Self-assembly of aromatic oligoamides into multihelical structures is a powerful strategy for developing complex and functional molecular architectures. As the hybridization process is directed by the folded state of the oligomers, inducing changes in the folding can be used to control the self-assembly. As one approach for this, Diels-Alder reactions on diazaanthracene monomers allow site-specific modification of aromatic oligoamides. The reaction leads to a bend in the monomer that, in turn, distorts the structure of the oligomer. Herein, we show that this strategy can be used to control the self-assembly of the oligomers. Using reversible Diels-Alder reactions allows switching between distinct folded states with different self-assembly preferences. This strategy can be applied during oligomer synthesis to prevent self-assembly or postsynthetically to disassemble multihelical structures. In complex systems containing multiple oligomers, we show that the modification can further be used to direct social versus narcissistic self-sorting, allowing for the switch between homomeric and heteromeric double helical assemblies.

A series of small molecule Cu(II) complexes based on tridentate N3 ligands relevant to the histidine brace of the active site of lytic polysaccharide monooxygenase were synthesized and characterized by X-ray crystallography and spectroscopic studies. In order to better understand the role of different structural features and to help bridge the differences between previously reported models, the methylation patterns, imidazole connectivity, linker nature, and type of heterocycle were systematically varied across the series. These modifications lead to important differences in the electrochemical properties of the complexes and their reactivity towards the oxidation of a model substrate.

BACKGROUND:Cardiac β3-adrenergic receptors (ARs) are upregulated in diseased hearts and mediate antithetic effects to those of β1AR and β2AR. β3AR agonists were recently shown to protect against myocardial remodeling in preclinical studies and to improve systolic function in patients with severe heart failure. However, the underlying mechanisms remain elusive. METHODS:To dissect functional, transcriptional, and metabolic effects, hearts and isolated ventricular myocytes from mice harboring a moderate, cardiac-specific expression of a human ADRB3 transgene (β3AR-Tg) and subjected to transverse aortic constriction were assessed with echocardiography, RNA sequencing, positron emission tomography scan, metabolomics, and metabolic flux analysis. Subsequently, signaling and metabolic pathways were further investigated in vivo in β3AR-Tg and ex vivo in neonatal rat ventricular myocytes adenovirally infected to express β3AR and subjected to neurohormonal stress. These results were complemented with an analysis of single-nucleus RNA-sequencing data from human cardiac myocytes from patients with heart failure. RESULTS:Compared with wild-type littermates, β3AR-Tg mice were protected from hypertrophy after transaortic constriction, and systolic function was preserved. β3AR-expressing hearts displayed enhanced myocardial glucose uptake under stress in the absence of increased lactate levels. Instead, metabolomic and metabolic flux analyses in stressed hearts revealed an increase in intermediates of the pentose-phosphate pathway in β3AR-Tg, an alternative route of glucose utilization, paralleled with increased transcript levels of NADPH-producing and rate-limiting enzymes of the pentose-phosphate pathway, without fueling the hexosamine metabolism. The ensuing increased content of NADPH and of reduced glutathione decreased myocyte oxidant stress, whereas downstream oxidative metabolism assessed by oxygen consumption was preserved with higher glucose oxidation in β3AR-Tg mice after transaortic constriction compared with wild type, together with increased mitochondrial biogenesis. Unbiased transcriptomics and pathway analysis identified NRF2 (NFE2L2) as an upstream transcription factor that was functionally verified in vivo and in β3AR-expressing cardiac myocytes, where its translocation and nuclear activity were dependent on β3AR activation of nitric oxide synthase and nitric oxide production through S-nitrosation of the NRF2-negative regulator Keap1. CONCLUSIONS:Moderate expression of cardiac β3AR, at levels observed in human cardiac myocardium, exerts metabolic and antioxidant effects through activation of the pentose-phosphate pathway and NRF2 pathway through S-nitrosation of Keap1, thereby preserving myocardial oxidative metabolism, function, and integrity under pathophysiological stress.

