Donor-Acceptor Substituted Benzo-, Naphtho- and Phenanthro-Fused Norbornadienes
Journal article, 2020

The photochromic norbornadiene/quadricyclane (NBD/QC) couple has found interest as a molecular solar thermal energy (MOST) system for storage of solar energy. To increase the energy difference between the two isomers, we present here the synthesis of a selection of benzo-fused NBD derivatives that contain an aromatic unit, benzene, naphthalene or phenanthrene, fused to one of the NBD double bonds, while the carbon atoms of the other double bond are functionalized with donor and acceptor groups. The synthesis protocols involve functionalization of benzo-fused NBDs with bromo/chloro substituents followed by a subjection of these intermediates to a cyanation reaction (introducing a cyano acceptor group) followed by a Sonogashira coupling (introducing an arylethynyl donor group, -CCC6H4NMe2 or -CCC6H4OMe). While the derivatives have good absorption properties in the visible region (redshifted relative to parent system) in the context of MOST applications, they lack the ability to undergo NBD-to-QC photoisomerization, even in the presence of a photosensitizer. It seems that loss of aromaticity of the fused aromatics is too significant to allow photoisomerization to occur. The concept of destroying aromaticity of a neighboring moiety as a way to enhance the energy density of the NBD/QC couple thus needs further structural modifications, in the quest for optimum MOST systems.

chromophore

polycyclic aromatic hydrocarbon

cycloaddition

Sonogashira coupling

ring strain

quadricyclane

norbornadiene

aromaticity

photoswitch

solar energy storage

Author

Mads Manso

University of Copenhagen

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Kasper Moth-Poulsen Group

Lorette Fernandez

Zhihang Wang

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Kasper Moth-Poulsen Group

Kasper Moth-Poulsen

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Kasper Moth-Poulsen Group

Mogens Brøndsted Nielsen

University of Copenhagen

Molecules

1420-3049 (ISSN)

Vol. 25 2

Subject Categories

Inorganic Chemistry

Theoretical Chemistry

Organic Chemistry

DOI

10.3390/molecules25020322

PubMed

31941131

More information

Latest update

2/12/2020