Cytotoxicity of Laser-Synthesized Nanoparticles of Elemental Bismuth

High X-ray absorption combined with photothermal properties make bismuth nanoparticles (Bi NP) a promising agent for multimodal cancer theranostics. However, the synthesis of Bi NP by the "classical" chemical methods has numerous limitations, including potential toxicity of the produced nanomaterials. Here we studied in vitro toxicity of laser-synthesized Bi NP coated with Pluronic F-127 on mouse fibroblast cell line L929. The survival of L929 cells decreased linearly with increasing the concentration of Bi NP in a concentration range of 3-500 μg/ml; the LC50 value was 57 μg/ml. The unique combination of functional properties and moderate toxicity of the laser-synthesized Bi NP makes them a new promising platform for sensitization of multimodal cancer theranostics.

Effect of Drug Encapsulation and Hydrothermal Exposure on the Structure and Molecular Dynamics of the Binary System Poly(3-hydroxybutyrate)-chitosan

In this work, film materials based on binary compositions of poly-(3-hydroxybutyrate) (PHB) and chitosan with different ratios of polymer components in the range from 0/100 to 100/0 wt. % were studied. Using a combination of thermal (DSC) and relaxation (EPR) measurements, the influence of the encapsulation temperature of the drug substance (DS) of dipyridamole (DPD) and moderately hot water (at 70 °C) on the characteristics of the PHB crystal structure and the diffusion rotational mobility of the stable TEMPO radical in the amorphous regions of the PHB/chitosan compositions is shown. The low-temperature extended maximum on the DSC endotherms made it possible to obtain additional information about the state of the chitosan hydrogen bond network. This allowed us to determine the enthalpies of thermal destruction of these bonds. In addition, it is shown that when PHB and chitosan are mixed, significant changes are observed in the degree of crystallinity of PHB, degree of destruction of hydrogen bonds in chitosan, segmental mobility, sorption capacity of the radical, and the activation energy of rotational diffusion in the amorphous regions of the PHB/chitosan composition. The characteristic point of polymer compositions was found to correspond to the ratio of the components of the mixture 50/50%, for which the inversion transition of PHB from dispersed material to dispersion medium is assumed. Encapsulation of DPD in the composition leads to higher crystallinity and to a decrease in the enthalpy of hydrogen bond breaking, and it also slows down segmental mobility. Exposure to an aqueous medium at 70 °C is also accompanied by sharp changes in the concentration of hydrogen bonds in chitosan, the degree of PHB crystallinity, and molecular dynamics. The conducted research made it possible for the first time to conduct a comprehensive analysis of the mechanism of action of a number of aggressive external factors (such as temperature, water, and the introduced additive in the form of a drug) on the structural and dynamic characteristics of the PHB/chitosan film material at the molecular level. These film materials have the potential to serve as a therapeutic system for controlled drug delivery.

[ICG technologies in surgical treatment of benign diseases in gynecology]

ICG (indocyanine green) angiography is a method of visualizing blood flow and tissue perfusion based on intravenous administration of ICG and assessment of vascular distribution through an infrared fluorescence camera. Since the advent of ICG as a near-infrared fluorophore, fluorescence imaging has become an important tool in many areas of surgery. Several options for ICG angiography have been recently proposed in surgical gynecology. The authors describe application of ICG including assessment of myometrial and endometrial perfusion in myomectomy or resection of adenomyosis, tissue perfusion in surgical treatment of endometriosis, blood flow in hard-to-reach places in laparoscopic procedures and reconstructive surgery. ICG was useful in laparoscopic management of some benign gynecological diseases. In particular, this technology can improve treatment of endometriosis, especially deep infiltrative endometriosis, benign neoplasms.

Polymorbidity and Polypragmasia in High and Very High Cardiovascular Risk Patients

Aim. Assessment of the level and structure of polymorbidity, features of pharmacotherapy therapy in patients of different age groups, belonging to the category of high and extremely high cardiovascular risk, observed in outpatient clinics.

