Probing Methyl Group Tunneling in [(CH3)2NH2][Zn(HCOO)3] Hybrid Perovskite Using Co2+ EPR

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 pero...

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Bibliographic Details
Published in:Molecules (Basel, Switzerland) Switzerland), 2023-01, Vol.28 (3), p.979
Main Authors: Usevičius, Gediminas, Eggeling, Andrea, Pocius, Ignas, Kalendra, Vidmantas, Klose, Daniel, Mączka, Mirosław, Pöppl, Andreas, Banys, Jūras, Jeschke, Gunnar, Šimėnas, Mantas
Format: Article
Language:English
Subjects:
Agreements
Carbon dioxide
Cobalt
Electron paramagnetic resonance
Electron spin
Electron spin resonance
EPR
ESEEM
Experiments
hybrid perovskite
Low temperature
Magnetic fields
Manganese ions
methyl group tunneling
Perovskites
Phase transitions
Quantum tunnelling
Rotors
Simulation
Spectrum analysis
Spin-lattice relaxation
Zinc
Zinc compounds
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Summary: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.
ISSN:1420-3049
1420-3049
DOI:10.3390/molecules28030979