The polypyrazole‐containing ligands, N,N,N′,N′‐tetrakis((5‐tert‐Butyl‐1H‐pyrazol‐3‐yl)methyl)‐1,2‐ethanediamine (L1) and N,N,N′,N′‐tetrakis((5‐Phenyl‐1H‐pyrazol‐3‐yl)methyl)‐1,2‐ethanediamine (L2) were synthesized and shown to form hexadentate monometallic coordination compounds with Co2+, Ni2+, Cu2+ and Zn2+ metal ions. Exchange studies with the metal ions show binding preference in the order of Ni2+>Co2+/Cu2+>Zn2+. The compounds were confirmed by NMR, UV‐Vis studies and the X‐ray crystals structures of [Co(L1)](PF6)2, [Ni(L1)](PF6)2, [Cu(L1)]ClPF6, [Zn(L1)](PF6)2 and [Ni(L2)]Cl2. In the solid state, the arrangement of the bulky pyrazole units leads to the formation of two distinct cationic pockets containing the N‐H groups of the pyrazoles. These cationic pockets are found to bind Cl‐ or PF6‐ counterions through hydrogen bonding and anions titrations revealed good affinity for Cl‐ and Br‐. The compounds can be deprotonated up to two times using mild organic bases, highlighting the potential of these ligands to tune the electronic properties of the metal center.

Non-covalent interactions play an essential role in the folding and self-assembly of large biological assemblies. These interactions are not only a driving force for the formation of large structures but also control conformation and com-plementary shapes of subcomponents that promote the diversity of structures and functions of the resulting assemblies. Understanding how non-covalent interactions direct self-assembly and the effect of conformation and complementary shapes on self-assembled structures will help design artificial supramolecular systems with extended components and functions. Herein, we develop a strategy for controlling more complex self-assembly with lower symmetry and flexible building blocks that combine endohedral non-covalent interactions with a dual curvature in the ligand backbone to give additional shape complementarity. A Diels-Alder reaction was used to break the symmetry of the diazaanthracene units of the ligands to give dual curvature ligands with different shapes and endohedral groups (L1-L3). The self-assembly studies of these ligands demonstrated that non-covalent interactions and shape complementary effectively control the self-assembly and enable the design of cages for supramolecular catalysis.

Structure-activity relationships of Ni particles with different morphologies, crystallinities and compositions were investigated for glucose hydrogenation. Nanorods and nanospheres were obtained respectively by altering hydrogen pressure during synthesis, and nanobead chains were synthesized for analogy analysis following a known procedure. Glucose hydrogenation over Ni nanosphere catalysts exhibits the lowest reaction barrier (Ea = 32 kJ/mol) compared to nanorods and nanobead chains (98 kJ/mol), and a constant sorbitol selectivity of 100 % was obtained at a temperature of 140 degrees C. A comprehensive characterization with ATR-IR, Raman, XPS, ICP, P-XRD, HRTEM and SAED revealed that the combined factors of poly-crystallinity, amorphous structure and P- dopant make Ni nanospheres superior. This provides a valuable path in the process of designing better non-noble catalysts to definitely avoid the use of noble metals in the future in biomass valorization reactions.(c) 2022 Elsevier Inc. All rights reserved.

Ni nanoparticles supported on carbon black (Ni/CB) with Ni particle sizes 6.9 nm - 23.5 nm were found to exhibit a size effect, with a significant impact on catalytic performance in the glucose hydrogenation reaction. A series of Ni nanoparticles with different sizes, as determined by statistical analysis of TEM images, were obtained by varying the synthesis temperature using a sol-gel method. The highest glucose conversion and sorbitol production in glucose hydrogenation was possible with Ni/CB catalysts with Ni particles size around 17 nm obtained at 550 o C. Similarly, GNP supported Ni with different particle sizes synthesized under different temperature conditions have an identical behaviour, that is, GNP-550 exhibits the highest catalytic performance. Therefore, it can be concluded that size effect appeared when the particle size is above 10 nm, which provides a reference for the design of subsequent catalysts for liquid phase hydrogenation reactions pertinent to biomass conversion.

