TY - JOUR

T1 - Structure and magnetic properties of spin-labeled N-alkyl-pyridinium nitrates

AU - Fokin, Sergey

AU - Tolstikov, Svyatoslav

AU - Chernavin, Platon

AU - Bogomyakov, Artem

AU - Romanenko, Galina

N1 - This work was supported by Russian Science Foundation (grant 23-13-00014). We thank the Ministry of Science and Higher Education of the Russian Federation for granting access to the equipment.

PY - 2025/11/1

Y1 - 2025/11/1

N2 - A series of new salts with paramagnetic cations – N-alkylpyridinium nitrates (NNp/mR)NO3 (where NNp/mR is 2-(4-N-R-pyridinium)- and 2-(3-N-R-pyridinium)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazo-1-oxyl-3-oxide; R = Me, Et) – were synthesized and structurally and magnetochemically characterized. All compounds – (NNpMe)NO3, (NNmMe)NO3•1/3MeCN•1/6H2O and (NNpEt)NO3 – were obtained by the interaction of iodides (NNp/mR)I with AgNO3, including a double complex salt of unusual composition (NNmEt)6[Ag(NO3)3](NO3)4. It is shown that cation-anionic interactions are decisive, facilitating the formation of cation-radical layers with short distances between paramagnetic fragments. The practically constant values of the effective magnetic moment for all the studied compounds in the temperature range 50–300 K are close to 1.73 μB. Quantum-chemical calculations have shown that such values, corresponding to the theoretical value for the monoradical, are associated with a combination of ferro- and antiferromagnetic exchange interactions between paramagnetic centers in numerous exchange channels. In this case, the contribution to the exchange energy is made by interactions not only between nitroxyl groups, but also between pyridine cycles.

AB - A series of new salts with paramagnetic cations – N-alkylpyridinium nitrates (NNp/mR)NO3 (where NNp/mR is 2-(4-N-R-pyridinium)- and 2-(3-N-R-pyridinium)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazo-1-oxyl-3-oxide; R = Me, Et) – were synthesized and structurally and magnetochemically characterized. All compounds – (NNpMe)NO3, (NNmMe)NO3•1/3MeCN•1/6H2O and (NNpEt)NO3 – were obtained by the interaction of iodides (NNp/mR)I with AgNO3, including a double complex salt of unusual composition (NNmEt)6[Ag(NO3)3](NO3)4. It is shown that cation-anionic interactions are decisive, facilitating the formation of cation-radical layers with short distances between paramagnetic fragments. The practically constant values of the effective magnetic moment for all the studied compounds in the temperature range 50–300 K are close to 1.73 μB. Quantum-chemical calculations have shown that such values, corresponding to the theoretical value for the monoradical, are associated with a combination of ferro- and antiferromagnetic exchange interactions between paramagnetic centers in numerous exchange channels. In this case, the contribution to the exchange energy is made by interactions not only between nitroxyl groups, but also between pyridine cycles.

KW - Cation radicals

KW - Crystal structure

KW - Magnetic properties

KW - Nitrates

KW - Quantum-chemical calculations

KW - Spin-labeled N-alkylpyridinium salts

UR - https://www.mendeley.com/catalogue/8b59126c-dd65-39e3-ad1a-7e5fcf1af9f7/

UR - https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=105012972068&origin=inward

U2 - 10.1016/j.poly.2025.117728

DO - 10.1016/j.poly.2025.117728

M3 - Article

VL - 281

JO - Polyhedron

JF - Polyhedron

SN - 0277-5387

M1 - 117728

ER -