Herein we present compelling evidence of the intervention of electrophilic silver vinylcarbenes in the carbene-alkyne metathesis (CAM) reaction, leading to a pivotal C(sp2)-H insertion process. The delicate equilibrium between the stability and reactivity of transient species is crucial for efficient detection. Through meticulous mechanistic exploration, we unveil that the mechanism for the C(sp2)-H insertion hinges on the substitution pattern. Indeed, it departs from the previously documented stepwise mechanism (involving Wheland intermediates), and it follows a concerted route, quite uncommon for this transformation.

Access to extended perylene‐based nanographenes (NGs) is severely limited and involves tedious multi‐step synthetic procedures. Here a two‐step synthesis shortcut to highly soluble, bent, and extended perylene‐based NGs from a nonperylene aromatic homologation precursor is reported. Moreover, the resulting scaffold, tetraphenyldibenzoperiflanthene (DBP), is further extended by Pd‐based postsynthetic ring fusion, taking advantage of the installation of an aminoquinoline directing group. The rational extension of the DBP scaffold allows synthesizing of highly NIR fluorescent pure‐red emitters ( λ em > 700 nm) with excellent quantum yields (Φ FI ) up to 0.78. Thorough theoretical analysis sheds light on the correlation between λ em , Φ FI , and scaffold molecular editing and extension, showcasing a rational design evolution process toward NGs with desired photophysical properties.

NMR relaxometry is a technique that allows the molecular dynamics study of chemical compounds across a broad time scale, ranging from slow translational diffusion or collective motions to fast rotations. The present work is a 1H NMR relaxometry and diffusometry study of systems based on [P6,6,6,14][Cl] and [P6,6,6,14]3[GdCl6] ionic liquids, complemented by X-ray diffractometry measurements. The use of the X-ray profiles enabled the determination of an almost temperature independent interdigitated disposition of the cations that is at the origin of local order fluctuations. This structure also affects the paramagnetic relaxation enhancement, which is very significant for these systems and is achieved at very low metal concentrations (around 1mM). The present study provides a comprehensive analysis that is consistent for all the analyzed systems and across the different experimental techniques, despite the experienced technical challenges related to extremely short relaxation times. Additionally, the Electrochemical Impedance Spectroscopy profiles of the neat [P6,6,6,14][Cl] sample were explained by an analogous equivalent circuit model that allowed for a global analysis consistent with the diffusometry and X-ray diffractometry results. The representation of the real and imaginary parts of the impedance allowed for a visual deconvolution of the contributions of the different circuit blocks considered in the model.

Molecules are typically synthesized through stepwise processes involving chemical reactions between simple molecular precursors. Here, we report an advance in the synthesis of new organic molecules based on the approach of clip-off chemistry, in which molecules are excised from ordered, extended organic structures. We synthesized macrocycles by selectively cleaving them out of covalent organic frameworks. The synthesized macrocycles include eight macrocyclic polyamides with 114-, 138-, and 162-atom rings, and one 114-atom ring macrocyclic polyimide. This excision approach expands the scope of chemical organic synthesis to previously inaccessible macromolecules.

The formation of carbon─nitrogen (C─N) bonds is a cornerstone of organic synthesis, underpinning the production of amines, imines, and nitriles found in numerous active ingredients. Among the methods for C─N bond formation, the aza-Michael addition stands out as a powerful and versatile approach. Herein, we present a biocatalytic strategy for the efficient aza-Michael addition of primary and secondary amines to acrylic acid, i.e., aza-Michaelase activity, leveraging the promiscuity of dimethylsulfoniopropionate (DMSP) lyase from Pelagibacter ubique HTCC1062 (DddK Pu ). In vivo DddK Pu catalyzes the β-elimination of DMSP to sodium acrylate and dimethylsulfide (i.e., a retro sulfa-Michael reaction). Here, we screened DddK Pu against a diverse library of 30 primary and 44 secondary amines. The wild-type enzyme achieved 90%–100% conversion and 40%–86% isolated yields of N , N -disubstituted-β-amino acids with secondary amines. For primary amines, the W26G variant proved optimal, furnishing 50%–100% conversion and 43%–81% isolated yields of N -substituted-β-amino acids. Notably, the enzyme exhibited remarkable chemoselectivity: for pyrrolidin-2-ylmethanamine, the reaction occurred exclusively at the secondary amine, while for piperidin-2-ylmethanamine, it reacted selectively at the primary amine. These findings highlight DddK Pu as a versatile biocatalyst for the selective synthesis of β-amino acids, expanding the toolbox for C─N bond formation.

