Unexpected Reactivity Research Articles

Palladium and Platinum Complexes Containing Diphenyl‐2‐(3‐methyl)indolylphosphine

Syntheses and characterisation of group ten complexes containing the ligand diphenyl‐2‐(3‐methyl)indolylphosphine are presented herein. The complexes [trans‐PdCl2{PPh2(C9H8N)}2] (1), [cis‐PtCl2{PPh2(C9H8N)}2] (2), [trans‐Pd(CH3)Cl{PPh2(C9H8N)}2] (3) and [trans‐Pt(CH3)Cl{PPh2(C9H8N)}2] (4) have all been structurally characterized by X‐ray crystallography. In all cases, the ligands coordinate to the metal centres via the phosphorus donor atom (κ1‐P) and the pendent NH groups on the indolyl rings of the ligand are orientated so that there is some degree of interaction with the metal–chloride bonds. The unexpected reactivity of 4 with Na[B{3,5‐C6H3(CF3)2}4] is also reported. In this case, the product resulting from this reaction was found to be [Pt{3,5‐C6H3(CF3)2}2{PPh2(C9H8N)}2].

Vestibular phenotype-genotype correlation in a cohort of 90 patients with Usher syndrome.

Usher syndrome has been historically categorized into one of three classical types based on the patient phenotype. However, the vestibular phenotype does not infallibly predict which Usher genes are mutated. Conversely, the Usher syndrome genotype is not sufficient to reliably predict vestibular function. Here we present a characterization of the vestibular phenotype of 90 patients with clinical presentation of Usher syndrome (59 females), aged 10.9 to 75.5 years, with genetic variants in eight Usher syndromic genes and expand the description of atypical Usher syndrome. We identified unexpected horizontal semicircular canal reactivity in response to caloric and rotational stimuli in 12.5% (3 of 24) and 41.7% (10 of 24), respectively, of our USH1 cohort. These findings are not consistent with the classical phenotypic definition of vestibular areflexia in USH1. Similarly, 17% (6 of 35) of our cohort with USH2A mutations had saccular dysfunction as evidenced by absent cervical vestibular evoked myogenic potentials in contradiction to the classical assumption of normal vestibular function. The surprising lack of consistent genotypic to vestibular phenotypic findings as well as no clear vestibular phenotypic patterns among atypical USH cases, indicate that even rigorous vestibular phenotyping data will not reliably differentiate the three USH types.

Tuberculosis-Related Uveitis in Patients under Anti-TNF-alpha Therapy: A Case Series

ABSTRACT Tumor necrosis factor inhibitors (anti-TNF) have emerged as an effective treatment in noninfectious uveitis (NIU). Anti-TNF may increase the predisposition to infectious disease as tuberculosis (TB). TB-related uveitis in the context of an uveitogenic concurrent systemic immune-mediated disease under anti-TNF treatment remain a diagnostic challenge, deserving special focus on this rare context. Retrospective chart review of patients on anti-TNF drugs for systemic immune-mediated diseases that developed a multicentric microbiologically confirmed active TB with concurrent intraocular involvement. Three patients were recorded. Screening for TB before starting anti-TNF resulted negative in two patients. The other patient had received anti-tuberculous treatment in the past. All showed a microbiologically confirmed extraocular TB after unexpected atypical reactivation of the uveitis shifting to chronic granulomatous pattern. Specialists should be aware of TB reactivation, even with previous negative screening, when ocular uveitis signs and activity do not match with the expected pattern in a patient on anti-TNF drugs.

Isoprene Reactivity on Water Surfaces from ab initio QM/MM Molecular Dynamics Simulations.