Material and methods. The single-stage study included 282 patients of high and very high cardiovascular risk who were divided into three groups: (1) age 45-59 years, (2) 60-74 years, (3) ≥75 years. The structure of polymorbidity and features of pharmacotherapy in different age groups patients were evaluated. The frequency of polypragmasia was determined, and treatment adequacy in patients over 65 years of age was analyzed using the STOPP / START criteria and the Beers criteria of 2019.

Results. High and very high cardiovascular risk patients have been found to be highly polymorbid, polimorbidity level increasing with age. Thus, among elderly patients, ischemic heart disease, chronic heart failure (CHF) were more often detected, as well as a high frequency of concomitant and background conditions, especially bone and joint system involvement (osteoarthritis, rheumatoid arthritis). Polypragmasia (administration of ≥5 drugs) was detected in 150 patients (53.2%) and was more common among elderly patients. According to Beers criteria, there were 48 cases of inadequate medication prescribing in 46 (28.0%) elderly patients. According to 80 STOPP criteria, 75 cases of prescribing potentially non-recommended drugs to 55 patients (32.1%) were detected. According to 34 START criteria, 116 cases of non-prescribing of necessary drugs to 52 (30.4%) elderly patients were found. When assessing the frequency of prognosis modifying medication prescribing, patients with CHF in 107 (63.0%) cases received angiotensin converting enzyme inhibitors, and in 42 cases (24.5%) angiotensin II receptor antagonists had been prescribed.  Thus,  87.5%  CHF patients were receiving renin-angiotensin-aldosterone system blockers. Statins were administered in 225 (79.8%) cases, antiplatelet agents were pre-scribed in 157 (67.9%) cases, and 23 persons (9.9%) were on oral anticoagulants for atrial fibrillation.

Conclusion. In the structure of the studied cohort most of the high and very high cardiovascular risk outpatients were polimorbid, elderly and senile. Polypragmasia has been detected in more than half of elderly outpatients (53%), irrational medication was found in 28% to 30% elderly patients. Most patients with CHF were on statins, antithrombotic therapy, and renin-angiotensin-aldosterone system blockers.

[Questionnaire of the Ryzhikh National Medical Research Centre for Coloproctology is a new tool for assessing chronic pelvic pain and pelvic organ dysfunction]

The article presents the work of a multidisciplinary team of experts from various fields of medicine to optimize the «Questionnaire for assessing chronic pelvic pain and pelvic organ dysfunction (QCPPD) of the Ryzhikh National Medical Research Centre for Coloproctology» for use in clinical practice. The survey of respondents was conducted from June 28 to September 28, 2021. As a result of this survey, by repeatedly making edits and clarifications during communication with respondents, the final version was obtained, which allows assessing the patient's subjective sensations by the nature and localization of pelvic pain, sensitivity disorders and pelvic organ function. The main objective of this Questionnaire is to differentiate patients with neurogenic pain from a huge number of patients with chronic pelvic pain. This aspect will allow a more targeted approach to the diagnosis and pathogenetically justified treatment of patients, including after appropriate instrumental examinations. The work of a multidisciplinary team implies a higher degree of objectification and terminological accuracy of the Questionnaire under discussion. The presented version of the «Questionnaire for assessing chronic pelvic pain and pelvic organ dysfunction (QCPPD) of the Ryzhikh National Medical Research Centre for Coloproctology» will be primarily used in coloproctological patients with pelvic pain problems and anal incontinence and obstructive defecation. Further studies will be directed to the clinical evaluation of the results of the work carried out.

