Elena Zaytseva - Academia.edu (original) (raw)
Papers by Elena Zaytseva
ChemPlusChem, 2021
With a view to fabricating a new remote input-output system by applying functional ionic liquid c... more With a view to fabricating a new remote input-output system by applying functional ionic liquid crystalline (ILC) materials, we have developed novel ILC compounds containing a nitroxide radical unit in the organic cations, which show an enantiotropic smectic A (SmA) phase. We have implemented the magnetic manipulation of a droplet of one of the ILC compounds on the basis of the intermolecular magnetic interactions between radical moieties. This ILC monoradical compound shows a 55 % larger increase in paramagnetic susceptibility at the solid-to-LC melting point in the first heating process than the non-ionic LC monoradical compounds. It is most likely owing to the nanosegregation of strongly bonded ionic and non-ionic moieties. The increased molar magnetic susceptibility is preserved not only in the SmA phase but also in the isotropic liquid and solid phases during the first cooling process.
Molecules
Spirocyclic nitroxyl radicals (SNRs) are stable paramagnetics bearing spiro-junction at α-, β-, o... more Spirocyclic nitroxyl radicals (SNRs) are stable paramagnetics bearing spiro-junction at α-, β-, or γ-carbon atom of the nitroxide fragment, which is part of the heterocyclic system. Despite the fact that the first representatives of SNRs were obtained about 50 years ago, the methodology of their synthesis and their usage in chemistry and biochemical applications have begun to develop rapidly only in the last two decades. Due to the presence of spiro-function in the SNRs molecules, the latter have increased stability to various reducing agents (including biogenic ones), while the structures of the biradicals (SNBRs) comprises a rigid spiro-fused core that fixes mutual position and orientation of nitroxide moieties that favors their use in dynamic nuclear polarization (DNP) experiments. This first review on SNRs will give a glance at various strategies for the synthesis of spiro-substituted, mono-, and bis-nitroxides on the base of six-membered (piperidine, 1,2,3,4-tetrahydroquinoline...
Molecules
Cyclic nitrones of the imidazole series, containing a sterically hindered phenol group, are promi... more Cyclic nitrones of the imidazole series, containing a sterically hindered phenol group, are promising objects for studying antioxidant activity; on the other hand, they can form persistent hybrid phenoxyl–nitroxyl radicals (HPNs) upon oxidation. Here, a series of 5-aryl-4,4-dimethyl-4H-imidazole 3-oxides was obtained by condensation of aromatic 2-hydroxylaminoketones with 4-formyl-2,6-dialkylphenols followed by oxidation of the initially formed N-hydroxy derivatives. It was shown that the antioxidant activity of both 1-hydroxy-2,5-dihydroimidazoles and 4H-imidazole 3-oxides increases with a decrease in steric volume of the alkyl substituent in the phenol group, while the stability of the corresponding HPNs generated from 4H-imidazole 3-oxides reveals the opposite tendency.
Journal of Fluorine Chemistry
Angewandte Chemie International Edition
Verdazyl-nitroxide diradicals were synthesized using the palladium-catalyzed cross-coupling react... more Verdazyl-nitroxide diradicals were synthesized using the palladium-catalyzed cross-coupling reaction of the corresponding iodoverdazyls with a nitronyl nitroxide-2-ide gold(I) complex with high yields (up to 82%). The synthesized diradicals were found to be highly thermally stable and have a singlet (DEST » -64 cm–1) or triplet ground state (DEST ³ 25 and 100 cm–1), depending on which canonical hydrocarbon diradical type they belong to. Upon crystallization, triplet diradicals form unique one-dimensional (1D) spin S = 1 chains of organic diradicals with intrachain ferromagnetic coupling of J′/kB from 3 to 6 K.
