| Autor: |
Lovell TC; Department of Chemistry & Biochemistry , Materials Science Institute , University of Oregon , Eugene , Oregon 97403 , USA . Email: rjasti@uoregon.edu., Colwell CE; Department of Chemistry & Biochemistry , Materials Science Institute , University of Oregon , Eugene , Oregon 97403 , USA . Email: rjasti@uoregon.edu., Zakharov LN; CAMCOR - Center for Advance Materials Characterization in Oregon , University of Oregon , Eugene , Oregon 97403 , USA., Jasti R; Department of Chemistry & Biochemistry , Materials Science Institute , University of Oregon , Eugene , Oregon 97403 , USA . Email: rjasti@uoregon.edu. |
| Abstrakt: |
[ n ]Cycloparaphenylenes, or "carbon nanohoops," are unique conjugated macrocycles with radially oriented π-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 coefficients 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 π-systems. |
