Tracking nuclear motion in single-molecule magnets using femtosecond X-ray absorption spectroscopy.

The development of new data storage solutions is crucial for emerging digital technologies. Recently, all-optical magnetic switching has been achieved in dielectrics, proving to be faster than traditional methods. Despite this, single-molecule magnets (SMMs), which are an important class of magnetic materials due to their nanometre size, remain underexplored for ultrafast photomagnetic switching. Herein, we report femtosecond time-resolved K-edge X-ray absorption spectroscopy (TR-XAS) on a Mn(III)-based trinuclear SMM. Exploiting the elemental specificity of XAS, we directly track nuclear dynamics around the metal ions and show that the ultrafast dynamics upon excitation of a crystal-field transition are dominated by a magnetically active Jahn-Teller mode. Our results, supported by simulations, reveal minute bond length changes from 0.01 to 0.05 Å demonstrating the sensitivity of the method. These geometrical changes are discussed in terms of magneto-structural relationships and consequently our results illustrate the importance of TR-XAS for the emerging area of ultrafast molecular magnetism.

A bis-calix[4]arene-supported [CuII16] cage.

Reaction of 2,2'-bis-p-tBu-calix[4]arene (H8L) with Cu(NO3)2·3H2O and N-methyldiethanolamine (Me-deaH2) in a basic dmf/MeOH mixture affords [CuII16(L)2(Me-dea)4(µ4-NO3)2(µ-OH)4(dmf)3.5(MeOH)0.5(H2O)2](H6L)·16dmf·4H2O (4), following slow evaporation of the mother liquor. The central core of the metallic skeleton describes a tetracapped square prism, [Cu12], in which the four capping metal ions are the CuII ions housed in the calix[4]arene polyphenolic pockets. The [CuII8] square prism is held together "internally" by a combination of hydroxide and nitrate anions, with the N-methyldiethanolamine co-ligands forming dimeric [CuII2] units which edge-cap above and below the upper and lower square faces of the prism. Charge balance is maintained through the presence of one doubly deprotonated H6L2- ligand per [Cu16] cluster. Magnetic susceptibility measurements reveal the predominance of strong antiferromagnetic exchange interactions and an S = 1 ground state, while EPR is consistent with a large zero-field splitting.

An [FeIII8] molecular oxyhydroxide.

An [FeIII8] hexagonal bipyramid displays antiferromagnetic exchange between the two capping tetrahedral ions and the six ring octahedral ions resulting in a spin ground state of S = 10.

Photoinduced Jahn-Teller switch in Mn(III) terpyridine complexes.

Ultrafast transient absorption spectra were recorded for [Mn(terpy)X3], where X = Cl, F, and N3, to explore photoinduced switching from axial to equatorial Jahn-Teller (JT) distortion. Strong oscillations were observed in the transients, corresponding to a wavepacket on the excited-state potential energy surface with oscillation frequency around 115 cm-1 for all three complexes. Multireference quantum chemistry calculations indicate that the reaction coordinate is a pincer-like motion of the terpyridine ligand arising from bond length changes in the excited state due to the JT switch. We observed long dephasing times of the wavepacket, with times of 620 fs for [Mn(terpy)Cl3], 450 fs for [Mn(terpy)F3], and 370 fs for [Mn(terpy)(N3)3]. The dephasing time of these coherences decreases with an increasing number of vibrational modes at lower energy than the mode dominating the reaction coordinate, suggesting they act as an effective bath to dissipate the excess energy obtained from photoexcitation.

Correction: The coordination chemistry of p-tert-butylcalix[4]arene with paramagnetic transition and lanthanide metal ions: an Edinburgh Perspective.

Correction for 'The coordination chemistry of p-tert-butylcalix[4]arene with paramagnetic transition and lanthanide metal ions: an Edinburgh Perspective' by Lucinda R. B. Wilson et al., Dalton Trans., 2022, DOI: 10.1039/d2dt00152g.

The coordination chemistry of p-tert-butylcalix[4]arene with paramagnetic transition and lanthanide metal ions: an Edinburgh Perspective.