The Journal of Physical Chemistry A
Molecules
The interaction of octafluorotoluene (1a), as well as pentafluorobenzonitrile (1b) with tert-buty... more The interaction of octafluorotoluene (1a), as well as pentafluorobenzonitrile (1b) with tert-butylamine, followed by the oxidation of thus formed tert-butylanilines (2a,b) with meta-chloroperoxybenzoic acid led to functionalized perfluorinated phenyl tert-butyl nitroxides [namely, 4-(N-tert-butyl(oxyl)amino)heptafluorotoluene (3a) and 4-(N-tert-butyl(oxyl)amino)tetrafluorobenzonitrile (3b)] with nearly quantitative total yields. The molecular and crystal structures of nitroxide 3a were proved by single crystal X-ray diffraction analysis. The radical nature of both nitroxides was confirmed by ESR data. The interaction of Cu(hfac)2 with the obtained nitroxides 3a,b gave corresponding trans-bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato-κ2O,O′)bis{4-(N-tert-butyl(oxyl)amino)perfluoroarene-κO}copper (II) complexes ([Cu(hfac)2(3a)2] and [Cu(hfac)2(3b)2]). X-ray crystal structure analysis showed square bipyramid coordination of a centrally symmetric Cu polyhedron with the axial positions o...
The Journal of Physical Chemistry A
Applied Magnetic Resonance
Crystals
New nitronyl nitroxides, namely, 2-(4,5-dimethylimidazol-2-yl)- and 2-(4,5-dichloroimidazol-2-yl)... more New nitronyl nitroxides, namely, 2-(4,5-dimethylimidazol-2-yl)- and 2-(4,5-dichloroimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl, were prepared in crystalline form. According to single-crystal X-ray data, intra- and intermolecular hydrogen bonds are formed between NH groups of the imidazole cycles and O atoms of the nitroxide moieties. The intermolecular H-bonds contribute to the alignment of molecules into chains along the a-axis; this alignment causes short intrachain contacts between O and C atoms carrying spin density of opposite signs. Such an arrangement of nitroxides induces ferromagnetic intrachain interactions (J ≈ 10 cm−1) between neighboring radicals.
Crystals
Spin-labelled compounds are widely used in chemistry, physics, biology, and material sciences, bu... more Spin-labelled compounds are widely used in chemistry, physics, biology, and material sciences, but the directed synthesis of some functionalized organic radicals is still a challenge. We succeeded in the preparation of a tetrazolyl-substituted nitronyl nitroxide radical in pure crystalline form. According to the single-crystal X-ray data, intra- (NH…O, 2.43 Å) and inter-molecular hydrogen bonds (NH…O, 1.91 Å) are formed between NH groups of the tetrazole cycles and O atoms of the paramagnetic moieties. The intermolecular H-bonds connect the molecules forming chains along the a-axis. Moreover, there are short intermolecular contacts between the O atoms (3.096 Å) and between the O and C atoms (3.096 Å) of the nitronyl nitroxide moieties within the chain. The spin-unrestricted broken-symmetry calculations performed at the BS-UB3LYP/def2-TZVP level of theory predicted a sufficient ferromagnetic interaction (J ≈ 20 cm–1) between the adjacent radicals inside the chain, but a weak antiferr...
Arkivoc
New non-conjugated functionalized 2,5-dihydroimidazole-type bi-and trinitroxyl radicals are descr... more New non-conjugated functionalized 2,5-dihydroimidazole-type bi-and trinitroxyl radicals are described. The synthesis of which was based on a nucleophilic substitution reaction between 2,4,6-trichloro-1,3,5-triazine or 2,4-dichloro-6-methoxy-1,3,5-triazine and spiro-fused 2,5-dihydroimidazole-type monoradicals bearing both a p-hydroxyaryl moiety at the C-4 atom of the heterocycle and a residue at the fourth position of the cyclohexane ring. The model tris-nitroxide with an unsubstituted cyclohexane unit was structurally characterized in the solid state.