A Method for Assessing the Efficiency of the Nucleotide Excision Repair System Ex Vivo

The nucleotide excision repair (NER) is one of the main repair systems present in the cells of living organisms. It is responsible for the removal of a wide range of bulky DNA lesions. We succeeded in developing a method for assessing the efficiency of NER in the cell (ex vivo), which is a method based on the recovery of TagRFP fluorescent protein production through repair of the damage that blocks the expression of the appropriate gene. Our constructed plasmids containing bulky nFlu or nAnt lesions near the tagrfp gene promoter were shown to undergo repair in eukaryotic cells (HEK 293T) and that they can be used to analyze the efficiency of NER ex vivo. A comparative analysis of the time dependence of fluorescent cells accumulation after transfection with nFlu- and nAnt-DNA revealed that there are differences in how efficient their repair by the NER system of HEK 293T cells can be. The method can be used to assess the cell repair status and the repair efficiency of different structural damages.

[Uterine adenosarcoma. Report of 5 cases and review of literature]

Uterine adenosarcoma is an uncommon biphasic tumor with benign epithelial and malignant mesenchymal components, often presenting difficulties for morphological diagnosis. We describe 5 cases of adenosarcoma of the uterine corpus and cervix, and vaginal stump in patients aged 46-76 years. Clinical data, ultrasound results, morphological data, including immunohistochemical studies with antibodies to CD10, estrogen and progesterone receptors, desmin, smooth muscle actin, and Ki-67 are presented. Large polypoid mass of the epithelial-mesenchymal structure within the uterine cavity in women of peri - and postmenopausal age require the exclusion of malignancy of the mesenchymal component with searchig for diagnostic criteria - periglandular cuffing of the stromal cells and mitoses.

[Optimization of treatment of acute poisoning with severe psychodisleptics]

OBJECTIVE

To increase the efficacy of acute poisoning with severe psychodisleptics.

MATERIAL AND METHODS

Fifty-two patients with acute psychoactive substance poisoning were studied. Patients of the main group (n=27) received cytoflavin infusion in combination with inhaled sedation with sevoflurane in addition to conventional therapy. The comparison group consisted of 25 patients who received conventional therapy.

RESULTS AND CONCLUSION

Augmentation of conventional therapy with cytoflavin in combination with inhaled sedation with sevoflurane, affecting various links in the pathogenesis of acute severe poisoning with psychodisleptics, made it possible to cope in a shorter time.

[Takayusu Arteritis on the background of congenital vascular anomaly?]

The article described a female patient with high-grade arterial hypertension diagnosed at her young age. Congenital abdominal aortic hyperplasia and conformity with criteria for Takayasu arteritis were diagnosed at 10 years following the clinical manifestation.

Clinical profile and drug therapy of outpatients with arterial hypertension

Aim. To study clinical profile and antihypertensive treatment features in outpatients observed in ambulatory facilities.

Material and methods. 140 arterial hypertension (AH) outpatients were examined, questioning and anthropometry were performed. Blood pressure (BP) was measured on both hands, then twice on the hand with larger value, the medium value was calculated. Tests results were obtained from outpatient cards.

Results. The sampling included 100 (71.4%) females and 40 (28.6%) males. Median of systolic BP at first measurement was 140.0 mm Hg (130.0;150.0), mean value of three BP measurements was 138.0 mm Hg (127.0;150.0) (p<0.001); median diastolic BP at first measurement was 83.0 mm Hg (80.0;90.0), mean BP value was 82.0 mm Hg (78.0;88.0) (p<0.001). Grade 1 AH was identified in 11.4% of patients, Grade 2 – in 35.7%, Grade 3 in 52.9%. No target organ damage was found in 26.4% of AH patients, asymptomatic target organ damage was diagnosed in 26.4%, and 61.4% had associated clinical conditions. Cardiovascular event risk was assessed as moderate in 13.6%, high – in 24.3% and very high – in 62.1% of patients. Every third patient had myocardial hypertrophy signs; Cornell index was detected more often than Sokolov-Layon index (p=0.006). Chronic kidney disease was diagnosed in 65.1% of patients: 44.0% of them had stage C2, 13.8% – stage C3A, 6.5% – stage C3B, and 1.8% – stage C4. 97.9% of AH patients received antihypertensive treatment. Daily medication consumption was reported by 127 people, and 10 patients reported taking medication as needed. Monotherapy was prescribed in 14.3% of patients; combined treatment was performed in 83.6% people. BP target value was achieved in 59 patients (42.1%) at first measurement results and in 71 (50.7%) ones at calculated mean value (p=0.002). Indications for statin use were identified in 86.4% of patients. Statins were administered in 56.2% patients having indications and in 21.1% of subjects without indications (p=0.006). Indications for antiplatelet therapy use were identified in 56.4% of patients. Antiplatelet treatment was administered in 58.2% of patients with indications and in 23.0% of subjects without indications (p<0.001).

