Ultrafast Quenching of the Xanthone Triplet by Energy Transfer:  New Insight into the Intersystem Crossing Kinetics

Satzger, Helmut; Schmidt, B.; Root, C.; Zinth, Wolfgang; Fierz, Beat; Krieger, Florian; Kiefhaber, Thomas; Gilch, Peter

doi:10.1021/jp047583+

Cited by 65 publications

(92 citation statements)

References 28 publications

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“…[31] More recently, also the role of ISC in organic molecules has captured the attention of researchers. Examples of molecules where ISC is important range from aldehydes [37] and small aromatic compounds like benzene, [38] naphthalene, anthracene, and their carbonylic derivatives [39][40][41][42][43][44][45][46][47][48][49][50][51] to nitrocompounds. [43,[52][53][54][55][56][57][58][59][60][61] Furthermore, ISC has been reported for thio-substituted, [62][63][64][65][66][67][68] aza-substituted, [69] bromo-substituted, [70] and canonical nucleobases.…”

Section: Introductionmentioning

confidence: 99%

A general method to describe intersystem crossing dynamics in trajectory surface hopping

Mai

Marquetand

González

2015

Int J of Quantum Chemistry

270

406

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Intersystem crossing is a radiationless process that can take place in a molecule irradiated by UV‐Vis light, thereby playing an important role in many environmental, biological and technological processes. This paper reviews different methods to describe intersystem crossing dynamics, paying attention to semiclassical trajectory theories, which are especially interesting because they can be applied to large systems with many degrees of freedom. In particular, a general trajectory surface hopping methodology recently developed by the authors, which is able to include nonadiabatic and spin‐orbit couplings in excited‐state dynamics simulations, is explained in detail. This method, termed SHARC, can in principle include any arbitrary coupling, what makes it generally applicable to photophysical and photochemical problems, also those including explicit laser fields. A step‐by‐step derivation of the main equations of motion employed in surface hopping based on the fewest‐switches method of Tully, adapted for the inclusion of spin‐orbit interactions, is provided. Special emphasis is put on describing the different possible choices of the electronic bases in which spin‐orbit can be included in surface hopping, highlighting the advantages and inconsistencies of the different approaches. © 2015 Wiley Periodicals, Inc.

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Section: Introductionmentioning

confidence: 99%

A general method to describe intersystem crossing dynamics in trajectory surface hopping

Mai

Marquetand

González

2015

Int J of Quantum Chemistry

270

406

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“…[1][2][3][4][5][6] It is well known that the polarity of a solvent greatly influences the energies of the electronic states as well as the photophysical properties in aromatic carbonyl systems. [7][8][9][10] An increase in the solvent polarity results in the stabilization of ππ * states, as well as a blue shift of n → π * transitions, as evidenced by a shift of the absorption maxima.…”

Section: Introductionmentioning

confidence: 99%

Dependence of the thioxanthone triplet-triplet absorption spectrum with solvent polarity and aromatic ring substitution

