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Abstract
Direct NDDO-based Born-Oppenheimer molecular dynamics (MD) have been implemented in the semiempirical molecular orbital program EMPIRE. Fully quantum mechanical MD simulations on unprecedented time and length scales are possible, since the calculation of self-consistent wavefunctions and gradients is performed in a massively parallel manner. MD simulations can be performed in the NVE and NVT ensembles, using either deterministic (Berendsen) or stochastic (Langevin) thermostats. Furthermore, dynamics for condensed-phase systems can be performed under periodic boundary conditions. We show three exemplary applications: the dynamics of molecular reorganization upon ionization, long timescale dynamics of an endohedral fullerene, and calculation of the vibrational spectrum of a nanoparticle consisting of more than eight hundred atoms.
Metal cations promote α-dicarbonyl formation in glucose-containing peritoneal dialysis fluids
(2021)
Abstract
Heat sterilization of peritoneal dialysis fluids (PDFs) leads to the formation of glucose degradation products (GDPs), which impair long-term peritoneal dialysis. The current study investigated the effects of metal ions, which occur as trace impurities in the fluids, on the formation of six major α-dicarbonyl GDPs, namely glucosone, glyoxal, methylglyoxal, 3-deoxyglucosone, 3-deoxygalactosone, and 3,4-dideoxyglucosone-3-ene. The chelation of metal ions by 2-[bis[2-[bis(carboxymethyl)amino]ethyl]amino]acetic acid (DTPA) during sterilization significantly decreased the total GDP content (585 μM vs. 672 μM), mainly due to the decrease of the glucose-oxidation products glucosone (14 μM vs. 61 μM) and glyoxal (3 μM vs. 11 μM), but also of methylglyoxal (14 μM vs. 31 μM). The glucose-dehydration products 3-deoxyglucosone, 3-deoxygalactosone, and 3,4-dideoxyglucosone-3-ene were not significantly affected by chelation of metal ions. Additionally, PDFs were spiked with eleven different metal ions, which were detected as traces in commercial PDFs, to investigate their influence on GDP formation during heat sterilization. Iron(II), manganese(II), and chromium(III) had the highest impact increasing the formation of glucosone (1.2–1.5 fold increase) and glyoxal (1.3–1.5 fold increase). Nickel(II) and vanadium(III) further promoted the formation of glyoxal (1.3 fold increase). The increase of the pH value of the PDFs from pH 5.5 to a physiological pH of 7.5 resulted in a decreased formation of total GDPs (672 μM vs 637 μM). These results indicate that the adjustment of metal ions and the pH value may be a strategy to further decrease the content of GDPs in PDFs.
Abstract
Proccessible FePt3 alloy nanoparticles with sizes smaller than 50 nm open the avenue to novel magnetic sensor, catalytic and biomedical applications. Our research objective was to establish a highly scalable synthesis technique for production of single-crystalline FePt3 alloy nanoparticles. We have elaborated a one-pot thermal decomposition technique for the synthesis of superparamagnetic FePt3 nanoparticles (FePt3 NPs) with mean sizes of 10 nm. Subsequent tiron coating provided water solubility of the FePt3 NPs and further processibility as bidental ligands enable binding to catalyst surfaces, smart substrates or biosensors. The chemical composition, structure, morphology, magnetic, optical and crystallographic properties of the FePt3 NPs were examined using high resolution transmission electron microscopy, high-angle annular dark field-scanning transmission electron microscopy, scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy mapping, Fourier transform infrared-attenuated total reflection, X-ray powder diffraction, X-ray photoelectron spectroscopy, vibrating sample magnetometry and UV–Vis absorption spectroscopy.