The calix[4]arene scaffold is an extremely versatile supramolecular platform that has found widespread use across many research areas due to its synthetic versatility, controllable conformation, and the presence of cavities or clefts for tailorable guest binding. The tetraphenolic lower-rim of p-tert-butylcalix[4]arene in the cone conformation is ideal for binding a variety of paramagnetic transition and lanthanide metals, and in this Perspective we review our endeavours in using such complexes as metalloligands in the synthesis of polymetallic clusters that have fascinating structural and magnetic properties. By varying reactants, stoichiometries and reaction or crystallisation conditions it is possible to access an incredible range of clusters, all of which show consistent trends in coordination preferences and assembly behaviours. p-tert-Butylcalix[4]arene has already given so much, yet it is likely that this remarkable parent calixarene will continue to surprise chemists and deliver even more in terms of novelty and function.

An [FeIII30] molecular metal oxide.

Dissolution of FeBr3 in a mixture of acetonitrile and 3,4-lutidine in the presence of an amine results in the formation of an [Fe30] molecular metal oxide containing alternating layers of tetrahedral and octahedral FeIII ions. Mass spectrometry suggests the cluster is formed quickly and remains stable in solution, while magnetic measurements and DFT calculations reveal competing antiferromagnetic exchange interactions.

Oxidation state variation in bis-calix[4]arene supported decametallic Mn clusters.

The reaction of MnCl2·4H2O, H8L (2,2'-bis-p-tBu-calix[4]arene) and NEt3 in a dmf/MeOH solvent mixture results in the formation of a mixed valent decametallic cluster of formula [MnII6MnIII4(L)2(µ3-OH)4(µ-OH)4(MeOH)4(dmf)4(MeCN)2]·MeCN (3). Complex 3 crystallises in the monoclinic space group P21/n with the asymmetric unit comprising half of the compound. Structure solution reveals that the bis-calix[4]arene ligands are arranged such that one TBC[4] moiety in each has undergone inversion in order to accommodate a [MnIII4MnII6] metallic skeleton that describes three vertex-sharing [MnIII2MnII2] butterflies. The structure is closely related to the species [MnIII6MnII4(L)2(µ3-O)2(µ3-OH)2(µ-OMe)4(H2O)4(dmf)8]·4dmf (4), the major difference being the oxidation level of the Mn ions in the core of the compound. DFT calculations on the full structures reveal that replacing the MnIII ions in 4 for MnII ions in 3 results in a significant decrease in the magnitude of some antiferromagnetic exchange contributions, a switch from ferromagnetic to antiferromagnetic in others, and the loss of significant spin frustration.

Patients With Definite and Inconclusive Evidence of Reflux According to Lyon Consensus Display Similar Motility and Esophagogastric Junction Characteristics.

BACKGROUND/AIMS: The role of esophageal high-resolution manometry (HRM) within Lyon consensus phenotypes, especially patients with inconclusive gastroesophageal reflux disease (GERD) evidence, has not been fully investigated. In this multicenter, observational study we aim to compare HRM parameters in patients with GERD stratified according to the Lyon consensus. METHODS: Clinical and endoscopic data, HRM and multichannel intraluminal impedance-pH (MII-pH) studies performed off proton pump inhibitor therapy in patients with esophageal GERD symptoms were reviewed. Lyon consensus criteria identified pathological GERD, reflux hypersensitivity, functional heartburn, and inconclusive GERD. Patients, with inconclusive GERD were further subdivided into 2 groups based on total reflux numbers (≤ 80 or > 80 reflux episodes) during the MII-pH recording time. RESULTS: A total of 264 patients formed the study cohort. Pathological GERD and inconclusive GERD patients were associated with higher numbers of reflux episodes, lower mean nocturnal baseline impedance (MNBI) values, and a higher proportion of patients with pathologic MNBI compared to functional heartburn (P < 0.05 for each comparison). On multivariate analysis, pathological GERD and inconclusive GERD patients, both with ≤ 80 or > 80 reflux episodes, were significantly associated with pathologic esophagogastric junction contractile integral values and with presence of hiatus hernia (type 2/3 esophagogastric junction). Patients with inconclusive GERD and > 80 reflux episodes were significantly associated with fragmented peristalsis and ineffective esophageal motility whilst inconclusive GERD with ≤ 80 reflux episodes were significantly associated with fragmented peristalsis. CONCLUSION: Esophageal motor parameters on HRM are similar between pathologic and inconclusive GERD according to the Lyon consensus.

A [Mn18] wheel-of-wheels.

A [Mn18] wheel of wheels is obtained from the reaction of MnBr2·4H2O and LH3 in MeOH. The metallic skeleton reveals two asymmetric [MnIII6MnII2] square wheels connected into a larger wheel via two MnII ions. Magnetic susceptibility and magnetisation data reveal competing exchange interactions, supported by computational studies.

