Using Molecular Design to Influence Intermolecular Interactions

This thesis describes the impact of molecular design on intermolecular interactions. Chapter 2 explores tuning the properties of contorted hexabenzocoronene (HBC) derivatives to improve photovoltaic performance. First, the interaction between contorted HBC derivatives with varying degrees of "bowl" character and fullerenes are explored in solution. Association constants were determined by fluorescence quenching experiments with fullerenes C70, C60, and Phenyl-C61-butyric acid methyl ester (PCBM). NMR titration experiments mimic fluorescence quenching results that suggest that association in solution increases with shape-complementarity between donor and acceptor. Second, efforts towards the synthesis of azulene HBC, an HBC derivative with red-shifted absorption, are discussed. Calculations of this target molecule and a selected intermediate are compared to those of the parent contorted HBC. Finally, an azulene HBC synthetic intermediate is explored as a potential sensor. Chapter 3 presents a study of the single molecule conductance of cobalt chalcogenide clusters. The synthesis of cobalt chalcogenide clusters decorated with a variety of conjugated molecular connectors was developed. Single molecule conductance of these clusters was shown to take place through the molecular connectors, and was tunable by controlling the substitution of the connectors. The tunability of cluster conductance that was demonstrated in the single molecule experiments was shown to extend to thin film experiments in chapter 4. Preliminary investigation into the mechanism of conductance of these films is discussed. In chapter 5, a family of nickel telluride clusters with a variety of ligands is synthesized. The X-ray crystal structures of these clusters are analyzed and insight into how ligand sterics and electronics influence the final cluster structure is discussed

Onset of occupational hand eczema among healthcare workers during the SARS‐CoV‐2 pandemic: Comparing a single surgical site with a COVID‐19 intensive care unit

Background As a result of the COVID‐19 outbreak, hygiene regulations have been revised and hand sanitation has been intensified. Objective To investigate the onset of hand eczema during the COVID‐19 pandemic in healthcare workers (HCWs) directly involved in intensive care of COVID‐19 patients and HCWs without direct contact with COVID‐19 patients. Hereby, we aim at increasing awareness about occupational hand eczema and preventive measures that can be adopted. Method A survey was distributed amongst 114 HCWs at a single surgical centre and at a COVID‐19 intensive care unit of the university hospital Ludwig Maximilian University Munich, Germany. Participants were questioned about the daily frequency of hand hygiene prior to and during the pandemic. Participants self‐reported the onset of hand eczema and associated symptoms. Results Our study revealed a significant increase in hand washing, disinfection, and use of hand cream across all participants (P‐value <.001), regardless of having direct contact with COVID‐19 patients. A high prevalence of symptoms associated with acute hand dermatitis of 90.4% was found across all HCWs, whereas hand eczema itself was underreported (14.9%). Conclusion The increase in hand sanitation during the COVID‐19 pandemic impairs the skin of the hands across all HCWs, independent of direct intensive care of affected patients

Nanoscale atoms in solid-state chemistry

Reports Conventional binary solid-state compounds, A x B y , are infinite, crystalline arrays of atoms A and B. Here we describe analogous binary solids in which the &quot;atomic&quot; building blocks are pseudo-spherical molecular clusters rather than simply atoms [for reviews on molecular clusters, see (1-3)]. We prepare these new solids by simply combining independently synthesized molecular clusters (4-6). The internal structures of the constituent clusters remain unchanged, but charge is transferred between them, forming ionic solids analogous to NaCl. We report three new solids: [ [C 60 ]. The former two assemble into a superatomic relative of the CdI 2 structure type, and the latter forms a simple rock-salt crystal. Despite their ready availability, molecular clusters have been used infrequently as electronic materials. Noteworthy examples of success in this area are the organic-inorganic hybrid materials reported by Batail and Mitzi (7-11). Nanocrystals have been assembled into striking superlattices (12-14), but they do not have discrete structural, electronic and magnetic properties and cannot be regarded as genuine artificial atoms. Here, we combine independently prepared electronically and structurally complementary molecular cluster building blocks to form atomically precise binary solid-state compounds. When the building blocks are atoms (ions), binary solids assemble into simple crystalline arrays such as the rock-salt and CdI 2 lattices [for an authoritative text on solid-state inorganic chemistry, see (15)]. We show that when similarlysized clusters combine the same lattice results, albeit at the dramatically increased length scale of nanometers rather than Angstroms. The constituent clusters interact to produce collective properties such as electrically conducting networks and magnetic ordering. Our strategy was to use constituent molecular clusters that have the same, roughly spherical, shape but very different electronic properties in order to encourage reaction and subsequent structural association. By analogy to &quot;atomic&quot; solid-state chemistry, we reasoned that the in situ transfer of charge would produce ions (or the equivalent) that could then form an ordered solid. Thus, we sought cluster pairs in which one cluster is relatively electron-poor and the other is relatively electron-rich. C 60 carbon clusters are good electron acceptors (16). The electrically neutral metal chalcogenide clusters Co 6 Se 8 (PEt 3 ) We combined 1 and two equivalents of C 60 in toluene and obtained black crystals after ~12 hours. Single-crystal x-ray diffraction (SCXRD) revealed that this solid is a 1:2 stoichiometric combination of 1 and C 60 (1•2C 60 ) Nanoscale Atoms in Solid-State Chemistry We measured how much charge was transferred between the components in the solid-state material using Raman spectroscopy. The A 2 g pentagonal pinch mode of C 60 (1468 cm -1 for pristine C 60 ) shifts to lower energy by 6 cm -1 per electron transferred to C 60 independent of the dopant or the crystal structure [see, for example, (19); for a review on discrete fulleride anions, see •− (20). Cluster 1 has four weak transitions between 350 and 700 nm that were observed in 1•2C 60 but not in 2•2C 60 . We can compare these solids to traditional simple M 2+ X 1-2 solids. The CdI 2 structure type (21) is formed by a hexagonally close-packed array of monoanions with half of the octahedral interstitial sites occupied by dications. The cations are ordered such that along the crystallographic c-direction the cation layers are alternatively empty and fully occupied, and the layers are held together by van der Waals bonding between anions of neighboring layers. The structures of compounds 1•2C 60 and 2•2C 60 can be appreciated in these same terms. Wireframe representation of 1•2C 60 are shown i