Control of selectivity in organic synthesis is essential for guiding chemical reactions towards a desired product when multiple outcomes are possible. Since organic reactions can often yield a range of products, selectivity control ensures that the target product is favoured over others. Herein, we present a new synthetic approach, Clip-off Chemistry, which provides precise selectivity control in the synthesis of organic (macro)molecules through selective orthogonal cleavage within extended structures containing such (macro)molecules, which, in turn, spontaneously form when these extended structures are assembled. We have applied this concept to the synthesis of seven novel macrocycles by selectively cleaving double or triple bonds via ozonolysis within covalent-organic frameworks (COFs). With this demonstration, we believe that Clip-off Chemistry will soon provide generalized access to previously inaccessible (macro)molecules and polymers for diverse applications.

Serum 1H-NMR metabolomics has been used as a diagnostic tool for screening type 2 diabetes (T2D) with chronic kidney disease (CKD) as comorbidity. This work aimed to evaluate 1H-NMR data to detect the initial kidney damage and CKD in T2D subjects, through multivariate statistical analysis. Clinical data and biochemical parameters were obtained for classifying five experimental groups using KDIGO guidelines: Control (healthy subjects), T2D, T2D-CKD-mild, T2D-CKD-moderate, and T2D-CKD-severe. Serum 1H-NMR spectra were recorded to follow two strategies: one based on metabolite-to-creatinine (Met/Cr) ratios as targeted metabolomics, and the second one based on untargeted metabolomics from the 1H-NMR profile. A prospective biomarkers panel of the early stage of T2D-CKD based in metabolite-to-creatinine ratio (ornithine/Cr, serine/Cr, mannose/Cr, acetate/Cr, acetoacetate/Cr, formate/Cr, and glutamate/Cr) was proposed. Later, a statistical model based on non-targeted metabolomics was used to predict initial CKD, and its metabolic pathway analysis allowed identifying the most affected pathways: phenylalanine, tyrosine, and tryptophan biosynthesis; valine, leucine, and isoleucine degradation; glyoxylate and dicarboxylate metabolism; glycine, serine, and threonine metabolism; and histidine metabolism. Nonetheless, further studies with a larger cohort are advised to precise ranges in metabolite-to-creatinine ratios and evaluate the prediction pertinency to detect initial CKD in T2D patients in both statistical models proposed.

Abstract Background The availability of soil phosphorus (P) often limits the productivities of wet tropical lowland forests. Little is known, however, about the metabolomic profile of different chemical P compounds with potentially different uses and about the cycling of P and their variability across space under different tree species in highly diverse tropical rainforests. Results We hypothesised that the different strategies of the competing tree species to retranslocate, mineralise, mobilise, and take up P from the soil would promote distinct soil 31P profiles. We tested this hypothesis by performing a metabolomic analysis of the soils in two rainforests in French Guiana using 31P nuclear magnetic resonance (NMR). We analysed 31P NMR chemical shifts in soil solutions of model P compounds, including inorganic phosphates, orthophosphate mono- and diesters, phosphonates, and organic polyphosphates. The identity of the tree species (growing above the soil samples) explained > 53% of the total variance of the 31P NMR metabolomic profiles of the soils, suggesting species-specific ecological niches and/or species-specific interactions with the soil microbiome and soil trophic web structure and functionality determining the use and production of P compounds. Differences at regional and topographic levels also explained some part of the the total variance of the 31P NMR profiles, although less than the influence of the tree species. Multivariate analyses of soil 31P NMR metabolomics data indicated higher soil concentrations of P biomolecules involved in the active use of P (nucleic acids and molecules involved with energy and anabolism) in soils with lower concentrations of total soil P and higher concentrations of P-storing biomolecules in soils with higher concentrations of total P. Conclusions The results strongly suggest “niches” of soil P profiles associated with physical gradients, mostly topographic position, and with the specific distribution of species along this gradient, which is associated with species-specific strategies of soil P mineralisation, mobilisation, use, and uptake.

