Unraveling factors leading to efficient norbornadiene-quadricyclane molecular solar-thermal energy storage systems
Journal article, 2017

Developing norbornadiene-quadricyclane (NBD-QC) systems for molecular solar-thermal (MOST) energy storage is often a process of trial and error. By studying a series of norbornadienes (NBD-R-2) doubly substituted at the C7-position with R = H, Me, and iPr, we untangle the interrelated factors affecting MOST performance through a combination of experiment and theory. Increasing the steric bulk along the NBD-R-2 series gave higher quantum yields, slightly red-shifted absorptions, and longer thermal lifetimes of the energy-rich QC isomer. However, these advantages are counterbalanced by lower energy storage capacities, and overall R = Me appears most promising for short-term MOST applications. Computationally we find that it is the destabilization of the NBD isomer over the QC isomer with increasing steric bulk that is responsible for most of the observed trends and we can also predict the relative quantum yields by characterizing the S-1/S-0 conical intersections. The significantly increased thermal half-life of NBD-iPr(2) is caused by a higher activation entropy, highlighting a novel strategy to improve thermal half-lives of MOST compounds and other photo-switchable molecules without affecting their electronic properties. The potential of the NBD-R-2 compounds in devices is also explored, demonstrating a solar energy storage efficiency of up to 0.2%. Finally, we show how the insights gained in this study can be used to identify strategies to improve already existing NBD-QC systems.

Derivatives

Organic-Photochemistry

Generalized-Gradient-Approximation

Substituted Norbornadienes

Isomerization

Excited-State Aromaticity

Density

Orbital Methods

Ab-Initio

Donor-Acceptor Norbornadiene

Author

K. Jorner

Uppsala University

Ambra Dreos

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Polymer Technology

R. Emanuelsson

Uppsala University

O. El Bakouri

Universitat de Girona

I. F. Galvan

Uppsala University

Karl Börjesson

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Polymer Technology

F. Feixas

Universitat de Girona

R. Lindh

Uppsala University

B. Zietz

Uppsala University

Kasper Moth-Poulsen

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Polymer Technology

H. Ottosson

Uppsala University

Journal of Materials Chemistry A

20507488 (ISSN) 20507496 (eISSN)

Vol. 5 24 12369-12378

Subject Categories

Materials Chemistry

DOI

10.1039/c7ta04259k

More information

Latest update

5/22/2018