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This work aims to determine whether the different crystallisation pathways of amorphous calcium carbonate (ACC) have an impact on the element and oxygen isotope partitioning of the final crystalline phase. In this study, special emphasis is placed on the sparsely investigated pathway of the so-called pseudomorphic transformation, which is a crystallisation process that preserves the disequilibrium morphology of the amorphous precursor. Since it is shown that the composition of ACC can be preserved under pseudomorphic conditions, the influence of a range of synthesis parameters and conditions on the material properties and chemical composition of ACC was scrutinised.
While solid-state transformation retains the chemical composition of doped ACC during crystallisation, the chemical composition is altered during dissolution-reprecipitation pathways. An alternative crystallisation pathway, namely the shape-preserving pseudomorphic transformation, is induced by additives such as poly(acrylic acid), polyaspartic acid and trace amounts of phosphate. Since ACC crystallisation in biominerals occurs in the presence of these or similar additives – especially aspartate-rich domains were found in unusually acidic biomineralisation proteins – a thorough mechanistic understanding of the pseudomorphic transformation is of importance for paleoclimate reconstructions. This work revealed that the pseudomorphic transformation not only preserves the morphology of the amorphous precursor, but also retains the partition coefficients, e.g., in case of Sr-doped ACC. Furthermore, the influence of the pseudomorphic transformation on the oxygen isotope composition demonstrated that this transformation is a quasi-solid to solid phase transformation process, although it takes place in aqueous solutions. Mechanistically, it seems that the presence of certain surface-active additives limits diffusional exchange with the surrounding liquid environment so that pseudomorphic transformation preserves the partition coefficients of ACC even in the final crystalline product.
As the pseudomorphic transformation preserves the composition of the amorphous precursor, it is necessary to understand how the formation of ACC and its partitioning coefficients, as well as its material properties, is influenced by the synthesis conditions. For instance, it was recently shown that it is possible to precipitate ACC with distinct short-range order by simply altering the pH slightly. Therefore, it is of high significance to analyse the influence of the synthesis conditions on ACC. In this thesis, three different approaches were conducted to achieve a better understanding of the structural and compositional synthesis dependence of ACC:
#1 The influence of the synthesis procedures revealed that material properties such as particle size, level of hydration, crystallisation temperature, and density are sensitive to simple changes in the synthesis conditions, which have much less effect on the chemical composition of ACC. Notably, density measurements indicated that synthesis-dependent microstructures of ACC structures exist. Furthermore, a microfluidic setup allowed for ACC synthesis at an exceptionally low pH (pH 7.5) by using ethanol as anti-solvent. Under these conditions, synthesis of ACC at varying pH revealed a significant increase of barium incorporation by decreasing pH.
#2 The influence of the mixing kinetics on the element partition was analysed by precipitating magnesium-, strontium-, and barium-doped ACC under varying flow rates. While less magnesium was incorporated at increasing flow rates, increasing partition coefficients were determined for Sr-doped ACC by increasing flow rates. Notably, no flow rate influence was determined for Ba-doped ACC. These results demonstrate that element partitioning is highly sensitive to changing mixing kinetics, which indicates that prenucleation clusters play a role during ACC formation and control element partitioning to a certain extent.
#3 To mimic ACC formation in a natural environment, ACC was synthesised in artificial seawater under varying synthesis conditions as flow rate, temperature, and pH, which resulted in multiple-doped ACC. Besides material properties such as particle size, the chemical composition was also affected by the synthesis conditions. A significant influence of the flow rate and temperature on magnesium and sulphur partitioning was determined. While less magnesium was incorporated by increasing flow rates, increasing sulphur incorporation was detected. Furthermore, both additives were better incorporated at enhanced temperatures. Notably, increasing concentrations of all dopants were determined with increasing pH.
In the final chapter, a feasibility study was conducted to assess whether a flow-through synthesis enables the synthesis of the fundamental building blocks of calcareous biominerals, namely calcium carbonate nanograins coated with organic matrices. This study demonstrated that the precipitation of Mg-doped ACC particles coated with negatively charged polyelectrolytes, such as polyacrylates or polystyrene sulfonate, is possible by using a flow-through synthesis.
A major part of this thesis covers the late-stage functionalization of pharmaceutical compounds meaning the selective modification of already existing active pharmaceutical ingredients (API).
