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Authors = Felix Plasser ORCID = 0000-0003-0751-148X

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14 pages, 3690 KiB  
Article
Solvent-Mediated Rate Deceleration of Diels–Alder Reactions for Enhanced Selectivity: Quantum Mechanical Insights
by Umatur Rehman, Asim Mansha and Felix Plasser
Chemistry 2024, 6(5), 1312-1325; https://doi.org/10.3390/chemistry6050076 - 21 Oct 2024
Viewed by 2318
Abstract
Solvents can have a tremendous influence on the rate and selectivity of chemical reactions, but their effects are not always well accounted for. In the present work, density functional theory computations are used to investigate the influence of solvent on the Diels–Alder reactions [...] Read more.
Solvents can have a tremendous influence on the rate and selectivity of chemical reactions, but their effects are not always well accounted for. In the present work, density functional theory computations are used to investigate the influence of solvent on the Diels–Alder reactions of 9-methylanthracene with (5-oxo-2H-furan-2-yl) acetate and different anhydrides considering the overall reaction rates as well as selectivity between possible isomeric products. Crucially, we find that overall reaction rates are higher in non-polar toluene, whereas selectivity is enhanced in the polar solvent acetone. In the case of (5-oxo-2H-furan-2-yl) acetate, the difference in the reaction barriers is enhanced by 2.4 kJ/mol in acetone as compared to the gas phase, halving the yield of the side product. Similar results are found for the reaction of 9-methylanthracene with chloro-maleic anhydride and cyano-maleic anhydride, highlighting the generality of the trends observed. After presenting the energetics, a detailed discussion of the reactivity is given using electrostatic potentials, frontier orbitals, reactivity indices and Fukui functions. In summary, this study highlights the importance of solvent in influencing reaction rates and illustrates the possibility of studying its effects computationally. Full article
(This article belongs to the Section Theoretical and Computational Chemistry)
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18 pages, 5943 KiB  
Article
Exploitation of Baird Aromaticity and Clar’s Rule for Tuning the Triplet Energies of Polycyclic Aromatic Hydrocarbons
by Felix Plasser
Chemistry 2021, 3(2), 532-549; https://doi.org/10.3390/chemistry3020038 - 14 Apr 2021
Cited by 22 | Viewed by 5613
Abstract
Polycyclic aromatic hydrocarbons (PAH) are a prominent substance class with a variety of applications in molecular materials science. Their electronic properties crucially depend on the bond topology in ways that are often highly non-intuitive. Here, we study, using density functional theory, the triplet [...] Read more.
Polycyclic aromatic hydrocarbons (PAH) are a prominent substance class with a variety of applications in molecular materials science. Their electronic properties crucially depend on the bond topology in ways that are often highly non-intuitive. Here, we study, using density functional theory, the triplet states of four biphenylene-derived PAHs finding dramatically different triplet excitation energies for closely related isomeric structures. These differences are rationalised using a qualitative description of Clar sextets and Baird quartets, quantified in terms of nucleus independent chemical shifts, and represented graphically through a recently developed method for visualising chemical shielding tensors (VIST). The results are further interpreted in terms of a 2D rigid rotor model of aromaticity and through an analysis of the natural transition orbitals involved in the triplet excited states showing good consistency between the different viewpoints. We believe that this work constitutes an important step in consolidating these varying viewpoints of electronically excited states. Full article
(This article belongs to the Special Issue A Special Issue in Honor of Professor Josef Michl)
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21 pages, 416 KiB  
Perspective
Challenges in Simulating Light-Induced Processes in DNA
by Philipp Marquetand, Juan J. Nogueira, Sebastian Mai, Felix Plasser and Leticia González
Molecules 2017, 22(1), 49; https://doi.org/10.3390/molecules22010049 - 29 Dec 2016
Cited by 19 | Viewed by 7478
Abstract
In this contribution, we give a perspective on the main challenges in performing theoretical simulations of photoinduced phenomena within DNA and its molecular building blocks. We distinguish the different tasks that should be involved in the simulation of a complete DNA strand subject [...] Read more.
In this contribution, we give a perspective on the main challenges in performing theoretical simulations of photoinduced phenomena within DNA and its molecular building blocks. We distinguish the different tasks that should be involved in the simulation of a complete DNA strand subject to UV irradiation: (i) stationary quantum chemical computations; (ii) the explicit description of the initial excitation of DNA with light; (iii) modeling the nonadiabatic excited state dynamics; (iv) simulation of the detected experimental observable; and (v) the subsequent analysis of the respective results. We succinctly describe the methods that are currently employed in each of these steps. While for each of them, there are different approaches with different degrees of accuracy, no feasible method exists to tackle all problems at once. Depending on the technique or combination of several ones, it can be problematic to describe the stacking of nucleobases, bond breaking and formation, quantum interferences and tunneling or even simply to characterize the involved wavefunctions. It is therefore argued that more method development and/or the combination of different techniques are urgently required. It is essential also to exercise these new developments in further studies on DNA and subsystems thereof, ideally comprising simulations of all of the different components that occur in the corresponding experiments. Full article
(This article belongs to the Special Issue Experimental and Computational Photochemistry of Bioorganic Molecules)
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