Predistortion amplified in the excited state

Fuß, Werner

doi:10.1016/j.jphotochem.2014.10.006

Cited by 11 publications

(11 citation statements)

References 116 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[11] Indeed, the timescale of the dynamics-few picoseconds-is faster than the time for the molecule to vibrationally relax and form aquasi-equilibrium state with the transition state,the cornerstone of standard transition state theories.N onstatistical behavior has been previously reported in thermal reactions [1,12] and also in excited state reactions mediated by decay through different conical intersections. [13] Thep resent case extends this to ultrafast reactions beginning in the excited state and decaying through the same conical intersection. In order to model the subsequent ground-state dynamics on ap icosecond timescale,w es witch from nonadiabatic dynamics to adiabatic BOMD at the PBE0 level.…”

mentioning

confidence: 81%

Rich Athermal Ground‐State Chemistry Triggered by Dynamics through a Conical Intersection

2016

View full text Add to dashboard Cite

A fundamental tenet of statistical rate theories (such as transition state theory and RRKM) is the rapidity of vibrational relaxation. Excited-state reactions happen quite quickly (sub-picosecond) and thus can exhibit nonstatistical behavior. However, it is often thought that any diversity of photoproducts results from different conical intersections connecting the excited and ground electronic states. It is also conceivable that the large energy of the photon, which is converted to vibrational energy after electronic transitions could lead to athermal hot ground state reactions and that these might be responsible for the diversity of photoproducts. Here we show that this is the case for sulfines, where a single conical intersection is implicated in the electronic transition but the excited state reaction leads to nine different products within less than a picosecond.

show abstract

mentioning

confidence: 81%

Rich Athermal Ground‐State Chemistry Triggered by Dynamics through a Conical Intersection

2016

View full text Add to dashboard Cite

show abstract

“…A similar acceleration is observed, if the pretwist eliminates a small barrier that would exist in a planar unhindered molecule and that would slow down the reaction. 30,42 In planar trienes and longer polyenes twist coordinates are not Franck-Condon active: as said above, excitation changes mainly the bond orders so that differences of C-C and CQC bond lengths are reduced. But the molecule remains planar in the pp* and p* 2 (1B and 2A) states.…”

Section: Barriers Pretwist Conformer Control and The Neer Principlementioning

confidence: 96%

“…30 and the recent results for substituted hemithioindigos 40 ) and confirmed also for Pre by calculations of dynamics in the gas phase. 41,43 More recently it was pointed out that the direction of leaving from the lower cone of the CI can be predetermined: 30,42 there can be some memory of a momentum acquired before the CI, for example via a predistortion of the molecule. In the condensed phase, this momentum conservation can last until 5-15 ps.…”

Section: Basicsmentioning

confidence: 99%

“…30 by a predistortion effect and extended to many more examples in ref. 42. If in competing ultrafast reactions such as HT-1 and HT-2 the molecule is predistorted in S 0 in a direction containing one of the photochemically active coordinates (twist of one of the single-bond neighbors of the double bond), vertical excitation puts the wave packet to a steep slope declining in just this direction; the coordinate should at the same time be Franck-Condon active.…”

Section: Barriers Pretwist Conformer Control and The Neer Principlementioning

confidence: 99%

“…If in competing ultrafast reactions such as HT-1 and HT-2 the molecule is predistorted in S 0 in a direction containing one of the photochemically active coordinates (twist of one of the single-bond neighbors of the double bond), vertical excitation puts the wave packet to a steep slope declining in just this direction; the coordinate should at the same time be Franck-Condon active. 42 The slope accelerates the molecule towards the pretwist. When the wave packet arrives in a branching region, this momentum helps in selecting the right CI (HT-1 over HT-2) or the right exit direction in a given CI ( Fig.…”

Section: Barriers Pretwist Conformer Control and The Neer Principlementioning

confidence: 99%

See 2 more Smart Citations

Previtamin D:Z–Ephotoisomerizationviaa Hula-twist conical intersection

Fuß¹

2019

Phys. Chem. Chem. Phys.

Self Cite

View full text Add to dashboard Cite

On photoisomerization of previtamin D -a steroid Z-triene -produced in situ by ring opening of 7-dehydrocholesterol in a cold matrix, it was found in A. M. Müller et al. [Angew. Chem., Int. Ed., 1998, 37, 505-507] that the product (tachysterol) had rotated not only its central double bond but also an adjacent single bond. This is called a Hula twist (HT) due to the alternative description, in which it is just one central CH group that rotates. It was pointed out that the results directly support the calculated molecular structure at a conical intersection, which mediates the Z-E isomerization of polyenes. With a more sophisticated technique, Saltiel et al. (J. Phys. Chem. Lett., 2013, 4, 716-721) confirmed this tachysterol rotamer as the main product but found two additional conformers. They believed to have seen also three previtamin D conformers, suggested to be a result of hot-ground-state reactions from the primary rotamer, and interpreted all tachysterol products to be a result of a double-bond twist (DBT), not a HT. On the basis of published circular dichroism data and consideration of other reactions, it is here shown that under these conditions hot-ground-state reactions are unimportant or even negligible and that there is practically only a single conformer of previtamin D after ring opening. All products can be easily understood on the basis of an HT-type conical intersection, which is thus further supported. Invoking a published pretwist model even rationalizes product ratios. The two twists in HT are concerted. Furthermore HT is fully consistent with the NEER principle (nonequilibration of excited rotamers) and even offers additional possibilities for conformer control.Scheme 1 Structures of 7-dehydrocholesterol (Dehy), lumisterol (Lumi), previtamin D (Pre) and tachysterol (Tachy). c and t denote s-cis and s-trans arrangement around the 5-6 and 7-8 single bonds. Obviously the molecules are not planar; the chromophores in Dehy and its primary ring-opening product cZc-Pre form a left-handed screw ((À)cZ(À)c-Pre), whereas in Lumi and its cZc-Pre product ((+)cZ(+)c-Pre) they correspond to a right-handed screw.Perspective PCCP

show abstract

Rich Athermal Ground‐State Chemistry Triggered by Dynamics through a Conical Intersection

2016

View full text Add to dashboard Cite

A fundamental tenet of statistical rate theories (such as transition state theory and RRKM) is the rapidity of vibrational relaxation. Excited‐state reactions happen quite quickly (sub‐picosecond) and thus can exhibit nonstatistical behavior. However, it is often thought that any diversity of photoproducts results from different conical intersections connecting the excited and ground electronic states. It is also conceivable that the large energy of the photon, which is converted to vibrational energy after electronic transitions could lead to athermal hot ground state reactions and that these might be responsible for the diversity of photoproducts. Here we show that this is the case for sulfines, where a single conical intersection is implicated in the electronic transition but the excited state reaction leads to nine different products within less than a picosecond.

show abstract

Predistortion amplified in the excited state

Cited by 11 publications

References 116 publications

Rich Athermal Ground‐State Chemistry Triggered by Dynamics through a Conical Intersection

Rich Athermal Ground‐State Chemistry Triggered by Dynamics through a Conical Intersection

Previtamin D:Z–Ephotoisomerizationviaa Hula-twist conical intersection

Rich Athermal Ground‐State Chemistry Triggered by Dynamics through a Conical Intersection

Contact Info

Product

Resources

About