Topology Effects in Molecular Organic Electronic Materials: Pyrene and Azupyrene. Issue 11 (7th May 2021)

• Record Type: Journal Article
• Authors: Klein, Benedikt P.; Ruppenthal, Lukas; Hall, Samuel J.; Sattler, Lars E.; Weber, Sebastian M.; Herritsch, Jan; Jaegermann, Andrea; Maurer, Reinhard J.; Hilt, Gerhard; Gottfried, J. Michael
• Is Part Of: Chemphyschem. Volume 22:Issue 11(2021)
• Page Start: 1065
• Page End: 1073
• Publication Date: 2021-05-07
• Subjects: organic electronics -- topologic design -- aromaticity -- photoelectron spectroscopy -- density functional calculations; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.202100222
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: Pyrene derivatives play a prominent role in organic electronic devices, including field effect transistors, light emitting diodes, and solar cells. The flexibility in the desired properties has previously been achieved by variation of substituents at the periphery of the pyrene backbone. In contrast, the influence of the topology of the central π‐electron system on the relevant properties such as the band gap or the fluorescence behavior has not yet been addressed. In this work, pyrene is compared with its structural isomer azupyrene, which has a π‐electron system with non‐alternant topology. Using photoelectron spectroscopy, near edge X‐ray absorption fine structure spectroscopy, and other methods, it is shown that the electronic band gap of azupyrene is by 0.72 eV smaller than that of pyrene. The difference of the optical band gaps is even larger with 1.09 eV, as determined by ultraviolet–visible absorption spectroscopy. The non‐alternant nature of azupyrene is also associated with a more localized charge distribution. Further insight is provided by density functional theory (DFT) calculations of the molecular properties and ab initio coupled cluster calculations of the optical transitions. The concept of aromaticity is used to interpret the major topology‐related differences. Abstract : Topological Tuning : Molecular organic materials for application in organic electronics can be tailored by topological design of their π‐electron systems, instead of conventional tailoring by peripheral substituents. This is shown by a multi‐technique comparison of pyrene with its topological isomer azupyrene. The non‐alternant topology of azupyrene causes a more localized charge distribution, smaller electronic and optical gaps, and different fluorescence behavior.