Thermally Ultrarobust S = 1/2 Tetrazolinyl Radicals: Synthesis, Electronic Structure, Magnetism, and Nanoneedle Assemblies on Silicon Surface
Year: 2023
Type: article
Abstract: Open-shell organic molecules, including S = 1/2 radicals, may provide enhanced properties for several emerging technologies; however, relatively few synthesized to date possess robust thermal stability and processability. We report the synthesis of S = 1/2 biphenylene-fused tetrazolinyl radicals 1 and 2 . Both radicals possess near-perfect planar structures based on their X-ray structures and density-functional theory (DFT) computations. Radical 1 possesses outstanding thermal stability as indicated by the onset of decomposition at 269 °C, based on thermogravimetric analysis (TGA) data. Both radicals possess very low oxidation potentials <0 V (vs. SCE) and their electrochemical energy gaps, E cell ≈ 0.9 eV, are rather low. Magnetic properties of polycrystalline 1 are characterized by superconducting quantum interference device (SQUID) magnetometry revealing a one-dimensional S = 1/2 antiferromagnetic Heisenberg chain with exchange coupling constant J ′/ k ≈ −22.0 K. Radical 1 in toluene glass possesses a long electron spin coherence time, T m ≈ 7 μs in the 40–80 K temperature range, a property advantageous for potential applications as a molecular spin qubit. Radical 1 is evaporated under ultrahigh vacuum (UHV) forming assemblies of intact radicals on a silicon substrate, as confirmed by high-resolution X-ray photoelectron spectroscopy (XPS). Scanning electron microscope (SEM) images indicate that the radical molecules form nanoneedles on the substrate. The nanoneedles are stable for at least 64 hours under air as monitored by using X-ray photoelectron spectroscopy. Electron paramagnetic resonance (EPR) studies of the thicker assemblies, prepared by UHV evaporation, indicate radical decay according to first-order kinetics with a long half-life of 50 ± 4 days at ambient conditions.
DOI: 10.1021/jacs.3c03402
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, Indiana University, European Commission, Deutsche Forschungsgemeinschaft, Eberhard Karls Universität Tübingen, National Institutes of Health, Horizon 2020 Framework Programme, NIH Office of the Director, National Institute of General Medical Sciences, Division of Chemistry
Awards: High-sensitivity upgrade of DEER/EPR spectrometer, G1584337712, G2589913962, Nitrogen Centered Radicals, G3257705099, Gated INTERfaces for FAST information processing, New Nitroxide Spin Labels for Distance Measurements in Biological Systems, G3562515488, G4126275445, Nitrogen Centered Radicals, G434337789, Decoherence of Molecular Spin Qubits, G5463381820, G6306859062, G670392301, G8646758398
OpenAlex ID: W4379618680