Kinetic selection of Pd4L2 metallocyclic and Pd6L3 trigonal prismatic assemblies.

The self-assembly of Pd4L2 metallocylcic and Pd6L3 trigonal prismatic assemblies are described. The selection of one species over the other has been achieved by careful choice of ancilliary ligands, which switch the dynamics of the Pd-pyridine bonds such that a highly unusual and distorted smaller assembly can be kinetically trapped en route to the more energetically favourable larger species. Both assemblies provide promise as easy to access multicavity reaction vessels.

Magneto-structural studies of an unusual [MnIIIMnIIGdIII(OR)4]4- partial cubane from 2,2'-bis-p-tBu-calix[4]arene.

Reaction of 2,2'-bis-p-tBu-calix[4]arene (H8L) with MnCl2·4H2O, GdCl3·6H2O and 2,6-pyridinedimethanol (H2pdm) affords [MnIIIMnIIGdIII(H3L)(pdmH)(pdm)(MeOH)2(dmf)]·3MeCN·dmf (3·3MeCN·dmf) upon vapour diffusion of MeCN into the basic dmf/MeOH mother liquor. 3 crystallises in the tetragonal space group P41212 with the asymmetric unit comprising the entire cluster. The highly unusual core contains a triangular arrangement of MnIIIMnIIGdIII ions housed within a [MnIIIMnIIGdIII(OR)4]4- partial cubane. Magnetic susceptibility and magnetisation data reveal best fit parameters JMn(II)-Mn(III) = +0.415 cm-1, JMn(III)-Gd(III) = +0.221 cm-1, JMn(II)-Gd(III) = -0.258 cm-1 and DMn(III) = -4.139 cm-1. Theoretically derived magnetic exchange interactions, anisotropy parameters, and magneto-structural correlations for 3 are in excellent agreement with the experimental data.

With complements of the ligands: an unusual S-shaped [Mn7]2 assembly from tethered calixarenes.

The reaction between MnCl2·4H2O, 2,2'-bis-p-tBu-calix[4]arene (H8L1) and 2-(hydroxymethyl)pyridine (hmpH) in a basic dmf/MeOH solution results in the formation of the complex [MnIII10MnII4(L1)3(hmp)4(µ3-O)4(µ3-OH)2(MeOH)4(dmf)6](dmf)4 (6) upon vapour diffusion of petroleum ether into the mother liquor. The crystals are in the monoclinic space group C2/c, with the asymmetric unit (ASU) comprising one half of the molecule. The structure describes a large S-shaped cluster (∼40 Å top to tail) where the unusual syn and anti conformations of the calixarene ligands results in two binding pockets each containing a [MnIII5MnII2] moiety comprised of two perpendicular, vertex-sharing [Mn4] butterflies. One butterfly possesses a [MnIII4O4] core and the second a [MnIII2MnII2O3] unit with the MnII ions in the central body positions. Magnetic susceptibility and magnetisation measurements reveal weak exchange interactions between the metal centres.

High-resolution Manometry Determinants of Refractoriness of Reflux Symptoms to Proton Pump Inhibitor Therapy.

Background/Aims: Impaired esophageal motility and disrupted esophagogastric junction (EGJ) on high-resolution manometry (HRM) have been associated with increased reflux severity in gastroesophageal reflux disease (GERD) patients. However, there are limited data evaluating HRM parameters in proton pump inhibitors (PPI) non-responders. Methods: Clinical and endoscopic data, HRM and multichannel intraluminal impedance-pH studies performed of PPI therapy in patients with typical GERD symptoms were reviewed from 3 international centers. Frequency of GERD symptoms was assessed on and off PPI therapy in both non-responders (< 50% symptom improvement on PPI therapy) and responders. Rome IV definitions identified non-erosive reflux disease, reflux hypersensitivity, and functional heartburn. Univariate and multivariate analyses were performed to determine predictors of non-response. Results: Of 204 patients, 105 were PPI non-responders and 99 were responders. Non-responders showed higher EGJ contractile integral values, and a lower frequency of type II and III EGJ morphology (P ≤ 0.03 for each comparison). Esophageal body diagnoses on HRM (fragmented peristalsis, ineffective esophageal motility, or absent peristalsis) did not predict non-response. On multivariate analysis, non-pathological acid exposure time (OR, 2.5; 95% CI, 1.2-5.0; P < 0.001), normal mean nocturnal baseline impedance values (OR, 2.7-2.4; 95% CI, 1.0-6.1; P < 0.05), normal EGJ contractile integral values (OR, 3; 95% CI, 1.3-7.4; P = 0.012), and presence of type I EGJ morphology (OR, 1.9; 95% CI, 1.0-3.4; P = 0.044) were associated with an unfavorable response to PPIs. Conclusions: Intact EGJ metrics on HRM complement normal reflux burden in predicting non-response to PPI therapy. HRM has value in the evaluation of PPI non-responders.

