Conformational preferences of endohedral metallofullerenes on Ag, Au, and MgO surfaces: Theoretical studies.

In this report, we study the ordering of C60 , Sc3 N@C80 , and Dy2 ScN@C80 molecules on different metallic and dielectric surfaces such as Ag(100), Au(111), and MgO(100). By using DFT techniques, we can classify different types of cage-to-surface arrangements and their relative energies. Using a proposed homogenous sampling of the conformational space for the M3 N cluster, we determine a potential energy map that is capable of providing a structural distribution for a given energy window. We find that Coulomb interaction is a dominant force that governs the system's stability and order. However, a deep analysis of the charge density rearrangements reveals that even though the integral charges may be considered as a qualitative control parameter, it fails to provide quantitative data due to the importance of spatial characteristics of charge densities.

Caught in Phase Transition: Snapshot of the Metallofullerene Sc3N@C70 Rotation in the Crystal.

The molecular structure of Sc3N@C2v(7854)-C70 was determined by single-crystal X-ray diffraction. Variable-temperature X-ray diffraction analysis unraveled the details of the phase transition caused by the temperature-driven jumplike rotation of the fullerene cage between two orientations. Whereas in the lower-temperature P21/c phase the fullerene predominantly occupies one orientation, two orientations become equally occupied in the higher-temperature C2/m phase. This work provides a rare example of the well-defined order-disorder transition in metallofullerene crystals and thus gives important insight into the problem of disorder impeding metallofullerene crystallography.

Substrate-Independent Magnetic Bistability in Monolayers of the Single-Molecule Magnet Dy2 ScN@C80 on Metals and Insulators.

Magnetic hysteresis is demonstrated for monolayers of the single-molecule magnet (SMM) Dy2 ScN@C80 deposited on Au(111), Ag(100), and MgO|Ag(100) surfaces by vacuum sublimation. The topography and electronic structure of Dy2 ScN@C80 adsorbed on Au(111) were studied by STM. X-ray magnetic CD studies show that the Dy2 ScN@C80 monolayers exhibit similarly broad magnetic hysteresis independent on the substrate used, but the orientation of the Dy2 ScN cluster depends strongly on the surface. DFT calculations show that the extent of the electronic interaction of the fullerene molecules with the surface is increasing dramatically from MgO to Au(111) and Ag(100). However, the charge redistribution at the fullerene-surface interface is fully absorbed by the carbon cage, leaving the state of the endohedral cluster intact. This Faraday cage effect of the fullerene preserves the magnetic bistability of fullerene-SMMs on conducting substrates and facilitates their application in molecular spintronics.

Endohedral metal-nitride cluster ordering in metallofullerene-NiII(OEP) complexes and crystals: a theoretical study.

The ordering of endohedral clusterfullerenes Sc3N@C80 and YSc2N@C80 co-crystallized with Ni(OEP) and isolated complexes with Ni(OEP) have been investigated theoretically. Having used multiple orientations of M3N clusters inside the cages with Fibonacci sampling, we describe the effect of intermolecular interactions on the orientation of the endohedral cluster.

High Blocking Temperature of Magnetization and Giant Coercivity in the Azafullerene Tb2 @C79 N with a Single-Electron Terbium-Terbium Bond.

The azafullerene Tb2 @C79 N is found to be a single-molecule magnet with a high 100-s blocking temperature of magnetization of 24 K and large coercivity. Tb magnetic moments with an easy-axis single-ion magnetic anisotropy are strongly coupled by the unpaired spin of the single-electron Tb-Tb bond. Relaxation of magnetization in Tb2 @C79 N below 15 K proceeds via quantum tunneling of magnetization with the characteristic time τQTM =16 462±1230 s. At higher temperature, relaxation follows the Orbach mechanism with a barrier of 757±4 K, corresponding to the excited states, in which one of the Tb spins is flipped.

Covalency versus magnetic axiality in Nd molecular magnets: Nd-photoluminescence, strong ligand-field, and unprecedented nephelauxetic effect in fullerenes NdM2N@C80 (M = Sc, Lu, Y).

Nd-based nitride clusterfullerenes NdM2N@C80 with rare-earth metals of different sizes (M = Sc, Y, Lu) were synthesized to elucidate the influence of the cluster composition, shape and internal strain on the structural and magnetic properties. Single crystal X-ray diffraction revealed a very short Nd-N bond length in NdSc2N@C80. For Lu and Y analogs, the further shortening of the Nd-N bond and pyramidalization of the NdM2N cluster are predicted by DFT calculations as a result of the increased cluster size and a strain caused by the limited size of the fullerene cage. The short distance between Nd and nitride ions leads to a very large ligand-field splitting of Nd3+ of 1100-1200 cm-1, while the variation of the NdM2N cluster composition and concomitant internal strain results in the noticeable modulation of the splitting, which could be directly assessed from the well-resolved fine structure in the Nd-based photoluminescence spectra of NdM2N@C80 clusterfullerenes. Photoluminescence measurements also revealed an unprecedentedly strong nephelauxetic effect, pointing to a high degree of covalency. The latter appears detrimental to the magnetic axiality despite the strong ligand field. As a result, the ground magnetic state has considerable transversal components of the pseudospin g-tensor, and the slow magnetic relaxation of NdSc2N@C80 could be observed by AC magnetometry only in the presence of a magnetic field. A combination of the well-resolved magneto-optical states and slow relaxation of magnetization suggests that Nd clusterfullerenes can be useful building blocks for magneto-photonic quantum technologies.

