Christian Feiler

Helmholtz-Zentrum Hereon | HZG

Highlights • Artificial neural network predicts performance of corrosion modulating agents for Mg. • Calculated HOMO LUMO gap correlates well with inhibition efficiencies for CP Mg. • Model predictions validated by subsequent investigation of untested compounds. • Trained model facilitates performance prediction for material of similar composit...

Prerequisite to unlock the full potential of Mg-based materials is to gain control of its degradation properties. Here we present a proof of concept for an efficient and robust alternative to the data-driven machine learning approaches that are currently on the rise to facilitate the discovery of corrosion modulating agents. The electronic properti...

Magnesium is the lightest structural engineering material and bears high potential to manufacture automotive components, medical implants and energy storage systems. However, the practical use of untreated magnesium alloys is restricted as they are prone to corrosion. An essential prerequisite for the control or prevention of the degradation proces...

Small organic molecules that modulate the degradation behavior of Mg constitute benign and useful materials to modify the service environment of light metal materials for specific applications. The vast chemical space of potentially effective compounds can be explored by machine learning-based quantitative structure-property relationship models, ac...

Aqueous primary Mg-air batteries have considerable potential as energy sources for sea applications and portable devices. However, some challenges at the anode-electrolyte interface related to self-corrosion, aging of the electrolyte...

Modelling Corrosion and activites at the Institute of Surface Science

The ability to assess the risk of corrosion of metallic structures in particular environments holds considerable significance in the field of automotive industry. In recent years, machine learning has evolved into a crucial tool to evaluate the complex and multidimensional corrosion phenomena. In this paper, the special case of non‐aqueous alcohola...

Creating durable, eco-friendly coatings for long-term corrosion protection requires innovative strategies to streamline design and development processes, conserve resources, and decrease maintenance costs. In this pursuit, machine learning emerges as a promising catalyst, despite the challenges presented by the scarcity of high-quality datasets in...

A Mg-air battery is a primary aqueous battery with high theoretical voltage and specific energy density. They have attracted much attention due to their high theoretical energy density, long shelf life, and safety. They consist of magnesium anode coupled to an air electrode. However, the performance of aqueous Mg-air batteries is relatively poor du...

Ultra‐high strength steel (UHSS) structures are plated with Zn‐Ni coatings because of their excellent corrosion resistance properties, but the plating process is accompanied by the production of hydrogen. The presence of hydrogen in steel results in hydrogen embrittlement. Hence, during the production of UHSS parts, dedicated outgassing steps are e...

Small organic molecules can alter the degradation rates of the magnesium alloy ZE41. However, identifying suitable candidate compounds from the vast chemical space requires sophisticated tools. The information contained in only a few molecular descriptors derived from recursive feature elimination was previously shown to hold the potential for dete...

Selecting effective corrosion inhibitors from the vast chemical space is not a trivial task, as it is essentially infinite. Fortunately, machine learning techniques have shown great potential in generating shortlists of inhibitor candidates prior to large-scale experimental testing. In this work, we used the corrosion responses of 58 small organic...

Leucine enkephalin (LeuEnk), a biologically active endogenous opioid pentapeptide, has been under intense investigation because it is small enough to allow efficient use of sophisticated computational methods and large enough to provide insights into low-lying minima of its conformational space. Here, we reproduce and interpret experimental infrare...

This work first describes the intercalation of corrosion inhibitors into layered double hydroxides LDH-OH/CO3 nanocontainers (parental LDH) obtained in situ on the surface of magnesium alloy AZ91 in the presence of a chelating agent. Vanadate, as a typical broad inhibitor for active metals, and oxalate, as an inhibitor suitable for magnesium, were...

Selecting effective corrosion inhibitors from the vast chemical space is not a trivial task, as it is essentially infinite. Fortunately, machine learning techniques have shown great potential in generating shortlists of inhibitor candidates prior to large-scale experimental testing. In this work, we used the corrosion responses of 58 small organic...

Digitisation is making huge progress, and it is not stopping at automotive corrosion either. Within the entire automotive material life cycle, computer-aided approaches can already assist corrosion engineering and management today. From constructive corrosion protection on galvanically active hybrid constructions to the virtual design of active or...

The large amount of corrosion inhibition efficiencies in literature, calls for a more efficient way to organize, access and compare this information. The CORDATA open data management application (https://datacor.shinyapps.io/cordata/) can help select appropriate corrosion inhibitors for application specific challenges.

Effective protective coatings are an essential component of lightweight engineering materials in a large variety of applications as they ensure structural integrity of the base material throughout its whole service life. Layered double hydroxides (LDHs) loaded with corrosion inhibitors depict a promising approach to realize an active corrosion prot...

Magnesium-based engineering materials are increasingly considered for transport applications due to their exceptional strength to weight ratios. [1] However, effective corrosion protection strategies are required due to the high chemical reactivity of magnesium (Mg). A promising approach to achieve the desired active corrosion protection are layere...

