TY - JOUR

T1 - Extended Tetrathiafulvalenes with Fluoreno[3,2-b]fluorene and Diindeno[1,2-b : 1′,2′-i]anthracene Cores

AU - Granhøj, Jeppe

AU - Zalibera, Michal

AU - Malček, Michal

AU - Bliksted Roug Pedersen, Viktor

AU - Erbs Hillers-Bendtsen, Andreas

AU - Mikkelsen, Kurt V.

AU - Rapta, Peter

AU - Brøndsted Nielsen, Mogens

N1 - Funding Information: We acknowledge Prof. Jesper Bendix (University of Copenhagen) for helping with EPR measurements of chemically oxidized structures and Prof. Morten Bjerrum (University of Copenhagen) for providing access to UV/Vis/NIR spectrophotometer. Furthermore, we would like to acknowledge Prof. Em. Ole Hammerich (University of Copenhagen) for fruitful discussions on the electrochemistry. The Novo Nordisk Foundation is acknowledged for financially supporting this work (grant #NNF20OC0061574). PR and MZ thank the Science and Technology Assistance Agency (grant APVV‐19‐0024), grant agency VEGA (contracts No.1/0078/21 and 1/0392/24) and the Operational Program Integrated Infrastructure for the project: “Support of research activities of Excellence laboratories STU in Bratislava”, Project no. 313021BXZ1, co‐financed by the European Regional Development Fund, for the financial support. MM is grateful to the HPC center at the Slovak University of Technology in Bratislava, which is a part of the Slovak Infrastructure of High Performance Computing (SIVVP project, ITMS code 26230120002, funded by the European Region Development Fund) for the computational time. Publisher Copyright: © 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.

PY - 2024

Y1 - 2024

N2 - In one-dimensional polycyclic aromatic hydrocarbons (PAHs) containing five- and six-membered rings fused together, one key question is whether the structures possess a quinoidal or aromatic diradical character. Here, we generate such PAHs by reversible oxidation of PAH-extended tetrathiafulvalenes (TTFs). Extended TTFs were thus prepared and studied for their geometrical properties (crystallography), redox properties, and UV/Vis/NIR/EPR characteristics as a function of charge state. The EPR measurements of radical cations showed unique features for each PAH-TTF. The dications, formally composed of fluoreno[3,2-b]fluorene and diindeno[1,2-b:1′,2′-i]anthracene cores, were experimentally found to exhibit singlet ground states. For the latter, calculations reveal the closed shell, quinoid singlet state to be isoenergetic with the open shell singlet diradical. Each charge state exhibited unique optical properties with radical cations absorbing strongly in the NIR region with signatures from π-dimers for the large core. The experimental results were paralleled and supported by detailed computations, including spin density distribution calculations, EPR simulations, and nucleus independent chemical shift (NICS) xy scans.

AB - In one-dimensional polycyclic aromatic hydrocarbons (PAHs) containing five- and six-membered rings fused together, one key question is whether the structures possess a quinoidal or aromatic diradical character. Here, we generate such PAHs by reversible oxidation of PAH-extended tetrathiafulvalenes (TTFs). Extended TTFs were thus prepared and studied for their geometrical properties (crystallography), redox properties, and UV/Vis/NIR/EPR characteristics as a function of charge state. The EPR measurements of radical cations showed unique features for each PAH-TTF. The dications, formally composed of fluoreno[3,2-b]fluorene and diindeno[1,2-b:1′,2′-i]anthracene cores, were experimentally found to exhibit singlet ground states. For the latter, calculations reveal the closed shell, quinoid singlet state to be isoenergetic with the open shell singlet diradical. Each charge state exhibited unique optical properties with radical cations absorbing strongly in the NIR region with signatures from π-dimers for the large core. The experimental results were paralleled and supported by detailed computations, including spin density distribution calculations, EPR simulations, and nucleus independent chemical shift (NICS) xy scans.

KW - conjugation

KW - diradicals

KW - fused-ring systems

KW - redox chemistry

KW - sulfur heterocycles

U2 - 10.1002/chem.202302688

DO - 10.1002/chem.202302688

M3 - Journal article

C2 - 37930277

AN - SCOPUS:85178433451

VL - 30

JO - Chemistry: A European Journal

JF - Chemistry: A European Journal

SN - 0947-6539

IS - 5

M1 - e202302688

ER -