TY - JOUR

T1 - High-field EPR of copper(II)-nitroxide compound exhibiting three-step phase transition: structural insights from the field-induced sample orientation

AU - Tumanov, Sergey V

AU - Ponomaryov, Alexey N

AU - Maryunina, Kseniya Yu

AU - Bogomyakov, Artem S

AU - Ovcharenko, Victor I

AU - Zvyagin, Sergei A

AU - Fedin, Matvey V

AU - Veber, Sergey L

N1 - EPR measurements were supported by the Russian Science Foundation through grant no. 17-13-01412. FTIR measurements and final data analysis were supported by the Russian Science Foundation through grant no. 22-13-00376. This work was partially supported by the HLD at HZDR, a member of the European Magnetic Field Laboratory (EMFL). We would like to thank M. Klopf (HZDR) for development of the optical part of the pulsed-field EPR spectrometer.

PY - 2023/7/11

Y1 - 2023/7/11

N2 - Copper(II)-nitroxide based Cu(hfac)2LR compounds exhibit unusual magnetic behavior that can be induced by various stimuli. In many aspects, the magnetic phenomena observed in Cu(hfac)2LR are similar to classical spin-crossover behavior. However, these phenomena originate from polynuclear exchange-coupled spin clusters Cu2+-O˙-N< or >N-˙O-Cu2+-O˙-N<. Such peculiarities may result in additional multifunctionality of Cu(hfac)2LR compounds, making them promising materials for spintronic applications. Herein, we investigate the Cu(hfac)2LMeMe material, which demonstrates a three-step temperature-induced magnetostructural transition between high-temperature, low-temperature, and intermediate states, as revealed by magnetometry. Two main steps were resolved using variable-temperature Fourier-transform infrared and Q-band electron paramagnetic resonance (EPR) spectroscopies. The intermediate-temperature states (∼40-90 K) are characterized by the coexistence of two types of copper(II)-nitroxide clusters, corresponding to the low-temperature and high-temperature phases. High-field EPR experiments revealed the effect of partial alignment of Cu(hfac)2LMeMe microcrystals in a strong (>20 T) magnetic field. This effect was used to unveil the structural features of the low-temperature phase of Cu(hfac)2LMeMe, which were inaccessible using single-crystal X-ray diffraction (XRD) technique. In particular, high-field EPR allowed us to determine the relative direction of the Jahn-Teller axes in CuO6 and CuO4N2 units.

AB - Copper(II)-nitroxide based Cu(hfac)2LR compounds exhibit unusual magnetic behavior that can be induced by various stimuli. In many aspects, the magnetic phenomena observed in Cu(hfac)2LR are similar to classical spin-crossover behavior. However, these phenomena originate from polynuclear exchange-coupled spin clusters Cu2+-O˙-N< or >N-˙O-Cu2+-O˙-N<. Such peculiarities may result in additional multifunctionality of Cu(hfac)2LR compounds, making them promising materials for spintronic applications. Herein, we investigate the Cu(hfac)2LMeMe material, which demonstrates a three-step temperature-induced magnetostructural transition between high-temperature, low-temperature, and intermediate states, as revealed by magnetometry. Two main steps were resolved using variable-temperature Fourier-transform infrared and Q-band electron paramagnetic resonance (EPR) spectroscopies. The intermediate-temperature states (∼40-90 K) are characterized by the coexistence of two types of copper(II)-nitroxide clusters, corresponding to the low-temperature and high-temperature phases. High-field EPR experiments revealed the effect of partial alignment of Cu(hfac)2LMeMe microcrystals in a strong (>20 T) magnetic field. This effect was used to unveil the structural features of the low-temperature phase of Cu(hfac)2LMeMe, which were inaccessible using single-crystal X-ray diffraction (XRD) technique. In particular, high-field EPR allowed us to determine the relative direction of the Jahn-Teller axes in CuO6 and CuO4N2 units.

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85163885072&origin=inward&txGid=a6d233751e288fe551055445e00ee595

UR - https://www.mendeley.com/catalogue/a229529b-0510-368b-a34d-2dd4a462fc5a/

U2 - 10.1039/d3dt01297b

DO - 10.1039/d3dt01297b

M3 - Article

C2 - 37350573

VL - 52

SP - 9337

EP - 9345

JO - Dalton Transactions

JF - Dalton Transactions

SN - 1477-9226

IS - 27

ER -