Some APIs led to selectively chlorinated or fluorinated products after treatment with Selectfluor, whereas others formed a mixture of both. All halogenated products were then subjected to radioligand binding studies, where some showed increased affinity and selectivity.
In another part of this work, aluminum oxide nanoparticles were functionalized with selfassembled
monolayers in order to obtain tunable shell-by-shell systems with desired properties.
Nowadays, catalysts are the basis of modern life, as without them, many vital industrial processes would be rendered useless. To broaden their versatility and improve their efficiency and functionality, it is important to specifically adapt catalysts. This is possible through the design of multicomponent organic-inorganic hybrid systems: the catalytic performance can be tuned by the chosen combination and many parameters during their fabrication and use, e.g., morphology and size.
To expand the field of catalysts, this thesis consists of four different multicomponent hybrid systems with either ZnO or NiO as the main catalyst. The catalytic versatility of well-known semiconductors is demonstrated, combining them with metal nanoparticles, porphyrins or polyoxometalates as co-catalysts and unique polymers as templates. Electrostatic self-assembly, biomineralization and electrostatic nanotemplating are used as powerful self-assembly strategies to control the interaction, size, and morphology via various building blocks, creating nanostructured hierarchical catalytically active particles with high-performance in solution. The hybrid materials are primarily characterized using light scattering, UV-Vis spectroscopy, different types of electron microscopy, and ζ-potential.
Specifically, a target-selective and photocatalytically active catalyst was created based on polyethylene oxide templated ZnO nanoparticles using biomineralization and extended with polyoxometalate as co-catalyst using electrostatic self-assembly in water. The catalytic selectivity is based on the chemical structure and charge of the dyes, while the efficiency of the photocatalytic degradation depends on the catalyst itself, showing potential for wastewater cleaning and solar energy conversion. The target-selectivity of the catalyst can be adapted for the appropriate task simply by adding a single component.
Further, to enable photocatalytic application in the visible light range with ZnO as main catalyst such as solar energy conversion and optoelectronics, and improved catalytic performance, porphyrins (TMPyP and TPPS) were added to polymer stabilized ZnO nanorods using electrostatic self-assembly, creating micro-rhombuses. The versatility of the system is demonstrated, tuning the shape of the micro-rhombuses and the amount of attached ZnO nanoparticles by adjusting the porphyrin ratio. To take advantage of further spectral ranges from ultraviolet light up to visible light, the advantages of inorganic co-catalysts and organic photosensitizers – Au nanoparticles and polythiophene − were combined with ZnO, while at the same time the conjugated polymer acted as a template for the formation of inorganic materials. Using a new concept of double-electrostatic nanotemplating, both inorganic compounds are formed within one supramolecular template of polythiophene-surfactant: The resulting polymer-inorganic hybrid nano-objects (hollow spheres with hydrodynamic radius of RH = 100 nm) contain both ZnO nanospheres (d = 2.6 nm) and Au nanospheres (d = 6.0 nm). The synthesis strategy can be used as a new general concept to design multicomponent hybrid systems in water using self-assembly.
With NiO as main catalyst and polystyrene sulfonate microgel as template in water, the versatility of electrostatic nanotemplating has been exploited for different semiconductors, as the chemical reactions to synthesize ZnO and NiO nanoparticles differ. Ni/NiO with possible application in non-enzymatic sensors and fuel cells was tested using the oxidation of aromatic amine as model reaction. Further, a ternary system (microgel-Ni/NiO) shows catalytic superiority in comparison to its binary analogue (microgel-NiO). The effect of the loading ratio, templating effect, and inorganic synthesis route on catalytic performance is elucidated.
Further, a light-switchable system was established by combining naphthol derivates with two sulfonate groups as photoacid and dendrimer using electrostatic self-assembly. Due to photoexcitation, the photoacid (aromatic molecule with enhanced acidity in the excited electronic state) dissociates, resulting in tunable assemblies. The assemblies depend on the molecular properties of the photoacids.
In this thesis, all multicomponent organic-inorganic hybrid systems, being designed using self-assembly strategies and versatile templates in solution, showed improved catalytic activity for advanced applications, demonstrating the large potential of supramolecular approaches.
