CASPT2 Study of Photodissociation Pathways of Ketene

The mechanism of various photodissociation channels of ketene involving the three lowest singlet states (S₀, S₁, and S₂) and the three lowest triplet states (T₁, T₂, and T₃) was investigated by means of the (MS-)­CAS­(8e,8o)­PT2/6-31+G* method. Stationary structures, i.e., global minima (GMs), local minima (LMs), transition states (TSs), minimum energy conical intersections (MECIs), and minima on seam of crossing (MSXs), were explored systematically by the global reaction route mapping (GRRM) strategy. On the basis of these structures, we discussed related dissociation channels starting from S₂ that have been studied experimentally with 193–215 nm excitation wavelength. Five working pathways were found for relaxation to the low-lying S₀, S₁, and T₁ potential energy surfaces (PESs) from the Franck–Condon region of S₂, and the relaxation is expected to occur very quickly. On these low-lying states, five dissociation channels are open: three CH₂ + CO channels for different CH₂ electronic states, H + HCCO, and H₂ + C₂O. Pathways for all of these five channels were identified and discussed, including new minor paths leading to H₂ + C₂O

sj-pdf-1-imr-10.1177_03000605221133704 - Supplemental material for Long-term nifekalant use in a patient with dilated cardiomyopathy and recurrent ventricular tachycardia

Supplemental material, sj-pdf-1-imr-10.1177_03000605221133704 for Long-term nifekalant use in a patient with dilated cardiomyopathy and recurrent ventricular tachycardia by Hongyan Xiao, Qitong Chen, Liang Tao in Journal of International Medical Research</p

Excited-State Roaming Dynamics in Photolysis of a Nitrate Radical

Roaming dynamics has been recognized as one of the key mechanisms in atmospheric and combustion processes. In this Letter, we report the first example of roaming dynamics that occurs on an excited-state potential energy surface. In the photodissociation of a nitrate radical, systematic CASPT2 reaction path search and DFT dynamics calculations show that the roaming dynamics occurs on the first excited doublet state (D₁). The direct dissociation on D₁ gives the minor vibrationally cold O₂, while the indirect dissociation after the nonadiabatic transition to the ground doublet state (D₀) produces the major vibrationally hot O₂; this proposal explains the recent experimental results

Theoretical Study on the Photodissociation of Methylamine Involving S₁, T₁, and S₀ States

Various photodissociation pathways of methylamine involving the three lowest electronic states, namely, singlet ground S₀ state, singlet first excited S₁ state, and triplet ground T₁ state, were studied by the (MS-)­CAS­(8e,8o)­PT2/6-31++G** method. All critical points, i.e., minima, transition states, minimum energy conical intersections, and minima on the seam of crossing, were explored systematically by the global reaction route mapping (GRRM) strategy utilizing the anharmonic downward distortion following (ADDF) and artificial force induced reaction (AFIR) methods. On the basis of obtained structures, we discuss the photodissociation mechanism of methylamine in the experimental excitation wavelength range 222–240 nm in detail. Especially, the T₁ potential energy surface was explored systematically for the first time. The N–H bond rupture is a primary channel on the S₁ state. Along the N–H dissociation path on S₁, there is a low-energy conical intersection (CI), and through this CI the system can go back to the S₀ state; from the CI the system can directly dissociate to CH₃NH + H or reproduce the original CH₃NH₂ on S₀. There is a seam of crossing between S₀ and T₁ in a partially dissociated CH₃---NH₂ geometry, and through this seam the system may go up to the T₁. On the T₁ state, a roaming-like pathway giving CH₄ + NH (X³Σ^–) products was found, which would explain the recently proposed intersystem crossing mediated roaming dynamics

