Computational High-Pressure Organic Chemistry (CHIPOC)
CHIPOC is a combination of the fields of high-pressure organic reactions in solution and computational chemistry. The former is largely an experimental field, popular and thriving between 1960-2000. Measuring activation volumes and reaction volumes were the main activities, in order to understand the effect of pressure on organic reactions. The field of computational chemistry evolved following a different trajectory; it has now matured in studying reliably organic reactions in the gas phase and at ambient pressure.
Combination of the two fields was not possible before due to the lack of computational methods that take pressure as a parameter in the calculation of electronic structure. With the recently developed eXtreme Pressure Polarizable Continuum Model (XP-PCM) method, and the proposed helium compression chamber (HCC) model, first-principles calculations on high-pressure organic reactions become possible.
The Chen group works on developing the above two computational methods and applying them to a variety of organic systems under pressure.
Nanothread Chemistry and Physics
Nanothreads are novel one-dimensional carbon-based nanomaterials. The first synthesis of nanothreads was achieved by slow compression (to ~20 GPa) induced polymerization of benzene. To date, nanothreads have been synthesized from a variety of aromatic molecules. Nanothreads generally assume ordered 2D packing in the solid state, which distinguishes them from the amorphous, polymerized materials derived from the same precursors. In some cases, order along the thread direction is observed.
One defining feature of nanothreads is the unique combination of extreme thinness (only a few Å in diameter) and rigidity (multiple covalent bonds connecting each unit). This feature distinguishes nanothreads from traditional polymers that are generally flexible (by rotation around single bonds) and nanotubes that are normally much thicker.
Functional groups can be introduced to nanothreads via proper choice of precursors or post-polymerization functionalization. The rigidity of nanothread backbone could allow desired alignment of functional groups in terms of order and spacing, which may open opportunities to many interesting applications. In a sense, a nanothread is a platform for functionality based on the properties associated with the functional groups.
The Chen group studies the structures, formation mechanisms, and electronic properties of nanothreads.
Check out this talk Bo gave in 2020 on nanothreads. link
Carbenes and Diradicals
Questions we try to answer
- How to tune the relative stability of the two nonbonding orbitals?
- How to make diradicals persistent?
- What are the reactivities of carbenes and diradicals?