Association Between COL5a1, COL11a1, and COL11a2 Gene Variations and Rotator Cuff Tendinopathy in Young Athletes.

OBJECTIVE: Tendinopathy is a prevalent condition in young athletes and in older nonathletic people. Recent tendinopathy research has shown a growing interest in the role played by genetic factors, basically genes involved in collagen synthesis and regulation, in view of collagen disorganization typically present in tendon pathologies. DESIGN: A case-control, genotype-phenotype association study. SETTING: La Ribera Hospital, Valencia, Spain. PARTICIPANTS: A group of 137 young athletes (49 with rotator cuff tendon pathology and 88 healthy counterparts) who played upper-limb-loading sports were clinically and ultrasound (US) assessed for rotator cuff tendinopathy were included. INTERVENTION: Genetic analysis was performed to determine whether there was a relationship between rotator cuff pathology and the genotype. MAIN OUTCOME MEASURES: We hypothesized that the following single nucleotide polymorphisms: COL5a1 rs12722, COL11a1 rs3753841, COL11a1 rs1676486, and COL11a2 rs1799907 would be associated with rotator cuff tendinopathy. RESULTS: A direct relationship between CC genotype and bilateral US pathological images was statistically significant (χ 2 = 0.0051) and confirmed by the Fisher test, with a correlation coefficient of 0.345 and a Cramer's v of 0.26. CONCLUSION: A significant association was found between COL5a1 rs12722 genotype and rotator cuff pathology, with the CC genotype conferring increased risk of tendon abnormalities and being associated with rotator cuff pathology.

WS2 /MoS2 Heterostructures through Thermal Treatment of MoS2 Layers Electrostatically Functionalized with W3 S4 Molecular Clusters.

The preparation of 2D stacked layers combining flakes of different nature gives rise to countless numbers of heterostructures where new band alignments, defined at the interfaces, control the electronic properties of the system. Among the large family of 2D/2D heterostructures, the one formed by the combination of the most common semiconducting transition metal dichalcogenides, WS2 /MoS2 , has awakened great interest owing to its photovoltaic and photoelectrochemical properties. Solution as well as dry physical methods have been developed to optimize the synthesis of these heterostructures. Here, a suspension of negatively charged MoS2 flakes is mixed with a methanolic solution of a cationic W3 S4 -core cluster, giving rise to a homogeneous distribution of the clusters over the layers. In a second step, a calcination of this molecular/2D heterostructure under N2 leads to the formation of clean WS2 /MoS2 heterostructures, where the photoluminescence of both counterparts is quenched, proving an efficient interlayer coupling. Thus, this chemical method combines the advantages of a solution approach (simple, scalable, and low-cost) with the good quality interfaces reached by using more complicated traditional physical methods.

On the Design of Radical-Radical Cocrystals.

Formation of radical-radical cocrystals is an important step towards the design of organic ferrimagnets. We describe a simple approach to generate radical-radical cocrystals through the identification and implementation of well-defined supramolecular synthons which favor cocrystallization over phase separation. In the current paper we implement the structure-directing interactions of the E-E bond (E=S, Se) of dithiadiazolyl (DTDA) and diselenadiazolyl (DSDA) radicals to form close contacts to electronegative groups. This is exemplified through the preparation and structural characterization of three sets of radical cocrystals; the 2:2 cocrystal [PhCNSSN]2 [MBDTA]2 (4) [MBDTA=methyl benzodithiazolyl] and the 2:1 cocrystals [C6 F5 CNEEN]2 [TEMPO] (E=S, 5; E=Se, 6). In 4 the two types of radical are linked via bifurcated inter-dimer δ+ S⋅⋅⋅Nδ- interactions whereas 5 and 6 exhibit a set of five-centre δ+ E⋅⋅⋅Oδ- contacts (E=S, Se).

Effects of the Inhibition of Late Sodium Current by GS967 on Stretch-Induced Changes in Cardiac Electrophysiology.

