Electron donor-acceptor complex enabled photocascade strategy for the synthesis of -dihydrofuro[3,2-]chromen-4-one scaffolds radical conjugate addition of pyridinium ylide.

A visible-light-induced photocascade strategy is disclosed for the synthesis of -dihydrofuro[3,2-]chromen-4-one scaffolds. The photocascade consists of electron donor-acceptor (EDA) complex enabled formation of arylidene coumarinone, followed by 1,4-radical conjugate addition (1,4-RCA) of an generated pyridinium ylide radical (PyYR) towards diastereoselective formation of the -dihydrofuro[3,2-]chromen-4-one scaffold in good to excellent yield. Thorough mechanistic investigations comprising photophysical, spectroscopic, electrochemical and DFT studies provide further insights into the reaction mechanism.

On the intramolecular vibrational energy redistribution dynamics of aromatic complexes: A comparative study on C6H6-C6H5Cl, C6H6-C6H3Cl3, C6H6-C6Cl6 and C6H6-C6H5F, C6H6-C6H3F3, C6H6-C6F6.

Chemical dynamics Simulation studies on benzene dimer (Bz2) and benzene-hexachlorobenzene (Bz-HCB) as performed in the past suggest that the coupling between the monomeric (intramolecular) vibrational modes and modes generated due to the association of two monomers (intermolecular) has to be neither strong nor weak for a fast dissociation of the complex. To find the optimum coupling, four complexes are taken into consideration in this work, namely, benzene-monofluorobenzene, benzene-monochlorobenzene, benzene-trifluorobenzene (Bz-TFB), and benzene-trichlorobenzene. Bz-TFB has the highest rate of dissociation among all seven complexes, including Bz2, Bz-HCB, and Bz-HFB (HFB stands for hexafluorobenzene).

Post-Transition State Direct Dynamics Simulations on the Ozonolysis of Catechol in an N Bath and Comparison with Gas-Phase Results.

Chemical dynamics simulations on the post-transition state dynamics of ozonolysis of catechol are performed in this article using a newly developed QM + MM simulation model. The reaction is performed in a bath of N molecules equilibrated at 300 K. Two bath densities, namely, 20 and 324 kg/m, are considered for the simulation.

Visiblelight-induced ternary electron donor-acceptor complex enabled synthesis of 2-(2-hydrazinyl) thiazole derivatives and the assessment of their antioxidant and antidiabetic therapeutic potential.

A mild and eco-friendly visible-light-induced synthesis of 2-(2-hydrazinyl) thiazole from readily accessible thiosemicarbazide, carbonyl, and phenacyl bromide in the absence of a metal catalyst and/or any extrinsic photosensitizer is reported. This approach only requires a source of visible light and a green solvent at room temperature to produce the medicinally privileged scaffolds of hydrazinyl-thiazole derivatives in good to outstanding yields. Experimental studies support the formation of a visible-light-absorbing, photosensitized colored ternary EDA complex.

An advanced bath model to simulate association followed by ensuing dissociation dynamics of benzene + benzene system: a comparative study of gas and condensed phase results.

The role of the environment (N molecules) on the association followed by the ensuing dissociation reaction of benzene + benzene system is studied here with the help of a new code setup. Chemical dynamics simulations are performed to investigate this reaction in vacuum as well as in a bath of 1000 N molecules, equilibrated at 300 K. Bath densities of 20 and 324 kg m are considered with a few results from the latter density.

Post-Transition-State Direct Dynamics Simulations on the Ozonolysis of Catechol.

On-the-fly dynamics simulations are performed for the reaction of catechol + O. The post transition state (TS) dynamics is studied at temperatures of 400 and 500 K. The PM7 semiempirical method is employed for calculating the potential energy gradient needed for integrating Hamilton's equations of motion.

Dynamical Behavior of Aromatic Trimer Complexes in Unimolecular Dissociation Reaction at High Temperatures. Case Studies on CH-CF-CH and CH Trimer Complexes.

