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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). The set of vibrational frequencies of Bz–TFB is mainly the reason for this fast dissociation. The mass of chlorine in Bz–HCB is optimized to match its vibrational frequencies similar to those of Bz–TFB, and the dissociation of Bz–HCB becomes faster. The power spectrum of Bz–TFB, Bz–HCB, and Bz–HCB with the modified mass of chlorine is also computed to understand the extent of the said coupling in these complexes. [ABSTRACT FROM AUTHOR]

The application of Machine Learning (ML) algorithms in chemical sciences, particularly computational chemistry, is a vastly emerging area of modern research. While many applications of ML techniques have already been in place to use ML based potential energies in various dynamical simulation studies, specific applications are also being successfully tested. In this work, the ML algorithms are tested to calculate the unimolecular dissociation time of benzene–hexachlorobenzene, benzene–trichlorobenzene, and benzene–monochlorobenzene complexes. Three ML algorithms, namely, Decision-Tree-Regression (DTR), Multi-Layer Perceptron, and Support Vector Regression are considered. The algorithms are trained with simulated dissociation times as functions (attributes) of complexes' intramolecular and intermolecular vibrational energies. The simulation data are used for an excitation temperature of 1500 K. Considering that the converged result is obtained with 1500 trajectories, an ML algorithm trained with 700 simulation points provides the same dissociation rate constant within statistical uncertainty as obtained from the converged 1500 trajectory result. The DTR algorithm is also used to predict 1000 K simulation results using 1500 K simulation data. [ABSTRACT FROM AUTHOR]

The work presented here establishes the experimental findings of the reaction between secondary/tertiary propargylic alcohol (PA) and 1,3,5‐trimethoxybenzene (TMB) in the presence of acetonitrile solvent (MeCN) based on theoretical calculations. When secondary PA reacts, the reaction goes via SN2 pathway, where the reaction barrier is about 14.32 kcal/mol. On the other hand, tertiary PA reacts with TMB via SN2′ and SN1′ pathway, and the corresponding reaction barriers are 17.59 and 17.86 kcal/mol. Other possible pathways, namely, SN1, SN1′, etc. for secondary PA, and SN2, SN1 pathways for tertiary PA are also investigated and the associated barrier heights are found higher. Rates of those reactions are also calculated considering the rate‐determining steps only. Reaction of secondary PA with TMB is found to be much faster than the reaction of tertiary PA and the results are in accordance with the experimental findings. [ABSTRACT FROM AUTHOR]

A novel, one-pot, three-component coupling (3-CCR) reaction of aromatic aldehydes, β-naphthol, and 6-amino-1,3-dimethyl uracil in a deep eutectic solvent (DES) has been developed as a highly efficient and selective method for the expedient synthesis of the densely functionalized 8,10-dimethyl-12-phenyl-8,12-dihydro-9H-benzo[5,6]chromeno[2,3-d]pyrimidine-9,11(10H)-dione framework in synthetically pleasing yield. The devised protocol adeptly harnesses the versatility of DESs, resulting in a straightforward, cost-effective, resilient, and environmentally sustainable synthetic approach. The resulting cascade adduct exhibits noteworthy antiproliferative activity against a variety of cancer cell lines, thereby showing promise as a potential anticancer drug candidate for breast and hepatocellular carcinoma with moderate to good IC50 values. The most potent compounds in the synthesized library, 4m and 4l, exhibit highly potent cytotoxicity against HepG2 and MCF7 cancer cell lines, with notable IC50 values of 46.39 and 28.21 μM, respectively. The present findings are corroborated by computational and molecular docking studies. The density functional theory (DFT) calculations underscore the pivotal role of the naphthyl ring in orchestrating the success of this intricate domino process in delivering the anticipated scaffolds in reasonable yields. [ABSTRACT FROM AUTHOR]

We perform ab initio calculation using quantum chemistry package (MOLPRO) on the excited states of Na3 cluster and present the adiabatic PESs for the electronic states 22E′ and 12A1′, and the non-adiabatic coupling (NAC) terms among those states. Since the ab initio calculated NAC elements for the states 22E′ and 12A1′ demonstrate the numerical validity of so called 'Curl Condition,' such states closely form a sub-Hilbert space. For this subspace, we employ the NAC terms to solve the 'adiabatic-diabatic transformation (ADT)' equations to obtain the functional form of the transformation angles and pave the way to construct the continuous and single valued diabatic potential energy surface matrix by exploiting the existing first principle based theoretical means on beyond Born-Oppenheimer treatment. Nuclear dynamics has been carried out on those diabatic surfaces to reproduce the experimental spectrum for system B of Na3 cluster and thereby, to explore the numerical validity of the theoretical development on beyond Born-Oppenheimer approach for adiabatic to diabatic transformation. [ABSTRACT FROM AUTHOR]