Hydrogenation of unsaturated bonds is a key step in both the fine and petrochemical industries. Homogeneous and heterogeneous catalysts are historically based on noble group 9 and 10 metals. Increasing awareness of sustainability drives the replacement of costly, and often harmful, precious metals by abundant 3d-metals or even main group metals. Although not as efficient as noble transition metals, metallic barium was recently found to be a versatile hydrogenation catalyst. Here we show that addition of finely divided Fe0, which itself is a poor hydrogenation catalyst, boosts activities of Ba0 by several orders of magnitude, enabling rapid hydrogenation of alkynes, imines, challenging multi-substituted alkenes and non-activated arenes. Metallic Fe0 also boosts the activity of soluble early main group metal hydride catalysts, or precursors thereto. This synergy originates from cooperativity between a homogeneous, highly reactive, polar main group metal hydride complex and a heterogeneous Fe0 surface that is responsible for substrate activation.
Reactive glucose degradation products (GDPs) are formed during heat sterilization of glucose-containing peritoneal dialysis fluids (PDFs) and may induce adverse clinical effects. Long periods of storage and/or transport of PDFs before use may lead to de novo formation or degradation of GDPs. Therefore, the present study quantified the GDP profiles of single- and double-chamber PDFs during storage. Glucosone, 3-deoxyglucosone (3-DG), 3-deoxygalactosone (3-DGal), 3,4-dideoxyglucosone-3-ene (3,4-DGE), glyoxal, methylglyoxal (MGO), acetaldehyde, formaldehyde, and 5-hydroxymethylfurfural (5-HMF) were quantified by two validated UHPLC-DAD methods after derivatization with o-phenylenediamine (dicarbonyls) or 2,4-dinitrophenylhydrazine (monocarbonyls). The PDFs were stored at 50 °C for 0, 1, 2, 4, 13, and 26 weeks. The total GDP concentration of single-chamber PDFs did not change considerably during storage (496.6 ± 16.0 µM, 0 weeks; 519.1 ± 13.1 µM, 26 weeks), but individual GDPs were affected differently. 3-DG (− 82.6 µM) and 3-DGal (− 71.3 µM) were degraded, whereas 5-HMF (+ 161.7 µM), glyoxal (+ 32.2 µM), and formaldehyde (+ 12.4 µM) accumulated between 0 and 26 weeks. Acetaldehyde, glucosone, MGO, and 3,4-DGE showed time-dependent formation and degradation. The GDP concentrations in double-chamber fluids were generally lower and differently affected by storage. In conclusion, the changes of GDP concentrations during storage should be considered for the evaluation of clinical effects of PDFs.
Myocardin-related transcription factors A and B (MRTFs) are coactivators of Serum Response Factor (SRF), which controls fundamental biological processes such as cell growth, migration, and differentiation. MRTF and SRF transcriptional activity play an important role in hepatocellular carcinoma (HCC) growth, which represents the second leading cause of cancer-related mortality in humans worldwide. We, therefore, searched for druggable targets in HCC that regulate MRTF/SRF transcriptional activity and can be exploited therapeutically for HCC therapy. We identified the G protein-coupled lysophosphatidic acid receptor 1 (LPAR1) as a novel interaction partner of MRTF-A and Filamin A (FLNA) using fluorescence resonance energy transfer-(FRET) and proximity ligation assay (PLA) in vitro in HCC cells and in vivo in organoids. We found that LPAR1 promotes FLNA phosphorylation at S2152 which enhances the complex formation of FLNA and MRTF-A, actin polymerization, and MRTF transcriptional activity. Pharmacological blockade or depletion of LPAR1 prevents FLNA phosphorylation and complex formation with MRTF-A, resulting in reduced MRTF/SRF target gene expression and oncogene-induced senescence. Thus, inhibition of the LPAR1–FLNA–MRTF-A interaction represents a promising strategy for HCC therapy.
