This work presents a high-throughput in silico screening of ruthenium(II) pincer complexes as potential catalysts for pyridine hydrogenation To explore how backbone architecture, substituent sterics, and hemilability govern substrate binding energetics, this study screened 24 Ru(II) pincer complexes comprising four distinct lutidine-based pincer backbones (PNpyP, PONpyOP, NONpyON, NNpyN) and six substituents (Me, iPr, tBu, Bu, Ph, Cy). Additionally, 18 complexes representing three specific coordination modes from the PNpyP ligand family were screened using pyridine as a model substrate.

MACE was employed to generate stereoisomer and conformer libraries without conformational bias. Structures were screened with the Universal Force Field, refined via DFT (PBE0-D3(BJ)/def2-SVP), and analysed using ensemble-averaged steric descriptors (percent buried volume and bite angle) and pyridine binding free energies across three coordination pathways: (i) carbonyl auxiliary substitution, (ii) central nitrogen donor dissociation, and (iii) phosphorus side-arm dissociation.

The results reveal that pyridine binding to form RuH₂(py)(𝜅³-PNP), RuH₂(CO)(𝜅²-P,N-PNP)(py), or RuH₂(CO)(𝜅²-P,P-PNP)(py) complexes is generally unfavorable. However, binding becomes more accessible via the hemilabile dissociation of either the nitrogen or phosphorus pincer donor. Dissociation of the nitrogen donor emerged as the most energetically accessible pathway (Δ𝐺 = 30–105 kJ/mol), particularly with phenyl substituents where 𝜋–𝜋 stacking stabilises binding (Δ𝐺 = 29.9 kJ/mol). Conversely, dissociation of the phosphorus pincer donor (Δ𝐺 = 60–105 kJ/mol) presents the most favorable binding energetics in the presence of bulky substituents, as the enhanced flexibility of the phosphine side-arm accommodates steric bulk more effectively. Substitution of the carbonyl remains largely inaccessible (Δ𝐺 = 100–150 kJ/mol), as it requires the coordination of pyridine to a fully occupied complex.

Analysis of the ensemble-averaged steric descriptors revealed that an optimal balance between ligand hemilability, steric constraints, and geometric flexibility governs substrate accessibility. A percent buried volume in the range of 40–50% and P–Ru–P bite angles near 95–115^◦ showed significantly improved pyridine binding energetics. This was exemplified by the RuH₂(CO)(𝜅²-P,P-PNP)(py) complex, where structural reorganisation upon nitrogen dissociation allows the complex to exploit conformational flexibility and stabilise substrate binding through non-covalent interactions. This creates a confined,welldefined pocket adjacent to the metal center that effectively accommodates the substrate. These findings warrant further investigation to bridge computational insights with improved catalytic performance.
... Read more

Addressing the resources needed to produce sustainable and environmentally friendly products is key within the field of catalysis. One of the key applications of catalysis is the storage of renewable hydrogen. This could be achieved through liquid organic hydrogen carriers (LOHCs), which participate in homogeneous catalysis. This field emphasizes high selectivity through the use of transition-metal complexes. A suitable LOHC candidate could be pyridine, a type of N-heterocycle, which serves as a benchmark for successful binding to the metal complex. The binding of pyridine can be enhanced by substituting noble metals with transition metals, such as manganese, which has shown promising catalytic activity. We perform high-throughput screening with DFT calculation for the following systems: PNP, PONOP, NNN, and NONON, which vary in their backbones. Every metal complex consists of three various configurations: the alignment of the auxiliary carbonyl ligand with the hydride atom (config 1), pyridine (config 2) and the lutidine part of the nitrogen pincer atom (config 3). The catalytic performance is studied by determining the stable and reactive complexes, as well as their specific configurations. Only positive binding energies, in terms of the ΔGreaction, are observed. This indicates that no complexes show strong binding of the metal to pyridine. However, the phenyl-substituted system exhibits the lowest binding energies, of which the third configuration is the most favored for all ligand types. This holds for the trans-positioning of the auxiliary carbonyl ligand with the lutidine part of the nitrogen pincer atom,mainly for the NNN-based complex. Still, the preferred configurations do not correlate with the strengthened metal-pyridine binding and weakening of the metal-auxiliary carbonyl ligand bond length. In terms of reactivity, the nitrogen-based complexes show the highest hydride charges, which could be assumed to provide high reactivity. However, the hydridic behavior of the complexes does not correspond with the stability of the phenyl substituents and all remaining complexes. After the reactivity of the complexes is considered, we can enable fine-tuning of specific backbones to forecast trends observed in reactivity. The phenyl-substituent can be used as a starting point due to its delocalized system and electron-donating property for fine-tuning. Nitrogen-based complexes enable fine-tuning of the reactivity because they depend on the ligand scaffold rather than the substituents. In addition, variation in binding energies for every substituent is most commonly observed for nitrogen-based complexes. The nitrogen-based complex can therefore be used to performimproved ligand design with the fine-tuning ability of the phenyl substituent. ... Read more