Mean Nocturnal Baseline Impedance Correlates With Symptom Outcome When Acid Exposure Time Is Inconclusive on Esophageal Reflux Monitoring.

BACKGROUND & AIMS: Abnormal acid exposure time (AET) is associated with good outcomes of symptoms from antireflux therapy. Low esophageal mean nocturnal baseline impedance (MNBI) is an additional marker of reflux disease. We aimed to evaluate the value of MNBI when analysis of AET produces borderline or inconclusive results. METHODS: We studied a retrospective cohort of 371 patients (mean age, 54.5 ± 0.7 y; 60.0% female) who had persistent reflux symptoms after treatment and underwent ambulatory pH-impedance monitoring off antisecretory therapy at 1 tertiary center in Europe or 1 in the United States. Total AET was determined from pH impedance studies (pathologic, >6%; physiologic, <4%; borderline or inconclusive, 4%-6%). Baseline impedance values were calculated at the 5-cm impedance channel at 3 nocturnal 10-minute periods and averaged to yield MNBI (abnormal, <2292 ohms). The primary outcome was response to antireflux therapy, defined as global symptom improvement of 50% or greater on patients' answers on standardized visual analog scales. RESULTS: Among the 371 patients, 107 (28.8%) had pathologic AET and 234 (63.1%) had abnormal MNBI. Low MNBI was concordant in 99.1% of patients with pathologic AET, in 91.2% with borderline AET, and in 33.7% with physiologic AET. During 38.7 ± 0.8 months of follow-up evaluation, 43.0% of patients had improved symptoms with medical therapy and 76.2% had improved symptoms with surgical antireflux therapy (P < .0001). When MNBI was low, response to medical therapy did not differ significantly between patients with borderline AET and patients with pathologic AET (P = .44), but did differ significantly when each group was compared with patients with physiologic AET, regardless of whether MNBI was normal or low (P < .0001 for each comparison). CONCLUSIONS: When low, MNBI identifies patients with pathologic and borderline AET who respond to antireflux therapy. MNBI analysis complements AET in defining esophageal reflux burden. MNBI correlates with response of symptoms to antireflux therapy.

Correlation between reflux burden, peristaltic function, and mucosal integrity in GERD patients.

BACKGROUND: Mean nocturnal baseline impedance (MNBI) augments the diagnostic yield of multichannel intraluminal impedance-pH (MII-pH) monitoring. While acid exposure time (AET) correlates with MNBI, it remains unclear whether esophageal motility affects MNBI values. The present study was aimed at evaluating the respective roles of esophageal motor function and AET on MNBI. METHODS: High-resolution manometry (HRM) studies and ambulatory 24-hour MII-pH monitoring tracings were retrospectively analyzed from consecutive endoscopy-negative GERD patients with typical symptoms responsive to previous acid-suppressive therapy from three tertiary care centers. Univariate and multivariate analyses were performed to determine predictors of pathologic MNBI values at 3 cm and 5 cm above the lower esophageal sphincter (LES). KEY RESULTS: Patients with pathological AET displayed lower MNBI values at 3 cm and 5 cm (P < .01) compared to patients with non-pathological AET. Similarly, significantly lower MNBI values were also noted at both sites with type 3 EGJ compared to type 1 EGJ (P ≤ .02 for each comparison), and with absent contractility compared to normal peristalsis (P ≤ .02 for each comparison). On multivariate analysis, the presence of type 2 or 3 EGJ and absent contractility were associated with a significantly higher probability of pathological MNBI values at 3 cm and 5 cm above the LES. CONCLUSIONS AND INFERENCES: Disruption of the EGJ and absent contractility on HRM are both associated with lower MNBI values. HRM findings complement reflux testing using MII-pH monitoring.

Updates in the field of non-esophageal gastroesophageal reflux disorder.