In this study, poly(AA-co-ACMO) and polyurethane-based nanofibers were prepared in a ratio of 1:1 (NF11) and 2:1 (NF21) as antimicrobial carriers for chronic wound management. Different techniques were used to characterize the nanofibers, and poly(AA-co-ACMO) was mostly found on the surface of PU. With an increase in poly(AA-co-ACMO) dose from 0 (PU) and 1:1 (NF11) to 2:1 (NF21) in the casting solution, the contact angle (CA) was reduced from 137 and 95 to 24, respectively, and hydrophilicity was significantly increased. As most medications inhibit biological processes by binding to a specific protein, in vitro protein binding was investigated mechanistically using a stopped-flow technique. Both NF11 and NF21 bind to BSA via two reversible steps: a fast second-order binding followed by a slow first-order one. The overall parameters for NF11 (Ka = 1.1 × 104 M−1, Kd = 89.0 × 10−6, ΔG0 = −23.1 kJ mol−1) and NF21 (Ka = 189.0 × 104 M−1, Kd = 5.3 × 10−6 M, ΔG0 = −27.5 kJ mol−1) were determined and showed that the affinity for BSA is approximately (NF11)/(NF21) = 1/180. This indicates that NF21 has much higher BSA affinity than NF11, although BSA interacts with NF11 much faster. NF21 with higher hydrophilicity showed effective antibacterial properties compared to NF11, in agreement with kinetic data. The study provided an approach to manage chronic wounds and treating protein-containing wastewater.
RNA interference (RNAi) using small interfering RNAs (siRNAs) is a powerful tool to target any protein of interest and is becoming more suitable for in vivo applications due to recent developments in RNA delivery systems. To exploit RNAi for cancer treatment, it is desirable to increase its selectivity, e.g., by a prodrug approach to activate the siRNAs upon external triggering, e.g., by using light. Red light is especially well suited for in vivo applications due to its low toxicity and higher tissue penetration. Known molecular (not nanoparticle-based) red-light-activatable siRNA prodrugs rely on singlet oxygen (1O2)-mediated chemistry. 1O2 is highly cytotoxic. Additionally, one of the side products in the activation of the known siRNA prodrugs is anthraquinone, which is also toxic. We herein report on an improved redlight-activatable siRNA prodrug, which does not require 1O2 for its activation. In fact, the 5′ terminus of the antisense strand is protected with an electron-rich azobenzene promoiety. It is reduced and cleaved upon red light exposure in the presence of Sn(IV)(pyropheophorbide a)dichloride acting as a catalyst and ascorbate as a bulk reducing agent. We confirmed the prodrug activation upon red light irradiation both in cell-free settings and in human ovarian cancer A2780 cells.
While phosphates are key additives in sausage production, their use conflicts with consumer preferences for “natural” foods. In this study, we investigated the potential of using vegetables as “clean-label” phosphate substitutes and their effects on water holding capacity, consumer acceptance, color, softness, and tenderness. Six freeze-dried vegetables with a pH above 6.0 were added to sausage meat on a laboratory scale. Adding 1.6% freeze-dried Brussels sprouts or Red Kuri squash resulted in a similar weight gain (7.0%) as the positive control of 0.6% commercial phosphate additive. Higher vegetable concentrations (2.2–4.0%) caused a significant increase in weight (p ≤ 0.05, 10.4–18.4% weight gain). Similar stress was needed to compress sausages containing 1.6/4.0% Brussels sprouts (14.2/11.2 kPa) and the positive control (13.2 kPa). Indentation tests also led to similar softness results for the sausages prepared with 1.6/4.0% Brussels sprouts (15.5 kPa/16.6 kPa) and the positive control (16.5 kPa). A force of 1.25 N was needed to shear the positive control, while 1.60 N/1.30 N was needed for the samples (1.6/4% Brussels sprouts). In summary, the present study indicates that freeze-dried vegetables have the potential to effectively replace phosphate in meat products.
We present an ARXPS study on the surface composition and interfacial behavior of commercial [Rh(COD)2][TfO] in [C2C1Im][TfO], [C4C1Im][TfO], [C8C1Im][TfO], and [C2C1Im][EtOSO3]. The complex was found to be non-intact in a solution of these ILs through the loss of COD ligands, accompanied by the depletion of the metal center from the IL/vacuum interface. Increasing the chain length of the aliphatic substituent on the imidazolium cation of the [TfO]−-based ILs led to a more pronounced depletion from the interface, due to the higher surface affinity of the solvent cations with the longer alkyl chains. The loss of COD ligands offered facile in situ ligand substitution with surface-active TPPTS to afford a moderate increase in the surface concentration of Rh. We propose the formation of a Schrock−Osborn-type catalyst [Rh(COD)(TPPTS)2][TfO]. Information on the surface composition and targeted design of the gas/IL interface is highly relevant for applications in IL-based catalytic systems, such as in supported ionic liquid phase (SILP) catalysis.
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.