Temperature Induced Reversible Switching of the Magnetic Anisotropy in a Neodymium Complex Adsorbed on Graphite

Controlling the magnetic anisotropy of molecular layers assembled on a surface is one of the challenges that needs to be addressed to create the next-generation spintronic devices. Recently, metal complexes that show a reversible solid-state switch of their magnetic anisotropy in response to physical stimuli, such as temperature and magnetic field, have been discovered. The complex Nd(trensal) (H3trensal = 2,2',2''-tris(salicylideneimino)triethylamine) is predicted to exhibit such property. An ultra-thin film of Nd(trensal) is deposited on highly ordered pyrolytic graphite as a proof-of-concept system to show that this property can be retained at the nanoscale on a layered material. By combining single crystal magnetometric measurements and synchrotron X-ray-based absorption techniques, supported by multiplet ligand field simulations based on the trigonal crystal field surrounding the lanthanide centre, it is demonstrated that changing the temperature reverses the magnetic anisotropy of an ordered film of Nd(trensal), thus opening significant perspectives for the realization of a novel family of temperature-controlled molecular spintronic devices.

LnDOTA puppeteering: removing the water molecule and imposing tetragonal symmetry

Complexes of lanthanide(iii) ions (Ln) with tetraazacyclododecane-N,N',N'',N'''-tetraacetate (DOTA) are a benchmark in the field of magnetism due to their well-investigated and sometimes surprising features. Ab initio calculations suggest that the ninth ligand, an axial water molecule, is key in defining the magnetic properties because it breaks the potential C4 symmetry of the resulting complexes. In this paper, we experimentally isolate the role of the water molecule by excluding it from the metal coordination sphere without altering the chemical structure of the ligand. Our complexes are therefore designed to be geometrically tetragonal and strict crystallographic symmetry is achieved by exploiting a combination of solution ionic strength and solid state packing effects. A thorough multitechnique approach has been used to unravel the electronic structure and magnetic anisotropy of the complexes. Moreover, the geometry enhancement allows us to predict, using only one angle obtained from the crystal structure, the ground state composition of all the studied derivatives (Ln = Tb to Yb). Therefore, these systems also provide an excellent platform to test the validity and limitations of the ab initio methods. Our combined experimental and theoretical investigation proves that the water molecule is indeed key in defining the magnetic anisotropy and the slow relaxation of these complexes.

Quantum spin coherence and electron spin distribution channels in vanadyl-containing lantern complexes

We herein investigate the heterobimetallic lantern complexes [PtVO(SOCR)4] as charge neutral electronic qubits based on vanadyl complexes (S = 1/2) with nuclear spin-free donor atoms. The derivatives with R = Me (1) and Ph (2) give highly resolved X-band EPR spectra in frozen CH2Cl2/toluene solution, which evidence the usual hyperfine coupling with the 51V nucleus (I = 7/2) and an additional superhyperfine interaction with the I = 1/2 nucleus of the 195Pt isotope (natural abundance ca. 34%). DFT calculations ascribe the spin density delocalization on the Pt2+ ion to a combination of π and δ pathways, with the former representing the predominant channel. Spin relaxation measurements in frozen CD2Cl2/toluene-d8 solution between 90 and 10 K yield Tm values (1-6 μs in 1 and 2-11 μs in 2) which compare favorably with those of known vanadyl-based qubits in similar matrices. Coherent spin manipulations indeed prove possible at 70 K, as shown by the observation of Rabi oscillations in nutation experiments. The results indicate that the heavy Group 10 metal ion is not detrimental to the coherence properties of the vanadyl moiety and that Pt-VO lanterns can be used as robust spin-coherent building blocks in materials science and quantum technologies.

Efficient Spin-Selective Electron Transport at Low Voltages of Thia-Bridged Triarylamine Hetero[4]helicenes Chemisorbed Monolayer

The Chirality Induced Spin Selectivity (CISS) effect describes the capability of chiral molecules to act as spin filters discriminating flowing electrons according to their spin state. Within molecular spintronics, efforts are focused on developing chiral-molecule-based technologies to control the injection and coherence of spin-polarized currents. Herein, for this purpose, we study spin selectivity properties of a monolayer of a thioalkyl derivative of a thia-bridged triarylamine hetero[4]helicene chemisorbed on a gold surface. A stacked device assembled by embedding a monolayer of these molecules between ferromagnetic and diamagnetic electrodes exhibits asymmetric magnetoresistance with inversion of the signal according to the handedness of molecules, in line with the presence of the CISS effect. In addition, magnetically conductive atomic force microscopy reveals efficient electron spin filtering even at unusually low potentials. Our results demonstrate that thia[4]heterohelicenes represent key candidates for the development of chiral spintronic devices.