Bistable molecules represent a potential miniaturization limit for high-density information technologies. However, molecules exhibit memory effect typically at very low temperatures. This is the case of spin-crossover (SCO) complexes, where the concept of a molecular memory has not been considered due to the fast spin-state intercon-version of all previous systems. Breaking this principle, here we report a slow relaxation process found in an SCO iron-triazole poly -anionic complex. Multiple experimental evidences confirm the opening of a thermal hysteresis upon solid dilution and even in liquid solution. Density functional theory (DFT) calculations reveal the origin of this unexpected phenomenon to the appearance of an energy barrier that slows down the spin-state relaxation pro-cesses at the molecular level. These results show how SCO mole-cules may store information at room temperature, opening unique opportunities for molecular data storage.

Spin crossover (SCO) complexes, through their reversible spin transition under external stimuli, can work as switchable memory materials. Here, we present a protocol for the synthesis and characterization of a specific polyanionic iron SCO complex and its diluted systems. We describe steps for its synthesis and the determination of crystallographic structure of the SCO complex in diluted systems. We then detail a range of spectroscopic and magnetic techniques employed to monitor the spin state of the SCO complex in both diluted solid- and liquid-state systems. For complete details on the use and execution of this protocol, please refer to Galán-Mascaros et al.1.

Chiral 2-hydroxy acids and 2-hydroxy-4-butyrolactone derivatives are structural motifs often found in fine and commodity chemicals. Here, we report a tandem biocatalytic stereodivergent route for the preparation of these compounds using three stereoselective aldolases and two stereocomplementary ketoreductases using simple and achiral starting materials. The strategy comprises (i) aldol addition reaction of 2-oxoacids to aldehydes using two aldolases from E. coli, 3-methyl-2-oxobutanoate hydroxymethyltransferase (KPHMTEcoli), 2-keto-3-deoxy-l-rhamnonate aldolase (YfaUEcoli), and trans-o-hydroxybenzylidene pyruvate hydratase-aldolase from Pseudomonas putida (HBPAPputida) and (ii) subsequent 2-oxogroup reduction of the aldol adduct by ketopantoate reductase from E. coli (KPREcoli) and a Δ1-piperidine-2-carboxylate/Δ1-pyrroline-2-carboxylate reductase from Pseudomonas syringae pv. tomato DSM 50315 (DpkAPsyrin) with uncovered promiscuous ketoreductase activity. A total of 29 structurally diverse compounds were prepared: both enantiomers of 2-hydroxy-4-butyrolactone (>99% ee), 21 2-hydroxy-3-substituted-4-butyrolactones with the (2R,3S), (2S,3S), (2R,3R), or (2S,3R) configuration (from 60:40 to 98:2 dr), and 6 2-hydroxy-4-substituted-4-butyrolactones with the (2S,4R) configuration (from 87:13 to 98:2 dr). Conversions of aldol adducts varied from 32 to 98%, while quantitative conversions were achieved by both ketoreductases, with global isolated yields between 20 and 45% for most of the examples. One-pot one-step cascade reactions were successfully conducted achieving isolated yields from 30 to 57%.

The addition of two unsymmetric malonate esters to the Buckminster fullerene C60 can lead to 22 spectroscopically distinguishable isomeric products and therefore represents a formidable synthesis challenge. In this work, we achieve 87 % selectivity for the formation of a single (in,out-trans-3) isomer by combining three approaches: (i) we use a starting material, in which the two malonates are covalently connected (tether approach); (ii) we form the strong supramolecular complex of C60 with the shape-persistent [10]CPP macrocycle (template approach) and (iii) we embed this complex further within a self-assembled nanocapsule (shadow mask approach). Variation of the spacer chain shed light on the limitations of the approach and the ring dynamics in the unusual [2]catenanes were studied in silico with atomistic resolution. This work significantly widens the scope of mechanically interlocked architectures comprising cycloparaphenylenes (CPP).