Many plants of the Berberis genus have been reported pharmacologically to possess anti-diabetic potential, and Berberis calliobotrys has been found to be an inhibitor of α-glucosidase, α-amylase and tyrosinase. Thus, this study investigated the hypoglycemic effects of Berberis calliobotrys methanol extract/fractions using in vitro and In vivo methods. Bovine serum albumin (BSA), BSA–methylglyoxal and BSA–glucose methods were used to assess anti-glycation activity in vitro, while in vivo hypoglycemic effects were determined by oral glucose tolerance test (OGTT). Moreover, the hypolipidemic and nephroprotective effects were studied and phenolics were detected using high performance liquid chromatography (HPLC). In vitro anti-glycation showed a significant reduction in glycated end-products formation at 1, 0.25 and 0.5 mg/mL. In vivo hypoglycemic effects were tested at 200, 400 and 600 mg/kg by measuring blood glucose, insulin, hemoglobin (Hb) and HbA1c. The synergistic effect of extract/fractions (600 mg/kg) with insulin exhibited a pronounced glucose reduction in alloxan diabetic rats. The oral glucose tolerance test (OGTT) demonstrated a decline in glucose concentration. Moreover, extract/fractions (600 mg/kg) exhibited an improved lipid profile, increased Hb, HbA1c levels and body weight for 30 days. Furthermore, diabetic animals significantly exhibited an upsurge in total protein, albumin and globulin levels, along with a significant improvement in urea and creatinine after extract/fractions administration for 42 days. Phytochemistry revealed alkaloids, tannins, glycosides, flavonoids, phenols, terpenoids and saponins. HPLC showed the presence of phenolics in ethyl acetate fraction that could be accountable for pharmacological actions. Therefore, it can be concluded that Berberis calliobotrys possesses strong hypoglycemic, hypolipidemic and nephroprotective effects, and could be a potential therapeutic agent for diabetes treatment.
Within this thesis we investigated and rationalised the interactions at self-assembled
monolayer (SAM) interfaces for all three common phases of matter. For SAM-
liquid and SAM-solid interactions we addressed the challenge of oil and plastic
removal from water by utilising SAM-functionalised magnetic nanoparticles. For
SAM-gas interactions the application of SAM-based gas sensors with molecule-
specific detection was studied. In all cases the use of MD simulations allowed
for precise understanding of the atomistic process leading to the specific function
within each application. Furthermore, molecular self-interactions that lead to the
formation of a SAM from solution were studied. By specific control of nucleation
and growth steps, solution epitaxy may provide well-defined multi-layer systems.
Combining results from DFT calculations and FF MD simulations at the air-water
interface, we shed light on the underlying mechanisms.
Abstract
We report the development of a metal‐free four‐step one‐pot synthetic strategy to access high‐value functionalized phthalazines using o‐methyl benzophenones as starting compounds. Combining a light‐mediated enolization of o‐methyl benzophenones/Diels‐Alder reaction domino process with a subsequent deprotection/aromatization domino reaction in one‐pot leads to sustainable and efficient organic synthesis. The tangible advantages, i. e., absence of catalysts or additives, utilization of commercially available and/or easily accessible substrates, mild reaction conditions, simplicity, and single work‐up procedure, make this combined process highly appealing for the direct construction of various 1‐aryl‐phthalazines. Importantly, in vitro bioactivity evaluation of these newly prepared heterocyclic compounds demonstrated a strong antiviral efficacy against major human pathogens like HCMV and SARS‐CoV‐2.
Abstract
We studied the formation and surface behavior of Pt(II) and Pd(II) complexes with ligand systems derived from two nitrile‐functionalized ionic liquids (ILs) in solution using angle‐resolved X‐ray photoelectron spectroscopy (ARXPS). These ligand systems enabled a high solubility of the metal complexes in IL solution. The complexes were prepared by simple ligand substitution under vacuum conditions in defined excess of the coordinating ILs, [C3CNC1Im][Tf2N] and [C1CNC1Pip][Tf2N], to immediately yield solutions of the final products. The ILs differ in the cationic head group and the chain length of the functionalized substituent. Our XPS measurements on the neat ILs gave insights in the electronic properties of the coordinating substituents revealing differences in donation capability and stability of the complexes. Investigations on the composition of the outermost surface layers using ARXPS revealed no surface affinity of the nitrile‐functionalized chains in the neat ILs. Solutions of the formed complexes in the nitrile ILs showed homogeneous distribution of the solute at the surface with the heterocyclic moieties preferentially orientated towards the vacuum, while the metal centers are rather located further away from the IL/vacuum interface.
Abstract
Molecular solar thermal (MOST) systems, such as the norbornadiene/quadricyclane (NBD/QC) couple, combine solar energy conversion, storage, and release in a simple one‐photon one‐molecule process. Triggering the energy release electrochemically enables high control of the process, high selectivity, and reversibility. In this work, the influence of the molecular design of the MOST couple on the electrochemically triggered back‐conversion reaction was addressed for the first time. The MOST systems phenyl‐ethyl ester‐NBD/QC (NBD1/QC1) and p‐methoxyphenyl‐ethyl ester‐NBD/QC (NBD2/QC2) were investigated by in‐situ photoelectrochemical infrared spectroscopy, voltammetry, and density functional theory modelling. For QC1, partial decomposition (40 %) was observed upon back‐conversion and along with a voltammetric peak at 0.6 Vfc, which was assigned primarily to decomposition. The back‐conversion of QC2, however, occurred without detectable side products, and the corresponding peak at 0.45 Vfc was weaker by a factor of 10. It was concluded that the electrochemical stability of a NBD/QC couple is easy tunable by simple structural changes. Furthermore, the charge input and, therefore, the current for the electrochemically triggered energy release is very low, which ensures a high overall efficiency of the MOST system.
