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Multiconfigurational Static and Dynamic Calculations Explain Tricyclo[4,2,0,02,5]octa-3,7-diene Photochemistry

preprint
submitted on 28.05.2020 and posted on 01.06.2020 by Jingbai Li, Steven Lopez

Sunlight is a renewable energy source that can be stored in chemical bonds using photochemical reactions. The synthesis of exotic and strained molecules is especially attractive with photochemical techniques because of the associated efficient and mild reaction conditions. We have used complete active space self-consistent field (CASSCF) calculations with an (8,7) active space and the ANO-S-VDZP basis set to understand the photophysics and subsequent photochemistry of a possible cubane precursor tricyclo[4,2,0,02,5]octa-3,7-diene (1). The energies were corrected with a second-order perturbative correction CASPT2(8,7)/ANO-S-VDZP. The S0→S1 vertical excitation energy of 1 is 6.25 eV, whose nature is π→π* excitation. The minimum energy path from the S1 Franck-Condon point leads directly to a 4π-disrotatory electrocyclic ring-opening reaction to afford bicyclo[4,2,0]octa-2,4,7-triene. The 2D potential energy surface scan located a rhomboidal S1/S0 minimum energy crossing point that connects 1 and cubane, suggesting that a cycloaddition is theoretically possible. We used the fewest switches surface hopping to study this reaction: 85% of 1,722 trajectories relaxed to 8 products; the major products are bicyclo[4,2,0]octa-2,4,7-triene (30%) and cycloocta-1,3,5,7-tetraene (32%). Only 0.4% of trajectories undergo a [2+2] cycloaddition to form cubane.

Funding

ONR N00014-12-1-0828

History

Email Address of Submitting Author

s.lopez@northeastern.edu

Institution

Northeastern University

Country

USA

ORCID For Submitting Author

0000-0002-8418-3638

Declaration of Conflict of Interest

None

Exports