Isoprene is the most abundant volatile organic compound in the atmosphere after methane. While gas-phase processes have been widely studied, the chemistry of isoprene in aqueous environments is less well known. Nevertheless, some experiments have reported unexpected reactivity at the air-water interface. In this work, we have carried out combined quantum-classical molecular dynamics simulations of isoprene at the air-water interface, as well as ab initio and density functional theory calculations on isoprene-water complexes. We report the first calculation of the thermodynamics of adsorption of isoprene at the water surface, examine how hydration influences its electronic properties and reactivity indices, and estimate the OH-initiated oxidation rate. Our study indicates that isoprene interacts with the water surface mainly through H-π bonding. This primary interaction mode produces strong fluctuations of the π and π* bond stabilities, and therefore of isoprene's chemical potential, nucleophilicity and ionization potential, anticipating significant dynamical effects on its reactivity at the air-water interface. Using data from the literature and free energies reported in our work, we have estimated the rate of the OH-initiated oxidation process at the air-water interface (5.0×1012 molecule cm-3 s-1 ) to be about 7 orders of magnitude larger than the corresponding rate in the gas phase (8.2×105 molecule cm-3 s-1 ). Atmospheric implications of this result are discussed.

Classic biomolecules continue to surprise with unexpected reactivity

Classic biomolecules continue to surprise with unexpected reactivity

Diagnostic of electromechanical system by fault-tolerant-control using piezoelectric sensors

Automated systems are fault-prone. The fault diagnosis via sensor and actuator piezoelectric is very important for the stability of the vibration control system and fault-tolerant control technology. Faults in process automation frequently lead to unexpected reactivity and the closure of a controlled plant, and the effects could be damage to technical parts of the plant, employees or the ecosystem. Fault-tolerant control is the combination between diagnostics and control techniques to cleverly handle faults. It provides improved availability and minimized safety risk. This article provides an overview of recent approaches to study and analyze the structure and other fundamental characteristics of an automated system. Thus, the starting point of this study was to investigate the Fault Tolerant Control strategy of an asynchronous machine. Ultimately, the aim is to achieve a disturbance- and/or fault-tolerant control, improving the functional reliability of this system. A decision-making device based on a piezoelectric (PZT) sensor and actuator has been developed to produce an opposite displacement to the vibratory displacement. It ensures the various reconfigurations of the control, adapted to the vibration disturbance acting on the system and modifying its characteristics. This will result in vibration attenuation. Finally, the advantages of this method are analyzed, and the fault diagnosis results with the best identification effect are determined.

Predictive modeling of complex ABO glycan phenotypes by lectin microarrays

AbstractSerological classification of individuals as A, B, O, or AB is a mainstay of blood banking. ABO blood groups or ABH antigens, in addition to other surface glycans, act as unique red blood cell (RBC) signatures and direct immune responses. ABO subgroups present as weakened, mixed field, or unexpected reactivity with serological reagents, but specific designations remain complex. Lectins detect glycan motifs with some recognizing ABH antigens. We evaluated a 45-probe lectin microarray to rapidly analyze ABO blood groups and associated unique glycan signatures within complex biological samples on RBC surface glycoproteins. RBC membrane glycoproteins were prepared from donor RBCs, n = 20 for each blood group. ABO blood group was distinguishable by lectin array, including variations in ABH antigen expression not observed with serology. Principal component analysis highlighted broad ABO blood group clusters with unexpected high and low antigen expression and variations were confirmed with ABH antibody immunoblotting. Using a subset of lectins provided an accurate method to predict an ABO serological phenotype. Lectin microarray highlighted the importance of ABO localization on glycoproteins and glycolipids and pointed to increased glycocalyx complexity associated with the expression of A and B antigens including high mannose and branched polylactosamine. Thus, lectins identified subtle surface ABO blood group glycoprotein density variations not detected by routine serological methods. Transfusion services observe alterations in ABH expression during malignancy, and ABO incompatible solid organ transplantation is not without risk of rejection. The presented methods may identify subtle but clinically significant ABO blood group differences for transfusion and transplantation.

Molybdenum(VI) bis-imido Complexes of Dipyrromethene Ligands.

