Journal of Computational Chemistry

doi: 10.1002/jcc.26918pmid: N/A

Wu, Yufeng; Kang, Jiajie; Gao, Wei; Bi, Mingshu; Yang, Dongcheng; Ji, Runlai; Meng, Qingwei; Ma, Cunfei

doi: 10.1002/jcc.27172pmid: 37283494

DFT calculations and kinetic analysis have been employed to comprehensively explore the possibility to prepare epoxides by one‐step method using the in‐situ generated peroxy radicals or hydroperoxides as epoxidizing agents. Computational studies demonstrated that the selectivities for the reaction systems of O2/R2/R1, O2/CuH/R1, O2/CuH/styrene, O2/AcH/R1 were 68.2%, 69.6%, 100% and 93.3%, respectively. The in‐situ generated peroxide radicals, such as HOO˙, CuOO˙ and AcOO˙, could react with R1 or styrene by attacking the CC double bond to form a CO bond and subsequently undergoing a cleavage of OO bond to yield epoxides. Peroxide radicals could abstract a hydrogen atom from methyl group on R1, forming unwanted by‐products. It should be noted that the hydrogen atoms of HOO˙ is easy to be abstracted by CC double bond and simultaneously the oxygen atom is connected to the CH moiety to form an alkyl peroxy radical (Rad11), greatly limiting the selectivity. The comprehensive mechanistic studies provide a deep understanding on preparing epoxides by one‐step method.

Dobrovolskiy, Ivan N.; Kostjukov, Victor V.

doi: 10.1002/jcc.27175pmid: 37294297

We performed a theoretical analysis of the BIPS photochemical cycle using an extensive set of forty hybrid functionals and taking into account a highly polar solvent (methanol). The functionals with a small fraction of the exact Hartree‐Fock exchange (%HF) showed the predominant S0 → S2 transition with the strengthening of the CspiroO bond. At the same time, functionals with medium and high %HF (including those with long‐range correction) gave a dominant S0 → S1 transition with weakening or breaking of the CspiroO bond, which corresponds to the experimental results. The influence of a highly polar solvent on the photochemical electrocyclic transformations of BIPS turned out to be significant. The number of functionals causing dissociation of the CspiroO bond decreased from 10 to 7 compared to the gas phase. The magnitude of the oscillator strength has increased by approximately one and a half times. Structural distortions of the BIPS molecule during excitation (both with and without CspiroO bond cleavage) significantly decreased in methanol compared to the gas phase. The two strong hydrogen bonds of methanol molecules with the oxygen and nitrogen atoms of spiropyran also have a significant effect on its excitation. They lead to a change in the predominant transition from S0 → S2 to S0 → S1 for five functionals. The number of functionals giving dissociation of the CspiroO bond decreased from seven to four (M08HX, M052X, CAM‐B3LYP, and M11). After the opening of the excited BIPS molecule, both of its strong H‐bonds with methanol are preserved. Of this set of four functionals, only M052X and CAM‐B3LYP exhibited the dominant HOMO‐1 → LUMO configuration observed in high‐level computations by other authors. Therefore, both of these functionals are recommended for modeling the photochemical cycle of this spiropyran. The photochemical cycle of BIPS was theoretically analyzed. The redistribution of the electron density in this cycle was quantitatively described using the differences in NPA of the atomic charges. The most important result of this analysis was the electrostatic mechanism of the approach of Cspiro and oxygen atoms at the fourth stage, which causes further reduction of the CspiroO bond.

Ghiami‐Shomami, Ali; Hättig, Christof

doi: 10.1002/jcc.27173pmid: 37309870

The possibilities and problems to predict excited‐state acidities and basicities in water with electronic structure calculations combined with a continuum solvation model are investigated for a test set of photoacids and photobases. Different error sources, like errors in the ground‐state pKa values, the excitation energies in solution for the neutral and (de‐)protonated species, basis set effects, and contributions beyond implicit solvation are investigated and their contributions to the total error in pKa∗ are discussed. Density functional theory in combination with the conductor like screening model for real solvents and an empirical linear Gibbs free energy relationship are used to predict the ground‐state pKa values. For the test set, this approach gives more accurate pKa values for the acids than for the bases. Time‐dependent density‐functional theory (TD‐DFT) and second‐order wave function methods in combination with the conductor like screening model are applied to compute excitation energies in water. Some TD‐DFT functionals fail for several species to predict correctly the order of the lowest excitations. Where experimental data for absorption maxima in water is available, the implicit solvation model leads with the applied electronic structure methods in most cases for the excitation energies in water to an overestimation for the protonated and to an underestimation for the deprotonated species. The magnitude and sign of the errors depend on the hydrogen bond donating and accepting ability of the solute. We find that for aqueous solution this results generally in an underestimation in the pKa changes from the ground to the excited state for photoacids and an overestimation for photobases.

Rezende, Umar Lucio; De Souza, Leonardo A.; Belchior, Jadson C.

doi: 10.1002/jcc.27174pmid: 37306361

A new genetic algorithm has been proposed focusing on direct ab initio potential energy surface (PES) global minima search. Besides the commonly used operators, this new approach uses an operator to: improve the initial cluster generation, classify and compare all generated clusters, and use machine learning to model the quantum PES used in parallel optimization. Part of the validation process for this methodology was done with CunAum (n+m≤X for X=14,19,38,55) and AunAgn (n=10,20,30,40,50,60,70, and 75). The results are in fair agreement with the literature and led to a new global minimum for Cu12Au7. A search has been done for the lowest energies of Lin nanoclusters with 2–8 atoms using the DFT approach and for Li3,Li4,Li2H, Li3H using DLPNO‐CCSD(T) approach. NQGA successfully performed the MP2 optimizations for (H2O)11 cluster. In all cases, the proposed genetic algorithm located the previously reported global minima with very efficient performance. The new proposed methodology makes it possible to optimize cluster geometries directly using high‐level ab initio methods relinquishing any bias introduced by a classical approach. Our results show that this proposed method has great potential applications due to its flexibility and efficiency in identifying global minima in the tested atomic systems.