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Abstract Fluorination of tris(2,6‐dimethoxyphenyl)‐methylium ((DMP)3C+) was achieved through the partial defluorination of the methyl 2,3,5,6‐tetrafluorobenzoate via nucleophilic aromatic substitution. Using the fluorinated2F((DMP)3C+) as a precursor, fluorinated tetramethoxy‐ and dimethoxyquin‐ acridinium salts (2F4and2F5respectively) and trioxo‐, azadioxo‐, and diazaoxo‐ triangulenium salts (2F6,2F7and2F8respectively) were synthesized successfully in good to moderate yields. Fluorination induced significant red shifts in absorption (16 to 29 nm) and emission (13 to 41 nm) maxima, and increased electrophilicity as evidenced by lower reduction potentials. X‐ray structural analysis showed distinct packing patterns compared to the non‐fluorinated analogues, indicating the presence of molecular dipoles.
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Fluorination Affects the Force Sensitivity and Nonequilibrium Dynamics of the Mechanochemical Unzipping of Ladderanes
When multiple reaction steps occur before thermal equilibration, kinetic energy from one reaction step can influence overall product distributions in ways that are not well predicted by transition state theory. An understanding of how the structural features of mechanophores, such as substitutions, affects reactivity, product distribution, and the extent of dynamic effects in the mechanochemical manifolds is necessary for designing chemical reactions and responsive materials. We synthesized two tetrafluorinated [4]-ladderanes with fluorination on different rungs and found that the fluorination pattern influenced the force sensitivity and stereochemical distribution of products in the mechanochemistry of these fluorinated ladderanes. The threshold forces for mechanochemical unzipping of ladderane were decreased by alpha-fluorination and increased by gamma-fluorination; these changes correlated to the different stabilizing or destabilizing effects of fluorination patterns on the first transition state. Using ab initio steered molecular dynamics (AISMD), we compared the product distributions of synthesized and hypothetical ladderanes with different substitution patterns. These calculations suggest that fluorination on the first two bonds of ladderane gives rise to a larger fraction of dynamic trajectories and a larger fraction of E alkene prod-uct through a mechanism resulting from larger momentum because of the greater atomic mass of fluorine. Fluorination on the third and fourth rungs instead gives a larger fraction of E alkene product primarily due to electronic effects. These com-bined experimental and computational studies of the mechanochemical unzipping of fluorinated ladderanes provide an example of how relatively simple substituents can affect the extent of non-statistical dynamics, and thus mechanochemical outcomes.
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- PAR ID:
- 10580382
- Publisher / Repository:
- ACS
- Date Published:
- Journal Name:
- Journal of the American Chemical Society
- Volume:
- 146
- Issue:
- 47
- ISSN:
- 0002-7863
- Page Range / eLocation ID:
- 32651 to 32659
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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