Conclusion. Glomerular filtration rate and left ventricular myocardial hypertrophy amplitude criteria calculation allow to diagnose subclinical target organ damage in outpatients at physician visit without additional costs. Compliance with the current antihypertensive therapy guidelines allows to achieve target BP in current practice. Compliance with the BP measuring rules allows to adequately assess the effectiveness of antihypertensive therapy. A significant proportion of AH outpatients have a very high cardiovascular risk, which requires lipid-lowering and antiplatelet therapy.

High resolution anorectal manometry. Recommendations on russian-language terminology based on interdisciplinary consensus

The aim of the paper — is to present the results of the consensus on the terminology used to describe data of high-resolution anorectal manometry.

Methods: Online survey was conducted with the help of the public platform “Google forms” with the aim to harmonize the terms, which are used to conduct high-resolution anorectal manometry (HRAM), to agree the conformity of the proposed Russian-language terms to those used in English-language literature, and their abbreviations.

Results: According to the aim, 56 specialists of different medical specialties who perform and use the results of HRAM in clinical practice and research were invited to participate in the survey. We received 45 answers from the respondents (42.2% coloproctologists, 22.2% gastroenterologists, 15.6% surgeons, 20% — representatives of other specialties). The response rate was 80.3%. According to the survey, 95.6% of respondents supported the need for harmonization of terms. Ten out of the 11 terms reached consensus level C1 (excellent), 1 term level of consistency was C2 (moderate). 90.9% of respondents (consensus level C1) were in favor of the appropriateness of using common abbreviations. However, the proposed abbreviations of the terms used in the conduct and description of the results of the HRAM can be accepted with reservations (in 10 cases out of 11 consensus level was C2).

Conclusions: The agreed in interdisciplinary consensus terms can be approved and recommended for the use in clinical practice and when research data are published in Russian-language scientific literature.

Geminate recombination in organic photovoltaic blend PCDTBT/PC71BM studied by out-of-phase electron spin echo spectroscopy

The key process in organic solar cell operation is charge separation under light illumination. Due to the low dielectric constant of organic materials, the Coulomb attraction energy within the interfacial charge-transfer state (CTS) is larger than the thermal energy. Understanding the mechanism of charge separation at the organic donor/acceptor interface still remains a challenge and requires knowledge of the CTS temporal evolution. To address this problem, the CTS in the benchmark photovoltaic blend PCDTBT/PC₇₁BM was studied by the out-of-phase Electron Spin Echo (ESE). The protocol for determining the CTS geminate recombination rate for certain electron-hole distances was developed. Simulating the out-of-phase ESE trace for the CTS in the PCDTBT/PC₇₁BM blend allows precise determination of the electron-hole distance distribution function and its evolution with the increase in the delay after the laser flash. Distances of charge separation up to 6 nm were detected upon thermalization at a temperature of 20 K. Assuming the exponential decay of the recombination rate, the attenuation factor β = 0.08 Å^-1 is estimated for the PCDTBT/PC₇₁BM blend. Such a low attenuation factor is probably caused by a high degree of hole delocalization along the PCDTBT chain.

[Efficacy and safety of anticoagulant treatment for non-valvular atrial fibrillation in multimorbid patients]

OBJECTIVE

Assessment of the safety and efficacy of anticoagulant treatment in patients with nonvalvular atrial fibrillation (AF) in a multimorbidity setting.