PURPOSE: Mechanical stretch increases sodium and calcium entry into myocytes and activates the late sodium current. GS967, a triazolopyridine derivative, is a sodium channel blocker with preferential effects on the late sodium current. The present study evaluates whether GS967 inhibits or modulates the arrhythmogenic electrophysiological effects of myocardial stretch. METHODS: Atrial and ventricular refractoriness and ventricular fibrillation modifications induced by acute stretch were studied in Langendorff-perfused rabbit hearts (n = 28) using epicardial multiple electrodes and high-resolution mapping techniques under control conditions and during the perfusion of GS967 at different concentrations (0.03, 0.1, and 0.3 µM). RESULTS: On comparing ventricular refractoriness, conduction velocity and wavelength obtained before stretch had no significant changes under each GS967 concentration while atrial refractoriness increased under GS967 0.3 µM. Under GS967, the stretch-induced changes were attenuated, and no significant differences were observed between before and during stretch. GS967 0.3 µM diminished the normal stretch-induced changes resulting in longer (less shortened) atrial refractoriness (138 ± 26 ms vs 95 ± 9 ms; p < 0.01), ventricular refractoriness (155 ± 18 ms vs 124 ± 16 ms; p < 0.01) and increments in spectral concentration (23 ± 5% vs 17 ± 2%; p < 0.01), the fifth percentile of ventricular activation intervals (46 ± 8 ms vs 31 ± 3 ms; p < 0.05), and wavelength of ventricular fibrillation (2.5 ±0.5 cm vs 1.7 ± 0.3 cm; p < 0.05) during stretch. The stretch-induced increments in dominant frequency during ventricular fibrillation (control = 38%, 0.03 µM = 33%, 0.1 µM = 33%, 0.3 µM = 14%; p < 0.01) and the stretch-induced increments in arrhythmia complexity index (control = 62%, 0.03µM = 41%, 0.1 µM = 32%, 0.3 µM = 16%; p < 0.05) progressively decreased on increasing the GS967 concentration. CONCLUSIONS: GS967 attenuates stretch-induced changes in cardiac electrophysiology.

Effects of JTV-519 on stretch-induced manifestations of mechanoelectric feedback.

JTV-519 is a 1,4-benzothiazepine derivative with multichannel effects that inhibits Ca2+ release from the sarcoplasmic reticulum and stabilizes the closed state of the ryanodine receptor, preventing myocardial damage and the induction of arrhythmias during Ca2+ overload. Mechanical stretch increases cellular Na+ inflow, activates the reverse mode of the Na+ /Ca2+ exchanger, and modifies Ca2+ handling and myocardial electrophysiology, favoring arrhythmogenesis. This study aims to determine whether JTV-519 modifies the stretch-induced manifestations of mechanoelectric feedback. The ventricular fibrillation (VF) modifications induced by acute stretch were studied in Langendorff-perfused rabbit hearts using epicardial multiple electrodes under control conditions (n=9) or during JTV-519 perfusion: 0.1 µmol/L (n=9) and 1 µmol/L (n=9). Spectral and mapping techniques were used to establish the baseline, stretch and post-stretch VF characteristics. JTV-519 slowed baseline VF and decreased activation complexity. These effects were dose-dependent (baseline VF dominant frequency: control=13.9±2.2 Hz; JTV 0.1 µmol/L=11.1±1.1 Hz, P<.01; JTV 1 µmol/L=6.6±1.1 Hz, P<.0001). The stretch-induced acceleration of VF (control=38.8%) was significantly reduced by JTV-519 0.1 µmol/L (19.8%) and abolished by JTV 1 µmol/L (-1.5%). During stretch, the VF activation complexity index was reduced in both JTV-519 series (control=1.60±0.15; JTV 0.1 µmol/L=1.13±0.3, P<.0001; JTV 1 µmol/L=0.57±0.21, P<.0001), and was independently related to VF dominant frequency (R=.82; P<.0001). The fifth percentile of the VF activation intervals, conduction velocity and wavelength entered the multiple linear regression model using dominant frequency as the dependent variable (R=-.84; P<.0001). In conclusion, JTV-519 slowed and simplified the baseline VF activation patterns and abolished the stretch-induced manifestations of mechanoelectric feedback.

