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Cycloparaphenylene Lemniscates and Trefoils.

Steven M Bachrach1

  • 1School of Science , Monmouth University , 400 Cedar Avenue , West Long Branch , New Jersey 07764 , United States.

The Journal of Organic Chemistry
|December 21, 2019
PubMed
Summary
This summary is machine-generated.

Researchers studied cycloparaphenylene lemniscates and trefoils, finding that increasing loop size reduces ring strain energy (RSE). Nitrogen substitution creates a more planar, ribbon-like structure with lower RSEs.

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Area of Science:

  • Organic Chemistry
  • Computational Chemistry
  • Materials Science

Background:

  • Cycloparaphenylenes (CPPs) are a class of molecular architectures with unique structural and electronic properties.
  • Recently synthesized cycloparaphenylene lemniscates (G) and trefoils (E) present novel topological structures for investigation.
  • Understanding the relationship between structure, strain, and substitution is crucial for designing new materials.

Purpose of the Study:

  • To computationally explore variants of cycloparaphenylene lemniscates (G) with different loop sizes and linkage bonds.
  • To investigate the impact of nitrogen substitution on the structure and ring strain energy (RSE) of lemniscates and trefoils.
  • To correlate structural modifications with changes in molecular strain and planarity.

Main Methods:

  • Density functional theory (DFT) calculations were performed using the ωB97X-D/6-311G(d) level of theory.
  • Geometric optimizations and frequency calculations were used to determine stable structures and RSEs.
  • Analysis of structural parameters, including planarity and bond lengths, was conducted.

Main Results:

  • Lemniscates (G) with four to eight phenyl rings adopted a figure-eight shape, irrespective of the N-N, C═C, or B-N linkage.
  • Ring strain energy (RSE) decreased systematically with increasing loop size for lemniscates.
  • Selective nitrogen substitution at ortho positions induced planarity, leading to ribbon-like structures and reduced RSEs in both lemniscates and trefoils (E).

Conclusions:

  • The RSE of cycloparaphenylene lemniscates is primarily dependent on loop size rather than the linkage bond type.
  • Nitrogen substitution offers a viable strategy to control the planarity and reduce the strain energy of these molecular architectures.
  • These findings provide insights into the design principles for novel strained organic materials with tunable properties.