VdW Mediated Strong Magnetic Exchange Interactions in Chains of Hydrogen-Free Sublimable Molecular Qubits

Sulfur-rich molecular complexes of dithiolene-like ligands are appealing candidates as molecular spin qubits because spin coherence properties are enhanced in hydrogen-free environments. Herein, we employ the hydrogen-free mononegative 1,3,2-dithiazole-4-thione-5-thiolate (dttt^-) ligand as an alternative to common dinegative dithiolate ligands. We report the first synthesis and structural characterization of its Cu²⁺, Ni²⁺, and Pt²⁺ neutral complexes. The XPS analysis of thermal deposition of [Cu(dttt)₂] in UHV conditions indicates that films of intact molecules can be deposited on surfaces by sublimation. Thanks to a combined approach employing DC magnetometry and DFT calculations, we highlighted AF exchange interactions of 108 cm^-1 and 36 cm^-1 attributed to the two different polymorph phases. These couplings are exclusively mediated by S···S VdW interactions, which are facilitated by the absence of counterions and made particularly efficient by the diffuse electron density on S atoms. Furthermore, the spin dynamics of solid-state magnetically diluted samples was investigated. The longest observed T _m is 2.3 μs at 30 K, which significantly diverges from the predicted T _m > 100 μs. These results point to the diluting matrix severely affecting the coherence lifetime of Cu²⁺ species via different factors, such as the contributions of neighboring ¹⁴N nuclei and the formation of radical impurities in a non-completely controllable way. However, the ease of processing [Cu(dttt)₂] via thermal sublimation can allow dispersion in matrices better suited for coherent spin manipulation of isolated molecules and the realization of AF-coupled VdW structures on surfaces.

Mixed-Sandwich Titanium(III) Qubits on Au(111): Electron Delocalization Ruled by Molecular Packing

Organometallic sandwich complexes are versatile molecular systems that have been recently employed for single-molecule manipulation and spin sensing experiments. Among related organometallic compounds, the mixed-sandwich S = 1/2 complex (η⁸-cyclooctatetraene)(η⁵-cyclopentadienyl)titanium, here [CpTi(cot)], has attracted interest as a spin qubit because of the long coherence time. Here the structural and chemical properties of [CpTi(cot)] on Au(111) are investigated at the monolayer level by experimental and computational methods. Scanning tunneling microscopy suggests that adsorption occurs in two molecular orientations, lying and standing, with a 3:1 ratio. XPS data evidence that a fraction of the molecules undergo partial electron transfer to gold, while our computational analysis suggests that only the standing molecules experience charge delocalization toward the surface. Such a phenomenon depends on intermolecular interactions that stabilize the molecular packing in the monolayer. This orientation-dependent molecule-surface hybridization opens exciting perspectives for selective control of the molecule-substrate spin delocalization in hybrid interfaces.

Direct detection of spin polarization in photoinduced charge transfer through a chiral bridge

It is well assessed that the charge transport through a chiral potential barrier can result in spin-polarized charges. The possibility of driving this process through visible photons holds tremendous potential for several aspects of quantum information science, e.g., the optical control and readout of qubits. In this context, the direct observation of this phenomenon via spin-sensitive spectroscopies is of utmost importance to establish future guidelines to control photo-driven spin selectivity in chiral structures. Here, we provide direct proof that time-resolved electron paramagnetic resonance (EPR) can be used to detect long-lived spin polarization generated by photoinduced charge transfer through a chiral bridge. We propose a system comprising CdSe quantum dots (QDs), as a donor, and C₆₀, as an acceptor, covalently linked through a saturated oligopeptide helical bridge (χ) with a rigid structure of ∼10 Å. Time-resolved EPR spectroscopy shows that the charge transfer in our system results in a C₆₀ radical anion, whose spin polarization maximum is observed at longer times with respect to that of the photogenerated C₆₀ triplet state. Notably, the theoretical modelling of the EPR spectra reveals that the observed features may be compatible with chirality-induced spin selectivity, but the electronic features of the QD do not allow the unambiguous identification of the CISS effect. Nevertheless, we identify which parameters need optimization for unambiguous detection and quantification of the phenomenon. This work lays the basis for the optical generation and direct manipulation of spin polarization induced by chirality.

Our work provides a first attempt to directly detect the spin polarisation of Chiral-Induced Spin Selectivity (CISS) effect by studying the photoinduced electron transfer in a CdSe Quantum Dot-chiral bridge-fullerene derivative (QD–χ–C₆₀) system.

A dysprosium single molecule magnet outperforming current pseudocontact shift agents

A common criterion for designing performant single molecule magnets and pseudocontact shift tags is a large magnetic anisotropy. In this article we present a dysprosium complex chemically designed to exhibit strong easy-axis type magnetic anisotropy that is preserved in dichloromethane solution at room temperature. Our detailed theoretical and experimental studies on the magnetic properties allowed explaining several features typical of highly performant SMMs. Moreover, the NMR characterization shows remarkably large chemical shifts, outperforming the current state-of-the art PCS tags.

A robust dysprosium(iii) single molecule magnet with large uniaxial magnetic anisotropy induces pseudocontact shifts at almost doubled distance compared to standard shift agents.

Hetero-tri-spin systems: an alternative stairway to the single molecule magnet heaven?

The search for molecule-based magnetic materials has stimulated over the years the development of extremely rich coordination chemistry. Various combinations of spin carriers have been investigated and illustrated by a plethora of hetero-spin complexes: 3d-nd, 3d-4f, 2p-3d, and 2p-4f. More recently, two other classes of hetero-spin complexes have grown rapidly: compounds containing three different paramagnetic metal ions, or one radical and two different paramagnetic metal ions (all within the same molecular entity). Such new classes of systems represent a challenge both from a synthetic and theoretical point of view. Indeed, the synthetic control and the understanding of the spin topology effect on the overall magnetic behavior from first-principles is a difficult problem to be solved. The presence of different spin carriers in a single molecule makes such compounds particularly interesting because they offer the possibility of developing new magnetic properties, different from those of hetero-bi-spin or homo-spin systems. A critical overview taking the case of 2p-3d-4f complexes is the focus of this perspective paper. An original organic picture of the state-of-art in this field and new hints about the main directions that should be pursued to achieve hetero-tri-spin systems with large anisotropy barriers, low quantum tunneling of magnetization and, possibly, large blocking temperatures are provided in this article through an analysis based on numerically revisiting already published data and a critical survey of the literature reported so far. The reasons for the limited success obtained for the largely used 3d-2p-4f topology are given along with the ones explaining the failure for the 2p-4f-3d case. The still never synthesized linear 2p-3d-4f spin topology seemed to be the most promising one based on the results obtained for the unique closed hetero-tri-spin closed triangular system synthesized so far.