Ranolazine Attenuates the Electrophysiological Effects of Myocardial Stretch in Langendorff-Perfused Rabbit Hearts.

PURPOSE: Mechanical stretch is an arrhythmogenic factor found in situations of cardiac overload or dyssynchronic contraction. Ranolazine is an antianginal agent that inhibits the late Na (+) current and has been shown to exert a protective effect against arrhythmias. The present study aims to determine whether ranolazine modifies the electrophysiological responses induced by acute mechanical stretch. METHODS: The ventricular fibrillation modifications induced by acute stretch were studied in Langendorff-perfused rabbit hearts using epicardial multiple electrodes under control conditions (n = 9) or during perfusion of the late Na(+) current blocker ranolazine 5 µM (n = 9). Spectral and mapping techniques were used to establish the ventricular fibrillation dominant frequency, the spectral concentration and the complexity of myocardial activation in three situations: baseline, stretch and post-stretch. RESULTS: Ranolazine attenuated the increase in ventricular fibrillation dominant frequency produced by stretch (23.0 vs 40.4 %) (control: baseline =13.6 ± 2.6 Hz, stretch = 19.1 ± 3.1 Hz, p < 0.0001; ranolazine: baseline = 1.4 ± 1.8 Hz, stretch =14.0 ± 2.4 Hz, p < 0.05 vs baseline, p < 0.001 vs control). During stretch, ventricular fibrillation was less complex in the ranolazine than in the control series, as evaluated by the lesser percentage of complex maps and the greater spectral concentration of ventricular fibrillation. These changes were associated to an increase in the fifth percentile of VV intervals during ventricular fibrillation (50 ± 8 vs 38 ± 5 ms, p < .01) and in the wavelength of the activation (2.4 ± 0.3 vs 1.9 ± 0.2 cm, p < 0.001) under ranolazine. CONCLUSIONS: The late inward Na(+) current inhibitor ranolazine attenuates the electrophysiological effects responsible for the acceleration and increase in complexity of ventricular fibrillation produced by myocardial stretch.

Vector Field Heterogeneity for the Assessment of Locally Disorganised Cardiac Electrical Propagation Wavefronts From High-Density Multielectrodes.

High-density multielectrode catheters are becoming increasingly popular in cardiac electrophysiology for advanced characterisation of the cardiac tissue, due to their potential to identify impaired sites. These are often characterised by abnormal electrical conduction, which may cause locally disorganised propagation wavefronts. To quantify it, a novel heterogeneity parameter based on vector field analysis is proposed, utilising finite differences to measure direction changes between adjacent cliques. The proposed Vector Field Heterogeneity metric has been evaluated on a set of simulations with controlled levels of organisation in vector maps, and a variety of grid sizes. Furthermore, it has been tested on animal experimental models of isolated Langendorff-perfused rabbit hearts. The proposed parameter exhibited superior capturing ability of heterogeneous propagation wavefronts compared to the classical Spatial Inhomogeneity Index, and simulations proved that the metric effectively captures gradual increments in disorganisation in propagation patterns. Notably, it yielded robust and consistent outcomes for [Formula: see text] grid sizes, underscoring its suitability for the latest generation of orientation-independent cardiac catheters.

Ventricular fibrillation conduction through an isthmus of preserved myocardium between radiofrequency lesions.