Metamagnetic transition and a loss of magnetic hysteresis caused by electron trapping in monolayers of single-molecule magnet Tb2@C79N.

Realization of stable spin states in surface-supported magnetic molecules is crucial for their applications in molecular spintronics, memory storage or quantum information processing. In this work, we studied the surface magnetism of dimetallo-azafullerene Tb2@C79N, showing a broad magnetic hysteresis in a bulk form. Surprisingly, monolayers of Tb2@C79N exhibited a completely different behavior, with the prevalence of a ground state with antiferromagnetic coupling at low magnetic field and a metamagnetic transition in the magnetic field of 2.5-4 T. Monolayers of Tb2@C79N were deposited onto Cu(111) and Au(111) by evaporation in ultra-high vacuum conditions, and their topography and electronic structure were characterized by scanning tunneling microscopy and spectroscopy (STM/STS). X-ray photoelectron spectroscopy (XPS), in combination with DFT studies, revealed that the nitrogen atom of the azafullerene cage tends to avoid metallic surfaces. Magnetic properties of the (sub)monolayers were then studied by X-ray magnetic circular dichroism (XMCD) at the Tb-M4,5 absorption edge. While in bulk powder samples Tb2@C79N behaves as a single-molecule magnet with ferromagnetically coupled magnetic moments and blocking of magnetization at 28 K, its monolayers exhibited a different ground state with antiferromagnetic coupling of Tb magnetic moments. To understand if this unexpected behavior is caused by a strong hybridization of fullerenes with metallic substrates, XMCD measurements were also performed for Tb2@C79N adsorbed on h-BN|Rh(111) and MgO|Ag(100). The co-existence of two forms of Tb2@C79N was found on these substrates as well, but magnetization curves showed narrow magnetic hysteresis detectable up to 25 K. The non-magnetic state of Tb2@C79N in monolayers is assigned to anionic Tb2@C79N- species with doubly-occupied Tb-Tb bonding orbital and antiferromagnetic coupling of the Tb moments. A charge transfer from the substrate or trapping of secondary electrons are discussed as a plausible origin of these species.

Metallofullerene photoswitches driven by photoinduced fullerene-to-metal electron transfer.

We report on the discovery and detailed exploration of the unconventional photo-switching mechanism in metallofullerenes, in which the energy of the photon absorbed by the carbon cage π-system is transformed to mechanical motion of the endohedral cluster accompanied by accumulation of spin density on the metal atoms. Comprehensive photophysical and electron paramagnetic resonance (EPR) studies augmented by theoretical modelling are performed to address the phenomenon of the light-induced photo-switching and triplet state spin dynamics in a series of Y x Sc3-x N@C80 (x = 0-3) nitride clusterfullerenes. Variable temperature and time-resolved photoluminescence studies revealed a strong dependence of their photophysical properties on the number of Sc atoms in the cluster. All molecules in the series exhibit temperature-dependent luminescence assigned to the near-infrared thermally-activated delayed fluorescence (TADF) and phosphorescence. The emission wavelengths and Stokes shift increase systematically with the number of Sc atoms in the endohedral cluster, whereas the triplet state lifetime and S1-T1 gap decrease in this row. For Sc3N@C80, we also applied photoelectron spectroscopy to obtain the triplet state energy as well as the electron affinity. Spin distribution and dynamics in the triplet states are then studied by light-induced pulsed EPR and ENDOR spectroscopies. The spin-lattice relaxation times and triplet state lifetimes are determined from the temporal evolution of the electron spin echo after the laser pulse. Well resolved ENDOR spectra of triplets with a rich structure caused by the hyperfine and quadrupolar interactions with 14N, 45Sc, and 89Y nuclear spins are obtained. The systematic increase of the metal contribution to the triplet spin density from Y3N to Sc3N found in the ENDOR study points to a substantial fullerene-to-metal charge transfer in the excited state. These experimental results are rationalized with the help of ground-state and time-dependent DFT calculations, which revealed a substantial variation of the endohedral cluster position in the photoexcited states driven by the predisposition of Sc atoms to maximize their spin population.

Magnetism in Ln molecular systems with 4f/valence-shell interplay (FV-magnetism).

The hunt for high-performance single-molecule magnets (SMM) revealed that atomic and molecular lanthanide systems combining 4f-shell and valence magnetism (FV-magnetism) may show magnetic bistability up to unexpectedly high temperatures. Here we rationalize the stability of the magnetism in the FV-systems from first principles on the example of LnII(CpiPr5)2 molecules.

