Nanoarchitecture through Strained Molecules: Cubane-Derived Scaffolds and the Smallest Carbon Nanothreads

2020 ◽  
Vol 142 (42) ◽  
pp. 17944-17955 ◽  
Author(s):  
Haw-Tyng Huang ◽  
Li Zhu ◽  
Matthew D. Ward ◽  
Tao Wang ◽  
Bo Chen ◽  
...  
Keyword(s):  
Strained Molecules

Straining strained molecules - I. The synthesis of the first cyclophane within a cyclophane - [2,2]paracyclo ([2,2]metacyclophane)

1976 ◽  
Vol 17 (30) ◽  
pp. 2585-2588 ◽  
Author(s):  
Reginald H. Mitchell ◽  
Robert J. Carruthers ◽  
Joanne C.M. Zwinkels
Keyword(s):  
Strained Molecules

Rhodium(I)-catalyzed rearrangements of strained molecules containing fused cyclobutane rings

1979 ◽  
Vol 101 (10) ◽  
pp. 2694-2698 ◽  
Author(s):  
Miriam Sohn ◽  
Jochanan Blum ◽  
Jack Halpern
Keyword(s):  
Strained Molecules

Chemomechanics with molecular force probes

2010 ◽  
Vol 82 (4) ◽  
pp. 931-951 ◽  
Author(s):  
Zhen Huang ◽  
Roman Boulatov
Keyword(s):  
Materials Science ◽  
Reaction Rates ◽  
Restoring Force ◽  
Strained Molecules ◽  
Multiple Length Scales ◽  
Molecular Force ◽  
Directional Motion ◽  
Restoring Forces ◽  
Highly Strained ◽  
Force Probes

Chemomechanics is an emerging area at the interface of chemistry, materials science, physics, and biology that aims at quantitative understanding of reaction dynamics in multiscale phenomena. These are characterized by correlated directional motion at multiple length scales—from molecular to macroscopic. Examples include reactions in stressed materials, in shear flows, and at propagating interfaces, the operation of motor proteins, ion pumps, and actuating polymers, and mechanosensing. To explain the up to 1015-fold variations in reaction rates in multiscale phenomena—which are incompatible within the standard models of chemical kinetics—chemomechanics relies on the concept of molecular restoring force. Molecular force probes are inert molecules that allow incremental variations in restoring forces of diverse reactive moieties over hundreds of piconewtons (pN). Extending beyond the classical studies of reactions of strained molecules, molecular force probes enable experimental explorations of how reaction rates and restoring forces are related. In this review, we will describe the utility of one such probe—stiff stilbene. Various reactive moieties were incorporated in inert linkers that constrained stiff stilbene to highly strained macrocycles. Such series provided the first direct experimental validation of the most popular chemomechanical model, demonstrated its predictive capabilities, and illustrated the diversity of relationships between reaction rates and forces.

Method to Derive Restoring Forces of Strained Molecules from Kinetic Measurements

2009 ◽  
Vol 131 (4) ◽  
pp. 1407-1409 ◽  
Author(s):  
Zhen Huang ◽  
Qing-Zheng Yang ◽  
Daria Khvostichenko ◽  
Timothy J. Kucharski ◽  
Joseph Chen ◽  
...  
Keyword(s):  
Kinetic Measurements ◽  
Strained Molecules ◽  
Restoring Forces

scholarly journals A Theoretical Stereoselectivity Model of Photochemical Denitrogenations of Diazoalkanes Towards Strained 1,3-Dihalogenated Bicyclobutanes

2020 ◽  
Author(s):  
Jingbai Li ◽  
Rachel Stein ◽  
Steven Lopez
Keyword(s):  
Minimum Energy ◽  
Photochemical Reactions ◽  
Basis Set ◽  
Strained Molecules ◽  
Complete Active Space ◽  
Active Space ◽  
Self Consistent Field ◽  
Shoulder Region ◽  
Highly Strained ◽  
Diastereomeric Excess

<p>Photochemical reactions exemplify ‘green’ chemistry and are essential for synthesizing highly strained molecules with mild conditions with light. The light-promoted denitrogenation of bicyclic azoalkanes affords functionalized, stereoenriched bicyclo[1.1.0]butanes. We revisited these reactions with multireference calculations and non-adiabatic molecular dynamics (NAMD) simulations for a series of diazabicyclo[2.1.1]hexenes to predict the photophysics, reactivities, and stereoselectivities. We used complete active space self-consistent field (CASSCF) calculations with an (8,8) active space and ANO-S-VDZP basis set; the CASSCF energies were corrected with CASPT2(8,8)/ANO-S-VDZP. The excitation is consistently n→π* and ranges from 3.77–3.91 eV for the diazabicyclo[2.1.1]hexenes. Minimum energy path calculations showed stepwise C–N bond breaking and led to a minimum energy crossing point, which favors the stereochemical ‘double inversion’ bicyclobutane product. Wigner sampling of <b>1</b> provided Franck-Condon points for 692 NAMD trajectories. We identified competing complete stereoselective and stereochemical scrambling pathways. The stereoselective pathways feature concerted bicyclobutane inversion and N<sub>2</sub> extrusion. The stereochemical scrambling pathways involve N<sub>2</sub> extrusion followed by bicyclobutane planarization, leading to non-stereoselective outcomes. The predicted diastereomeric excess almost exactly match experiment (calc<i>.d.e.</i>=46% <i>vs.</i> exp<i>.d.e.</i>=47%). Our NAMD simulations with 672, 568, and 596 trajectories for <b>1-F</b>, <b>1-Cl</b>, and <b>1-Br</b> predicted diastereomeric excess (<i>d.e.</i>) of 94–97% for the double inversion products. Halogenation significantly perturbs the potential energy surface (PES) towards the retention products because of powerful hyperconjugative interactions. The n<sub>C</sub>→σ<sup>*</sup><sub>C–X</sub>,<sub> </sub>X = F, Cl, Br hyperconjugative interaction leads to a broadened shoulder region on the PES for double inversion.</p>

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

2020 ◽  
Author(s):  
Jingbai Li ◽  
Steven Lopez
Keyword(s):  
Minimum Energy ◽  
Photochemical Reactions ◽  
Basis Set ◽  
Strained Molecules ◽  
Complete Active Space ◽  
Vertical Excitation ◽  
Active Space ◽  
Ring Opening Reaction ◽  
Self Consistent Field ◽  
Surface Scan

<p>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[4,2,0,0<sup>2,5</sup>]octa-3,7-diene (<b>1</b>). The energies were corrected with a second-order perturbative correction CASPT2(8,7)/ANO-S-VDZP. The S<sub>0</sub>→S<sub>1</sub> vertical excitation energy of <b>1</b> is 6.25 eV, whose nature is π→π<sup>*</sup> excitation. The minimum energy path from the S<sub>1</sub> 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 S<sub>1</sub>/S<sub>0</sub> minimum energy crossing point that connects <b>1</b> 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.<i></i></p>

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