Global ab Initio Potential Energy Surfaces for Low-Lying Doublet States of NO₃

We report analytical global potential energy surfaces (PESs) for three low-lying doublet states (D₀, D₁, and D₂) of NO₃. The fits are made on roughly 74000 MS-CAS­(17e,13o)­PT2/aug-cc-pVTZ calculations of electronic energies, where these PESs are invariant of permutations of oxygen atoms. The surfaces describe two roaming pathways for NO₃ → NO₂-----O → NO + O₂ involving different electronic states discovered in the photolysis of NO₃ [Xiao, H. Y. et al. <i>J. Phys. Chem. Lett.</i> <b>2011</b>, <i>2</i>, 934]. These pathways become accessible at excess energy of ∼210 kJ/mol above the ground-state global minimum of NO₃. The ab initio data below 360 kJ/mol are reproduced very well by the fitted PESs with the fitting rms errors of less than 5.5 kJ/mol for all the three states. Moreover, key local minima and energy profiles along the roaming pathways on the fitted PESs are compared with those on the ab initio PESs. In addition, potential contour maps in the roaming region are also compared. These careful evaluations of the fitted PESs suggest that the present fitted PESs are well suited for future dynamics calculations of this system

Proton Transfer Mechanism of Organocatalyzed Isomerization of Alkynoates into Allenoates: Enantioselectivity and Reversibility. A DFT Study

The mechanisms of organocatalyzed isomerization of α-unsubstituted (system I) and α-substituted (system II) alkynoates into allenoates mediated by benzothiadiazine catalyst were systematically investigated using the density functional theory (DFT) method. Four reaction paths in both systems were explored in detail, all involving two proton-transfer steps and some including a conformational change step in the intermediate. In all of these paths, the first proton transfer involves the proton (H7) of the substrate transferred to the amine nitrogen (N13) of the catalyst, giving the intermediate, and the other involves the same proton (H7) in the intermediate transferred back from the catalyst to the carbon atom (C6) of the substrate, forming the final product complex. The most favorable reaction path in system I, the anti-cis path, is very similar to the best path in system II, the anti-R path. The rate-determining (first proton transfer) barrier height for the anti-cis path of system I is substantially smaller (by about 15 kJ/mol) than that for the anti-R path of system II, indicating that system I is more reactive than system II. The reverse barrier from the product complex back to the reactant complex in system I is only 20.4 kJ/mol higher than the forward barrier. On the other hand, the reverse barrier is 29.4 kJ/mol higher than the forward barrier in system II. Thus, making this isomerization in system I is more reversible at room temperature, while the isomerization in system II is irreversible. The origins of differences in reactivity, reversibility, and selectivity are revealed in terms of hydrogen-bond structures, charge distributions, and energy decomposition analysis of some key structures

Quasiclassical Trajectory Studies of the Photodissociation Dynamics of NO₃ from the D₀ and D₁ Potential Energy Surfaces

We report new global potential energy surfaces (PESs) for the D0 and D1 states of NO3. The PESs are permutationally invariant fits to roughly 90 000 electronic energies (MS-CAS­(17e,13o)­PT2/aug-cc-pVTZ). Hundreds of thousands of quasiclassical trajectories are run from the D0 global minimum and one previously identified “roaming saddle point” as well as a roaming saddle point on D1, identified previously [Xiao, H.; Maeda, S.; Morokuma, K. J. Chem. Theory Comput. 2012, 8, 2600]. The calculations are done at a total energy of relevance to recent experiments where, together with theoretical analysis [Grubb, M. P.; Warter, M. L.; Xiao, H.; Maeda, S.; Morokuma, K.; North, S. W. Science 2012, 335, 1075], point to roaming pathways to the O2+NO products on both D1 and D0. Detailed comparisons with experiment are made for the distributions of O2 vibrational and rotational states, the relative translational energy and the NO rotational states, and the NO v-j vector correlation

Flooding conditions at different altitudes during July 1, 2009 to August 31, 2011.

<p>The duration of continuous flooding was more than four months at 168 m above sea level, and there were about 225 accumulated days of flooding at that elevation.</p

Supplementary Data from Pharmacologic Inactivation of Kinase Suppressor of Ras1 Sensitizes Epidermal Growth Factor Receptor and Oncogenic Ras-Dependent Tumors to Ionizing Radiation Treatment

Includes Supplementary Figures 1 through 5 with corresponding figure legends</p

LWE of the littoral zone of Hanfeng Lake in Kaixian town, Chongqing Municipality (photographed by Kang Liu on Nov. 14, 2014).

<p>Afforestation has enriched the waterfront landscape in winter.</p