The degradation behaviour of magnesium and its alloys can be tuned by small organic molecules. However, an automatic identification of effective organic additives within the vast chemical space of potential compounds needs sophisticated tools.Herein, we propose two systematic approaches of sparse feature selection for identifying molecular descript...

Aqueous Mg batteries are promising energy storage and conversion systems to cope with the increasing demand for green, renewable and sustainable energy. Realization of high energy density and long endurance system is significant for fully delivering the huge potential of aqueous Mg batteries, which has drawn increasing attention and investigations...

Degradation and damage of a material caused by the influence of adverse environments has a significant impact on the lifetime of products and infrastructures. Hence, reducing the impact of corrosion and the development of effective protection measures is an important step in saving costs and burden on natural resources. Corrosion is a multi physica...

Until now, detecting weak spots in composite structures remains a key challenge in the aviation industry. The correct assessment of the load-bearing capability after structural overloading or the occurrence of barely-visible damages is particularly important to maintain structural integrity. Nonetheless, a reliable and overarching non-destructive i...

Chemists usually synthesize molecules using stochastic bond-forming collisions of the reactant molecules in solution. Nature follows a different strategy in biochemical synthesis. The majority of biochemical reactions are driven by machine-type protein complexes that bind and position the reactive molecules for selective transformations. Artificial...

Magnesium exhibits a high potential for a variety of applications in areas such as transport, energy and medicine. However, untreated magnesium alloys are prone to corrosion, restricting their practical application. Therefore, it is necessary to develop new approaches that can prevent or control corrosion and degradation processes in order to adapt...

The individual and combined influence of 53 small molecule bio-relevant organic compounds on the corrosion of CP Mg and Mg-0.8Ca is investigated. The results demonstrate that tested amino acids, vitamins and saccharides, do not critically influence the in vitro corrosion of tested materials. The presence of penicillin and streptomycin at low concen...

Femtosecond time-resolved absorption measurements of a magnetically bi-stable azopyridine Ni-porphyrin in solution at room temperature show that the photo-induced dynamics are dominated by transient low-spin ⇄ high-spin interconversion involving Ni (d ² ) and (d, d) states.

Diazocines, bridged azobenzenes, exhibit superior photo-physical properties compared to parent azobenzenes such as high switching efficiencies, quantum yields, and particularly switching wavelengths in the visible range. Synthesis, however, proceeds with low yields, and derivatives are difficult to prepare. We now present two heterodiazocines which...

We herein report the synthesis and switching properties of an azo-1-methylimidazole-functionalized Ni2+ porphyrin. Upon irradiation and cis/trans isomerization of the azo unit, 1-methylimidazole is reversibly coordinated as an axial ligand to the Ni2+ porphyrin. Consequently, the Ni2+ is switched between a diamagnetic low-spin state (trans) and a p...

Azo-N-methylimidazole functionalized Ni(ii)porphyrins were rationally designed and synthesized and their performance as molecular spin switches was investigated. They perform intramolecular light-driven coordination-induced spin state switching (LD-CISSS) in the presence of water and therefore are an important step towards spin switches for medicin...

Indeno[1,2-b]fluorenes (IFs), while containing 4np-electrons, are best described as two aromatic benzene rings fused to a weakly paratropics-indacene core. In this study, we find that replacement of the outer benzene rings of an IF with benzothiophenes allows the antiaromaticity of the centrals-indacene to strongly reassert itself. Herein we report...

Light switchable azoimidazoles were rationally designed, synthesized, and their performance was investigated as photodissociable ligands (PDL), and for spin state switching of Ni-porphyrins. The rationally designed ligands exhibit a high photochemical conversion rate (trans --> cis > 98%), and no measurable fatigue over a large number of switching...

We present the first coordination-induced spin-state switching with nickel chlorin and nickel isobacteriochlorin. The spin-state switching was monitored by UV-vis spectroscopy and NMR titration experiments. The association constants (K1 and K2) and thermodynamic parameters (ΔH and ΔS) of the coordination of pyridine were determined. The first X-ray...

Molecules with Möbius topology have drawn increasing attention from scientists in a variety of fields, such as organic chemistry, inorganic chemistry, and material science. However, synthetic difficulties and the lack of functionality impede their fundamental understanding and practical applications. Here, we report the facile synthesis of an aggre...

Triazatriangulenium (TATA) platform molecules allow the preparation of functionalized surfaces with well-defined lateral spacings of freestanding functional groups. Using scanning tunneling microscopy, synchrotron-based X-ray photoelectron spectroscopy, near edge X-ray absorption fine structure spectroscopy and complementary density functional theo...