This study is an in silico screening of zinc PNP and NNN pincer complexes with variation of the R groups in the ligands for the homogeneous catalysis of the hydrogenation of pyridine. This was done by investigating geometry, hemilability, and binding energies. The scope lies in identifying which complexes are thermodynamically capable of binding pyridine, which is researched using the Gibbs free energy of the binding reaction. Energies and optimized geometries were obtained using Density Functional Theory with ORCA and the supercomputer Snellius. The screening revealed that PNP-R complexes favor tetrahedral geometries after optimization, but three and five coordinated structures are also possible. Hemilability of the phosphorus and/or nitrogen arm were observed. All PNP-complexes showed thermodynamically unfavored binding of pyridine. Additionally, NNN-R complexes did not bind to pyridine. Only when phenyl was used as the R group in the NNN backbone did pyridine bind. This is believed to be due to a hydride migrating to one of the phenyl rings, but even then, the binding energy was not thermodynamically favorable. Moreover, research on ligand substitution by pyridine showed that in most complexes this reaction is unfavorable. Only in three coordinated structures of NNN was this reaction thermodynamically feasible. These findings contribute to understanding the pincer ligand dynamics of PNP and NNN complexes and suggest directions for future research. ... Read more

As the transition to cleaner energy intensifies, N-heterocycles as liquid organic hydrogen carriers (LOHCs) offer a promising approach. However, their reliance on noble metals such as ruthenium, iridium, and platinum poses sustainability challenges.
In this study, 60 Mo(I) pincer complexes were screened using a combination of MACE and DFT. MACE was used to generate initial 3D molecular structures via force field optimization. These were further analysed using DFT calculations with the PBE0-D3BJ functional and def2-SVP basis set under standard conditions. Gibbs free energies were computed and used to evaluate pyridine binding energies across the ligand set.
The results indicate that pyridine binding to Mo(I) complexes is unfavourable, despite several complexes exhibiting sufficiently hydridic Mo-H bonds to suggest potential catalytic activity. The hydride charge appears to be conformation dependent, with certain configurations decreasing or increasing the hydridic charge. Oxidation of Mo(I) was observed in some systems, leading to pincer ligand decomposition. Additionally, nitrogen donor arms often dissociate from the metal centre, resulting in 5-coordinated geometries.
The unfavourable binding energy suggest that inner sphere mechanisms are unlikely. Instead, the findings support the plausibility of outer sphere pathways, especially given the lack of correlation between pyridine binding energy and the hydridic charge. Furthermore, the observed dissociation of nitrogen donor arms hint at potential ligand hemilability, which may influence catalytic dynamics and warrants further investigation.
... Read more

This thesis investigates why EEG-based neurophysiological research in architecture remains primarily confined to the design guideline phase, despite its potential for direct integration into design development. Through historical, philosophical, and empirical analysis, the study argues that neuroarchitecture possesses a sufficiently mature theoretical foundation for application across all design phases. A systematic review analysis demonstrates that research complexity increases substantially in design development, requiring advanced computational methods such as machine learning and real-time brain-computer interfaces. The findings suggest that the limited adoption of neuroscience during the act of designing is not due to theoretical shortcomings, but rather to the absence of accessible computational tools, pipelines, and shared datasets. The thesis concludes that broader integration of neuroscience in architecture depends on the development of practical and accessible infrastructures for designers. ... Read more

The global plastic waste issue demands recycling technology development beyond the conventional ones, which is limited by contamination, polymer degradation, and energy inefficiency. The thesis describes the potential of main-group-based acid species supported on a zirconia as a catalyst for chemical upcycling of polypropylene (PP), one of the most widely used plastic but difficult to recycle. Inspired by previous study on sulfated zirconia (SZO), which abstract the hydride via its Lewis acidic site, this work explores whether the same activity can be achieved with phosphoric acid, tetraboric acid, boric acid, fluorosulfuric acid, triflic acid, and bistriflimide. Density Functional Theory (DFT) was used to determine adsorption energies, surface saturation effects, Lewis acidity (via probemolecules), and hydride abstraction barriers using Nudged Elastic Band (NEB) analysis. Fluorosulfuric acid and triflic acid were found to activate polyolefins, demonstrating their potential for catalytic upcycling. Also, fluorosulfuric and triflic acid were found to have comparable energy barriers to SZO; however no system studied surpassed SZO in terms of Lewis acidity or overall reactivity. ... Read more