BACKGROUND: Selective local acceleration of myocardial activation during ventricular fibrillation (VF) contributes information on the interactions between neighboring zones during the arrhythmia. This study analyzes these interactions, centering the observations on an isthmus of myocardium between two radiofrequency (RF) lesions. METHODS: In nine isolated rabbit hearts, a gap of preserved myocardium was established between two RF lesions in the anterolateral left ventricle (LV) wall. Before, during, and after increasing the spatial heterogeneity of VF by local myocardial stretching, VF epicardial recordings were obtained. RESULTS: Local stretch in the anterior LV wall decreased the excitable window (17 ± 7 ms vs 26 ± 7 ms; P < 0.05) and increased the dominant frequency (DFr; 18.9 ± 5.0 Hz vs 15.2 ± 3.6 Hz; P < 0.05) in this zone, without changes in the non-stretched posterolateral zone (25 ± 4 ms vs 27 ± 6 ms, ns and 14.1 ± 2.7 Hz vs 14.3 ± 3.0 Hz, ns). The DFr ratio at both sides of the gap was inversely correlated to the excitable window ratio (R = -0.57; P = 0.002). Before (31% vs 26%), during (29% vs 22%), and after stretch suppression (35% vs 25%), the wavefronts passing through the gap from the posterolateral to the anterior LV wall were seen to predominate. The number of wavefronts that passed from the anterior to the posterolateral LV wall was related to the excitable window in this zone (R = 0.41; P = 0.03). CONCLUSIONS: The VF acceleration induced in the stretched zone does not increase the flow of wavefronts toward the non-stretched zone in the adjacent gap of preserved myocardium. The absence of significant changes in the electrophysiological parameters of the non-stretched myocardium limits the arrival of wavefronts in this zone.

Differences in Long-Term Heart Rate Variability between Subjects with and without Metabolic Syndrome: A Systematic Review and Meta-Analysis.

BACKGROUND: Our aim was to determine the impact that metabolic syndrome (MS) produces in long-term heart rate variability (HRV), quantitatively synthesizing the results of published studies to characterize the cardiac autonomic dysfunction in MS. METHODS: We searched electronic databases for original research works with long-term HRV recordings (24 h) that compared people with MS (MS+) versus healthy people as a control group (MS-). This systematic review and meta-analysis (MA) was performed according to PRISMA guidelines and registered at PROSPERO (CRD42022358975). RESULTS: A total of 13 articles were included in the qualitative synthesis, and 7 of them met the required criteria to be included in the MA. SDNN (-0.33 [-0.57, 0.09], p = 0.008), LF (-0.32 [-0.41, -0.23], p < 0.00001), VLF (-0.21 [-0.31, -0.10], p = 0.0001) and TP (-0.20 [-0.33, -0.07], p = 0.002) decreased in patients with MS. The rMSSD (p = 0.41), HF (p = 0.06) and LF/HF ratio (p = 0.64) were not modified. CONCLUSIONS: In long-term recordings (24 h), SDNN, LF, VLF and TP were consistently decreased in patients with MS. Other parameters that could be included in the quantitative analysis were not modified in MS+ patients (rMSSD, HF, ratio LF/HF). Regarding non-linear analyses, the results are not conclusive due to the low number of datasets found, which prevented us from conducting an MA.

Mini Peltier Cell Array System for the Generation of Controlled Local Epicardial Heterogeneities.

The present study aims to design and fabricate a system capable of generating heterogeneities on the epicardial surface of an isolated rabbit heart perfused in a Langendorff system. The system consists of thermoelectric modules that can be independently controlled by the developed hardware, thereby allowing for the generation of temperature gradients on the epicardial surface, resulting in conduction slowing akin to heterogeneities of pathological origin. A comprehensive analysis of the system's viability was performed through modeling and thermal simulation, and its practicality was validated through preliminary tests conducted at the experimental cardiac electrophysiology laboratory of the University of Valencia. The design process involved the use of Fusion 360 for 3D designs, MATLAB/Simulink for algorithms and block diagrams, LTSpice and Altium Designer for schematic captures and PCB design, and the integration of specialized equipment for animal experimentation. The objective of the study was to efficiently capture epicardial recordings under varying conditions.Clinical relevance- The proposed system aims to induce local epicardial heterogeneities to generate labeled correct signals that can serve as a golden standard for improving algorithms that identify and characterize fibrotic substrates. This improvement will enhance the efficacy of ablation processes and potentially reduce the ablated surface area.

Evaluation and assessment of clique arrangements for the estimation of omnipolar electrograms in high density electrode arrays: an experimental animal model study.

