Vibronic interaction between nπ and ππ states and phosphorescence of Norharmane

Tomás, F.; Olba, A.; Medina, Piedad; Zabala, I.

doi:10.1016/0022-2860(86)85082-7

Cited by 6 publications

(2 citation statements)

References 6 publications

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“…The photophysics of aromatic carbonyl compounds have been extensively reported in the literature to involve low-lying np* states of both singlet and triplet character, 24,27,[68][69][70][71][72][73][74][75] with intersystem crossing (ISC) being a kinetically competitive photophysical process. 76,77 For example, Spighi et al 77 suggested a kinetic model for benzophenone, in which a 1 pp* state decays into a 3 np* state within 5 ps, followed by repopulation to the ground state within 400 ns.…”

Section: Discussionmentioning

confidence: 99%

Towards elucidating the photochemistry of the sunscreen filter ethyl ferulate using time-resolved gas-phase spectroscopy

et al. 2016

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Ultrafast time-resolved ion yield (TR-IY) and velocity map imaging spectroscopies are employed to reveal the relaxation dynamics after photoexcitation in ethyl 4-hydroxy-3-methoxycinnamate (ethyl ferulate, EF), an active ingredient in commercially available sunscreens. In keeping with a bottom-up strategy, the building blocks of EF, 2-methoxy-4-vinylphenol (MVP) and 4-hydroxy-3-methoxycinnamyl alcohol (coniferyl alcohol, ConA), were also studied to assist in our understanding of the dynamics of EF as we build up in molecular complexity. In contrast to the excited state dynamics of MVP and ConA, which are described by a single time constant (>900 ps), the dynamics of EF are described by three time constants (15 ± 4 ps, 148 ± 47 ps, and >900 ps). A mechanism is proposed involving internal conversion (IC) between the initially excited S(1ππ*) and S(1nπ*) states followed by intramolecular vibrational redistribution (IVR) on both states, in competition with intersystem crossing onto neighbouring triplet states (15 ± 4 ps). IVR and IC within the triplet manifold then ensues (148 ± 47 ps) to populate a low-lying triplet state (>900 ps). Importantly, the fluorescence spectrum of EF at the S origin, along with the associated lifetime (6.9 ± 0.1 ns), suggests that population is trapped, during initial IVR, on the S(1ππ*) state. This serves to demonstrate the complex, competing dynamics in this sunscreen filter molecule.

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Section: Discussionmentioning

confidence: 99%

Towards elucidating the photochemistry of the sunscreen filter ethyl ferulate using time-resolved gas-phase spectroscopy

et al. 2016

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“…Guided by the previous literature, which suggests that the photochemistry of carbonyl compounds is closely linked with the existence of triplet states [54,127,[142][143][144][145][146][147][148][149], Rodrigues et al used computational methods to search for such states in EF. These studies revealed three near isoenergetic triplet states approximately 2000 cm −1 lower in energy than the S 2 (1 1 nπ *) energy minimum (T 2 (2 3 ππ*), T 3 (3 3 ππ*) and T 4 (1 3 nπ *)) and a fourth, lying approximately 10 500 cm −1 below these (T 1 (1 3 ππ*)).…”

Section: (Ii) Ethyl Ferulatementioning

confidence: 99%

Photophysics of sunscreen molecules in the gas phase: a stepwise approach towards understanding and developing next-generation sunscreens

2016

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The relationship between exposure to ultraviolet (UV) radiation and skin cancer urges the need for extra photoprotection, which is presently provided by widespread commercially available sunscreen lotions. Apart from having a large absorption cross section in the UVA and UVB regions of the electromagnetic spectrum, the chemical absorbers in these photoprotective products should also be able to dissipate the excess energy in a safe way, i.e. without releasing photoproducts or inducing any further, harmful, photochemistry. While sunscreens are tested for both their photoprotective capability and dermatological compatibility, phenomena occurring at the molecular level upon absorption of UV radiation are largely overlooked. To date, there is only a limited amount of information regarding the photochemistry and photophysics of these sunscreen molecules. However, a thorough understanding of the intrinsic mechanisms by which popular sunscreen molecular constituents dissipate excess energy has the potential to aid in the design of more efficient, safer sunscreens. In this review, we explore the potential of using gas-phase frequency- and time-resolved spectroscopies in an effort to better understand the photoinduced excited-state dynamics, or photodynamics, of sunscreen molecules. Complementary computational studies are also briefly discussed. Finally, the future outlook of expanding these gas-phase studies into the solution phase is considered.

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