A Highly Strained Al–Al σ-Bond in Dianionic Aluminum Analog of Oxirane for Molecule Activation

Symmetry Breaking and the Turn-On Fluorescence of Small, Highly Strained Carbon Nanohoops

10.26434/chemrxiv.7580027.v1 ◽

2019 ◽

Author(s):

Terri Lovell ◽

Curtis Colwell ◽

Lev N. Zakharov ◽

Ramesh Jasti

Keyword(s):

Symmetry Breaking ◽

Theoretical Work ◽

P Systems ◽

Quantum Yields ◽

Size Dependent ◽

New Class ◽

Carbon Carbon Bond ◽

Conjugated Macrocycles ◽

Structural Manipulation ◽

Highly Strained

[n]Cycloparaphenylenes, or “carbon nanohoops,” are unique conjugated macrocycles with radially oriented p-systems similar to those in carbon nanotubes. The centrosymmetric nature and conformational rigidity of these molecules lead to unusual size-dependent photophysical characteristics. To investigate these effects further and expand the family of possible structures, a new class of related carbon nanohoops with broken symmetry is disclosed. In these structures, referred to as meta[n]cycloparaphenylenes, a single carbon-carbon bond is shifted by one position in order to break the centrosymmetric nature of the parent [n]cycloparaphenylenes. Advantageously, the symmetry breaking leads to bright emission in the smaller nanohoops, which are typically non-fluorescent due to optical selection rules. Moreover, this simple structural manipulation retains one of the most unique features of the nanohoop structures-size dependent emissive properties with relatively large extinction coefficents and quantum yields. Inspired by earlier theoretical work by Tretiak and co-workers, this joint synthetic, photophysical, and theoretical study provides further design principles to manipulate the optical properties of this growing class of molecules with radially oriented p-systems.

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Symmetry Breaking and the Turn-On Fluorescence of Small, Highly Strained Carbon Nanohoops

10.26434/chemrxiv.7580027 ◽

2019 ◽

Author(s):

Terri Lovell ◽

Curtis Colwell ◽

Lev N. Zakharov ◽

Ramesh Jasti

Keyword(s):

Symmetry Breaking ◽

Theoretical Work ◽

P Systems ◽

Quantum Yields ◽

Size Dependent ◽

New Class ◽

Carbon Carbon Bond ◽

Conjugated Macrocycles ◽

Structural Manipulation ◽

Highly Strained

[n]Cycloparaphenylenes, or “carbon nanohoops,” are unique conjugated macrocycles with radially oriented p-systems similar to those in carbon nanotubes. The centrosymmetric nature and conformational rigidity of these molecules lead to unusual size-dependent photophysical characteristics. To investigate these effects further and expand the family of possible structures, a new class of related carbon nanohoops with broken symmetry is disclosed. In these structures, referred to as meta[n]cycloparaphenylenes, a single carbon-carbon bond is shifted by one position in order to break the centrosymmetric nature of the parent [n]cycloparaphenylenes. Advantageously, the symmetry breaking leads to bright emission in the smaller nanohoops, which are typically non-fluorescent due to optical selection rules. Moreover, this simple structural manipulation retains one of the most unique features of the nanohoop structures-size dependent emissive properties with relatively large extinction coefficents and quantum yields. Inspired by earlier theoretical work by Tretiak and co-workers, this joint synthetic, photophysical, and theoretical study provides further design principles to manipulate the optical properties of this growing class of molecules with radially oriented p-systems.

Download Full-text