High-density catheters combined with Orientation Independent Sensing (OIS) methods have emerged as a groundbreaking technology for cardiac substrate characterisation. In this study, we aim to assess the arrangements and constraints to reliably estimate the so-called omnipolar electrogram (oEGM). Performance was evaluated using an experimental animal model. Thirty-eight recordings from nine retrospective experiments on isolated perfused rabbit hearts with an epicardial HD multielectrode were used. We estimated oEGMs according to the classic triangular clique (4 possible orientations) and a novel cross-orientation clique arrangement. Furthermore, we tested the effects of interelectrode spacing from 1 to 4 mm. Performance was evaluated by means of several parameters that measured amplitude rejection ratios, electric field loop area, activation pulse width and morphology distortion. Most reliable oEGM estimations were obtained with cross-configurations and interelectrode spacings [Formula: see text] mm. Estimations from triangular cliques resulted in wider electric field loops and unreliable detection of the direction of the propagation wavefront. Moreover, increasing interelectrode distance resulted in increased pulse width and morphology distortion. The results prove that current oEGM estimation techniques are insufficiently accurate. This study opens a new standpoint for the design of new-generation HD catheters and mapping software.

Short-Term Heart Rate Variability in Metabolic Syndrome: A Systematic Review and Meta-Analysis.

BACKGROUND: Our aim was to determine the differences in short-term heart rate variability (HRV) between patients with metabolic syndrome (MS) and healthy controls. METHODS: We searched electronic databases for primary works with short-term HRV recordings (≤30 min) that made comparisons between individuals with MS versus healthy controls. This systematic review and meta-analysis (MA) was performed according to PRISMA guidelines and registered at PROSPERO (CRD42022358975). RESULTS: Twenty-eight articles were included in the qualitative synthesis and nineteen met the criteria for the MA. Patients with MS showed decreased SDNN (-0.36 [-0.44, -0.28], p < 0.001), rMSSD (-7.59 [-9.98, -5.19], p < 0.001), HF (-0.36 [-0.51, -0.20], p < 0.00001) and LF (-0.24 [-0.38, -0.1], p = 0.001). In subsequent subanalyses, we found a decrease in SDNN (-0.99 (-1.45, -0.52], p < 0.001), rMSSD (-10.18 [-16.85, -3.52], p < 0.01) and HF (-1.04 [-1.97, -0.1] p < 0.05) in women. In men, only LF showed a significant lower value (-0.26 [-0.5, -0.02], p < 0.05). We could not perform MA for non-linear variables. CONCLUSIONS: Patients with MS showed changes in time-domain analyses, with lower values in SDNN and rMSSD. Regarding frequency-domain analyses, MS patients showed a decrease in HF and LF When sex was used as a grouping variable, the MA was only possible in one of both sexes (men or women) in rMSSD and LF/HF. Lastly, when data for both men and women were available, subanalyses showed a different behavior compared to mixed analyses for SDNN, HF and LF, which might point towards a different impact of MS in men and women.

Two stage magnetic ordering and spin idle behavior of the coordination polymer Co3(OH)2(C4O4)2·3H2O determined using neutron diffraction.

We report the magnetic structure of two of the magnetically ordered phases of Co(3)(OH)(2)(C(4)O(4))(2)·3H(2)O, a coordination polymer that consists of a triangular framework decorated with anisotropic Co(II) ions. The combination of neutron diffraction experiments and magnetic susceptibility data allows us to identify one phase as displaying spin idle behavior, where only a fraction of the moments order at intermediate temperatures, while at the lowest temperatures the system orders fully. This novel magnetic behavior is discussed within the framework of a simple Hamiltonian and representational analysis and rationalizes this multiphase behavior by considering the combination of frustration and anisotropy.

A short, versatile route towards benzothiadiazinyl radicals.

A family of substituted 1,2,4-benzothiadiazine 1-chlorides have been prepared by treatment of N-arylamidines in neat thionyl chloride at reflux. The S(iv) 1-chlorides are readily reduced under mild conditions to persistent 1,2,4-benzothiadiazinyl radicals which have been characterised by EPR spectroscopy and cyclic voltammetry. Crystallographic studies on isolated radicals indicate that the radicals dimerise via pancake bonding in the solid-state, resulting in spin-pairing and net diamagnetism.

