An accurate prediction of adiabatic excitation energies to the low-lying electronic states for acetophenone and the related carbonyl compounds

Wang, Yuwen; He, Hong-Yuan; Fang, Wei‐Hai

doi:10.1016/s0166-1280(03)00380-4

Cited by 15 publications

(19 citation statements)

References 24 publications

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“…In fact, the S 1 , T 1 , and T 2 surfaces intersect in the same region (S 1 /T 2 /T 1 ) for the aromatic carbonyl compounds. [29][30][31][32] The structure of the PhCO moiety is very similar in the S 1 /T 2 /T 1 intersections for all of the aromatic carbonyl compounds investigated so far. The S 1 /T 2 /T 1 surface intersection is likely a common feature for a wide variety of aromatic carbonyl compounds with a nearly constant structure.…”

Section: The S 1 /T 2 /T 1 Three-surface Intersectionmentioning

confidence: 78%

“…[29][30][31][32] The CASSCF-optimized bond parameters for these carbonyl molecules in the five lowest electronic states have been reported in the previous calculations. [29][30][31][32] For comparison, the CsC and CsO bond lengths for benzaldehyde and acetophenone in the T 2 state are listed in Table 1, where the available experimental values are also given. In the ground state, the aromatic ring was predicted to be almost a regular hexagon with the CsCsC angle in the range of 119.8°-120.3°and the largest difference of 0.012 Å in the ring CsC bond length.…”

Section: Equilibrium Geometriesmentioning

confidence: 99%

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Ab Initio Determination of Dark Structures in Radiationless Transitions for Aromatic Carbonyl Compounds

Fang

2008

Acc. Chem. Res.

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Mechanistic photodissociation of a polyatomic molecule has long been regarded as an intellectually challenging area of chemical physics, the results of which are relevant to atmospheric chemistry, biological systems, and many application fields. Carbonyl compounds play a unique role in the development of our understanding of the spectroscopy, photochemistry, and photophysics of polyatomic molecules and their photodissociation has been the subject of numerous studies over many decades. Upon irradiation, a molecule can undergo internal conversion (IC) and intersystem crossing (ISC) processes, besides photochemical and other photophysical processes. Transient intermediates formed in the IC and ISC radiationless processes, which are termed "dark", are not amenable to detection by conventional light absorption or emission. However, these dark intermediates play critical roles in IC and ISC processes and thus are essential to understanding mechanistic photochemistry of a polyatomic molecule. We have applied the multiconfiguration complete active space self-consistent field (CASSCF) method to determine the dark transient structures involved in radiationless processes for acetophenone and the related aromatic carbonyl compounds. The electronic and geometric structures predicted for the dark states are in a good agreement with those determined by ultrafast electron diffraction experiments. Intersection structure of different electronic states provides a very efficient "funnel" for the IC or ISC process. However, experimental determination of the intersection structure involved in radiationless transitions of a polyatomic molecule is impossible at present. We have discovered a minimum energy crossing point among the three potential energy surfaces (S1, T1, and T2) that appears to be common to a wide variety of aromatic carbonyl compounds with a constant structure. This new type of crossing point holds the key to understanding much about radiationless processes after photoexcitation of aromatic carbonyl compounds. The importance of ab initio determination of transient structures in the photodissociation dynamics has been demonstrated for the case of the aromatic carbonyl compounds. In addition, the detailed knowledge of mechanistic photochemistry for aromatic carbonyl compounds forms the basis for further investigating photodissociation dynamics of a polyatomic molecule.

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Section: The S 1 /T 2 /T 1 Three-surface Intersectionmentioning

confidence: 78%

Section: Equilibrium Geometriesmentioning

confidence: 99%

Ab Initio Determination of Dark Structures in Radiationless Transitions for Aromatic Carbonyl Compounds

Fang

2008

Acc. Chem. Res.

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“…Despite being one of the simplest ketones of this type, its photochemistry is not yet fully understood. [7][8][9][10][11][12] Acetophenone has two close-lying triplet 3 (np*) and 3 (pp*) states, right below a singlet 1 (np*) state. Absorption to the almost dark first singlet state (S 1 ) leads to a fast population of the triplet manifold and a subsequent phosphorescence decay to the ground state with an overall quantum yield of almost one.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of the photochemical generation of triplet acetophenone

Huix‐Rotllant

Siri

Ferré

2013

Phys. Chem. Chem. Phys.

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Acetophenone has a rich photochemistry, which strongly depends on the absorbing state. For example, the excitation to the lowest singlet excited state (S1) leads to a triplet population with a phosphorescence quantum yield of one, while the excitation to S2 leads to photocleavage reactions. Here, we rationalize the photochemistry of acetophenone after being absorbed into the S1, S2 and S3 states by performing a systematic study of all the singlet and triplet minimum energy structures and state crossings between the relevant electronic states. We calculate these structures at the complete-active space self-consistent field (CASSCF) level of theory and at the correlated extended second-order quasi-degenerate multi-reference perturbation theory (XMCQDPT2), emphasizing the importance of correlation effects in the determination of structures.

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“…The electronic excited states of the acetophenone have already been studied by several authors. These theoretical works have mainly focused on vertical and adiabatic excitation energies [4] as well as on their photodissociation mechanisms [5], while theoretical studies on its nonradiative relaxation through the socalled conical intersections (CIs) are rather limited. With close-lying n → π * and π → π * excited states in both singlet and triplet manifolds AP is also ideally suited for the experimental study of the physical processes of intersystem crossing and phosphorescence, as well as photochemical reactions of valence isomerization, bond breakage, and atom transfer [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Low-lying excited-states and relaxation pathways of acetophenone

Bende¹

2013

AIP Conference Proceedings

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A numerical study is reported concerning the first and second singlet excited-states of acetophenone using the multireference self-consistent field (state-averaged CASSCF) method and tripla ζ basis set. The vertical excitation energies of low-lying excited-states were characterized using the SA-CASSCF method, as well as higher-level methods, such as CASPT2, MRCI and EOM-CCSD. The local minims and conical intersections found on the potential energy surfaces (PESs) were characterized in terms of molecular geometry and Mulliken population analysis. Different relaxation pathways on the PESs are identified and discussed.

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An accurate prediction of adiabatic excitation energies to the low-lying electronic states for acetophenone and the related carbonyl compounds

Cited by 15 publications

References 24 publications

Ab Initio Determination of Dark Structures in Radiationless Transitions for Aromatic Carbonyl Compounds

Ab Initio Determination of Dark Structures in Radiationless Transitions for Aromatic Carbonyl Compounds

Theoretical study of the photochemical generation of triplet acetophenone

Low-lying excited-states and relaxation pathways of acetophenone

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