MATERIALS AND METHODS

The cross-sectional study included 104 patients diagnosed with nonvalvular AF and followed in the medical facilities of Yekaterinburg. The subjects were interviewed, anthropometric measurements were made, and the risk of thromboembolic complications was evaluated using the CHA2DS2-VASc score. The Charlson multimorbidity index was calculated, and patients were divided into two groups: Group 1 with a low level of multimorbidity (not more than 5 points) and Group 2 with a high level of multimorbidity (6 points or more). The data are presented as a median and interquartile range (25%; 75%).

RESULTS

The study population included 40 males and 64 females. The median age was 71 (62.5; 80) years. The level of multimorbidity was estimated as 5 (3; 6) points. Group 1 included 64 patients, and Group 2 included 40 patients. Thirty-nine percent of the sample patients had a paroxysmal form of AF, 10% had a persistent form, and 51% had permanent AF. The group of patients with a high level of multimorbidity included more patients with permanent AF and fewer patients with paroxysmal AF as compared with a moderate level of multimorbidity (p&lt;0.01). Anticoagulant treatment was indicated for 92 (88.5%) patients. It was administered to 70.7% of patients; 29.3% did not receive it. Among patients receiving anticoagulants, warfarin was administered to 18.5%, and new oral anticoagulants (NOACs) were administered to 81.5%. Complications were reported in 15.2% of anticoagulant treatment cases. Bleeding was reported in 21.7% of cases of warfarin administration and 12.5% of cases of NOAC treatment (p=0.32). The median number of risk factors for bleeding per patient was 5 (4; 5.5). The Charlson index and the total number of risk factors are significantly correlated (R=0.37, p&lt;0.05).

CONCLUSION

In real-world clinical practice in Ekaterinburg, Russia, 7 of 10 patients with AF for whom anticoagulant treatment was indicated actually received it; NOACs are prescribed four times more often than warfarin. With a higher level of multimorbidity, the risk of bleeding under the pressure of anticoagulant treatment increases; thus, NOACs should be preferred over warfarin for treatment of multimorbid patients.

Mixed dysprosium-lanthanide nitride clusterfullerenes DyM2N@C80-Ih and Dy2MN@C80-Ih (M = Gd, Er, Tm, and Lu): synthesis, molecular structure, and quantum motion of the endohedral nitrogen atom

Systematic exploration of the synthesis of mixed-metal Dy-M nitride clusterfullerenes (NCFs, M = Gd, Er, Tm, Lu) is performed, and the impact of the second metal on the relative yield is evaluated. We demonstrate that the ionic radius of the metal appears to be the main factor allowing explanation of the relative yields in Dy-M mixed-metal systems with M = Sc, Lu, Er, and Gd. At the same time, Dy-Tm NCFs show anomalously low yields, which is not consistent with the relatively small ionic radius of Tm³⁺ but can be explained by the high third ionization potential of Tm. Complete separation of Dy-Gd and Dy-Er, as well as partial separation of Dy-Lu M₃N@C₈₀ nitride clusterfullerenes, is accomplished by recycling HPLC. The molecular structures of DyGd₂N@C₈₀ and DyEr₂N@C₈₀ are analyzed by means of single-crystal X-ray diffraction. A remarkable ordering of mixed-metal nitride clusters is found despite similar size and electronic properties of the metals. Possible pyramidalization of the nitride clusters in these and other nitride clusterfullerenes is critically analyzed with the help of DFT calculations and reconstruction of the nitrogen inversion barrier in M₃N@C₈₀ molecules is performed. Although a double-well potential with a pyramidal cluster structure is found to be common for most of them, the small size of the inversion barrier often leads to an apparent planar structure of the cluster. This situation is found for those M₃N@C₈₀ molecules in which the energy of the lowest vibrational level exceeds that of the inversion barrier, including Dy₃N@C₈₀ and DyEr₂N@C₈₀. The genuine pyramidal structure can be observed by X-ray diffraction only when the lowest vibrational level is below the inversion barrier, such as those found in Gd₃N@C₈₀ and DyGd₂N@C₈₀. The quantum nature of molecular vibrations becomes especially apparent when the size of the inversion barrier is comparable to the energy of the lowest vibrational levels.