A Complete Ab Initio View of Orbach and Raman Spin-Lattice Relaxation in a Dysprosium Coordination Compound

The unique electronic and magnetic properties of lanthanide molecular complexes place them at the forefront of the race toward high-temperature single-molecule magnets and magnetic quantum bits. The design of compounds of this class has so far being almost exclusively driven by static crystal field considerations, with an emphasis on increasing the magnetic anisotropy barrier. Now that this guideline has reached its maximum potential, a deeper understanding of spin-phonon relaxation mechanisms presents itself as key in order to drive synthetic chemistry beyond simple intuition. In this work, we compute relaxation times fully ab initio and unveil the nature of all spin-phonon relaxation mechanisms, namely Orbach and Raman pathways, in a prototypical Dy single-molecule magnet. Computational predictions are in agreement with the experimental determination of spin relaxation time and crystal field anisotropy, and show that Raman relaxation, dominating at low temperature, is triggered by low-energy phonons and little affected by further engineering of crystal field axiality. A comprehensive analysis of spin-phonon coupling mechanism reveals that molecular vibrations beyond the ion’s first coordination shell can also assume a prominent role in spin relaxation through an electrostatic polarization effect. Therefore, this work shows the way forward in the field by delivering a novel and complete set of chemically sound design rules tackling every aspect of spin relaxation at any temperature.

Magnetic anisotropy on demand exploiting high-pressure as remote control: an ab initio proof of concept

Lanthanide based single molecule magnets have recently become very promising systems for creating single molecule devices working at high temperatures (nitrogen boiling temperature). However, the variation of the direction of the anisotropy tensor as a function of the applied pressure still represents a quite unexplored field. Application of external pressure can be a promising method toward neat control of magnetic anisotropy and relaxation processes in the bulk phase. Required criteria for being eligible for such systems are as follows: the presence of first excited energy levels with significantly different orientations of its anisotropy tensor; sufficiently low energies of such levels so that they can mix with the ground state; and the possibility of tuning their energies by small geometrical perturbations. The archetype compound {Na[DyDOTA(H2O)]·4H2O} (1) (H4DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-N,N',N'',N'''-tetraacetic acid) fulfils all such criteria. A state-of-the-art in silico proof of concept study on the possibility of controlling the orientation of the anisotropy tensor as a function of pressure in [DyDOTA(H2O)]- by inducing different apical water molecule (AWM) orientations and/or DOTA-induced crystal field is presented.

Single-Ion Anisotropy and Intramolecular Interactions in CeIII and NdIII Dimers

This article reports the syntheses, characterization, structural description, together with magnetic and spectroscopic properties of two isostructural molecular magnets based on the chiral ligand N,N'-bis((1,2-diphenyl-(pyridine-2-yl)methylene)-(R,R/S,S)-ethane-1,2-diamine), L1, of general formula [Ln2(RR-L1)2(Cl6)]·MeOH·1.5H2O, (Ln = Ce (1) or Nd (2)). Multifrequency electron paramagnetic resonance (EPR), cantilever torque magnetometry (CTM) measurements, and ab initio calculations allowed us to determine single-ion magnetic anisotropy and intramolecular magnetic interactions in both compounds, evidencing a more important role of the anisotropic exchange for the NdIII derivative. The comparison of experimental and theoretical data indicates that, in the case of largely rhombic lanthanide ions, ab initio calculations can fail in determining the orientation of the weakest components, while being reliable in determining their principal values. However, they remain of paramount importance to set the analysis of EPR and CTM on sound basis, thus obtaining a very precise picture of the magnetic interactions in these systems. Finally, the electronic structure of the two complexes, as obtained by this approach, is consistent with the absence of zero-field slow relaxation observed in ac susceptibility.

Magnetic Anisotropy Trends along a Full 4f-Series: The fn+7 Effect

The combined experimental and computational study of the 13 magnetic complexes belonging to the Na[LnDOTA(H₂O)] (H₄DOTA = tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid and Ln = Ce-Yb) family allowed us to identify a new trend: the orientation of the magnetic anisotropy tensors of derivatives differing by seven f electrons practically coincide. We name this trend the fⁿ⁺⁷ effect. Experiments and theory fully agree on the match between the magnetic reference frames (e.g., the easy, intermediate, and hard direction). The shape of the magnetic anisotropy of some couples of ions differing by seven f electrons might seem instead different at first look, but our analysis explains a hidden similarity. We thus pave the way toward a reliable predictivity of the magnetic anisotropy of lanthanide complexes with a consequent reduced need of computational and synthetical efforts. We also offer a way to gain information on ions with a relatively small total angular momentum (i.e., Sm³⁺ and Eu³⁺) and on the radioactive Pm³⁺, which are difficult to investigate experimentally.