Introduction: Gastroesophageal reflux disease (GERD) is one of the most prevalent conditions in Western Countries, normally presenting with heartburn and regurgitation. Extra-esophageal (EE) GERD manifestations, such as asthma, laryngitis, chronic cough and dental erosion, represent the most challenging aspects from diagnostic and therapeutic points of view because of their multifactorial pathogenesis and low response to proton pump inhibitors (PPIs). In fact, in the case of EE, other causes must by preventively excluded, but instrumental methods, such as upper gastrointestinal endoscopy and laryngoscopy, have low specificity and sensitivity as diagnostic tools. In the absence of alarm signs and symptoms, empirical therapy with a double-dose of PPIs is recommended as a first diagnostic approach. Subsequently, impedance-pH monitoring could help to define whether the symptoms are GERD-related. Areas covered: This article reviews the current literature regarding established and proposed EE-GERD, reporting on all available options for its correct diagnosis and therapeutic management. Expert opinion: MII-pH could help to identify a hidden GERD that causes EE. Unfortunately, standard MII-pH analysis results are often unable to define this association. New parameters such as the mean nocturnal baseline impedance and post-reflux swallow-induced peristaltic wave index may have an improved diagnostic yield, but prospective studies using impedance-pH are needed.

Advancements in the use of manometry and impedance testing for esophageal functional disorders.

INTRODUCTION: The utilization of high-resolution manometry (HRM) has enhanced our understanding and assessment of esophageal motor disorders. Moreover, the combination of impedance technology with HRM (HRIM) has further improved our knowledge of esophageal physiology and the clinical evaluation of dysmotility, thanks to the addition of accurate measurement of bolus transit. Areas covered. This paper provides an overview of current knowledge in the use of HRIM for the study of esophageal functional disorders by reporting mainly the results of many publications and several systematic reviews in this field. Expert opinion. HRIM has represented a relevant improvement in the assessment of esophageal motility and has required the development of new metrics, such as the esophageal impedance integral ratio, the bolus flow time, the nadir impedance pressure and the impedance bolus height, which increase the evaluation of esophageal bolus transit. An extension of impedance is represented by functional lumen imaging probe (FLIP), which determines the biophysical properties and the distensibility of the esophagus and permits to detect contractility patterns not seen on HRM alone. We eagerly wait for a new and fruitful iteration of the Chicago Classification, now in version 3.0, which can cover the ongoing clinical experience of HRIM.

A safety review of proton pump inhibitors to treat acid-related digestive diseases.

INTRODUCTION: Proton pump inhibitors (PPIs) have become the first choice medical treatment of acid-related disease and, as with any pharmacological agent, they have been reported to be associated with some adverse events mainly linked to their chronic use. The most important postulated harms are represented by serum electrolyte alterations, vitamin B12 and iron deficiency, gastric tumors, enteric infections, spontaneous bacterial peritonitis, pneumonia, ischemic heart attacks, bone fractures, chronic kidney disease, dementia, and Alzheimer disease. Specific pathophysiological mechanisms have been identified for some of them and not for other manifestations. AREAS COVERED: However, studies on PPIs safety have generally important limitations because of their frequent retrospective design and other methodological drawbacks, such as patients' selection and residual confounders. EXPERT OPINION: Obviously, in the vast majority of the cases, adverse drug reactions cannot be assessed by means of randomized clinical trials due to the high costs, ethical reasons, and difficulties in performing prospective observational studies. So far, assessment of retrospective observational investigations remains the only method to evaluate adverse events with any drug in general and, although the weaknesses of these studies are evident, the awareness of the reported associations with the medications analyzed is important for physicians in order to manage adequately their individual patients.

The remarkable influence of N,O-ligands in the assembly of a bis-calix[4]arene-supported [MnMnMn] cluster.

Calix[4]arenes are versatile ligands, capable of supporting the formation of a wide variety of polymetallic clusters comprising 3d, 4f or 3d-4f metal ions. Calixarene-based metal ion fragments act as both bridging and structure capping moieties in these systems, and this behaviour is systematically extended upon moving to bis-calix[4]arene, a relatively new ligand in which two calix[4]arenes are tethered at the methylene bridge position. N,O-Ligands greatly influence cluster formation with bis-calix[4]arene, affording a remarkable mixed-valence [MnMnMn] cluster that displays coordination chemistry typical of each ligand type, but also new structure capping behaviour for the latter.