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Usevičius G, Eggeling A, Pocius I, Kalendra V, Klose D, Mączka M, Pöppl A, Banys J, Jeschke G, Šimėnas M. Probing Methyl Group Tunneling in [(CH 3) 2NH 2][Zn(HCOO) 3] Hybrid Perovskite Using Co 2+ EPR. Molecules 2023; 28:molecules28030979. [PMID: 36770643 PMCID: PMC9920925 DOI: 10.3390/molecules28030979] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 01/14/2023] [Accepted: 01/16/2023] [Indexed: 01/21/2023] Open
Abstract
At low temperature, methyl groups act as hindered quantum rotors exhibiting rotational quantum tunneling, which is highly sensitive to a local methyl group environment. Recently, we observed this effect using pulsed electron paramagnetic resonance (EPR) in two dimethylammonium-containing hybrid perovskites doped with paramagnetic Mn2+ ions. Here, we investigate the feasibility of using an alternative fast-relaxing Co2+ paramagnetic center to study the methyl group tunneling, and, as a model compound, we use dimethylammonium zinc formate [(CH3)2NH2][Zn(HCOO)3] hybrid perovskite. Our multifrequency (X-, Q- and W-band) EPR experiments reveal a high-spin state of the incorporated Co2+ center, which exhibits fast spin-lattice relaxation and electron spin decoherence. Our pulsed EPR experiments reveal magnetic field independent electron spin echo envelope modulation (ESEEM) signals, which are assigned to the methyl group tunneling. We use density operator simulations to extract the tunnel frequency of 1.84 MHz from the experimental data, which is then used to calculate the rotational barrier of the methyl groups. We compare our results with the previously reported Mn2+ case showing that our approach can detect very small changes in the local methyl group environment in hybrid perovskites and related materials.
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Affiliation(s)
- Gediminas Usevičius
- Faculty of Physics, Vilnius University, Sauletekio 3, 10257 Vilnius, Lithuania
| | - Andrea Eggeling
- Department of Physical Chemistry, ETH-Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Ignas Pocius
- Faculty of Physics, Vilnius University, Sauletekio 3, 10257 Vilnius, Lithuania
| | - Vidmantas Kalendra
- Faculty of Physics, Vilnius University, Sauletekio 3, 10257 Vilnius, Lithuania
| | - Daniel Klose
- Department of Physical Chemistry, ETH-Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Mirosław Mączka
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okólna 2, 50-422 Wroclaw, Poland
| | - Andreas Pöppl
- Felix Bloch Institute for Solid State Physics, Leipzig University, 04103 Leipzig, Germany
| | - Jūras Banys
- Faculty of Physics, Vilnius University, Sauletekio 3, 10257 Vilnius, Lithuania
| | - Gunnar Jeschke
- Department of Physical Chemistry, ETH-Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland
| | - Mantas Šimėnas
- Faculty of Physics, Vilnius University, Sauletekio 3, 10257 Vilnius, Lithuania
- Correspondence:
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