Ferreira¹,

Cavalheiro²,

Neumann³

2006

J. Braz. Chem. Soc.

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Foram estudadas as absorções triplete-triplete (TT) e de transientes de tioxantonas substituídas e não substituídas em diferentes solventes, com a finalidade de avaliar o efeito do solvente, assim como dos substituintes no anel aromático. Os espectros determinados alguns microssegundos depois da excitação mostram absorções de três transientes principais: o estado triplete (600-650 nm), o radical cetila da tioxantona (~450 nm) e uma superposição de ambos (~300 nm). A quantidade de radicais formados em solventes não-hidroxílicos é muito menor do que em álcoois. O máximo da absorção TT mostra uma boa correlação com o parâmetro E T (30) dos solventes.The triplet-triplet (TT) and transient absorptions of non-substituted and substituted thioxanthones has been studied in different solvents in order to ascertain the effect of the solvent, as well as the substituents on the aromatic ring. Spectra taken after a couple of μs after the flash show three main transient absorptions due to the triplet state (600-650 nm), the thioxanthone ketyl radical (~450 nm) and an overlap of both (~300 nm). The amount of radicals formed in non hydroxylic solvents is much lower than in alcohols. The maxima of the TT absorption peaks show a good correlation with the E T (30) solvent parameter. Keywords: thioxanthone, triplet-triplet absorption IntroductionDue to their role in photochemical and photobiological reactions, the triplet states of aromatic ketones continue to receive attention from both experimental and theoretical points of view. [1][2][3][4][5][6] It is well known that the polarity of a solvent greatly influences the energies of the electronic states as well as the photophysical properties in aromatic carbonyl systems. [7][8][9][10] An increase in the solvent polarity results in the stabilization of ππ * states, as well as a blue shift of n → π * transitions, as evidenced by a shift of the absorption maxima. 11,12 Similar shifts have been observed in the triplet energy levels as a function of solvent polarity. 13 Among the aromatic carbonyl compounds, xanthones and thioxanthones (TX) were extensively studied from a solvent effect point of view.Thioxanthones are efficiently and extensively used as photoinitiators in dentistry resins [14][15][16] and other curing and photopolymerization systems. 17,18 Singlet and triplet excited states are involved in the photoinitiation. 19 This process can be strongly dependent on the polarity of the medium showing a distinct solvent effect on its properties and its triplet-triplet absorption spectra (TTA). 1,3 Actually, the polarity of mixtures used in industrial applications are not well defined but the academic comprehension of polarity effect on the excited states gives support to studies leading to the optimization of the photoinitiators' efficiency. 20,21 In this work we report on the changes in the transient absorption spectra due to different solvents, as well as substitutions on the aromatic ring of thioxanthones. ExperimentalEthyl acetate (AcOEt, Mallinckrodt) used in this work was spec...

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“…1), TTET can occur by van der Waals contact to the state C*. Because TTET between these groups is an irreversible process (12)(13)(14), the overall reaction can be described by the three-state model shown in Fig. 1.…”

mentioning

confidence: 99%

Testing the diffusing boundary model for the helix–coil transition in peptides

Neumaier

Reiner

Büttner

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The dynamics of peptide α-helices have been studied extensively for many years, and the kinetic mechanism of the helix-coil dynamics has been discussed controversially. Recent experimental results have suggested that equilibrium helix-coil dynamics are governed by movement of the helix/coil boundary along the peptide chain, which leads to slower unfolding kinetics in the helix center compared with the helix ends and position-independent helix formation kinetics. We tested this diffusion of boundary model in helical peptides of different lengths by triplet-triplet energy transfer measurements and compared the data with simulations based on a kinetic linear Ising model. The results show that boundary diffusion in helical peptides can be described by a classical, Einstein-type, 1D diffusion process with a diffusion coefficient of 2.7·10 7 (amino acids) 2 /s or 6.1·10 −9 cm 2 /s. In helices with a length longer than about 40 aa, helix unfolding by coil nucleation in a helical region occurs frequently in addition to boundary diffusion. Boundary diffusion is slowed down by helix-stabilizing capping motifs at the helix ends in agreement with predictions from the kinetic linear Ising model. We further tested local and nonlocal effects of amino acid replacements on helix-coil dynamics. Single amino acid replacements locally affect folding and unfolding dynamics with a ϕ f -value of 0.35, which shows that interactions leading to different helix propensities for different amino acids are already partially present in the transition state for helix formation. Nonlocal effects of amino acid replacements only influence helix unfolding (ϕ f = 0) in agreement with a diffusing boundary mechanism.α-helix capping | ϕ-value | protein folding

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Ultrafast Quenching of the Xanthone Triplet by Energy Transfer: New Insight into the Intersystem Crossing Kinetics

Cited by 65 publications

References 28 publications

A general method to describe intersystem crossing dynamics in trajectory surface hopping

A general method to describe intersystem crossing dynamics in trajectory surface hopping

Dependence of the thioxanthone triplet-triplet absorption spectrum with solvent polarity and aromatic ring substitution

Testing the diffusing boundary model for the helix–coil transition in peptides

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