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Azaacene Diradicals Based on Non-Kekulé Meta- Quinodimethane

03 April 2024, Version 1
Working Paper
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Non-Kekulé quinoidal azaacences m-A (1a,b) were synthesized and compared to their para- and ortho-quinodimethane analogues. m-A display high diradical characters (1b: y0 = 0.88) due to their meta-quinodimethane (m-QDM) topology. Electron paramagnetic (EPR), nuclear magnetic resonance (NMR) spectroscopies and supraquantum interference device (SQUID) measurements in combination with quantum-chemical calculations revealed singlet ground states for m-A with singlet-triplet gaps ΔEST (0.13-0.25 kcal mol-1) and thermally populated triplet states. These non-Kekulé structures are void of zwitterionic character and possess record high two-photon absorption cross sections over a broad spectral range in the near-infrared.

Keywords

aromaticity
azaacene
Clar sextets
non-Kekulé diradical
regioisomerism
two-photon absorption

Supplementary materials

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Description
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Supporting Information
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Experimental procedures, material characterization data and details regarding quantum chemical calculations.
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Version History

Apr 03, 2024 Version 1

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The content is available under CC BY NC ND 4.0 [opens in a new tab]

DOI

10.26434/chemrxiv-2024-77p4z
D O I: 10.26434/chemrxiv-2024-77p4z [opens in a new tab]

Funding

Deutsche Forschungsgemeinschaft
Project Number 281029004 - SFB 1249, projects A1, B1, and B6

Author’s competing interest statement

The author(s) have declared they have no conflict of interest with regard to this content

Ethics

The author(s) have declared ethics committee/IRB approval is not relevant to this content

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