Ordered arrays of gold nanoparticles crosslinked by dithioacetate linkers for molecular devices

The final performance of a molecular electronic device is determined by the chemical structure of the molecular wires used in its assembly. Molecular place-exchange was used to incorporate di-thioacetate terminated molecules into ordered arrays of dodecanethiol capped gold nanoparticles. X-Ray photoelectron spectroscopy confirmed successful molecular replacement. Room-temperature molecular conductance of a statistically large number of devices reveals that conductance is enhanced by up to two orders of magnitude for the di-thioacetate terminated molecules. Density functional theory transport calculations were performed on five different configurations of the di-thioacetate molecules between gold electrodes, and the calculated average conductance values are in good agreement with the experimentally-observed conductance trend. Our findings highlight important cooperative effects of bridging neighboring gold nanoparticles and choice of appropriate molecular wires when designing devices for efficient transport

Mechanical Manipulation of Quantum Interference in Single-Molecule Junctions

Mechanosensitive molecular junctions, where conductance is sensitive to an applied stress such as force or displacement, are a class of nanoelectromechanical systems unique for their ability to exploit quantum mechanical phenomena. Most studies so far relied on reconfiguration of the molecule-electrode interface to impart mechanosensitivity, but this approach is limited and, generally, poorly reproducible. Alternatively, devices that exploit conformational flexibility of molecular wires have been recently proposed. The mechanosensitive properties of molecular wires containing the 1,1'-dinaphthyl moiety are presented here. Rotation along the chemical bond between the two naphthyl units is possible, giving rise to two conformers (transoid and cisoid) that have distinctive transport properties. When assembled as single-molecule junctions, it is possible to mechanically trigger the transoid to cisoid transition, resulting in an exquisitely sensitive mechanical switch with high switching ratio (> 102 ). Theoretical modeling shows that charge reconfiguration upon transoid to cisoid transition is responsible for the observed behavior, with generation and subsequent lifting of quantum interference features. These findings expand the experimental toolbox of molecular electronics with a novel chemical structure with outstanding electromechanical properties, further demonstrating the importance of subtle changes in charge delocalization on the transport properties of single-molecule devices

Connectivity-Dependent Conductance of 2,2′-Bipyridine-Based Metal Complexes

The present work provides an insight into the effect of connectivity isomerization of metal-2,2′-bipyridine complexes. For that purpose, two new 2,2′-bipyridine (bpy) ligand systems, 4,4′-bis­(4-(methylthio)­phenyl)-2,2′-bipyridine (Lmeta) and 5,5′-bis­(3,3-dimethyl-2,3-dihydrobenzothiophen-5-yl)-2,2′-bipyridine (Lpara) were synthesized and coordinated to rhenium and manganese to obtain the corresponding complexes MnLmeta(CO)3Br, ReLmeta(CO)3Br, MnLpara(CO)3Br, MoLpara(CO)4 and ReLpara(CO)3Br. The experimental and theoretical results revealed that coordination to the para system, i.e., the metal ion peripheral to the conductance path, gave a slightly increased conductance compared to the free ligand attributed to the reduced highest occupied molecular orbital (HOMO)–least unoccupied molecular orbital (LUMO) gap. The meta-based system formed a destructive quantum interference feature that reduced the conductance of a S···S contacted junction to below 10–5.5 G o, reinforcing the importance of contact group connectivity for molecular wire conductance

The Elephant in the Room: A Cross-Sectional Study on the Stressful Psychological Effects of the COVID-19 Pandemic in Mental Healthcare Workers

Despite extensive research on COVID-19’s impact on healthcare workers, few studies have targeted mental health workers (MHWs) and none have investigated previous traumatic events. We investigated psychological distress in MHWs after the first lockdown in Italy to understand which COVID-19, sociodemographic, and professional variables represented greater effects, and the role of previous trauma. The survey included sociodemographic and professional questions, COVID-19 variables, and the questionnaires Life Events Checklist for DSM-5 (LEC-5), Impact of Event Scale—Revised (IES-R), and Depression Anxiety Stress Scales 21 (DASS-21). On the 271 MHWs who completed the survey (73.1% female; mean age 45.37), we obtained significant effects for contagion fear, experience of patients’ death, increased workload, and worse team relationship during the first wave. Nurses were more affected and showed more post-traumatic stress symptoms, assessed by IES-R, and more depressive, anxiety, and stress symptoms, assessed by DASS-21. The strongest risk factors for distress were greater age, professional role, increased workload, worse team relationship, and separation from family members. Previous experience of severe human suffering and unwanted sexual experiences negatively impacted IES-R and DASS-21 scores. Being a psychiatrist or psychologist/psychotherapist and good team relationships were protective factors. Recent but also previous severe stressful events might represent relevant risk factors for distress, reducing resilience skills. Identifying vulnerable factors and professional categories may help in the development of dedicated measures to prevent emotional burden and support psychological health. Highlights: Psychological distress in mental health workers in the COVID-19 pandemic is more frequent in nurses, who experience more depression, anxiety, and post-traumatic stress symptoms. Previous and recent stressful events are risk factors for distress and should guide intervention strategies