Chemistry - A European Journal
The development of metal-free magnetic nanocrystalline or soft materials whose motion can be cont... more The development of metal-free magnetic nanocrystalline or soft materials whose motion can be controlled by a weak magnetic field at ambient temperature is one of challenging subjects in magnetic materials chemistry. We report that a unique superparamagnetic-like behavior and a large 'positive magneto-LC effect' were observed in the solid phases and the liquid crystalline (LC) phases, respectively, of novel achiral non--delocalized nitroxide diradical compounds 1 which showed a rare phase transition behavior; the existence of polymorphism in the solid phases (solids I and II) at low temperatures and the coexistence of hexagonal columnar and smectic LC phases at high temperatures. The gradual formation of chiral helical columnar structure in the hexagonal columnar phase was confirmed by a preliminary SHG measurement. By SQUID magnetization measurement, it was revealed that (1) 1 possessed an unusual temperatureindependent magnetic susceptibility (TIM > 0) component in the original nanocrystalline solid I which was responsible for the observed superparamagnetic-like behavior at low magnetic fields and did not arise from the contamination by extrinsic magnetic metal or metal ion impurities, besides ordinary temperaturedependent paramagnetic susceptibility (para > 0) and temperature-independent diamagnetic susceptibility
Chemistry of Heterocyclic Compounds, 2014
Alkylaromatic α-hydroxylamino ketones with a p-hydroxy(alkoxy)aryl substituent were used for the ... more Alkylaromatic α-hydroxylamino ketones with a p-hydroxy(alkoxy)aryl substituent were used for the preparation of stable diastereomeric spirocyclic nitroxyl radicals of 3-imidazoline series, having two different or identical mesogenic groups in the molecule. The molecular structure of these compounds was determined by NMR study of their diamagnetic reduced derivatives.
Russian Journal of Organic Chemistry, 2014
Stable spirocyclic 2,5-dihydro-1H-imidazole 1-oxyl radicals containing a mesogenic fragment were ... more Stable spirocyclic 2,5-dihydro-1H-imidazole 1-oxyl radicals containing a mesogenic fragment were synthesized on the basis of 1-[4-hydroxy(alkoxy)phenyl]-2-hydroxyamino-2-methylpropan-1-ones. The crystalline structure of two aminoxyl radicals was determined by X-ray analysis.
Arkivoc, 2014
N/C-Hydroxylated spirofused derivatives of 2,5-dihydroimidazole which were synthesized by condens... more N/C-Hydroxylated spirofused derivatives of 2,5-dihydroimidazole which were synthesized by condensation of 4-(4-hydroxyphenyl)cyclohexanone with aryl hydroxylaminoalkyl ketones in the presence of ammonia were determined to be trans-ee-isomers of 1,4-cyclohexane framework by NMR spectroscopy. Oxidation of the cyclic hydroxylamino moiety followed by acylation of the phenolic hydroxyl group with 4-alkyloxybenzoic acid chlorides led to the corresponding spirocyclic nitroxides bearing two mesogenic fragments.
ChemPlusChem, 2021
With a view to fabricating a new remote input-output system by applying functional ionic liquid c... more With a view to fabricating a new remote input-output system by applying functional ionic liquid crystalline (ILC) materials, we have developed novel ILC compounds containing a nitroxide radical unit in the organic cations, which show an enantiotropic smectic A (SmA) phase. We have implemented the magnetic manipulation of a droplet of one of the ILC compounds on the basis of the intermolecular magnetic interactions between radical moieties. This ILC monoradical compound shows a 55 % larger increase in paramagnetic susceptibility at the solid-to-LC melting point in the first heating process than the non-ionic LC monoradical compounds. It is most likely owing to the nanosegregation of strongly bonded ionic and non-ionic moieties. The increased molar magnetic susceptibility is preserved not only in the SmA phase but also in the isotropic liquid and solid phases during the first cooling process.
Molecules
Spirocyclic nitroxyl radicals (SNRs) are stable paramagnetics bearing spiro-junction at α-, β-, o... more Spirocyclic nitroxyl radicals (SNRs) are stable paramagnetics bearing spiro-junction at α-, β-, or γ-carbon atom of the nitroxide fragment, which is part of the heterocyclic system. Despite the fact that the first representatives of SNRs were obtained about 50 years ago, the methodology of their synthesis and their usage in chemistry and biochemical applications have begun to develop rapidly only in the last two decades. Due to the presence of spiro-function in the SNRs molecules, the latter have increased stability to various reducing agents (including biogenic ones), while the structures of the biradicals (SNBRs) comprises a rigid spiro-fused core that fixes mutual position and orientation of nitroxide moieties that favors their use in dynamic nuclear polarization (DNP) experiments. This first review on SNRs will give a glance at various strategies for the synthesis of spiro-substituted, mono-, and bis-nitroxides on the base of six-membered (piperidine, 1,2,3,4-tetrahydroquinoline...
