Theoretical Prediction of the Structures and Energies of Olympicene and its Isomers

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2013-10, Vol.117 (39), p.9746-9752
• Main Authors: Valentine, Andrew J. S, Mazziotti, David A
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Calculations and mathematical techniques in atomic and molecular physics (excluding electron correlation calculations); Complement; Correlation; Density; Electronic structure of atoms, molecules and their ions: theory; Exact sciences and technology; Isomers; Mathematical analysis; Organic semiconductors; Pentacene; Physics; Polyaromatic hydrocarbons; Variational techniques
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp312384b

Pentacene, a linear five-ringed polyaromatic hydrocarbon, has recently been used as an organic semiconductor in field-effect transistors. The recently synthesized olympicene molecule, so named because of its resemblance to the olympic rings, is a more compact five-ringed structure. This paper offers the first theoretical study of the kinetic stability of olympicene and its isomers. We use the parametric two-electron reduced density matrix (2-RDM) method, which takes the 2-RDM as the basic variable in lieu of the traditional wave function in calculations [ Mazziotti D. A. Phys. Rev. Lett. 2008, 101, 253002 ]. Our calculations demonstrate that olympicene’s isomers may be separated into aromatic and diradical isomers, the latter of which require accurate treatment of strong electron correlation to detect multireference character. Albeit formally a single-reference method, the parametric 2-RDM captures the multireference correlation of the diradical isomers; relative to olympicene, the 2-RDM predicts five diradical isomers that are 16–22 kcal/mol lower in energy than those from coupled cluster with single and double excitationsa significant change that causes these isomers to be stable to dissociation by 2–20 kcal/mol. We characterize the transition states between olympicene’s isomers, observe differences in aromaticity among the different isomers, and compare the electronic properties of olympicene to those of pentacene. The olympicene molecule has the potential to complement pentacene as an organic semiconductor.