The intramolecular vibrational energy redistribution (IVR) dynamics during unimolecular dissociation of aromatic trimers at high temperatures is the primary interest of this study. Chemical dynamics simulations are performed for the unimolecular dissociation of benzene-hexafluorobenzene-benzene (Bz-HFB-Bz) and benzene trimer (Bz-trimer) complexes at a temperature range of 1000-2000 K. Partial dissociation of both the complexes is observed, which leads to a dimer and a monomer in the dynamics.

Unimolecular Dissociation of CH-CCl Complex and Effect of Mode-Mode Coupling.

The unimolecular dissociation dynamics of the CH-CCl (Bz-HCB) complex is studied with initial excitation of all vibrational modes for a temperature range of 1000-2000 K and with mode-specific excitations at 1500 K. The results are compared with those of the CH-CF [Bz- HFB] complex. When all modes of Bz-HCB are initially excited, the rate of dissociation is slower with respect to Bz-HFB.

A Photochemical Intramolecular C-N Coupling Toward the Synthesis of Benzimidazole-Fused Phenanthridines.

Herein, we report a direct photochemical dehydrogenative C-N coupling of unactivated C(sp)-H and N(sp)-H bonds. The catalysts or additive-free transformation of 2-([1,1'-biphenyl]-2-yl)-1-benzo[]imidazole to benzo[4,5]imidazo[1,2-]phenanthridine was achieved at ∼350 nm of irradiation via ε-hydrogen abstraction. DFT calculations helped to understand that the N-H···π interaction was essential for the reaction to proceed at a lower energy than expected.

Comparison of intermolecular energy transfer from vibrationally excited benzene in mixed nitrogen-benzene baths at 140 K and 300 K.

Gas phase intermolecular energy transfer (IET) is a fundamental component of accurately explaining the behavior of gas phase systems in which the internal energy of particular modes of molecules is greatly out of equilibrium. In this work, chemical dynamics simulations of mixed benzene/N baths with one highly vibrationally excited benzene molecule (Bz) are compared to experimental results at 140 K. Two mixed bath models are considered.

A Competition between Dissociation Pathway and Energy Transfer Pathway: Unimolecular Dissociation of a Benzene-Hexafluorobenzene Complex in Nitrogen Bath.

The unimolecular dissociation of a benzene-hexafluorobenzene complex at 1000, 1500, and 2000 K is studied inside a bath of 1000 N molecules kept at 300 K using chemical dynamics simulation. Three bath densities of 20, 324, and 750 kg/m are considered. The dissociation dynamics of the complex at a 20 kg/m bath density is found to be similar to that in the gas phase, whereas the dynamics is drastically different at higher bath densities.

Chemical Dynamics Simulations on Association and Ensuing Dissociation of a Benzene-Hexafluorobenzene Molecular System.

Chemical dynamics simulations are performed to study the association of benzene (Bz) and hexafluorobenzene (HFB) followed by the ensuing dissociation of the Bz-HFB complex. The calculations are done for 1000, 1500, and 2000 K with an impact parameter ( b) range of 0-10 Å at each temperature. Almost no complexes are observed to form at b = 8 and 10 Å.

A Better Understanding of the Unimolecular Dissociation Dynamics of Weakly Bound Aromatic Compounds at High Temperature: A Study on CH-CF and Comparison with CH Dimer.

Chemical dynamics simulations are performed to study the unimolecular dissociation of the benzene (Bz)-hexafluorobenzene (HFB) complex at five different temperatures ranging from 1000 to 2000 K, and the results are compared with that of the Bz dimer at common simulation temperatures. Bz-HFB, in comparison with Bz dimer, possesses a much attractive intermolecular interaction, a very different equilibrium geometry, and a lower average quantum vibrational excitation energy at a given temperature. Six low-frequency modes of Bz-HFB are formed by Bz + HFB association which are weakly coupled with the vibrational modes of Bz and HFB.

Non-statistical intermolecular energy transfer from vibrationally excited benzene in a mixed nitrogen-benzene bath.

A chemical dynamics simulation was performed to model experiments [N. A. West , J.

Collisional Intermolecular Energy Transfer from a N Bath at Room Temperature to a Vibrationlly "Cold" CF Molecule Using Chemical Dynamics Simulations.

Chemical dynamics simulations were performed to study collisional intermolecular energy transfer from a thermalized N bath at 300 K to vibrationally "cold" CF. The vibrational temperature of CF is taken as 50 K, which corresponds to a classical vibrational energy of 2.98 kcal/mol.