The Adhesion of Human Dermal Fibroblasts on Anodized Nanotube-layered Titanium, Modified for Implantology Application

Anodization of titanium implants is accompanied by the formation of titanium oxide nanotubes improving osseointegration. An excessive fibroblast adhesion on the surface might lead to the formation of fibrous capsule resulting in implant rejection. In our research, we demonstrated that the adhesion activity of human dermal fibroblasts on anodized surface was not elevated, which is promising for the use of titanium with nanotube-layered surface for implantology.

Takayasu's arteritis: the retrospective analysis of patients from the Ural population

Takayasu's arteritis (TA) is a rare disease that can be overlooked during the first visit to a GP, rheumatologist, or any other medical specialist due to a variety of its symptoms. The aim of this study was to describe the clinical presentation and the course of patients with TA residing in the Middle Ural. A retrospective analysis was conducted using the medical records of 183 patients treated at the Sverdlovsk Regional Clinical Hospital 1 from 1979 through 2018. The male to female ratio was 1:3. The mean age was 33.5 years for women and 35.2 for men. The most frequently involved arteries were subclavian (101 cases; 55%), carotid (98 cases; 53%) and renal (77 cases; 42%). Type V was the most common angiographic type. Arterial stenosis was present in 94 (51%) patients. Sixty-six patients received surgical interventions. Of all patients included in the analysis, 31 died. The observed 5-year survival was 92%, 10-year survival, 90% and 15-year survival, 80%. Seventy-two patients (39%) developed major adverse cardiovascular events (MACE), including myocardial infarction, ischemic stroke, and thrombosis of large arteries/veins. The clinical presentation of TA may vary in different geographical regions.

Nuclear nanomedicine using Si nanoparticles as safe and effective carriers of 188Re radionuclide for cancer therapy

Nuclear nanomedicine, with its targeting ability and heavily loading capacity, along with its enhanced retention to avoid rapid clearance as faced with molecular radiopharmaceuticals, provides unique opportunities to treat tumors and metastasis. Despite these promises, this field has seen limited activities, primarily because of a lack of suitable nanocarriers, which are safe, excretable and have favorable pharmacokinetics to efficiently deliver and retain radionuclides in a tumor. Here, we introduce biodegradable laser-synthesized Si nanoparticles having round shape, controllable low-dispersion size, and being free of any toxic impurities, as highly suitable carriers of therapeutic 188Re radionuclide. The conjugation of the polyethylene glycol-coated Si nanoparticles with radioactive 188Re takes merely 1 hour, compared to its half-life of 17 hours. When intravenously administered in a Wistar rat model, the conjugates demonstrate free circulation in the blood stream to reach all organs and target tumors, which is radically in contrast with that of the 188Re salt that mostly accumulates in the thyroid gland. We also show that the nanoparticles ensure excellent retention of 188Re in tumor, not possible with the salt, which enables one to maximize the therapeutic effect, as well as exhibit a complete time-delayed conjugate bioelimination. Finally, our tests on rat survival demonstrate excellent therapeutic effect (72% survival compared to 0% of the control group). Combined with a series of imaging and therapeutic functionalities based on unique intrinsic properties of Si nanoparticles, the proposed biodegradable complex promises a major advancement in nuclear nanomedicine.