Abstract
We investigate the gas‐phase chemistry of noncovalent complexes of [10]cycloparaphenylene ([10]CPP) with C60 and C70 by means of atmospheric pressure photoionization and electrospray ionization mass spectrometry. The literature‐known [1 : 1] complexes, namely [10]CPP⊃C60 and [10]CPP⊃C70, are observed as radical cations and anions. Their stability and charge distribution are studied using energy‐resolved collision‐induced dissociation (ER‐CID). These measurements reveal that complexes with a C70 core exhibit a greater stability and, on the other hand, that the radical cations are more stable than the respective radical anions. Regarding the charge distribution, in anionic complexes charges are exclusively located on C60 or C70, while the charges reside on [10]CPP in the case of cationic complexes. [2 : 1] complexes of the ([10]CPP2⊃C60/70)+⋅/−⋅ type are observed for the first time as isolated solitary gas‐phase species. Here, C60‐based [2 : 1] complexes are less stable than the respective C70 analogues. By virtue of the high stability of cationic [1 : 1] complexes, [2 : 1] complexes show a strongly reduced stability of the radical cations. DFT analyses of the minimum geometries as well as molecular dynamics calculations support the experimental data. Furthermore, our novel gas‐phase [2 : 1] complexes are also found in 1,2‐dichlorobenzene. Insights into the thermodynamic parameters of the binding process as well as the species distribution are derived from isothermal titration calorimetry (ITC) measurements.
Abstract
The synthesis of covalent organic frameworks (COFs) based on a novel thiophene‐extended benzotrithiophene (BTT) building block is described, which in combination with triazine‐based amines (1,3,5‐triazine‐2,4,6‐triyl)trianiline (TTA) or (1,3,5‐triazine‐2,4,6‐triyl)tris(([1,1´‐biphenyl]‐4‐amine)) (TTTBA)) affords crystalline, and porous imine‐linked COFs, BTT TTA and BTT TTTBA, with surface areas as high as 932 and 1200 m2 g−1, respectively. Oriented thin films are grown successfully on different substrates, as indicated by grazing incidence diffraction (GID). Room‐temperature in‐plane electrical conductivity of up to 10−4 S m−1 is measured for both COFs. Temperature‐dependent electrical conductivity measurements indicate activation energies of ≈123.3 meV for BTT TTA and ≈137.5 meV for BTT TTTBA and trap‐dominated charge transport via a hopping mechanism for both COFs. Moreover, conductive atomic force microscopy reveals directional and defect‐dominated charge transport in the oriented BTT COF films with a strong preference for the in‐plane direction within the molecular 2D‐planes. Quantum mechanical calculations predict BTT TTTBA to conduct holes and electrons effectively in both in‐plane and out‐of‐plane directions. In‐plane, charge carrier transport is of hopping character where the triazine cores represent the barrier. Out‐of‐plane, a continuous charge‐carrier pathway is calculated that is hampered by an imposed structural defect simulated by a rotated molecular COF layer.
Abstract
Within the scope of this paper, nine π‐expanded mono‐substituted 5,8,11,14,17‐pentakis‐(tert‐butyl)‐hexa‐peri‐hexabenzocoronenes (HBC) are introduced. 2‐Iodo‐5,8,11,14,17‐pentakis‐(tert‐butyl)‐hexa‐peri‐hexabenzocoronene served as precursor and was reacted with ethynyltrimethylsilane in a Sonogashira coupling reaction. The acetylene unit is used as a linker and can undergo another Sonogashira coupling reaction combining different phenyl coupling partners with the HBC core. The electron‐withdrawing groups such as nitrile, pyridine and carbonyl species (aldehyde, methylester, carboxylic acid) as well as the three quinoxaline based species (diphenylquinoxaline, dibenzo[a,c]phenazine, phenanthro[4’,5’‐a,b,c]phenazine) serve as substitution moieties. Their influence on the optoelectronic properties were investigated by UV/Vis absorption spectroscopy demonstrating a maximum redshift of 7 nm compared to starting compound 2‐Iodo‐5,8,11,14,17‐pentakis‐(tert‐butyl) HBC. As for the phenanthro[4’,5’‐a,b,c]phenazine substituted HBC a dramatic decrease in the intensity of the absorption of the UV/Vis spectrum was observed. The fluorescence spectroscopy pointed out that the dibenzo[a,c]phenazine and phenanthro[4’,5’‐a,b,c]phenazine substitution changed the spectra to one broad peak departing from the characteristic HBC‐like emission pattern.