We present a fully reversible and highly efficient on-off photo switching of magnetic resonance imaging (MRI) contrast with green (500 nm) and violet-blue (435 nm) light. The contrast change is based on the intramolecular Light-Driven Coordination-Induced Spin State Switch (LD-CISSS) which was performed with azopyridine substituted Ni-porphyrins. T...

The conductances of molecular model junctions comprising a triazatriangulenium platform with or without an ethynyl spacer and an upright Zn-porphyrin are probed with a low-temperature scanning probe microscope. The platform alone is found to be highly conductive. The ethynyl-linked Zn-porphyrin moiety reduces the conductance by three orders of magn...

Extensive use of quantum chemical calculations has been made to rationally design a molecule whose spin state can be switched reversibly using light of two different wavelengths at room temperature in solution. Spin change is induced by changing the coordination number of a nickel complex. The coordination number in turn is switched using a photoch...

Spectroscopic evidence of a reversible, photoinduced trans ↔ cis photoisomerization is provided for an azobenzene-functionalized triazatriangulene (TATA) platform on Au(111). As shown by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS), these molecules form a well-ordered self-assembled monolayer (SAM) on Au(111). The...

The controlled attachment of chromophores to metal or semiconducting surfaces is a prerequisite for the construction of photonic devices and artificial surface based light harvesting systems. We present an approach to mount porphyrins in ordered monolayers on Au(111) by self-assembly and verify it, employing STM, absorption spectros-copy, and quant...

Zwei stabile, kernmodifizierte Rubyrine mit einer oder zwei Diethienylethen(DTE)-Einheiten (1 und 2) wurden hergestellt. Das Rubyrin 1 mit einer “geschlossenen” DTE-Einheit zeigt 26 π-Aromatizität, während bei Einführung einer “offenen” DTE-Einheit in den Makrocyclus 2 dieser sich als nichtaromatische Verbindung verhält.

Two stable core-modified rubyrins bearing one and two dithienylethene (DTE) units (1 and 2) have been synthesized. With one "closed-form" DTE unit, 1 shows aromaticity associated with its conjugated circuit of 26 π-electrons. In contrast, rubyrin 2 containing one "open-form" DTE unit has nonaromatic properties.

Octyl functionalized triazatriangulenium (tri-octyl-TATA) deposited on Au(111) and Ag(111) surfaces by electrospray ionization is investigated using low temperature scanning tunneling microscopy. The molecule surprisingly adsorbs with gauche conformations of the octyl groups rather than in the anti form. We observe chiral amplification in the islan...

The bistability of spin states (e.g., spin crossover) in bulk materials is well investigated and understood. We recently extended spin-state switching to isolated molecules at room temperature (light-driven coordination-induced spin-state switching, or LD-CISSS). Whereas bistability and hysteresis in conventional spin-crossover materials are caused...

Easy as π: A stable nonaromatic heteroporphyrin bearing a thienopyrrole moiety has been prepared. The nonaromatic nature of this compound is clearly evident based on UV/Vis absorption, (1) H NMR spectroscopy, and theoretical calculations. Single-crystal X-ray analysis demonstrates that the molecule adopts a planar conformation with clear alternatio...

The photo- and thermally induced switching of well-ordered molecular arrays of free-standing functional groups, formed by self-assembly on Au surfaces, were studied by photoelectrochemical methods (cyclic voltammetry, chronoamperometry) and surface plasmon resonance spectroscopy. These molecular adlayers exhibit azobenzene functions mounted vertica...

The electronic properties of FePc molecules adsorbed on hydrogen-passivated Si(111) surfaces are investigated by scanning tunneling microscopy at low temperatures. Spatially resolved spectroscopy reveals a significant variation of the electronic states at different positions above the molecule. The highest occupied ligand- and metal-based orbitals...

In contrast to azobenzenes, heterocyclic azo compounds are less well investigated. Phenylazoimidazoles would be versatile as photodissociable ligands (PDLs) because imidazole is an important donor in coordination chemistry. Here, we present the synthesis of 4- and 5-phenylazoimidazoles via a novel azo-coupling method. 1,2-Protected imidazole is lit...

Magnetic bistability in spin-crossover materials generally is a collective phenomenon that arises from the cooperative interaction of a large number of microscopic magnetic moments within the crystal lattice in the solid state. We now report on individual molecules in homogeneous solution that are switched between the diamagnetic and paramagnetic s...

Irradiation of compound (II) with sunlight leads to the formation of the oxido-bridged diheptamolybdate (III).

Treatment of MoO3 with butan-1-amine (BuNH2) or pyrrolidine (PyrNH2) results in the formation of (BuNH3)8[(Mo7O24)(MoO4)]·3H2O (1; BuNH3 = butan-1-aminium) or (PyrNH2)6[(Mo7O24]·2H2O (2; PyrNH2 = pyrrolidinium), respectively. On irradiation with sunlight, compound 1, which is an organic heptamolybdate [Mo7O24]6– that contains a cocrystallized monom...