Exploring the Organometallic Route to Molecular Spin Qubits: The [CpTi(cot)] Case

The coherence time of the 17-electron, mixed sandwich complex [CpTi(cot)], (η⁸ -cyclooctatetraene)(η⁵ -cyclopentadienyl)titanium, reaches 34 μs at 4.5 K in a frozen deuterated toluene solution. This is a remarkable coherence time for a highly protonated molecule. The intramolecular distances between the Ti and H atoms provide a good compromise between instantaneous and spin diffusion sources of decoherence. Ab initio calculations at the molecular and crystal packing levels reveal that the characteristic low-energy ring rotations of the sandwich framework do not yield a too detrimental spin-lattice relaxation because of their small spin-phonon coupling. The volatility of [CpTi(cot)] and the accessibility of the semi-occupied, non-bonding d z 2 orbital make this neutral compound an ideal candidate for single-qubit addressing on surface and quantum sensing in combination with scanning probe microscopy.

Quantum dynamics of a single molecule magnet on superconducting Pb(111)

Magnetic materials interfaced with superconductors may reveal new physical phenomena with potential for quantum technologies. The use of molecules as magnetic components has already shown great promise, but the diversity of properties offered by the molecular realm remains largely unexplored. Here we investigate a submonolayer of tetrairon(III) propeller-shaped single molecule magnets deposited on a superconducting lead surface. This material combination reveals a strong influence of the superconductor on the spin dynamics of the single molecule magnet. It is shown that the superconducting transition to the condensate state switches the single molecule magnet from a blocked magnetization state to a resonant quantum tunnelling regime. Our results open perspectives to control single molecule magnetism via superconductors and to use single molecule magnets as local probes of the superconducting state.

Covalency and magnetic anisotropy in lanthanide single molecule magnets: the DyDOTA archetype

The unexpected covalent contribution in the DOTADy-OH₂ bond revealed by ab initio calculations of the easy axis of magnetization through simple H₂O rotations.

Lanthanide ions when complexed by polyamino-polycarboxylate chelators form a class of compounds of paramount importance in several research and technological areas, particularly in the fields of magnetic resonance and molecular magnetism. Indeed, the gadolinium derivative is one of the most employed contrast agents for magnetic resonance imaging while the dysprosium one belongs to a new generation of contrast agents for T₂-weighted MRI. In molecular magnetism, Single Molecule Magnets (SMMs) containing lanthanide ions have become readily popular in the chemistry and physics communities since record energy barriers to the reversal of magnetization were reported. The success of lanthanide complexes lies in their large anisotropy due to the contribution of the unquenched orbital angular momentum. However, only a few efforts have been made so far to understand how the f-orbitals can be influenced by the surrounding ligands. The outcomes have been rationalized using mere electrostatic perturbation models. In the archetype compound [Na{Dy(DOTA) (H₂O)}]·4H₂O (Na{DyDOTA}·4H₂O) an unexpected easy axis of magnetization perpendicular to the pseudo-tetragonal axis of the molecule was found. Interestingly, a dependency of the orientation of the principal magnetization axis on the simple rotation of the coordinating apical water molecule (AWM) – highly relevant for MRI contrast – around the Dy-O_AWM bond was predicted by ab initio calculations, too. However, such a behaviour has been contested in a subsequent paper justifying their conclusions on pure electrostatic assumptions. In this paper, we want to shed some light on the nature of the subtle effects induced by the water molecule on the magnetic properties of the DyDOTA archetype complex. Therefore, we have critically reviewed the structural models already published in the literature along with new ones, showing how the easy axis orientation can dangerously depend on the chosen model. The different computed behaviors of the orientation of the easy axis of magnetization have been rationalized as a function of the energy gap between the ground and the first excited doublet. Magneto-structural correlations together with a mapping of the electrostatic potential generated by the ligands around the Dy(iii) ion through a multipolar expansion have also been used to evidence and quantify the covalent contribution of the AWM orbitals.

Magnetic Cationic Copper(II) Chains and a Mononuclear Cobalt(II) Complex Containing [Ln(hfac)4]- Blocks as Counterions

Four new heterospin compounds with molecular formula {[Cu₂(hfac)₃(TlTrzNIT)₂][Ln(hfac)₄]} _n·C₇H₁₆ (Ln^III = Gd (1), Tb (2), or Dy (3)) and [Co(hfac)(TlTrzNIT)₂][Dy(hfac)₄] (4), where hfac is hexafluoroacetylacetonato and TlTrzNIT is the nitronylnitroxide radical 1-( m-tolyl)-1 H-1,2,3-triazole-4-(4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), were obtained. All structures were determined by single-crystal X-ray diffraction. In compounds 1-3, the TlTrzNIT radical is bridge-coordinated to copper(II) ions, leading to positively charged copper(II)-radical chains containing [Ln(hfac)₄]^- as counterions. In compound 4, the cobalt(II) ion is coordinated to two TlTrzNIT radicals and one hfac ligand in bidentate mode leading to a mononuclear cationic complex that contains [Dy(hfac)₄]^- as counterion. Magnetic measurements of all complexes were performed. Magnetic data were fit considering the contributions of the copper(II)-radical chain and a paramagnetic gadolinium(III) ion for 1. The sign and magnitude of the magnetic coupling constants extracted from the fit were confirmed by density functional theory calculations. The obtained spin topology shows an alternated ferro-antiferromagnetic chain. Field-induced single molecule magnet behavior was observed for the Dy derivatives 3 and 4, in agreement with CASSCF calculations performed for the latter system.