A chiral ferromagnetic molecular metal.

The first molecular material with the coexistence of ferromagnetism, metal-like conductivity, and chirality has been prepared using an organic/inorganic approach. In this case, a two-dimensional packing of chiral organic radical cations (responsible for both the electrical conductivity and optical activity) was assembled with a layered bimetallic oxalate-based anionic network (responsible for the magnetic properties). Shubnikov-de Haas oscillations confirmed the presence of a Fermi surface even when the transport properties suggested "insulating"-type behavior at very low temperatures.

Spin-spin interactions in porphyrin-based monoverdazyl radical hybrid spin systems.

The spin-spin interactions in a complex consisting of a metalloporphyrin with a verdazyl radical attached at one of the beta positions of the porphyrin ring are investigated. The X-ray crystal structure of the copper porphyrin complex shows that the plane of the verdazyl moiety is oriented such that it is nearly perpendicular to the plane of the porphyrin ring so that weak magnetic interactions between the metal and radical are expected. Consistent with this expectation, magnetic susceptibility and continuous-wave electron paramagnetic resonance (EPR) measurements of the copper (d(9)) and vanadyl (d(1)) versions of the porphyrin show that the metal and radical are weakly antiferromagnetically coupled. Thus, the ground state is a singlet, but the triplet state is thermally accessible above approximately 5 K. Spin-polarized transient EPR measurements of the free-base analogue show that its lowest excited state is a quartet, indicating that the verdazyl radical couples ferromagnetically to the triplet excited state of the porphyrin. Low-temperature transient EPR measurements on the vanadyl porphyrin reveal that the lowest excited quintet state is populated. This implies that the antiferromagnetic coupling between the metal and radical observed in the ground state is switched to a ferromagnetic arrangement in the excited state by the presence of the unpaired electrons in the pi and pi* orbitals of the porphyrin.

Development and Long-Term Follow-Up of an Experimental Model of Myocardial Infarction in Rabbits.

A chronic model of acute myocardial infarction was developed to study the mechanisms involved in adverse postinfarction ventricular remodeling. In an acute myocardial infarction (AMI), the left circumflex coronary artery of New Zealand White rabbits (n = 9) was occluded by ligature for 1 h, followed by reperfusion. A specific care protocol was applied before, during, and after the intervention, and the results were compared with those of a sham operated group (n = 7). After 5 weeks, programmed stimulation and high-resolution mapping were performed on isolated and perfused hearts using the Langendorff technique. The infarct size determined by 2,3,5-triphenyltetrazolium chloride inside of the area at risk (thioflavin-S) was then determined. The area at risk was similar in both groups (54.33% (experimental infarct group) vs. 58.59% (sham group), ns). The infarct size was 73.16% as a percentage of the risk area. The experimental infarct group had a higher inducibility of ventricular arrhythmias (100% vs. 43% in the sham group, p = 0.009). A reproducible chronic experimental model of myocardial infarction is presented in which the extent and characteristics of the lesions enable the study of the vulnerability to develop ventricular arrhythmias because of the remodeling process that occurs during cardiac tissue repair.

Pharmacological modifications of the stretch-induced effects on ventricular fibrillation in perfused rabbit hearts.