When a set of three states is coupled with each other but shows negligibly weak interaction with other states of the Hilbert space, these states form a sub-Hilbert space. In case of such subspace [J. Chem. Phys. 124, 074101 (2006)], (a) the adiabatic-diabatic transformation (ADT) condition, ∇vector A+τvector A=0 [Chem. Phys. Lett. 35, 112 (1975)], provides the explicit forms of the nonadiabatic coupling (NAC) elements in terms of electronic basis function angles, namely, the ADT angles, and (b) those NAC terms satisfy the so-called curl conditions [Chem. Phys. Lett. 35, 112 (1975)], which ensure the removal of the NAC elements [could be singular also at specific point(s) or along a seam in the configuration space] during the ADT to bring the diabatic representation of the nuclear Schrödinger equation with a smooth functional form of coupling elements among the electronic states. Since the diabatic to adiabatic representation of the Hamiltonian is related through the same unitary transformation (∇A+τA=0), it could be quite interesting to explore the nature of the nonadiabatic coupling terms starting from a diabatic Hamiltonian and, thereafter, to formulate the extended Born–Oppenheimer (EBO) equation for those adiabatic states transformed from diabatic ones. We consider a three-state diabatic potential matrix constructed for the excited states of Na3 cluster [J. Chem. Phys. 88, 6068 (1988)] at the pseudo-Jahn–Teller model situation, which can reproduce experimentally measured vibrationally resolved absorption lines [Surf. Sci. 156, 770 (1985)] with appropriate choice of coupling parameters, analytically calculate the nonadiabatic coupling elements along with their curls, and numerically evaluate the ADT angles to explore the nature of its nonadiabaticity. While formulating the single surface beyond the BO equation, our theoretical derivation demonstrates that the existence of zero curls of the NAC terms is a necessity. Indeed, when the energy gap between the third state (12 A1′/22 A1′) and the doubly degenerate states (22 E′/32 E′) of the model Hamiltonian for Na3 cluster is considered to be either identically or approximately zero, the curl for each NAC element naturally approaches zero, leading to a theoretically valid EBO equation. We demonstrate the numerical validity of the EBO equation by calculating the nonadiabatic effects on the photoabsorption spectrum starting with the initial wave function located on the ground electronic state and compare with the corresponding diabatic spectrum when the three states are either degenerate at a point or approaching to form three-state degeneracy at the same point. Finally, we calculate the vibrational eigenspectrum of the ground adiabatic state by using (so to say) theoretically and numerically valid EBO equation to compare with those experimentally measured and BO/geometric phase calculated spectra (Tables I-III). [ABSTRACT FROM AUTHOR]

We demonstrate the workability of a parallelized algorithm of the time-dependent discrete variable representation (TDDVR) method to explore the detailed dynamical aspects of vibronic interaction in two three-state model Hamiltonians (X 2E1g, B 2E2g, C 2A2u and B 2E2g, D 2E1u, E 2B2u) of benzene radical cation along with a preliminary investigation on its five electronic states (X 2E1g, B 2E2g, C 2A2u, D 2E1u, and E2B2u). Since those electronic states are interconnected through a series of conical intersections, we have used six and nine vibronically important modes for the three- and five-state Hamiltonians, respectively, in order to perform the quantum dynamics on such system. The population profiles calculated by using our TDDVR approach show reasonably good agreement with the results obtained by exact quantum mechanical (multiconfiguration time-dependent Hartree) method, whereas the corresponding (calculated) photoabsorption spectra originating from various electronic states agree well with the experimental ones. It is important to note that the parallelized algorithm of our TDDVR approach reduces the computation cost by more than an order of magnitude compared to its serial analog. The TDDVR approach appears to be a good compromise between accuracy and speed for such large molecular system, where quantum mechanical description is needed in a restricted region. [ABSTRACT FROM AUTHOR]