Virtual simulation, preoperative planning and intraoperative navigation during laparoscopic partial nephrectomy.

INTRODUCTION: The use of computer navigation systems is a new and actively explored method used for surgical procedures concerning the abdominal and retroperitoneal organs. In this paper, we propose an original hardware - software complex, which forms a virtual body model, based on preoperative computer tomography data, transmitted to the operating screen monitor using a surgical navigation system, involving a mechanical digitizer. MATERIAL AND METHODS: During a laparoscopic procedure, a three-dimensional (3D) model of a kidney with a tumor was used to obtain additional information on the primary or secondary monitor or for combining the virtual model and video images on the main or additional monitor in the operating room. This method was used for laparoscopic partial nephrectomy, where twelve patients were operated with an average age of 45.4 (38-54) years, with clear cell renal cell carcinoma size 27.08 (15-40) mm. RESULTS: All patients successfully underwent laparoscopic partial nephrectomy with intraoperative navigation. The mean operative time was 97.2 (80-155) minutes, warm ischemia time - 18.0 (12-25) minutes. Selective clamping of segmental renal arteries was performed in 7 (58.3%) cases, in the remaining 5 (41.6%) cases the renal artery was clamped. There were no serious complications. The average duration of hospital stay was 7.0 (5-10) days. CONCLUSIONS: Preliminary results of our clinical study have shown the success of 3D modeling for qualitative visualization of kidney tumors in the course of surgical intervention, both for the surgeon and for the patient to understand the nature of the pathological process.

Gasless minimum incision access used for extracorporeal orthotopic bladder substitution after laparoscopic radical cystectomy.

INTRODUCTION: Radical cystectomy is the gold standard for treating invasive bladder cancer. We report our outcomes of gasless minimum incision access (GMIA) for extracorporeal orthotopic bladder substitution (ECOBS) after laparoscopic radical cystectomy. MATERIAL AND METHODS: Radical surgery was performed in patients in the same hospital suffering from bladder cancer in T2N0M0 G1-2 stage. Group 1 included 11 patients aged 56.6 (42-72) years, which underwent laparoscopic radical cystectomy and ECOBS using GMIA. Group 2 included 18 patients aged 56.7 (41-76) years, which were operated by open radical cystectomy and orthotopic bladder substitution. RESULTS: The average duration of operation was 492.0 ±85.7 minutes in Group 1 and 318.0 ±58.0 in Group 2 (p = 0.001). Estimated blood loss was 290.0 ±120.0 and 613.2 ±359.0 ml in groups respectively. In the postoperative period, narcotic analgesics were used in the amount of 166.0 ±28.0 mg and 264.0 ±112.0 mg (p = 0.05), intestinal function recovery was observed on 3.5 ±0.9 and 6.0 ±2.9 days after the operation (p = 0.05) in the groups respectively. Minor postoperative complications were observed in 36.4% and 56.0%, major complications - in 9.1% and 11.2% in groups respectively. Median hospitalization time was 19.0 ±2.0 days in Group 1 and 24.9 ±6.5 in Group 2 (p = 0.01). CONCLUSIONS: GMIA in ECOBS can be used as an effective surgical approach after laparoscopic radical cystectomy; this method requires further observation.

Choice of surgical access for retroperitoneoscopic ureterolithotomy according to the results of 3D reconstruction of operational zone agreed with the patient: initial experience.

INTRODUCTION: For the procedure retroperitoneoscopic ureterolithotomy, the problems of access choice and thus visualization with utilizing minimally invasive surgical access (either with gasless single port method or gas insufflation) are solved. The decisions are based on the method of presurgery planning, grounded on matching the patient with a 3D model of the zone of surgical interest reconstructed according to the results of tomographic examination. MATERIAL AND METHODS: We used a hardware-software complex (HSC) for virtual modeling of the surgery zone and choosing the optimum points for minimally invasive surgical access. The HSC was recruited to choose optimum surgical access, realize presurgery planning, and estimation of the safety of the way of access chosen. The original method of matching the system of coordinates of a virtual model with the patient was offered. RESULTS: 12 patients with the calculus in the upper part of ureter averaging 11.5 (9-14) mm in size underwent gasless retroperitoneoscopic ureterolithotomy with use of the HSC. Mean age of the patients was 36.4 (25-49) years old. The surgeries lasted an average of 35.5 (25-40) minutes. Blood loss was averaged at 55.0 (30-90) ml. Healing by first intention was registered with all the patients. The mean hospitalization time was 6.0 (4-7) days. There were neither any complications nor difficulties, nor conversions from incorrectly chosen surgical access. CONCLUSIONS: The choice of the optimum surgical access according to the results of a virtual 3D model of the operation zone, matching the system of coordinates of the model with patient concurrence, and presurgery planning, was effective in cases of gasless single port and with gas insufflation retroperitoneoscopic ureterolithotomy.