Tunable Spin-Superconductor Coupling of Spin 1/2 Vanadyl Phthalocyanine Molecules

Atomic-scale magnetic moments in contact with superconductors host rich physics based on the emergence of Yu-Shiba-Rusinov (YSR) magnetic bound states within the superconducting condensate. Here, we focus on a magnetic bound state induced into Pb nanoislands by individual vanadyl phthalocyanine (VOPc) molecules deposited on the Pb surface. The VOPc molecule is characterized by a spin magnitude of 1/2 arising from a well-isolated singly occupied d _xy-orbital and is a promising candidate for a molecular spin qubit with long coherence times. X-ray magnetic circular dichroism (XMCD) measurements show that the molecular spin remains unperturbed even for molecules directly deposited on the Pb surface. Scanning tunneling spectroscopy and density functional theory (DFT) calculations identify two adsorption geometries for this "asymmetric" molecule (i.e., absence of a horizontal symmetry plane): (a) oxygen pointing toward the vacuum with the Pc laying on the Pb, showing negligible spin-superconductor interaction, and (b) oxygen pointing toward the Pb, presenting an efficient interaction with the Pb and promoting a Yu-Shiba-Rusinov bound state. Additionally, we find that in the first case a YSR state can be induced smoothly by exerting mechanical force on the molecules with the scanning tunneling microscope (STM) tip. This allows the interaction strength to be tuned continuously from an isolated molecular spin case, through the quantum critical point (where the bound state energy is zero) and beyond. DFT indicates that a gradual bending of the VO bond relative to the Pc ligand plane promoted by the STM tip can modify the interaction in a continuously tunable manner. The ability to induce a tunable YSR state in the superconductor suggests the possibility of introducing coupled spins on superconductors with switchable interaction.

Can Teledialysis Help in the Clinical Management of Patients on Remote Hemodialysis?

This study investigated whether transmission of the parameters monitored from a remote center to the main center could improve the control of a dialysis session. The parameters of the computer connection module Monitral SC in remote and main centers, were transmitted by means of the Hospal data collection software (Demoplus) by modem, to the host computer. Each remote center can be temporarily disconnected, if necessary, from the telephone line and linked directly to a local computer. We checked 101 hemodialyses. The dialysis was monitored from filter washing to disconnection of the patients and the following parameters were selected: backfiltration during washing and hemodialysis: ultrafiltration, conductivity and temperature. From the sessions recorded (93%) we observed that backfiltration during the filter preparation phase was high (30%) in 28 sessions. Backfiltration during the preparatory phase is the major problem for correct management of dialysis sessions. The high percentage in which ultrafiltration had to be stopped shows that control of this parameter is still not ideal. Finally, the collection of monitor parameters and the comparative analysis of clinical data is useful for improving dialytic management.

A chimeric design of heterospin 2p–3d, 2p–4f, and 2p–3d–4f complexes using a novel family of paramagnetic dissymmetric compartmental ligands

Original end-off bicompartmental ligands bearing a nitronyl–nitroxide arm have been designed for synthesizing various heterospin molecular systems.

Relaxation Dynamics and Magnetic Anisotropy in a Low-Symmetry Dy(III) Complex

The magnetic behaviour of a Dy(LH)3 complex (LH(-) is the anion of 2-hydroxy-N'-[(E)-(2-hydroxy-3-methoxyphenyl)methylidene]benzhydrazide) was analysed in depth from both theoretical and experimental points of view. Cantilever torque magnetometry indicated that the complex has Ising-type anisotropy, and provided two possible directions for the easy axis of anisotropy due to the presence of two magnetically non-equivalent molecules in the crystal. Ab initio calculations confirmed the strong Ising-type anisotropy and disentangled the two possible orientations. The computed results obtained by using ab initio calculations were then used to rationalise the composite dynamic behaviour observed for both pure Dy(III) phase and Y(III) diluted phase, which showed two different relaxation channels in zero and non-zero static magnetic fields. In particular, we showed that the relaxation behaviour at the higher temperature range can be correctly reproduced by using a master matrix approach, which suggests that Orbach relaxation is occurring through a second excited doublet.

First coordination compounds based on a bis(imino nitroxide) biradical and 4f metal ions: synthesis, crystal structures and magnetic properties

The synthesis, structure and magnetic properties of lanthanide-biradical complexes are reported.

[Mesh infection in inguinal hernioplasty by Streptococcus dysgalactiae subspecies equisimilis. Case report and review of the literature]

INTRODUCTION

Mesh infection in inguinal herniography is usually caused by Staphilococcus aureus and Staphilcoccus epidermidis. Generally it obliges to prosthesis removal with hernia relapse and increase of social costs for the prolongation of hospitalization.

CASE REPORT

A 60-year-old woman, obese, undergone 4 months before to left inguinal prosthetic herniorrhaphy complicated by infection of the surgical site which didn't require the explantation of the mesh, although determining an early hernia relapse. She is submitted by the authors to a surgical intervention for left groin hernia relapse with placement of a polypropylene monofilament fixed with prolene. Six hours after the operation she shows systemic symptoms and local signs of prosthesis infection. Cultural examination of the surgical wound secretion allows the identification of Streptococcus dysgalactiae subspecies equisimilis (SDSE). A therapy with Amoxicillin-Clavulanic Acid and Levofloxacine leads to resolution, in 10 weeks, of the infection.

DISCUSSION

In our case the infection of the new mesh, appearing prematurely, has been probably favoured by obesity and operative time longer than 3 hours. Conservative treatment has been fulfilled by success for the elevated sensitivity of the SDSE bacterium to penicillin and fluoroquinolones.