Evidence-Based Guidelines for Cardiovascular Disease Prevention in Women

Significant advances in our knowledge about interventions to prevent cardiovascular disease (CVD) have occurred since publication of the first female-specific recommendations for preventive cardiology in 1999.1 Despite research-based gains in the treatment of CVD, it remains the leading killer of women in the United States and in most developed areas of the world.2–3 In the United States alone, more than one half million women die of CVD each year, exceeding the number of deaths in men and the next 7 causes of death in women combined. This translates into approximately 1 death every minute.2 Coronary heart disease (CHD) accounts for the majority of CVD deaths in women, disproportionately afflicts racial and ethnic minorities, and is a prime target for prevention.1–2 Because CHD is often fatal, and because nearly two thirds of women who die suddenly have no previously recognized symptoms, it is essential to prevent CHD.2 Other forms of atherosclerotic/thrombotic CVD, such as cerebrovascular disease and peripheral arterial disease, are critically important in women. Strategies known to reduce the burden of CHD may have substantial benefits for the prevention of noncoronary atherosclerosis, although they have been studied less extensively in some of these settings

Conductance of Single Cobalt Chalcogenide Cluster Junctions

Understanding the electrical properties of semiconducting quantum dot devices have been limited due to the variability of their size/composition and the chemistry of ligand/electrode binding. Furthermore, to probe their electrical conduction properties and its dependence on ligand/electrode binding, measurements must be carried out at the single dot/cluster level. Herein we report scanning tunneling microscope based break junction measurements of cobalt chalcogenide clusters with Te, Se and S to probe the conductance properties. Our measured conductance trends show that the Co-Te based clusters have the highest conductance while the Co-S clusters the lowest. These trends are in very good agreement with cyclic voltammetry measurements of the first oxidation potentials and with density functional theory calculations of their HOMO-LUMO gapsclos

Conserved regulation of neurodevelopmental processes and behavior by FoxP in Drosophila

International audienceFOXP proteins form a subfamily of evolutionarily conserved transcription factors involved in the development and functioning of several tissues, including the central nervous system. In humans, mutations in FOXP1 and FOXP2 have been implicated in cognitive deficits including intellectual disability and speech disorders. Drosophila exhibits a single ortholog, called FoxP, but due to a lack of characterized mutants, our understanding of the gene remains poor. Here we show that the dimerization property required for mammalian FOXP function is conserved in Drosophila. In flies, FoxP is enriched in the adult brain, showing strong expression in ~1000 neurons of cholinergic, glutamatergic and GABAergic nature. We generate Drosophila loss-of-function mutants and UAS-FoxP transgenic lines for ectopic expression, and use them to characterize FoxP function in the nervous system. At the cellular level, we demonstrate that Drosophila FoxP is required in larvae for synaptic morphogenesis at axonal terminals of the neuromuscular junction and for dendrite development of dorsal multidendritic sensory neurons. In the developing brain, we find that FoxP plays important roles in α-lobe mushroom body formation. Finally, at a behavioral level, we show that Drosophila FoxP is important for locomotion, habituation learning and social space behavior of adult flies. Our work shows that Drosophila FoxP is important for regulating several neurodevelopmental processes and behaviors that are related to human disease or vertebrate disease model phenotypes. This suggests a high degree of functional conservation with vertebrate FOXP orthologues and established flies as a model system for understanding FOXP related pathologies

Conserved regulation of neurodevelopmental processes and behavior by FoxP in Drosophila.

FOXP proteins form a subfamily of evolutionarily conserved transcription factors involved in the development and functioning of several tissues, including the central nervous system. In humans, mutations in FOXP1 and FOXP2 have been implicated in cognitive deficits including intellectual disability and speech disorders. Drosophila exhibits a single ortholog, called FoxP, but due to a lack of characterized mutants, our understanding of the gene remains poor. Here we show that the dimerization property required for mammalian FOXP function is conserved in Drosophila. In flies, FoxP is enriched in the adult brain, showing strong expression in ~1000 neurons of cholinergic, glutamatergic and GABAergic nature. We generate Drosophila loss-of-function mutants and UAS-FoxP transgenic lines for ectopic expression, and use them to characterize FoxP function in the nervous system. At the cellular level, we demonstrate that Drosophila FoxP is required in larvae for synaptic morphogenesis at axonal terminals of the neuromuscular junction and for dendrite development of dorsal multidendritic sensory neurons. In the developing brain, we find that FoxP plays important roles in α-lobe mushroom body formation. Finally, at a behavioral level, we show that Drosophila FoxP is important for locomotion, habituation learning and social space behavior of adult flies. Our work shows that Drosophila FoxP is important for regulating several neurodevelopmental processes and behaviors that are related to human disease or vertebrate disease model phenotypes. This suggests a high degree of functional conservation with vertebrate FOXP orthologues and established flies as a model system for understanding FOXP related pathologies