Abstract
Luminomagnetic composites have been synthesized that allow for an individual tuning of luminescence intensity, chromaticity and magnetization by combination of superparamagnetic, citrate‐stabilized iron oxide nanoparticles with the luminescent MOFs 3∞[Ln2(BDC)3(H2O)4] (Ln=Eu, Tb; BDC2−=terephthalate). The components are arranged to a concept of inverse structuring compared to previous luminomagnetic composites with MOF@magnetic particle (shell@core) composition so that the luminescent MOF now acts as core and is covered by magnetic nanoparticles forming the satellite shell. Thereby, the magnetic and photophysical properties are individually tuneable between high emission intensity (1.2 ⋅ 106 cps mg−1) plus low saturation magnetization (6 emu g−1) and the direct opposite (0.09 ⋅ 106 cps mg−1; 42 emu g−1) by adjusting the particle coverage of the MOF. This is not achievable with a core‐shell structure having a magnetic core and a dense MOF shell. The composition of the composites and the influence of different synthesis conditions on their properties were investigated by SEM/EDX, PXRD, magnetization measurements and photoluminescence spectroscopy.
Abstract
Counterfeit electronic products not only cause financial losses but also come with safety risks. The worst‐case failure scenario certainly is a fire event. Since manufacturers are liable for damages and suffer image loss, fire‐proof postmortem taggants are needed, enabling differentiation between originals and counterfeits even after a fire incident. This work presents such taggants: optomagnetic supraparticles (SPs), i.e., complex microscale particles composed of luminescent and magnetic nanoparticles (NPs) are generated. Their hybrid nature is pivotal, as magnetic separation can effectively remove the tags from light‐absorbing fire debris, and a fire‐proof identification (ID) fingerprint is based on ratiometric luminescence signals. To achieve thermally stable magnets, iron oxide (IO) NPs are wet‐chemically coated with a SiO2‐3‐aminopropyltriethoxysilane (APTES) shell. Subsequently, these magnetic NPs are assembled with luminescent nanophosphors (lanthanide‐doped calcium phosphate NPs with a SiO2‐core) and SiO2‐APTES spacer NPs by spray‐drying to form hybrid SPs. The careful choice of type and ratios of the NPs and process parameters make it possible to achieve and precisely tune the desired functionality of the resulting fire‐proof taggants. A proof‐of‐concept is demonstrated, in which the taggants are incorporated as additives into coatings and subjected to real fire simulations.
Tetra(peri‐naphthylene)anthracene: A Near‐IR Fluorophore with Four‐Stage Amphoteric Redox Properties
(2023)
Abstract
A novel, benign synthetic strategy towards soluble tetra(peri‐naphthylene)anthracene (TPNA) decorated with triisopropylsilylethynyl substituents has been established. The compound is perfectly stable under ambient conditions in air and features intense and strongly bathochromically shifted UV/vis absorption and emission bands reaching to near‐IR region beyond 900 nm. Cyclic voltammetry measurements revealed four facilitated reversible redox events comprising two oxidations and two reductions. These remarkable experimental findings were corroborated by theoretical studies to identify the TPNA platform a particularly useful candidate for the development of functional near‐IR fluorophores upon appropriate functionalization.
Abstract
Complex [(DIPePBDI)Ca]2(C6H6), with a C6H62− dianion bridging two Ca2+ ions, reacts with benzene to yield [(DIPePBDI)Ca]2(biphenyl) with a bridging biphenyl2− dianion (DIPePBDI=HC[C(Me)N‐DIPeP]2; DIPeP=2,6‐CH(Et)2‐phenyl). The biphenyl complex was also prepared by reacting [(DIPePBDI)Ca]2(C6H6) with biphenyl or by reduction of [(DIPePBDI)CaI]2 with KC8 in presence of biphenyl. Benzene‐benzene coupling was also observed when the deep purple product of ball‐milling [(DIPPBDI)CaI(THF)]2 with K/KI was extracted with benzene (DIPP=2,6‐CH(Me)2‐phenyl) giving crystalline [(DIPPBDI)Ca(THF)]2(biphenyl) (52 % yield). Reduction of [(DIPePBDI)SrI]2 with KC8 gave highly labile [(DIPePBDI)Sr]2(C6H6) as a black powder (61 % yield) which reacts rapidly and selectively with benzene to [(DIPePBDI)Sr]2(biphenyl). DFT calculations show that the most likely route for biphenyl formation is a pathway in which the C6H62− dianion attacks neutral benzene. This is facilitated by metal‐benzene coordination.