CONCLUSIONS

Recent epidemiologic studies have demonstrated an increase of infections caused by SDSE, which will probably gain clinical relevance in the next future relatively to surgical prosthetic hernioplasty. In all cases of infection the authors suggest cultural isolation of the casual germ and the execution of the antibiogram because the conservative medical treatment can avoid mesh removal with consequent elevated risk of hernia relapse.

[Gallbladder polypoid lesions. Three clinical cases with difficult diagnosis and literature review]

INTRODUCTION

Gallbladder polypoid lesions occur in 1.3%-6.9% of cases. The preoperative diagnosis between benign, malignant and potentially malignant lesions is difficult. Therefore it is not possible any.

PATIENTS AND METHODS

The Authors describe three cases. The case 1 was a gallbladder diffuse adenomyomatosis; the ultrasound and the CT were of little help in defining preoperatively the nature and the gravity of the thickening. Case 2 was an adenomyomatosis of the fundus: the ultrasound examinations were not able to establish preoperatively lesion's nature, site and dimensions. In the case 3, ultrasounds showed polypoid lesions and calculi concrections not found in colecistectomy.

DISCUSSION

The ultrasound is the most widely used diagnostic tool in the evaluation of gallbladder polypoid lesions; its accuracy is only 66%. CT, which has an accuracy level of 75%, must be carried out there is any possibility of malignant degeneration of the polyp. If doubts persist, a MR, 93% accuracy, is indicated. In selected cases, PET can be of further help.

CONCLUSIONS

The preoperative diagnosis of the nature of gallbladder polypoid lesions is "difficult" and this justifies the lack of consensus on treatment. However, the adenoma-carcinoma sequence, widely discussed in literature, can justifies to the use of CT, MR, PET and surgical treatment after an ultrasound examination.

Endoscopic sphincterotomy of the major duodenal papilla in acute relapsing pancreatitis associated with pancreas divisum: a case report

We report a case of acute relapsing pancreatitis associated with pancreas divisum, who underwent major papilla sphincterotomy after failed minor papilla cannulation. Long-term results were satisfactory. The possible explanations of the efficacy of major papilla endoscopic resection in this particular case are discussed.

[Umbilical primary endometrioma. Case report]

Umbilical primary endometrioma is a rare extra-uterine localization of endometriosis with a documented neoplastic risk. It is often difficult to distinguish primary umbilical endometriosis from other benign and malignant tumors of the abdominal wall. The Authors report a case of umbilical endometriosis in a 36-year old female. Endometriosis was suspected because of the presence of the typical cyclic bleeding and swelling. Abdominal CT excluded the presence of other endometriotic localizations. The umbilical mass was widely excised together with umbilicus, fascia and peritoneum. The tissue defect was primary closed without prosthetic mesh. Histological examination of the specimen showed the presence of endometrial glands with stromal component, compatible with the diagnosis of endometriosis. The Authors suggest that surgery should be performed in the first 3-4 days of the follicular phase, to minimize the risk of diffusion of endometriotic cells. Moreover, the excision should be wide in order to prevent local recurrence.

[Massive haemoperitoneum due to traumatic rupture of multifocal hepatocarcinoma in the right hepatic lobe. Case report]

Abdominal blunt trauma is the main cause of death in people younger than 40 years old. The liver injury still represents a challenging problem. Isolated hepatic injury is rare and it occurs more frequentely in polytraumatizated patients and causes massive haemoperitoneum. The Authors report a case of a 83 years-old woman admitted to Emergency Department for syncope due to an active bleeding arising from a rupture of a right hepatic lobe unsuspected tumor. The computer tomography (CT) scans showed a clear pattern of liver laceration of the VI segment with contrast enhancement spreading in the surrounding tissues, and detected a multifocal hepatocarcinoma located in the VI, VII and VIII segments. Patient's haemodinamically unstable conditions suggested an urgent laparotomy. An accurate perihepatic packing with sterile-drape were successfully employed to control liver hemorrage. Temporary abdominal closure, followed by hepatic arteriography and the right hepatic artery embolization, completed the damage control. Re-exploration laparotomy after 72 hours confirmed the definitive haemostasis and the pack removal was performed without complications.

CONCLUSIONS

CT plays a leading role in the diagnosis of liver damage. The patient's haemodynamic status is the principal criterion determining conservative or operative therapy in blunt liver injury. The early perihepatic packing followed by artheriographic embolization to stop liver hemorrhage showed efficacy and safety for the patient. The packing performed with sterile-drape is able to avoid removal complications and 72 hours timing for the pack removal is effective to avoid re-bleeding.

[A case of uterine carcinosarcoma]

Uterine carcinosarcoma is a highly aggressive neoplasm with tendency to early recurrence and/or metastasis. The neoplasia has both epithelial and stromal malignant components. Clinically, it is characterized by a postmenopausal metrorrhagia, associated sometimes with abdominal pain. The Authors describe a case of carcinosarcoma in a 82-year old woman with a vaginal bleeding since 10 months and an ingravescent hypochromic anemia. The RMN of the abdomen and pelvis showed a mass occupying the whole uterine lumen, without signs of pelvic diffusion. A bilateral hystero-oophorectomy was performed; the patient's critical conditions and a high anaesthesiological risk advised us not to perform a bilateral pelvic lymphadenectomy with aortic sampling. Six months after operation, a clinical follow-up with a total-body CT didn't show any sign of local recurrence and/or distant metastasis. From the analysis of this case report and from the data of the literature some important considerations can be done: a) gynecologic check up in post-menopausal women with associated risk factors (obesity and hypertension) can allow an early diagnosis also in asymptomatic patients; b) sovrapubic and transvaginal US, abdomino-pelvic CT and MRI are essential for a correct clinical staging; c) surgical excision followed by the histological examination of the specimen is mandatory to establish a correct diagnosis.