Chemical Dynamics Simulations of Intermolecular Energy Transfer: Azulene + N2 Collisions.

Chemical dynamics simulations were performed to investigate collisional energy transfer from highly vibrationally excited azulene (Az*) in a N2 bath. The intermolecular potential between Az and N2, used for the simulations, was determined from MP2/6-31+G* ab initio calculations. Az* is prepared with an 87.

Zero-Point Energy Constraint for Unimolecular Dissociation Reactions. Giving Trajectories Multiple Chances To Dissociate Correctly.

A zero-point energy (ZPE) constraint model is proposed for classical trajectory simulations of unimolecular decomposition and applied to CH4* → H + CH3 decomposition. With this model trajectories are not allowed to dissociate unless they have ZPE in the CH3 product. If not, they are returned to the CH4* region of phase space and, if necessary, given additional opportunities to dissociate with ZPE.

Chemical Dynamics Simulations of Benzene Dimer Dissociation.

Classical chemical dynamics simulations were performed to study the intramolecular and unimolecular dissociation dynamics of the benzene dimer, Bz2 → 2 Bz. The dissociation of microcanonical ensembles of Bz2 vibrational states, at energies E corresponding to temperatures T of 700-1500 K, were simulated. For the large Bz2 energies and large number of Bz2 vibrational degrees of freedom, s, the classical microcanonical (RRKM) and canonical (TST) rate constant expressions become identical.

Dynamics of Na(+)(Benzene) + Benzene Association and Ensuing Na(+)(Benzene)2* Dissociation.

Chemical dynamics simulations were used to study Bz + Na(+)(Bz) → Na(+)(Bz)2* association and the ensuing dissociation of the Na(+)(Bz)2* cluster (Bz = benzene). An interesting and unexpected reaction found from the simulations is direct displacement, for which the colliding Bz molecule displaces the Bz molecule attached to Na(+), forming Na(+)(Bz). The rate constant for Bz + Na(+)(Bz) association was calculated at 750 and 1000 K, and found to decrease with increase in temperature.

Potential energy surfaces for the HBr(+) + CO2 → Br + HOCO(+) reaction in the HBr(+) (2)Π3/2 and (2)Π1/2 spin-orbit states.

Quantum mechanical (QM) + molecular mechanics (MM) models are developed to represent potential energy surfaces (PESs) for the HBr(+) + CO2 → Br + HOCO(+) reaction with HBr(+) in the (2)Π3/2 and (2)Π1/2 spin-orbit states. The QM component is the spin-free PES and spin-orbit coupling for each state is represented by a MM-like analytic potential fit to spin-orbit electronic structure calculations. Coupled-cluster single double and perturbative triple excitation (CCSD(T)) calculations are performed to obtain "benchmark" reaction energies without spin-orbit coupling.

Energy and temperature dependent dissociation of the Na(+)(benzene)1,2 clusters: importance of anharmonicity.

Chemical dynamics simulations were performed to study the unimolecular dissociation of randomly excited Na(+)(Bz) and Na(+)(Bz)2 clusters; Bz = benzene. The simulations were performed at constant energy, and temperatures in the range of 1200-2200 K relevant to combustion, using an analytic potential energy surface (PES) derived in part from MP2/6-311+G* calculations. The clusters decompose with exponential probabilities, consistent with RRKM unimolecular rate theory.

Crystal structure of 2,2-di-phenyl-hydrazinium chloride.

In the title compound, C12H13N2 (+)·Cl(-), the chloride salt of 1,1'-di-phenyl-hydrazine, the phenyl rings are inclined to one another by 78.63 (17)°. The N-(+)NH3 bond lengths is 1.

A unified model for simulating liquid and gas phase, intermolecular energy transfer: N₂ + C₆F₆ collisions.

Molecular dynamics simulations were used to study relaxation of a vibrationally excited C6F6* molecule in a N2 bath. Ab initio calculations were performed to develop N2-N2 and N2-C6F6 intermolecular potentials for the simulations. Energy transfer from "hot" C6F6 is studied versus the bath density (pressure) and number of bath molecules.