Magneto-Optická a THz Spektroskopie
Browse
Recent Submissions
- ItemPhotoswitchable hydrazones with pyridine-based rotors and halogen substituents(ROYAL SOC CHEMISTRY, 2024-06-27) Kotásková, Lucie; Jewula, Pawel; Herchel, Radovan; Nemec, Ivan; Neugebauer, PetrThe Z,E-photoisomerization of pyridine-based hydrazone switches is typically suppressed due to the presence of pyridine-based rotors. The crystal structures of studied compounds were investigated using theoretical methods combining DFT and QT-AIM calculations to unveil the nature and properties of the intramolecular hydrogen bonding. In this study, we introduced a new series of pyridine-based hydrazones anchored with o-halogen substituents (2-X) and investigated their photoswitching abilities using 1H NMR and UV-Vis spectroscopy. The efficiency of the photoisomerization from initial 2-X-Z to the 2-X-E isomer varied, with the highest yield observed for 2-Cl-E (55%). Our findings, supported by DFT calculations, revealed the formation of a new diastereomer, 2-X-E*, upon back-photoisomerization. We demonstrated that hydrazones from the 2-X series can be reversibly photoswitched using irradiation from the UV-Vis range, and additionally, we explored the effect of the halogen atom on their switching capabilities and also on their thermodynamics and kinetics of photoswitching, determining their molecular solar thermal energy storage potential. We report on the E,Z-photoisomerization of hydrazone switches with pyridine-based rotors and halogen-substituted stators.
- ItemLattice solvent- and substituent-dependent spin-crossover in isomeric iron(ii) complexes(Royal Society of Chemistry, 2024-07-02) Senthil Kumar, Kuppusamy; Mizuno, Asato; Kämmerer, Lea; Salamon, Soma; Heinrich, Benoît; Bailly, Corinne; Šalitroš, Ivan; Wende, Heiko; Ruben, MarioSpin-state switching in iron(ii) complexes composed of ligands featuring moderate ligand-field strength-for example, 2,6-bi(1H-pyrazol-1-yl)pyridine (BPP)-is dependent on many factors. Herein, we show that spin-state switching in isomeric iron(ii) complexes composed of BPP-based ligands-ethyl 2,6-bis(1H-pyrazol-1-yl)isonicotinate (BPP-COOEt, L1) and (2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)methylacetate (BPP-CH2OCOMe, L2)-is dependent on the nature of the substituent at the BPP skeleton. Bi-stable spin-state switching-with a thermal hysteresis width (Delta T-1/2) of 44 K and switching temperature (T-1/2) = 298 K in the first cycle-is observed for complex 1CH3CN composed of L1 and BF4- counter anions. Conversely, the solvent-free isomeric counterpart of 1CH3CN-complex 2a, composed of L2 and BF4- counter anions-was trapped in the high-spin (HS) state. For one of the polymorphs of complex 2bCH3CN-2bCH3CN-Y, Y denotes yellow colour of the crystals-composed of L2 and ClO4- counter anions, a gradual and non-hysteretic SCO is observed with T-1/2 = 234 K. Complexes 1CH3CN and 2bCH3CN-Y also underwent light-induced spin-state switching at 5 K due to the light-induced excited spin-state trapping (LIESST) effect. Structures of the low-spin (LS) and HS forms of complex 1CH3CN revealed that spin-state switching goes hand-in-hand with pronounced distortion of the trans-N{pyridyl}-Fe-N{pyridyl} angle (phi), whereas such distortion is not observed for 2bCH3CN-Y. This observation points that distortion is one of the factors making the spin-state switching of 1CH3CN hysteretic in the solid state. The observation of bi-stable spin-state switching with T-1/2 centred at room temperature for 1CH3CN indicates that technologically relevant spin-state switching profiles based on mononuclear iron(ii) complexes can be obtained.
- ItemGraphene quantum dot bolometer for on-chip detection of organic radical(AIP Publishing, 2024-03-18) Hrubý, Jakub; Laguta, Oleksii; Sojka, Antonín; St. Marie, Luke; Myers-Ward, Rachael; Gaskill, Kurt; El Fatimy, Abdelouahad; Barbara, Paola; Neugebauer, PetrWe present a proof-of-concept magnetic resonance detection of organic radical 2,2-diphenyl-1-picrylhydrazyl via a nanostructured on-chip graphene quantum dot bolometer. In a common electron paramagnetic resonance setup, the microwave propagates from a source into a sample and back to a detector. Yet, by using on-chip detection, it is possible to skip the whole detection arm and, thus, mitigate lab expenses on instrument and cooling costs. The bolometric detection was demonstrated at a frequency of 151 GHz and a temperature of 15 K. (c) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
- ItemA Versatile Setup for Fourier-Transform Infrared Magneto-Spectroscopy(IEEE, 2023-06-09) Dubnická Midlíková, Jana; Šedivý, Matúš; Sojka, Antonín; Santana, Vinicius Tadeu; Dubroka, Adam; Neugebauer, PetrFourier-transform infrared (FTIR) magneto-spectroscopy is a powerful spectroscopic technique used to investigate many important effects in materials, e.g., electron spin resonance (ESR), cyclotron resonance, and transitions between Landau levels (LLs). Despite their enormous potential in material science, infrared (IR) magneto-spectrometers are still relatively rare and custom-made since such systems generally require complex infrastructure. This article presents a versatile broadband setup for FTIR magneto-spectroscopy spanning the range from THz/far-IR (FIR) to near-IR (NIR), high magnetic field up to 16 T, and cryogenic temperatures down to 2 K. It consists of a commercial FTIR spectrometer and 16 T cryogen-free superconducting magnet coupled with custom-designed optical coupling and transmission probes for experiments with various detectors. The functionality of the FTIR magneto-spectroscopic setup is demonstrated by the magneto-optical measurements on a cobalt-based single-molecule magnet (SMM) in the FIR region and germanium (Ge) in the NIR region.
- ItemSample Holders for Sub-THz Electron Spin Resonance Spectroscopy(IEEE, 2022-04-29) Sojka, Antonín; Šedivý, Matúš; Lagiň, Adam; Gabriš, Andrej; Láznička, Tomáš; Santana, Vinicius Tadeu; Laguta, Oleksii; Neugebauer, PetrElectron spin resonance (ESR) is a powerful spectroscopic technique used to investigate samples with unpaired electrons in a broad range of scientific fields. High-frequency ESR (HF-ESR) spectrometers operating at sub-THz frequencies are mostly custom-made with non-standard solutions. This article presents a set of six different exchangeable sample holders with a fast-loading flange for a sub-THz ESR spectrometer operating at high magnetic fields up to 16 T and temperature ranges of 4-400 K. Here, we report on the concept, design, and illustrative measurements of non-resonant ESR sample holders for the measurements of samples in a liquid solution, polycrystalline-compressed powders, oriented single crystals, electrical devices under sub-THz irradiation, as well as for samples transferred from the ultrahigh vacuum (UHV) systems without air contamination. Our solution expands the usage possibilities for HF-ESR spectroscopy, showing that one spectrometer with the presented concept of sample holders enables a wide range of applications.