[A possible cause of misdiagnosis in tumors of the axilla: schwannoma of the brachial plexus]

The Authors report a rare case of a 57 years old man affected by a left radial nerve schwannoma that occurred as an asymptomatic lesion of the axilla. At clinical examination the lump was undistinguishable from the most common axillary lymphadenopathy. A lymphoadenopathy was erroneously diagnosed with ultrasonography (US). This mistake was due to the low specificity of the instrumental methodology and to the rarity of an asymptomatic schwannoma of the infraclavicular brachial plexus. The neoplasia was excised without using the microscope. In the early post-operative follow up, a "falling" attitude of the wrist, the hand and the fingers appeared, peculiar for a lesion of the radial nerve. Furthermore a hypoaesthesia of the skin of first finger and of the first interosseus space was associated. The sensitive and motor electromyography showed a radial nerve suffering. The "stupor" of the nerve trunk was treated with steroid therapy for 7 days and the patient underwent to some series of neuro-rehabilitative physical therapy for 12 weeks. The postoperative total body CT, showed that the lesion was unique: therefore it was possible to exclude the diagnosis of neurofibromatosis. After 28 months electromyography and axillary US were performed showing the complete resolution of the motor and sensitive deficit and the absence of local recurrence.

Carcinosarcoma of the uterus: a case report and review of the literature

Carcinosarcoma is a rare tumor of the uterus with a poor prognosis. We present a case of uterine carcinosarcoma in an 82-year-old woman who suffered from pervaginal bleeding for ten months duration with progressive anemia. Abdominopelvic nuclear magnetic resonance (NMR) imaging showed the presence of an intrauterine mass, infiltrating the myometrium and reaching the cervix. The patient was submitted to total abdominal hysterectomy with bilateral salpingo-oophorectomy. The carcinosarcoma, arising from the lumen of the uterus, infiltrated the inner one-third of the myometrial layer (pT1b, pNx, pMx; FIGO Stage 1B). A CT of the total body performed six months after surgery showed no signs of recurrent and/or metastatic tumor. The clinicopathological features, treatment options and prognosis of this aggressive neoplasm are reviewed.

[On-line haemodiafiltration with sorbent-regenerated ultrafiltrate as replacement fluid: Beta2-microglobulin removal versus filtration fraction]

PURPOSE

In order to encourage the removal of middle molecules in hemodiafiltration (HDF) techniques an attempt is made to maximize convective clearance by increasing the ultrafiltration rate. However, convective clearance is limited by the maximum filtration fraction (FF%) obtainable, by the pre- or post reinfusion method and by the convective surface and the capacity of the filter used. This study aimed to evaluate the effect of the FF% in the removal of Beta2-microglobulin (Beta2-m) during hemodiafiltration reinfusion (HFR) to identify the best ultrafiltration strategies; and therefore, a better removal of medium molecular weight solutes in this hemodiafiltrative technique recently introduced in clinical practice.

METHODS

Ten chronic uremic patients (eight males, two females; age 66 +/- 18 yrs) already on renal dialysis therapy (RDT) for 80 +/- 36 months, were subjected to four HFR sessions, with Td=240 +/- 10 min, Qb=312 +/- 18 and Qd=500 mL/min; the reinfusion rates (Qr) used were 43.6 +/- 7.2 mL/min (25-58) with FF% rates varying from 20-34 (24.2 +/- 3.8) for hematocritic levels of 34.6 +/- 4.2% at the start of the dialysis session. For each session the intradialytic reduction rates (RR%) of urea, creatinine (Cr), phosphate, uric acid and Beta2-m and its average clearance (KBeta2-m mL/min) were evaluated.

RESULTS

The results obtained gave a RR% for urea of 69.4 +/- 5 (Kt/Veq=1.23 +/- 0.2) and for Cr, phosphate and uric acid values of, respectively, 61.2 +/- 5.4, 47.5 +/- 10 and 75.8 +/- 6.7. The intradialytic reductions in Beta2-m were 49.3 +/- 10.3% with a variability range from 29-69% and with average KBeta2-m values of 63.8 +/- 13.5 mL/min. The RR% of ss2-m and KBeta2-m were inversely correlated (p<0.01) to the FF% rate applied during the treatment; 75% of the HRF sessions in which we observed a reduction in Beta2-m levels >40% were those where a FF% between 20 and 26% was applied. CONCLUSIONS. From our study, it appears that in HFR the best ultrafiltration strategy from the convective sector in removing Beta2-m has FF% values in the range 20-26%. The occurrence of lower intradialytic reductions of Beta2-m with increasing FF% can be interpreted as a consequence of phenomena related to high intradialytic hemoconcentrations, to the excessive increase in the TMP and/or the increase in the protein cake with a consequent reduction in permeability and mass transfer. Although using a limited convective surface with a limited possibility of increasing the FF%, nevertheless, HFR seems capable of ensuring a satisfactory uremic toxin removal of low and medium molecular weight, which combined with the high biocompatibility deriving from the use of reinfused endogen, can be considered an effective dialytic strategy for preventing or retarding the complications in dialytic patients.