We report the synthesis of high-valent molybdenum(VI) bis-imido complexes 1-4 with dipyrromethene (DPM) supporting ligands of the general formula (DPMR)Mo(NR')2Cl (R, R' = mesityl (Mes) or tert-butyl (tBu)). The electrochemical and chemical properties of 1-4 reveal unexpected ligand noninnocence and reactivity. 15N NMR spectroscopy is used to assess the electronic properties of the imido ligands in the tert-butyl complexes 1 and 3. Complex 1 is inert toward ligand (halide) exchange with bulky phenolates such as KOMes or amides (e.g., KN(SiMe3)2), whereas the use of the lithium alkyl LiCH2SiMe3 results in a rare nucleophilic β-alkylation of the DPM ligand. While the reductions of the complexes occur at molybdenum, the oxidation is centered at the DPM ligand. Quantum-chemical calculations (complete active space self-consistent field, density functional theory) suggest facile (near-infrared) interligand charge transfer to the imido ligand, which might preclude the isolation of the oxidized complex [1]+ in the experiment.

Heck arylation of acyclic olefins employing arenediazonium salts and chiral N,N ligands: new mechanistic insights from quantum-chemical calculations

A quantum-chemical study based on the Kohn–Sham density functional theory (DFT) has been performed in order to investigate the asymmetric Heck–Matsuda (HM) reactions involving a chiral N,N ligand pyrimidine-oxazoline. The oxidative addition (OA) of arenediazonium cation was analyzed to provide further insights in the unexpected high reactivity of N,N-ligated palladium(0)-based catalysts observed in these HM processes. DFT calculations suggest that the ionogenic nature of metal center promoted by the arenediazonium cation addition increases the electronic reactivity of palladium(0) toward the donor N,N ligand. The concerted and multi-step mechanisms were computed for the OA step, in which the cationic aryl-palladium(II) complex formation was revealed as the thermodynamic driving force for this process. The importance of conformational analyses was highlighted, particularly when an acyclic alkenol olefin is taken as substrate, since its absence could lead to misleading predictions about the selectivity of these HM systems. While the enantioselectivity is controlled by the combination of steric and dispersion interactions between ligand and substrate, the regioselectivity is mostly oriented by the electronic nature of olefinic carbons. DFT predictions on the selectivity were shown to be in quantitative agreement with experimental results.

Counter-Intuitive Gas-Phase Reactivities of [V2 ]+ and [V2 O]+ towards CO2 Reduction: Insight from Electronic Structure Calculations.

[V2O]+ remains “invisible” in the thermal gas‐phase reaction of bare [V2]+ with CO2 giving rise to [V2O2]+; this is because the [V2O]+ intermediate is being consumed more than 230 times faster than it is generated. However, the fleeting existence of [V2O]+ and its involvement in the [V2]+ → [V2O2]+ chemistry are demonstrated by a cross‐over labeling experiment with a 1:1 mixture of C16O2/C18O2, generating the product ions [V2 16O2]+, [V2 16O18O]+, and [V2 18O2]+ in a 1:2:1 ratio. Density functional theory (DFT) calculations help to understand the remarkable and unexpected reactivity differences of [V2]+ versus [V2O]+ towards CO2.

Enantiodivergent Formation of C-P Bonds: Synthesis of P-Chiral Phosphines and Methylphosphonate Oligonucleotides.

Phosphorus Incorporation (PI, abbreviated Π) reagents for the modular, scalable, and stereospecific synthesis of chiral phosphines and methylphosphonate nucleotides are reported. Synthesized from trans-limonene oxide, this reagent class displays an unexpected reactivity profile and enables access to chemical space distinct from that of the Phosphorus-Sulfur Incorporation reagents previously disclosed. Here, the adaptable phosphorus(V) scaffold enables sequential addition of carbon nucleophiles to produce a variety of enantiopure C-P building blocks. Addition of three carbon nucleophiles to Π, followed by stereospecific reduction, affords useful P-chiral phosphines; introduction instead of a single methyl group reveals the first stereospecific synthesis of methylphosphonate oligonucleotide precursors. While both Π enantiomers are available, only one isomer is required-the order of nucleophile addition controls the absolute stereochemistry of the final product through a unique enantiodivergent design.