Abstract
Tuning the morphology of supraparticles can crucially influence their final properties and is, thus, important for their application in chemical, pharmaceutical, and food industries. The present study reveals how varied nanoparticle sizes, concentrations, and weight ratios in multicomponent dispersions influence the morphology of supraparticles assembled by these nanoparticle building blocks via spray‐drying. In a droplet containing monodisperse nanoparticles, smaller nanoparticles form a coherent elastic shell due to lower cohesive forces. As the solvent enclosed in the shell evaporates less easily due to the narrow pores between the nanoparticles, this ultimately results in rather non‐spherical supraparticles, while larger nanoparticles tend to yield spherical supraparticles. When small nanoparticles outweigh large ones in binary or trinary dispersions, the small nanoparticles form the outer shell that shrinks into a mushroom cap‐like shape upon drying of the spray‐droplet, while larger nanoparticles stay in the center of the droplet, resulting in non‐spherical supraparticles. Furthermore, the findings give a more systematic insight into structures that potentially arise from multimodal‐sized building blocks, thus, paving the way to tune the supraparticle morphology upon spray‐drying, when working with more complex, multicomponent dispersions.
Abstract
Hydrogen‐doped In2O3 (In2O3:H) is highly conductive while maintaining extraordinary transparency, thus making it a very attractive material for applications in optoelectronic devices such as (multijunction) solar cells or light‐emitting devices. However, the corresponding metal/In2O3:H contacts may exhibit undesirably high resistances, significantly deteriorating device performance. To gain insight into the underlying efficiency‐limiting mechanism, hard X‐ray photoelectron spectroscopy is employed to in‐situ monitor annealing‐induced changes in the chemical structure of the Ag/In2O3:H interface system that is further complemented by ex‐situ electron microscopy analyses and contact resistance measurements. The observed evolution of the Ag‐ and In‐related photoelectron line intensities can be explained by significant intermixing across the Ag/In2O3:H interface. The corresponding lineshape broadening of the Ag 3d spectra is attributed to the formation of Ag2O and AgO, which becomes significant at temperatures above approximately 160 °C. However, after annealing to 300 °C, instead of the formation of an insulating AgOx interfacial layer, it is found i) In to be rather homogeneously distributed in the complete Ag/In2O3:H stack, ii) Ag diffusing into the In2O3:H, and iii) an improvement of the contact resistance rather than its often‐reported deterioration.
Abstract
The excited‐state version of the Creutz–Taube ion was prepared via visible light excitation of [(NH3)5RuII(μ‐pz)RuII(NH3)5]4+. The resulting excited state is a mixed valence {RuIII–δ(μ‐pz⋅−)RuII+δ} transient species, which was characterized using femtosecond transient absorption spectroscopy with vis‐NIR detection. Very intense photoinduced intervalence charge transfers were observed at 7500 cm−1, revealing an excited‐state electronic coupling element HDA=3750 cm−1. DFT calculations confirm a strongly delocalized excited state. A notable consequence of strong electron delocalization is the nanosecond excited state lifetime, which was exploited in a proof‐of‐concept intermolecular electron transfer. The excited‐state Creutz–Taube ion is established as a reference, and demonstrates that electron delocalization in the excited state can be leveraged for artificial photosynthesis or other photocatalytic schemes based on electron transfer chemistry.
Abstract
Alkenes that normally do not react with LiAlH4 (3‐hexene, cyclohexene, 1‐Me‐cyclohexene), can be reduced to the corresponding alkanes by a mixture of LiAlH4 and Fe0 (the iron was activated by Metal‐Vapour‐Synthesis). This alkene‐to‐alkane conversion with a stoichiometric quantity of LiAlH4/Fe0 does not need quenching with water or acids, implying that both H's originate from LiAlH4. The LiAlH4/Fe0 combination is also a remarkably potent cooperative catalyst for hydrogenation of multi‐substituted alkenes and benzene or toluene. An induction period of circa two hours and the minimally required temperature of 120 °C, suggests that the actual catalyst is a combination of Fe0 and the decomposition product of LiAlH4 (LiH and Al0). A thermally pre‐activated LiAlH4/Fe0 catalyst did not need an induction time and is also active at room temperature and 1 bar H2. A combination of AliBu3 and Fe0 is an even more active hydrogenation catalyst. Without pre‐activation, tetra‐substituted alkenes like Me2C=CMe2 and toluene could be fully hydrogenated.