Enhancing the photocatalytic upcycling of polystyrene to benzoic acid: a combined computational-experimental approach for acridinium catalyst design

Converting polystyrene into value-added oxygenated aromatic compounds is an attractive end-of-life upcycling strategy. However, identification of appropriate catalysts often involves laborious and time-consuming empirical screening. Herein, after demonstrating the feasibility of using acridinium salts for upcycling polystyrene into benzoic acid by photoredox catalysis for the first time, we applied low-cost descriptor-based combinatorial in silico screening to predict the photocatalytic performance of a family of potential candidates. Through this approach, we identified a non-intuitive fluorinated acridinium catalyst that outperforms other candidates for converting polystyrene to benzoic acid in useful yields at low catalyst loadings (≤5 mol%). In addition, this catalyst also proved effective with real-life polystyrene waste containing dyes and additives. Our study underscores the potential of computer-aided catalyst design for valorizing polymeric waste into essential chemical feedstock for a more sustainable future.

67 million natural product-like compound database generated via molecular language processing

Natural products are a rich resource of bioactive compounds for valuable applications across multiple fields such as food, agriculture, and medicine. For natural product discovery, high throughput in silico screening offers a cost-effective alternative to traditional resource-heavy assay-guided exploration of structurally novel chemical space. In this data descriptor, we report a characterized database of 67,064,204 natural product-like molecules generated using a recurrent neural network trained on known natural products, demonstrating a significant 165-fold expansion in library size over the approximately 400,000 known natural products. This study highlights the potential of using deep generative models to explore novel natural product chemical space for high throughput in silico discovery.

Dynamics of the fcc-to-bcc phase transition in single-crystalline PdCu alloy nanoparticles

Two most common crystal structures in metals and metal alloys are body-centered cubic (bcc) and face-centered cubic (fcc) structures. The phase transitions between these structures play an important role in the production of durable and functional metal alloys. Despite their technological significance, the details of such phase transitions are largely unknown because of the challenges associated with probing these processes. Here, we describe the nanoscopic details of an fcc-to-bcc phase transition in PdCu alloy nanoparticles (NPs) using in situ heating transmission electron microscopy. Our observations reveal that the bcc phase always nucleates from the edge of the fcc NP, and then propagates across the NP by forming a distinct few-atoms-wide coherent bcc-fcc interface. Notably, this interface acts as an intermediate precursor phase for the nucleation of a bcc phase. These insights into the fcc-to-bcc phase transition are important for understanding solid - solid phase transitions in general and can help to tailor the functional properties of metals and their alloys.

Pyrrolo[3,4-c]pyridine-1,2-dione: A New Electron Acceptor for Electrochromic Conjugated Polymers

A new pyrrolo[3,4-c]pyridine-1,2-dione (PPyD) electron acceptor was synthesized via the Diels Alder reaction between N-alkyl maleimide dienophile and 1,2,4-triazine moieties. PPyD was subsequently used to construct five donor-acceptor type conjugated...

Nature of halogen bonding involving π-systems, nitroxide radicals and carbenes: a highlight of the importance of charge transfer

The recently developed adiabatic absolutely localized molecular orbital energy decomposition analysis (ALMO-EDA) has proven to be useful in determining the effects of different energy components on the geometries of complexes bound by intermolecular interactions. The authors have applied it to systems such as the water dimer, water-ion complexes, metallocenes and lone-pair type halogen-bonded (XB) dimers. In this study, we have extended the second-generation ALMO-EDA method to 40 different XB complexes by benchmarking against its classical counterpart and symmetry-adapted perturbation theory (SAPT). In addition, we have examined the nature of halogen bonding involving less studied XB acceptors, namely π-systems, radicals and carbenes, using the adiabatic ALMO-EDA analyses, particularly to shed light on how each energy component affects the geometries of the XB complexes. Our results show that the second-generation ALMO-EDA predicts a higher electrostatic energy contribution in all XB complexes compared to SAPT and classical ALMO-EDA schemes. On the other hand, when comparing across different XB acceptors, all three partition schemes produced the same qualitative finding. The adiabatic ALMO-EDA analyses indicate that while the inclusion of a charge transfer contribution is important in achieving accurate XB bond lengths and interaction energies, as well as recovering the binding site specificity of XB involving benzene and naphthalene acceptors, it is sufficient to obtain the linearity of the XB complexes in the frozen approximation.

Site specificity of halogen bonding involving aromatic acceptors

Based on Cambridge structural database survey and quantum chemical studies, aromatic halogen bond (XB) acceptors are found to have unique pattern of XB binding sites and rim specificity.

Spatial and temporal expression of Wnt and Dickkopf genes during murine lens development

Recent studies indicate a role for Wnt signalling in regulating lens cell differentiation (Stump et al., 2003). To further our understanding of this, we investigated the expression patterns of Wnts and Wnt signalling regulators, the Dickkopfs (Dkks), during murine lens development. In situ hybridisation showed that Wnt5a, Wnt5b, Wnt7a, Wnt7b, Wnt8a and Wnt8b genes are expressed throughout the early lens primordia. At embryonic day 14.5 (E14.5), Wnt5a, Wnt5b, Wnt7a, Wnt8a and Wnt8b are reduced in the primary fibres, whereas Wnt7b remains strongly expressed. This trend persists up to E15.5. At later embryonic stages, Wnt expression is predominantly localised to the epithelium and elongating cells at the lens equator. As fibre differentiation progresses, Wnt expression becomes undetectable in the cells of the lens cortex. The one exception is Wnt7b, which continues to be weakly expressed in cortical fibres. This pattern of expression continues through to early postnatal stages. However, by postnatal day 21 (P21), expression of all Wnts is distinctly weaker in the central lens epithelium compared with the equatorial region. This is most notable for Wnt5a, which is barely detectable in the central lens epithelium at P21. Dkk1, Dkk2 and Dkk3 have similar patterns of expression to each other and to the majority of the Wnts during lens development. This study shows that multiple Wnt and Dkk genes are expressed during lens development. Expression is predominantly in the epithelial compartment but is also associated, particularly in the case of Wnt7b, with early events in fibre differentiation.