Unconventional Reactivity of Ethynylbenziodoxolone Reagents and Thiols: Scope and Mechanism.

1,2-Dithio-1-alkenes are biologically active compounds widely implemented throughout organic synthesis, functional materials, coordination chemistry, and pharmaceuticals. Traditional methods for accessing 1,2-dithio-1-alkenes often demand transition metal catalysts, specialized or air-sensitive ligands, high temperatures, and disulfides (R2 S2 ). Herein, a general and efficient strategy utilizing ethynylbenziodoxolone (EBX) reagents and thiols is presented that results in the formation of 1,2-dithio-1-alkenes with excellent regioselectivity and stereoselectivity through unprecedented reactivity between the EBX and the thiol. This operationally simple procedure utilizes mild conditions, which result in a broad substrate scope and high functional-group tolerance. The observed unexpected reactivity has been rationalized through both experimental results and DFT calculations.

Low-Level Fusion of Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Data Sets for the Characterization of Nitrogen and Sulfur Compounds in Vacuum Gas Oils.

A total of 18 vacuum gas oils have been analyzed by Fourier transform ion cyclotron resonance mass spectrometry considering six replicates in three different ionization modes (electrospray ionization (ESI)(+), ESI(-), and atmospheric pressure photoionization (APPI)(+)) to characterize the nitrogen and sulfur compounds contained in these samples. Classical data analysis has been first performed on generated data sets using double bond equivalents (DBE) versus number of carbon atoms (#C) plots in order to observe similarities and differences within the nitrogen and sulfur-containing molecular classes from samples produced by different industrial processes. In a second step, three-way arrays have been generated for each ionization mode considering three dimensions: DBE related to aromaticity, number of carbon atoms related to alkylation, and sample. These three-way arrays have then be concatenated using low-level data fusion strategy to obtain a new tensor with three new modes: aromaticity, alkylation, and sample. The PARAFAC method has then been applied for the first time to this three-way data structure. A two components decomposition has allowed us to highlight unique samples with unexpected reactivity behaviors throughout hydrotreatment. The obtained loadings led to the identification of the variables responsible for this specific character. This original strategy has provided a fast visualization tool able to highlight simultaneously the impact of the three ionization modes in order to explain the differences between the samples and compare them.

6-Deoxy-6-fluoro galactofuranosides: regioselective glycosylation, unexpected reactivity, and anti-leishmanial activity.

Selective glycosylation of the C-6 fluorinated galactofuranosyl acceptor 2 was studied with four galactofuranosyl donors. It was highlighted that this electron-withdrawing atom strongly impacted the behavior of the acceptor, thus leading to unprecedented glycosylation pathways. Competition between expected glycosylation of 2, ring expansion of this acceptor and furanosylation, and intermolecular aglycon transfer was observed. Further investigation of the fluorinated synthetic compounds showed that the presence of fluorine atom contributed to increase the inhibition of the growth of Leishmania tarentolae, a non-pathogenic strain of Leishmania.

A DFT study on the oxidation of cyclotrisilene by nitrous oxide: the σ- and π-bonds reactivity

The chemistry of heteroatom analogues of cyclopropane derivatives has been receiving considerable interest because of their unexpected reactivities. Herein, the density functional theory (DFT) method was applied to understand reactivity and selectivity of sigma (σ) and pi (π) bonds in methyl and aryl (2,4,6-iPr3C6H2)-substituted cyclotrisilenes, as silicon analogue of cyclopropane, for the reaction with nitrous oxide. The DFT calculations at the APFD/def2-TZVPP level of theory show that three types of isomers with Si3O subunit can be considered as potential products for methylated system. The further DFT calculations on the proposed reactions favor the π-bond reactivity of the methyl-substituted cyclotrisilene to yield a structure that adopted the cyclic planar-trans geometry with the lower energy barrier and considerably high exergonic nature. Moreover, π-bond reactivity of the cyclotrisilene with aryl group promotes the formation of the folded isomer of the planar-trans structure with only 0.3 kcal mol−1 energy gap at the B3LYP-D3/6-31G(d,p) level of theory. The theoretical results provide a crucial guide for the reaction to be tackled experimentally.