Ethylene-oxide and steam-sterilised polysulfone membrane in dialysis patients with eosinophilia

Eosinophilia and some acute dialysis side-effects, such as itching, flushing and bronchospasm, are often associated with the presence of ethylene oxide (ETO) as dialyzer sterilizing agent. This study evaluated the effects of two different polysulfone (PS) hollow-fiber dialysers sterilized with ETO and steam in 31 chronic dialysis patients with eosinophilia. Clinical symptoms, metabolic and biochemical parameters, complement (C3a and C5a) activation and production were evaluated in each patient dialysed for two months at a time with Cuprophan dialyser, ETO-PS dialyser and steam-PS dialyser. The steam-sterilizer agent does not alter the purifying capacity of the PS membrane which maintains its superiority over Cuprophan in terms of biocompatibility. Using steam-PS, intradialytic eosinophil kinetics seems to improve. In some patients with high serum levels of ETO-specific IgE these levels tend to diminish. Generic intradialytic symptoms do not differ between the two sterilization methods, although some hypersensitivity symptoms during the first dialysis hour are considerably lower in some patients when steam-sterilized PS is used.

Longitudinal assessment of body composition in CAPD patients using bioelectric impedance analysis. A comparison with hemodialysis patients

The utility of bioelectric impedance analysis was assessed for longitudinal evaluation of body composition in two groups of uremic patients, one on CAPD and one on hemodialysis treatment, with no clinical marks of hyperhydration or infection. Nineteen CAPD patients (11 men 8 women) and 21 HD patients (12 men 9 women) were studied with bioelectric impedance analysis for a period of 12 months; total body water, fat free mass, and fat mass were calculated from bioelectric impedance analysis data of resistance and reactance at time 0 and 12 months later. No significant differences in body composition were found in the two groups at time 0 and 12 months later, with a similar trend for total body water, fat free mass, and fat mass. In CAPD, a significant increase in body weight was observed due mainly to a rise in fat mass, particularly evident in women with uremia. Bioelectric impedance analysis appears to be an instrument easily repeatable and reliable in CAPD and HD patients, reflecting at the same time body composition, the dialytic adequacy of a technique, and the patient's well being.

Analysis of the factors influencing bicarbonate balance during acetate-free biofiltration

In acetate-free biofiltration (AFB), the physical separation between the base losses and the gains could facilitate the modeling of intradialytic bicarbonate (HCO3) balance. In order to verify this hypothesis, we analyzed in a multicenter study, 126 AFB sessions in which differing parameters were evaluated (dialysis time, blood flow, ultrafiltration, infused HCO3, pre- and post-dialytic HCO3, hematocrit and body wt). Statistical analysis performed with multiple linear regression showed that the post-dialysis HCO3 was significantly dependent (F = 21.68, d.f. 5.95, P < 0.001) directly on the amount of infused HCO3, the level of pre-dialysis HCO3 and the final body weight, and inversely on the dialysis time and the blood flow. HCO3 values predicted by the statistical model correlated well with the observed ones (r = 0.788, P < 0.0001) with a mean absolute difference of 2.138 mEq/liter. This modeling approach allowed us to predict, with a computer-aided procedure, the quantities of HCO3 to be infused to obtain a desired and personalized acidosis correction.

Can teledialysis help in the clinical management of patients on remote hemodialysis?

This study investigated whether transmission of the parameters monitored from a remote center to the main center could improve the control of a dialysis session. The parameters of the computer connection module Monitral SC in remote and main centers, were transmitted by means of the Hospal data collection software (Demoplus) by modem, to the host computer. Each remote center can be temporarily disconnected, if necessary, from the telephone line and linked directly to a local computer. We checked 101 hemodialyses. The dialysis was monitored from filter washing to disconnection of the patients and the following parameters were selected: backfiltration during washing and hemodialysis: ultrafiltration, conductivity and temperature. From the sessions recorded (93%) we observed that backfiltration during the filter preparation phase was high (30%) in 28 sessions. Backfiltration during the preparatory phase is the major problem for correct management of dialysis sessions. The high percentage in which ultrafiltration had to be stopped shows that control of this parameter is still not ideal. Finally, the collection of monitor parameters and the comparative analysis of clinical data is useful for improving dialytic management.

Comparison of clinical and neurological status in elderly patients treated with two different hemodialysis techniques

Five patients with a mean age of 63.4 years (range 62-67) who had frequent episodes of intradialytic intolerance during acetate hemodialysis (HDA) received biofiltration (BF). For each period of study (6 months on HDA and 6 months on BF), the patients underwent a complete clinical assessment, with evaluation of the electroencephalographic (EEG) pattern and acid-base status. During BF, we observed a reduction of hypotensive episodes (10% on BF vs. 26% on HDA) and EEG disturbances (18% on BF vs. 70% on HDA), with a more physiological correction of uremic acidosis. We conclude that BF improves clinical status and neurological tolerance with a better compensation of acidosis in the elderly.

The acid-base balance and the electroencephalographic pattern in patients on biofiltration treatment

Electroencephalogram (EEG) monitoring and arterial blood gases was performed during biofiltration (BF) treatment and during conventional acetate hemodialysis (HDA). Biofiltration is an ultrashort hemodiafiltration with 3 liters of substitution fluid (Na+ 145 mEq/l, HCO-3 100 mEq/l). Our data show a better correction of acid-base balance during BF than during HDA. Moreover, we observe a lower incidence of EEG disturbancies on BF, that suggests a better neurological tolerance of this treatment.