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“…Ashfold reported the use of broadband transient electronic and vibrational absorption spectroscopies for an insightful study of the Paternò-Büchi reaction between benzaldehyde and cyclohexene. 16 Quantum yields and rates constants for competing pathways were determined.…”

Section: Electronic and Vibrational Absorption Spectroscopiesmentioning

confidence: 99%

Oxetanes and Oxetenes: Fused-Ring Derivatives

Blanchard

Bizet

Brach

et al. 2022

Comprehensive Heterocyclic Chemistry IV

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“…16 The observed coherent oscillations in the ultrafast dynamics of solute molecules provide information on their wavepacket motion in the ground state, the excited state or in both the ground and excited states. 3,4,11,[17][18][19][20][21][22][23][24][25] This technique has also been used to observe coherent oscillations in molecular systems and materials. 12,15,16,26 Depending on the characteristics of the excitation wavelength and phase (frequency chirping) of the laser pulses, the coherent oscillations can arise from the wavepacket motion in the ground state, excited state or in both ground and excited states.…”

Section: Introductionmentioning

confidence: 99%

Observing ground state vibrational coherence and excited state relaxation dynamics of a cyanine dye in pure solvents

Das

Makhal

Goswami

2018

Phys. Chem. Chem. Phys.

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Using a degenerate pump probe technique at 800 nm, Ground State Vibrational Coherence (GSVC) of a cyanine dye (IR780) is explored in various solvents. Five representative solvents were studied, of which GSVC is present in three: methanol (MeOH), ethanol (EtOH) and dichloromethane (DCM). The maximum number of damped oscillations was observed in DCM solvent and the oscillations persisted for 1.2 ps. However, GSVC is absent in two solvents: acetonitrile (ACN) and dimethyl sulfoxide (DMSO). For nondegenerate pump probe studies with a 400 nm pump and a supercontinuum probe, GSVC was absent for IR780 in all of the five solvents studied. Instead these studies showed excited state absorption corresponding to S1 → Sn absorption bands in the 450 to 650 nm range. Decay profiles for these correspond to the higher electronic states (Sn, n ≥ 2) in contrast to the degenerate case involving S1. Complete dynamics of IR780 with 30 fs pulses are reported by invoking three time-constants to fit the kinetic traces that can, in turn, be assigned as: vibrational cooling, intermediate state time, and ground state recovery (GSR). All these dynamics exhibit noticeable solvent dependence. A plateau region is also observed in the early part of the GSR dynamics, strongly suggesting the existence of an intermediate state between the ground (S0) and excited singlet (S1) states.

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Tracking a Paternò–Büchi Reaction in Real Time Using Transient Electronic and Vibrational Spectroscopies

Cited by 8 publications

References 33 publications

Photoinduced formation mechanism of the thymine–thymine (6–4) adduct in DNA; a QM(CASPT2//CASSCF):MM(AMBER) study

Photoinduced formation mechanism of the thymine–thymine (6–4) adduct in DNA; a QM(CASPT2//CASSCF):MM(AMBER) study

Oxetanes and Oxetenes: Fused-Ring Derivatives

Observing ground state vibrational coherence and excited state relaxation dynamics of a cyanine dye in pure solvents

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