Globally stabilized bent carbon-carbon triple bond by hydrogen-free inorganic-metallic scaffolding Al4F6.

For over 100 years, known bent C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C compounds have been limited to those with organic (I) and all-carbon (II) scaffoldings. Here, we computationally report a novel type (III) of bent CC compound, i.e., C2Al4F6-01, which is the energetically global minimum isomer and bears an inorganic–metallic scaffolding and unexpected click reactivity.

Unexpected reactivity of a PONNOP 'expanded pincer' ligand.

We report the synthesis, characterization and coordination chemistry of a new naphthyridine-derived phosphinite PONNOP expanded pincer ligand. As envisioned, the dinucleating ligand readily binds two copper(i) centers in close proximity, but undergoes an unexpected rearrangement in the presence of nickel(ii) salts to form an interesting PONNP pincer platform.

Unexpected reactivity of ferrocenyl-iminoboronates: Breaking ortho-imine bonds by oxidation in the presence of non-aqueous sodium chloride

The boronic acid moiety in the proximity of electron-donating structures in ((ferrocenylimino)methyl)phenylboronic acid 1 significantly improves the reactivity of the molecule. The ortho regioisomer 1a exhibits a two-fold higher affinity to NaCl compared to its meta1b and para1c isomers, respectively. Moreover, the double imine bond in 1a was broken by the interaction with NaCl in methanol upon activation by electrochemical oxidation.

Wenjun Tang.

"My greatest achievement has been the development of a series of chiral phosphorus ligands that are useful in asymmetric catalysis. The most exciting thing about my research is the unexpected reactivity and selectivity observed with a newly designed catalyst …" Find out more about Wenjun Tang in his Author Profile.

Facial Reactivity and Attentional Processing of Facial Expressions and Gaze Direction

Abstract. Patterns of facial reactivity and attentional allocation to emotional facial expressions, and how these are moderated by gaze direction, are not clearly established. Among a sample of undergraduate university students, aged between 17 and 22 years (76% female), corrugator and zygomatic reactivity, as measured by facial electromyography, and attention allocation, as measured by the startle reflex and startle-elicited N100, was examined while viewing happy, neutral, angry and fearful facial expressions, which were presented at either 0- or 30-degree gaze. Results indicated typically observed facial mimicry to happy faces but, unexpectedly, “smiling” facial responses to fearful, and to a lesser extent, angry faces. This facial reactivity was not influenced by gaze direction. Furthermore, emotional facial expressions did not elicit increased attentional allocation. Likewise, matched facial expressions did not elicit increased attentional allocation. Rather, happy and fearful faces with direct (0°) gaze elicited increased controlled attentional allocation, and averted (30°) gaze faces, regardless of emotional expression, elicited preferential, early cortical processing. These findings suggest typical facial mimicry to happy faces, but unexpected facial reactivity to angry and fearful faces, perhaps due to an attempt to regulate social bonds during threat perception. Findings also suggest a divergence in controlled versus preferential, early cortical attentional processing for direct compared to averted gaze faces. These findings relate to young, mostly female, adults attending university. The experiment should be repeated with a larger sample drawn from the general community, with a broader age range and gender balance, and with a stimulus set with validated subjective valence and arousal ratings. This can reduce Type II error and establish normative patterns of facial reactivity and attentional processing of emotional facial expressions with different gaze directions.