Single-Molecule Conductance Behavior of Molecular Bundles

Controlling the orientation of complex molecules in molecular junctions is crucial to their development into functional devices. To date, this has been achieved through the use of multipodal compounds (i.e., containing more than two anchoring groups), resulting in the formation of tri/tetrapodal compounds. While such compounds have greatly improved orientation control, this comes at the cost of lower surface coverage. In this study, we examine an alternative approach for generating multimodal compounds by binding multiple independent molecular wires together through metal coordination to form a molecular bundle. This was achieved by coordinating iron(II) and cobalt(II) to 5,5′-bis(methylthio)-2,2′-bipyridine (L1) and (methylenebis(4,1-phenylene))bis(1-(5-(methylthio)pyridin-2-yl)methanimine) (L2) to give two monometallic complexes, Fe-1 and Co-1, and two bimetallic helicates, Fe-2 and Co-2. Using XPS, all of the complexes were shown to bind to a gold surface in a fac fashion through three thiomethyl groups. Using single-molecule conductance and DFT calculations, each of the ligands was shown to conduct as an independent wire with no impact from the rest of the complex. These results suggest that this is a useful approach for controlling the geometry of junction formation without altering the conductance behavior of the individual molecular wires

Hyperactive Akt1 Signaling Increases Tumor Progression and DNA Repair in Embryonal Rhabdomyosarcoma RD Line and Confers Susceptibility to Glycolysis and Mevalonate Pathway Inhibitors

In pediatric rhabdomyosarcoma (RMS), elevated Akt signaling is associated with increased malignancy. Here, we report that expression of a constitutively active, myristoylated form of Akt1 (myrAkt1) in human RMS RD cells led to hyperactivation of the mammalian target of rapamycin (mTOR)/70-kDa ribosomal protein S6 kinase (p70S6K) pathway, resulting in the loss of both MyoD and myogenic capacity, and an increase of Ki67 expression due to high cell mitosis. MyrAkt1 signaling increased migratory and invasive cell traits, as detected by wound healing, zymography, and xenograft zebrafish assays, and promoted repair of DNA damage after radiotherapy and doxorubicin treatments, as revealed by nuclear detection of phosphorylated H2A histone family member X (γH2AX) through activation of DNA-dependent protein kinase (DNA-PK). Treatment with synthetic inhibitors of phosphatidylinositol-3-kinase (PI3K) and Akt was sufficient to completely revert the aggressive cell phenotype, while the mTOR inhibitor rapamycin failed to block cell dissemination. Furthermore, we found that pronounced Akt1 signaling increased the susceptibility to cell apoptosis after treatments with 2-deoxy-D-glucose (2-DG) and lovastatin, enzymatic inhibitors of hexokinase, and 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR), especially in combination with radiotherapy and doxorubicin. In conclusion, these data suggest that restriction of glucose metabolism and the mevalonate pathway, in combination with standard therapy, may increase therapy success in RMS tumors characterized by a dysregulated Akt signaling

Not So Innocent After All: Interfacial Chemistry Determines Charge-Transport Efficiency in Single-Molecule Junctions.

Most studies in molecular electronics focus on altering the molecular wire backbone to tune the electrical properties of the whole junction. However, it is often overlooked that the chemical structure of the groups anchoring the molecule to the metallic electrodes influences the electronic structure of the whole system and, therefore, its conductance. We synthesised electron-accepting dithienophosphole oxide derivatives and fabricated their single-molecule junctions. We found that the anchor group has a dramatic effect on charge-transport efficiency: in our case, electron-deficient 4-pyridyl contacts suppress conductance, while electron-rich 4-thioanisole termini promote efficient transport. Our calculations show that this is due to minute changes in charge distribution, probed at the electrode interface. Our findings provide a framework for efficient molecular junction design, especially valuable for compounds with strong electron withdrawing/donating backbones

Redox‐Addressable Single‐Molecule Junctions Incorporating a Persistent Organic Radical**

Integrating radical (open‐shell) species into non‐cryogenic nanodevices is key to unlocking the potential of molecular electronics. While many efforts have been devoted to this issue, in the absence of a chemical/electrochemical potential the open‐shell character is generally lost in contact with the metallic electrodes. Herein, single‐molecule devices incorporating a 6‐oxo‐verdazyl persistent radical have been fabricated using break‐junction techniques. The open‐shell character is retained at room temperature, and electrochemical gating permits in situ reduction to a closed‐shell anionic state in a single‐molecule transistor configuration. Furthermore, electronically driven rectification arises from bias‐dependent alignment of the open‐shell resonances. The integration of radical character, transistor‐like switching, and rectification in a single molecular component paves the way to further studies of the electronic, magnetic, and thermoelectric properties of open‐shell species