TY - JOUR
T1 - Improving the Stability of Organic Semiconductors: Distortion Energy versus Aromaticity in Substituted Bistetracene
AU - Thomas, Simil
AU - Ly, Jack
AU - Zhang, Lei
AU - Briseno, Alejandro L.
AU - Bredas, Jean-Luc
N1 - KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported by King Abdullah University of Science and Technology (KAUST) and by ONR-Global (Award No. N62909-15-1-2003). We are grateful to the KAUST Supercomputing Laboratory and the KAUST IT Research Computing Team for providing continuous assistance as well as computational and storage resources. J.L. acknowledges funding from the National Science Foundation (DMR-1508627); L.Z. thanks the Office of Naval Research (N000147-14-1-0053); S.T. thanks Dr. Manjaly J. Ajitha for useful discussions.
PY - 2016/11/28
Y1 - 2016/11/28
N2 - Polycyclic aromatic hydrocarbons (PAHs) have been widely explored as molecular semiconductors in organic electronic devices such as field-effect transistors or solar cells. However, their tendency to undergo photooxidation is a primary limitation to their practical applications. Bistetracene derivatives have recently been demonstrated to possess much larger photo oxidation stability than the widely investigated pentacene and rubrene, while maintaining high charge-carrier mobilities. Here, using several levels of density functional theory, we identify the origin of the increased stability of bistetracene with respect to molecular oxygen by systematically investigating the [4 + 2] cycloaddition (Diels Alder) photooxidation reaction mechanism. Importantly, our computational results indicate that endoperoxide formation in bis(2-(trimethylsilyl)ethynyl) bistetracene (BT) occurs not on the ring with least aromaticity, but rather on the ring with smallest distortion energy. This feature was subsequently confirmed by experimental NMR analyses. The oxidation activation barriers of bistetracene, pentacene, and rubrene are found to be 17.7, 13.6, and 14.4 kcal/mol, respectively, in agreement with the observed order of stability of these molecules with respect to oxidation reactions in solution. In the cases of BT and pentacene, the rates of electron transfer to create charged species (PAH(+) and O-2) are at least two orders of magnitude lower than that of the charge recombination process (back to PAH and O-2); for rubrene, both of these processes are calculated to be of the same order of magnitude, in agreement with experimental electron paramagnetic resonance spectroscopy observations.
AB - Polycyclic aromatic hydrocarbons (PAHs) have been widely explored as molecular semiconductors in organic electronic devices such as field-effect transistors or solar cells. However, their tendency to undergo photooxidation is a primary limitation to their practical applications. Bistetracene derivatives have recently been demonstrated to possess much larger photo oxidation stability than the widely investigated pentacene and rubrene, while maintaining high charge-carrier mobilities. Here, using several levels of density functional theory, we identify the origin of the increased stability of bistetracene with respect to molecular oxygen by systematically investigating the [4 + 2] cycloaddition (Diels Alder) photooxidation reaction mechanism. Importantly, our computational results indicate that endoperoxide formation in bis(2-(trimethylsilyl)ethynyl) bistetracene (BT) occurs not on the ring with least aromaticity, but rather on the ring with smallest distortion energy. This feature was subsequently confirmed by experimental NMR analyses. The oxidation activation barriers of bistetracene, pentacene, and rubrene are found to be 17.7, 13.6, and 14.4 kcal/mol, respectively, in agreement with the observed order of stability of these molecules with respect to oxidation reactions in solution. In the cases of BT and pentacene, the rates of electron transfer to create charged species (PAH(+) and O-2) are at least two orders of magnitude lower than that of the charge recombination process (back to PAH and O-2); for rubrene, both of these processes are calculated to be of the same order of magnitude, in agreement with experimental electron paramagnetic resonance spectroscopy observations.
UR - http://hdl.handle.net/10754/622759
UR - http://pubs.acs.org/doi/abs/10.1021/acs.chemmater.6b02552
UR - http://www.scopus.com/inward/record.url?scp=85006250757&partnerID=8YFLogxK
U2 - 10.1021/acs.chemmater.6b02552
DO - 10.1021/acs.chemmater.6b02552
M3 - Article
SN - 0897-4756
VL - 28
SP - 8504
EP - 8512
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 23
ER -