The direct and unambiguous detection and identification of individual metabolite molecules present in complex biological mixtures constitute a major challenge in (bio)analytical research. In this context, nuclear magnetic resonance (NMR) spectroscopy has proven to be particularly powerful owing to its ability to provide both qualitative and quantitative atomic-level information on multiple analytes simultaneously in a noninvasive manner. Nevertheless, NMR suffers from a low inherent sensitivity and, moreover, lacks selectivity regarding the number of individual analytes to be studied in a mixture of a myriad of structurally and chemically very different molecules, e.g., metabolites in a biofluid. Here, we describe a method that circumvents these shortcomings via performing selective, photochemically induced dynamic nuclear polarization (photo-CIDNP) enhanced NMR spectroscopy on unmodified complex biological mixtures, i.e., human urine and serum, which yields a single, background-free one-dimensional NMR spectrum. In doing this, we demonstrate that photo-CIDNP experiments on unmodified complex mixtures of biological origin are feasible, can be performed straightforwardly in the native aqueous medium at physiological metabolite concentrations, and act as a spectral filter, facilitating the analysis of NMR spectra of complex biofluids. Due to its noninvasive nature, the method is fully compatible with state-of-the-art metabolomic protocols providing direct spectroscopic information on a small, carefully selected subset of clinically relevant metabolites. We anticipate that this approach, which, in addition, can be combined with existing high-throughput/high-sensitivity NMR methodology, holds great promise for further in-depth studies and development for use in metabolomics and many other areas of analytical research.

The surface chemistry of Metal-Organic Polyhedra (MOPs) is crucial to their physicochemical properties because it governs how they interact with external substances such as solvents, synthetic organic molecules, metal ions, and even biomolecules. Consequently, the advancement of synthetic methods that facilitate the incorporation of diverse functional groups onto MOP surfaces will significantly broaden the range of properties and potential applications for MOPs. This study describes the use of copper(I)-catalysed, azide-alkyne cycloaddition (CuAAC) click reactions to post-synthetically modify the surface of alkyne-functionalised cuboctahedral MOPs. To this end, a novel Rh(II)-based MOP with 24 available surface alkyne groups was synthesised. Each of the 24 alkyne groups on the surface of the "clickable" Rh-MOP can react with azide-containing molecules at room temperature, without compromising the integrity of the MOP. The wide substrate catalogue and orthogonal nature of CuAAC click chemistry was exploited to densely functionalise MOPs with diverse functional groups, including polymers, carboxylic and phosphonic acids, and even biotin moieties, which retained their recognition capabilities once anchored onto the surface of the MOP.

AbstractDie Addition von zwei unsymmetrischen Malonsäureestern an das Buckminster‐Fulleren C60 kann zu 22 spektroskopisch unterscheidbaren isomeren Produkten führen und stellt daher eine beachtliche synthetische Herausforderung dar. In dieser Arbeit erreichen wir eine Selektivität von 87 % für die Bildung eines einzigen (in,out‐trans‐3)‐Isomers, indem wir drei Methoden kombinieren: (i) wir verwenden ein Ausgangsmaterial, in dem die beiden Malonsäureester kovalent verbunden sind (Tether); (ii) wir bilden den starken supramolekularen Komplex von C60 mit dem formstabilen [10]CPP‐Makrozyklus (Nanohoop‐Template) und (iii) wir schlossen diesen Komplex weiter in eine selbstorganisierte Nanokapsel ein (Schattenmaske). Die Variation der Alkylkette zeigte die Limitationen der Methode auf und die Ringdynamik in den ungewöhnlichen [2]Catenanen wurde in silico mit atomistischer Auflösung untersucht. Diese Arbeit erweitert das Spektrum der mechanisch ineinandergreifenden Architekturen mit Cycloparaphenylen (CPP) erheblich.

Pulsed-field gradients (PFGs) play an important role in the development and understanding of modern NMR methods. With the ultimate goal of constructing robust pulse sequences that create high-quality NMR spectra with minimum set-up, PFGs are utilized to achieve an exclusive selection of a specific coherence transfer pathway as well as to purge all kinds of undesired magnetization. PFGs reduce the number of needed phase cycle steps to a bare minimum, allowing for accelerated NMR data acquisition in shorter spectrometer times. The potential and diversity of several PFG-based NMR elements are presented, as well as instances of their implementation in time-efficient NMR solutions. Practical aspects such as NMR data collection needs and the attainment of pure in-phase absorption lineshapes are discussed for the most useful NMR experiments.