Molecules
Cyclic nitrones of the imidazole series, containing a sterically hindered phenol group, are promi... more Cyclic nitrones of the imidazole series, containing a sterically hindered phenol group, are promising objects for studying antioxidant activity; on the other hand, they can form persistent hybrid phenoxyl–nitroxyl radicals (HPNs) upon oxidation. Here, a series of 5-aryl-4,4-dimethyl-4H-imidazole 3-oxides was obtained by condensation of aromatic 2-hydroxylaminoketones with 4-formyl-2,6-dialkylphenols followed by oxidation of the initially formed N-hydroxy derivatives. It was shown that the antioxidant activity of both 1-hydroxy-2,5-dihydroimidazoles and 4H-imidazole 3-oxides increases with a decrease in steric volume of the alkyl substituent in the phenol group, while the stability of the corresponding HPNs generated from 4H-imidazole 3-oxides reveals the opposite tendency.
Journal of Fluorine Chemistry
Angewandte Chemie International Edition
Verdazyl-nitroxide diradicals were synthesized using the palladium-catalyzed cross-coupling react... more Verdazyl-nitroxide diradicals were synthesized using the palladium-catalyzed cross-coupling reaction of the corresponding iodoverdazyls with a nitronyl nitroxide-2-ide gold(I) complex with high yields (up to 82%). The synthesized diradicals were found to be highly thermally stable and have a singlet (DEST » -64 cm–1) or triplet ground state (DEST ³ 25 and 100 cm–1), depending on which canonical hydrocarbon diradical type they belong to. Upon crystallization, triplet diradicals form unique one-dimensional (1D) spin S = 1 chains of organic diradicals with intrachain ferromagnetic coupling of J′/kB from 3 to 6 K.
The Journal of Physical Chemistry A
Molecules
The interaction of octafluorotoluene (1a), as well as pentafluorobenzonitrile (1b) with tert-buty... more The interaction of octafluorotoluene (1a), as well as pentafluorobenzonitrile (1b) with tert-butylamine, followed by the oxidation of thus formed tert-butylanilines (2a,b) with meta-chloroperoxybenzoic acid led to functionalized perfluorinated phenyl tert-butyl nitroxides [namely, 4-(N-tert-butyl(oxyl)amino)heptafluorotoluene (3a) and 4-(N-tert-butyl(oxyl)amino)tetrafluorobenzonitrile (3b)] with nearly quantitative total yields. The molecular and crystal structures of nitroxide 3a were proved by single crystal X-ray diffraction analysis. The radical nature of both nitroxides was confirmed by ESR data. The interaction of Cu(hfac)2 with the obtained nitroxides 3a,b gave corresponding trans-bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato-κ2O,O′)bis{4-(N-tert-butyl(oxyl)amino)perfluoroarene-κO}copper (II) complexes ([Cu(hfac)2(3a)2] and [Cu(hfac)2(3b)2]). X-ray crystal structure analysis showed square bipyramid coordination of a centrally symmetric Cu polyhedron with the axial positions o...
The Journal of Physical Chemistry A
Applied Magnetic Resonance
Crystals
New nitronyl nitroxides, namely, 2-(4,5-dimethylimidazol-2-yl)- and 2-(4,5-dichloroimidazol-2-yl)... more New nitronyl nitroxides, namely, 2-(4,5-dimethylimidazol-2-yl)- and 2-(4,5-dichloroimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl, were prepared in crystalline form. According to single-crystal X-ray data, intra- and intermolecular hydrogen bonds are formed between NH groups of the imidazole cycles and O atoms of the nitroxide moieties. The intermolecular H-bonds contribute to the alignment of molecules into chains along the a-axis; this alignment causes short intrachain contacts between O and C atoms carrying spin density of opposite signs. Such an arrangement of nitroxides induces ferromagnetic intrachain interactions (J ≈ 10 cm−1) between neighboring radicals.
Crystals
Spin-labelled compounds are widely used in chemistry, physics, biology, and material sciences, bu... more Spin-labelled compounds are widely used in chemistry, physics, biology, and material sciences, but the directed synthesis of some functionalized organic radicals is still a challenge. We succeeded in the preparation of a tetrazolyl-substituted nitronyl nitroxide radical in pure crystalline form. According to the single-crystal X-ray data, intra- (NH…O, 2.43 Å) and inter-molecular hydrogen bonds (NH…O, 1.91 Å) are formed between NH groups of the tetrazole cycles and O atoms of the paramagnetic moieties. The intermolecular H-bonds connect the molecules forming chains along the a-axis. Moreover, there are short intermolecular contacts between the O atoms (3.096 Å) and between the O and C atoms (3.096 Å) of the nitronyl nitroxide moieties within the chain. The spin-unrestricted broken-symmetry calculations performed at the BS-UB3LYP/def2-TZVP level of theory predicted a sufficient ferromagnetic interaction (J ≈ 20 cm–1) between the adjacent radicals inside the chain, but a weak antiferr...