Stretch induces modifications in myocardial electrical and mechanical activity. Besides the effects of substances that block the stretch-activated channels, other substances could modulate the effects of stretch through different mechanisms that affect Ca(2+) handling by myocytes. Thirty-six Langendorff-perfused rabbit hearts were used to analyze the effects of the Na(+)/Ca(2+) exchanger blocker KB-R7943, propranolol, and the adenosine A(2) receptor antagonist SCH-58261 on the acceleration of ventricular fibrillation (VF) produced by acute myocardial stretching. VF recordings were obtained with two epicardial multiple electrodes before, during, and after local stretching in four experimental series: control (n = 9), KB-R7943 (1 microM, n = 9), propranolol (1 microM, n = 9), and SCH-58261 (1 microM, n = 9). Both the Na(+)/Ca(2+) exchanger blocker KB-R7943 and propranolol induced a significant reduction (P < 0.001 and P < 0.05, respectively) in the dominant frequency increments produced by stretching with respect to the control and SCH-58261 series (control = 49.9%, SCH-58261 = 52.1%, KB-R7943 = 9.5%, and propranolol = 12.5%). The median of the activation intervals, the functional refractory period, and the wavelength of the activation process during VF decreased significantly under stretch in the control and SCH-58261 series, whereas no significant variations were observed in the propranolol and KB-R7943 series, with the exception of a slight but significant decrease in the median of the fibrillation intervals in the KB-R7943 series. KB-R7943 and propranolol induced a significant reduction in the activation maps complexity increment produced by stretch with respect to the control and SCH-58261 series. In conclusion, the electrophysiological effects responsible for stretch-induced VF acceleration in the rabbit heart are reduced by the Na(+)/Ca(2+) exchanger blocker KB-R7943 and by propranolol but not by the adenosine A(2) receptor antagonist SCH-58261.

Molecular conductors based on the mixed-valence polyoxometalates [SMo12O40]n- (n = 3 and 4) and the organic donors bis(ethylenedithio)tetrathiafulvalene and bis(ethylenedithio)tetraselenafulvalene.

The synthesis, crystal structure, and physical characterization of two new radical salts formed by the organic donors bis(ethylenedithio)tetrathiafulvalene (ET) and bis(ethylenediseleno)tetrathiafulvalene (BETS) and the Keggin polyoxometalate (POM) [SMo(12)O(40)](n-) are reported. The salts isolated are ET(8)[SMo(12)O(40)] x 10 H(2)O (1) (crystal data: (1) monoclinic, space group I2/m with a = 13.9300(10) A, b = 43.467(3) A, c = 13.9929(13) A, beta = 107.979(6) degrees, V = 8058.9(11) A(3), Z = 2) and BETS(8)[SMo(12)O(40)] x 10 H(2)O (2) (crystal data: monoclinic, space group I2/m with a = 14.0878(2) A, b = 44.1010(6) A, c = 14.0930(2) A, beta = 106.739(3) degrees, V = 8384.8 A(3), Z = 2). Both compounds are isostructural and consist of alternating layers of the organic donors (with an alpha or theta(42+40) packing mode) and POM anions. The structural data, as well as the magnetic susceptibility, ESR measurements, and band structure calculations, indicate that the Keggin POMs have been reduced by one electron in 1 and by two electrons in 2, leading to the POMs [SMo(12)O(40)](3-) and [SMo(12)O(40)](4-) in 1 and 2, respectively. At ambient pressure 1 is a classical semiconductor with a room temperature conductivity of about 1 S cm(-1) and an activation energy of about 130 meV. Salt 2 also exhibits an activated behavior although it does not follow a classical semiconducting regime. The conductivity of 2 under applied pressure shows an enhanced conductivity, in agreement with the analysis of the electronic structure, although no metallic behavior is detected below about 10 kbar.

A density functional theory study of the magnetic exchange coupling in dinuclear manganese(II) inverse crown structures.

The magnetic exchange coupling constants between two Mn(II) centers for a set of five inverse crown structures have been investigated by means of a methodology based on broken-symmetry unrestricted density functional theory. These novel and highly unstable compounds present superexchange interactions between two Mn centers, each one with S = 5/2 through anionic "guests" such as oxygen, benzene, or hydrides or through the cationic ring formed by amide ligands and alkali metals (Na, Li). Magnetic exchange couplings calculated at B3LYP/6-31G(d,p) level yield strong antiferromagnetic couplings for compounds linked via an oxygen atom or hydride and very small antiferromagnetic couplings for those linked via a benzene molecule, deprotonated in either 1,4- or 1,3- positions. Analysis of the magnetic orbitals and spin polarization maps provide an understanding of the exchange mechanism between the Mn centers. The dependence of J with respect to 10 different density functional theory potentials employed and the basis set has been analyzed.