The regioselective poly-functionalization of highly symmetric spherical Ih-C60 is extremely challenging and usually leads to the formation of regio-isomeric mixtures not amenable for HPLC purification. Recently, we have pioneered the regioselective functionalization of C60 fullerene under a supramolecular mask strategy, using tetragonal prismatic nanocapsules to encapsulate C60 and performing the Bingel tetrakis-cyclopropanation at the exposed fullerene surface through the four windows of the nanocapsule. Here, we describe an extension of the supramolecular mask strategy for the selective Diels-Alder (DA) functionalization of Ih-C60 using acenes. The supramolecular mask allows the chemo- and regioselective synthesis of e,e-bis-anthracene-C60 (functionalization at 90o) or the synthesis of trans-1-bis-pentacene-C60 (functionalization at 180o), only by changing the acene length. Moreover, the mask strategy allows to obtain unprecedented equatorial hetero-tris-functionalized-C60 adducts combining Diels-Alder with Bingel mask regiofunctionalization. Computational modelling revealed significant differences in the host-guest interactions and equilibrium established between the firstly formed anthracene- and pentacene-based monoadducts with the nanocapsule, respectively, which finally determine the observed orthogonal regioselectivity. The combination of Molecular Dynamics (MD) simulations and analysis of Frontier Molecular Orbital (FMO) involved in the Diels-Alder cycloadditions provide crucial insights to rationalize the regioselective control exerted by the supramolecular mask.

Type 2 diabetes mellitus (DM2) is a multimorbidity, long-term condition, and one of the worldwide leading causes of chronic kidney disease (CKD) -a silent disease, usually detected when non-reversible renal damage have already occurred. New strategies and more effective laboratory methods are needed for more opportune diagnosis of DM2-CKD. This study comprises clinical parameters and nuclear magnetic resonance (NMR)-based urine metabolomics data from 60 individuals (20-65 years old, 67.7% females), sorted in 5 experimental groups (healthy subjects; diabetic patients without any clinical sign of CKD; and patients with mild, moderate, and severe DM2-CKD), according to KDIGO. DM2-CKD produces a continuous variation of the urine metabolome, characterized by an increase/decrement of a group of metabolites that can be used to monitor CKD progression (trigonelline, hippurate, phenylalanine, glycolate, dimethylamine, alanine, 2-hydroxybutyrate, lactate, and citrate). NMR profiles were used to obtain a statistical model, based on partial least squares analysis (PLS-DA) to discriminate among groups. The PLS-DA model yielded good validation parameters (sensitivity, specificity, and area under the curve (AUC) of the receiver operating characteristic curve (ROC) plot: 0.692, 0.778 and 0.912, respectively) and, thus, it can differentiate between subjects with DM2-CKD in early stages, from subjects with a mild or severe condition. This metabolic signature exhibits a molecular variation associated to DM2-CKD, and data suggests it can be used to predict risk of DM2-CKD in patients without clinical signs of renal disease, offering a new alternative to current diagnosis methods.

Detecting and identifying individual metabolites in biological mixtures constitutes a challenge in analytical research. In this context, nuclear magnetic resonance (NMR) has proven to be powerful providing precise qualitative and quantitative information non-invasively. However, NMR is inherently insensitive and lacks selectivity regarding the analysis of molecular targets in complex mixtures. Here, we present a method that circumvents these shortcomings performing photo-chemically induced dynamic nuclear polarisation (photo-CIDNP) on unmodified biofluids, i.e. human urine and serum. We demonstrate that photo-CIDNP on biofluids is feasible, can be performed straightforwardly in the native aqueous medium at physiological concentrations, and acts as a spectral filter highlighting a clinically relevant metabolite subset. The method is compatible with standard metabolomics protocols and holds great promise for in-depth studies for use in metabolomics and other areas of analytical research.

Cobalt-catalyzed C-H amination via M-nitrenoid species is spiking the interest of the research community. Understanding this process at a molecular level is a challenging task, and here we report a well-defined macrocyclic system featuring a pseudo-Oh aryl-CoIII species that reacts with aliphatic azides to effect intramolecular Csp2-N bond formation. Strikingly, a putative aryl-Co═NR nitrenoid intermediate species is formed and is rapidly trapped by a carboxylate ligand to form a carboxylate masked-nitrene, which functions as a shortcut to stabilize and guide the reaction to productive intramolecular Csp2-N bond formation. On one hand, several intermediate species featuring the Csp2-N bond formed have been isolated and structurally characterized, and the essential role of the carboxylate ligand has been proven. Complementarily, a thorough density functional theory study of the Csp2-N bond formation mechanism explains at the molecular level the key role of the carboxylate-masked nitrene species, which is essential to tame the metastability of the putative aryl-CoIII═NR nitrene species to effectively yield the Csp2-N products. The solid molecular mechanistic scheme determined for the Csp2-N bond forming reaction is fully supported by both experimental and computation complementary studies.