Arkivoc
New non-conjugated functionalized 2,5-dihydroimidazole-type bi-and trinitroxyl radicals are descr... more New non-conjugated functionalized 2,5-dihydroimidazole-type bi-and trinitroxyl radicals are described. The synthesis of which was based on a nucleophilic substitution reaction between 2,4,6-trichloro-1,3,5-triazine or 2,4-dichloro-6-methoxy-1,3,5-triazine and spiro-fused 2,5-dihydroimidazole-type monoradicals bearing both a p-hydroxyaryl moiety at the C-4 atom of the heterocycle and a residue at the fourth position of the cyclohexane ring. The model tris-nitroxide with an unsubstituted cyclohexane unit was structurally characterized in the solid state.
Chemistry - A European Journal
The development of metal-free magnetic nanocrystalline or soft materials whose motion can be cont... more The development of metal-free magnetic nanocrystalline or soft materials whose motion can be controlled by a weak magnetic field at ambient temperature is one of challenging subjects in magnetic materials chemistry. We report that a unique superparamagnetic-like behavior and a large 'positive magneto-LC effect' were observed in the solid phases and the liquid crystalline (LC) phases, respectively, of novel achiral non--delocalized nitroxide diradical compounds 1 which showed a rare phase transition behavior; the existence of polymorphism in the solid phases (solids I and II) at low temperatures and the coexistence of hexagonal columnar and smectic LC phases at high temperatures. The gradual formation of chiral helical columnar structure in the hexagonal columnar phase was confirmed by a preliminary SHG measurement. By SQUID magnetization measurement, it was revealed that (1) 1 possessed an unusual temperatureindependent magnetic susceptibility (TIM > 0) component in the original nanocrystalline solid I which was responsible for the observed superparamagnetic-like behavior at low magnetic fields and did not arise from the contamination by extrinsic magnetic metal or metal ion impurities, besides ordinary temperaturedependent paramagnetic susceptibility (para > 0) and temperature-independent diamagnetic susceptibility
Chemistry of Heterocyclic Compounds, 2014
Alkylaromatic α-hydroxylamino ketones with a p-hydroxy(alkoxy)aryl substituent were used for the ... more Alkylaromatic α-hydroxylamino ketones with a p-hydroxy(alkoxy)aryl substituent were used for the preparation of stable diastereomeric spirocyclic nitroxyl radicals of 3-imidazoline series, having two different or identical mesogenic groups in the molecule. The molecular structure of these compounds was determined by NMR study of their diamagnetic reduced derivatives.
Russian Journal of Organic Chemistry, 2014
Stable spirocyclic 2,5-dihydro-1H-imidazole 1-oxyl radicals containing a mesogenic fragment were ... more Stable spirocyclic 2,5-dihydro-1H-imidazole 1-oxyl radicals containing a mesogenic fragment were synthesized on the basis of 1-[4-hydroxy(alkoxy)phenyl]-2-hydroxyamino-2-methylpropan-1-ones. The crystalline structure of two aminoxyl radicals was determined by X-ray analysis.
Arkivoc, 2014
N/C-Hydroxylated spirofused derivatives of 2,5-dihydroimidazole which were synthesized by condens... more N/C-Hydroxylated spirofused derivatives of 2,5-dihydroimidazole which were synthesized by condensation of 4-(4-hydroxyphenyl)cyclohexanone with aryl hydroxylaminoalkyl ketones in the presence of ammonia were determined to be trans-ee-isomers of 1,4-cyclohexane framework by NMR spectroscopy. Oxidation of the cyclic hydroxylamino moiety followed by acylation of the phenolic hydroxyl group with 4-alkyloxybenzoic acid chlorides led to the corresponding spirocyclic nitroxides bearing two mesogenic fragments.