New functional material: spark plasma sintered Si/SiO2 nanoparticles – fabrication and properties

A bulk nanostructured material based on oxidized silicon nanopowder was fabricated using a spark plasma sintering technique. Structural investigations revealed that this material has the composition of ∼14 nm core Si granules inside an SiO₂ shell. Photoluminescence measurements have shown that the emission spectra lie in the energy range of 0.6–1.1 eV, which is not typical of the emissions of the Si/SiO₂ nanostructures reported in numerous papers. This result can be explained by the formation of energy states in the bandgap and the participation of these states in both electronic transport and photoluminescence emission. Annealing of the sample leads to a decrease in defect density, which in turn leads to quenching of the 0.6–1.1 eV photoluminescence. In this case ∼1.13 eV inter-band transitions in the Si core start to play a dominant role in radiative recombination. Thus, the possibility of controlling the photoluminescence emission over a broad wavelength range was demonstrated.

A bulk nanostructured material based on oxidized silicon nanopowder was fabricated using a spark plasma sintering technique.

Electrostatic Interaction across a Single-Layer Carbon Shell

Ions inside of fullerene molecules are model systems for the study of the electrostatic interaction across a single layer of carbon. For TbSc₂N@C₈₀ on h-BN/Ni(111), we observe with high-resolution X-ray photoelectron spectroscopy a splitting of the C 1s core level. The data may be explained quantitatively with density functional theory. The correlation of the C 1s eigenvalues and the Coulomb potential of the inside ions at the corresponding carbon sites indicates incomplete screening of the electric field due to the endohedral ions. The screening comprises anisotropic charge transfer to the carbon atoms and their polarization. This behavior is essential for the ordering of endohedral single-molecule magnets and is expected to occur in any single-layer material.

Magnetic hysteresis in self-assembled monolayers of Dy-fullerene single molecule magnets on gold

Fullerene single molecule magnets (SMMs) DySc2N@C80 and Dy2ScN@C80 are functionalized via a 1,3-dipolar cycloaddition with surface-anchoring thioether groups. The SMM properties of Dy-fullerenes are substantially affected by the cycloaddition. Submonolayers of the physisorbed derivatives exhibit magnetic hysteresis on an Au(111) surface at 2 K as revealed by X-ray magnetic circular dichroism.

Magnetization relaxation in the single-ion magnet DySc2N@C80: quantum tunneling, magnetic dilution, and unconventional temperature dependence

Quantum tunneling and relaxation of magnetization in single molecule magnet DySc₂N@C₈₀ is thoroughly studied as a function of magnetic dilution, temperature, and magnetic field.

Relaxation of magnetization in endohedral metallofullerenes DySc₂N@C₈₀ is studied at different temperatures, in different magnetic fields, and in different molecular arrangements. Magnetization behavior and relaxation are analyzed for powder sample, and for DySc₂N@C₈₀ diluted in non-magnetic fullerene Lu₃N@C₈₀, adsorbed in voids of a metal–organic framework, and dispersed in a polymer. The magnetic field dependence and zero-field relaxation are also studied for single-crystals of DySc₂N@C₈₀ co-crystallized with Ni(ii) octaethylporphyrin, as well as for the single crystal diluted with Lu₃N@C₈₀. Landau–Zener theory is applied to analyze quantum tunneling of magnetization in the crystals. The field dependence of relaxation rates revealed a dramatic dependence of the zero-field tunneling resonance width on the dilution and is explained with the help of an analysis of dipolar field distributions. AC magnetometry is used then to get access to the relaxation of magnetization in a broader temperature range, from 2 to 87 K. Finally, a theoretical framework describing the spin dynamics with dissipation is proposed to study magnetization relaxation phenomena in single molecule magnets.

Giant exchange coupling and field-induced slow relaxation of magnetization in Gd2@C79N with a single-electron Gd-Gd bond

Magnetic properties of the azafullerene Gd2@C79N are studied by SQUID magnetometry. The effective exchange coupling constant jGd,e between the Gd spins and the spin of unpaired electron residing on the single-electron Gd-Gd bond is determined to be 170 ± 10 cm-1. Low temperature AC measurements revealed field-induced millisecond-long relaxation of magnetization.