Accurately modeling heterogeneous catalytic systems while maintaining computational efficiency is a persistent challenge, as conventional methods like Density Functional Theory (DFT) offer high accuracy but are computationally expensive, whereas classical force fields provide efficiency without precision. In recent year, Machine Learning Potentials (MLPs) have emerged as a powerful tool to bridge the gap between the efficiency of classical force fields and the precision of first-principles methods. In this study, I assess the accuracy, efficiency, and limitations of MACEMLP-models when applied to a challenging catalytic system: cationic zirconocene hydride grafted onto an amorphous silica slab model. My results demonstrate that MACE models, even with minimal training data, achieve impressive accuracy with energy RMSE below 0.05 eV/atom and force errors under 0.2 eV/Å, highlighting the efficiency of foundational models. Nonetheless, challenges such as a sub-unity slope in energy predictions and dynamically unstable MD simulations due to catastrophic forgetting remain, even with the application of active learning techniques. A novel multihead replay technique shows promise in enhancing stability, though additional validation is necessary. Furthermore, thermodynamic reweighting proves effective in refining bond length distributions, especially with hybrid functionals like PBE0+D3, but its robustness remains sensitive to model accuracy and bias. Overall, these results demonstrate the potential of MLP-based approaches in accelerating calculations by orders of magnitude while emphasizing the importance of thorough validation for accurate predictions. ... Read more

A large portion of plastic waste is burned or put into a landfill, which are unsustainable practices. Recycling is a good solution to increase circularity, but currently a significant part of plastic is recycled mechanically. Mechanical recycling reduces the quality of the plastic, consequently plastic can only be recycled a few times before it needs to be discarded. This significant downside can be solved by chemical recycling aided by catalysis. The investigated zirconium catalyst (BuCp2ZrH – OSi) is supported on an amorphous silica surface. The ISE group at the TU Delft has developed a configurational space exploration algorithm that has found states of this supported catalyst, which are far more thermodynamically stable compared to a chemical guess. Many stable states are the result of the hydride transfer from Zr to Si. The thermodynamic stability does not only determine if the state can be accessible at the reaction conditions (80∘C), the kinetics must also be considered as well. To determine the kinetic accessibility, the hydride transfer activation energies were estimated for various amorphous silica surfaces as well as perfect beta-cristobalite. The Cristobalite and minimum strain silica surface showed relatively high energy reaction barriers (≈96-107 kJ/mol) compared to the higher strain surfaces (≈15-54 kJ/mol). This shows that the reaction barrier is highly dependent on the surface structure. The found barriers show that the configurational space exploration algorithm can find kinetically accessible states at reaction conditions. ... Read more

Amorphous silica is a widely used material with many applications. Industrially, it has found common use as a catalyst support or adsorbent. As it is an amorphous material, the lack of long-range periodicity makes it difficult to reason about what its surface looks like. As a consequence, when we construct atomic models, it is difficult to determine whether they are representative. Furthermore, this difficulty extends to the active sites, as there are many different possibilities with different local topologies and varying amounts of strain. This makes the computational modeling of the material a challenge to modern chemistry.

This work aims to generate periodic models of amorphous silica of varying roughness and strain and use the topological features of the created models as descriptors for strain. To generate these models, classical molecular dynamics is used to generate bulks and equilibrate cleaved surfaces using a randomly generated stochastic Fourier expansion. DFT is then used to optimize the geometry of the resulting surfaces and their saturated counterparts. The calculated energies are compared to those of the most relaxed states of the substituents the surfaces are composed of.

It was found that the method of cleaving surfaces resulted in varying roughness after re-equilibration and that roughness has a correlation with strain. Varying the roughness had the greatest effect on the amount of strained topological features in the model. Algorithmically saturating models showed that strain is generally decreased through the addition of water and strain is most effectively decreased through the removal of two-membered rings on the surface.

The main result of this study is that, using purely topological features, the strain of a model can be predicted using a multivariate linear regression. Using the coordination of O atoms, average bond lengths, and angles as descriptors, multivariate linear regression was found to result in an R² of 0.925. ... Read more