Reported here is the first Fe-II based supramolecular cage with pyridyl-hydrazone ligand scaffolds that exhibits temperature induced spin crossover behaviour. Density functional theory calculations were employed to investigate the cause of the occurrence of this phenomenon based on the ligand structure. These results indicate that the reported low-spin cages with pyridyl-imine sites could be reconsidered for spin crossover by carefully manipulating the functional groups in the ligand system.

The design and construction of colorimetric ammonia (NH3) sensors with high selectivity, great stability and short response times at room temperature are highly needed for human health and food safety. We report herein a chiral supramolecular FeII4L4 metal-organic cage (MOC-1) able to detect NH3(g) at room temperature in less than 10 s, which we used to monitor food safety at 4 degrees C on fresh bacon bits. The detection is accompanied by a dramatic colour change from light brown to purple. In addition, MOC-1 exhibits superior selectivity among NH3(g) and twelve analytes including common solvents and amines. The reproducibility was studied by five continuous cyclic tests. Simple and low-cost smartphone-based and chemometrics analytical methods were used to study the sensing performance. The thermal stability is more than 200 degrees C. The sensing mechanism is associated with a high-spin to low-spin transition of the Fe-II ions, as expected for a ligand field strength that meets spin crossover conditions. These results show the high potential of MOC-1 as a convenient and inexpensive NH3 gas sensor at room temperature, which could be used in the field of food safety assessment.

Diversification of the structures and the applications possible for foldamers rely on expansion of the building block library available for their synthesis. In this work, we describe the synthesis of a range of three dimensional heteroaromatic monomers, based on iptycene scaffolds, that are suitable for the synthesis of aromatic oligoamide foldamers. These units can be obtained in gram quantities in up to 80 % yield through [4+2] cycloaddition between diester, diamine, and amino acid derivatives of 1,8-diazaanthracenes and a variety of dienophiles. X-ray structural studies of the monomers and an oligomer show that the new motif orients the two heterocyclic rings and attached groups at an angle of approximately 120° to each other, opening new geometric considerations for the design of this class of foldamer.

Carbon black (CB) supported Ni, Fe, or Fe-Ni alloy catalysts were synthesized by sol-gel to elucidate the reaction pathways over each catalyst, as well as synergistic effects in glucose to sorbitol hydrogenation. The bimetallic materials presented small and alloyed nanoparticles that were richer in reduced metallic sites at the surface than their monometallic counterparts. Glucose isomerization to fructose was favoured over Fe/CB, while glucose hydrogenation to sorbitol is the dominating pathway over Ni/CB catalyst. By contrast, sorbitol production was promoted and undesired isomerization was suppressed when Fe and Ni formed a nanoalloy. In addition, the alloy catalyst presented better stability than the corresponding monometallic catalyst. A comparison with a mechanical mixture of Fe/CB and Ni/CB monometallic catalysts demonstrated the synergy at the nanoscale in the alloy. By comparing different Fe:Ni ratios, the 1:1 formulation was identified as the best compromise to achieve a high activity while maintaining high sorbitol selectivity.

Correction for ‘Water binding stabilizes stacked conformations of ferrocene containing sheet-like aromatic oligoamides’ by Ya-Zhou Liu et al., Org. Biomol. Chem., 2021, DOI: 10.1039/d1ob00580d.

Efficient excited-state electron transfer between an iron(III) photosensitizer and organic electron donors was realized with green light irradiation. This advance was enabled by the use of the previously reported iron photosensitizer, [Fe(phtmeimb)2]+ (phtmeimb = {phenyl[tris(3-methyl-imidazolin-2-ylidene)]borate}, that exhibited long-lived and luminescent ligand-to-metal charge-transfer (LMCT) excited states. A benchmark dehalogenation reaction was investigated with yields that exceed 90% and an enhanced stability relative to the prototypical photosensitizer [Ru(bpy)3]2+. The initial catalytic step is electron transfer from an amine to the photoexcited iron sensitizer, which is shown to occur with a large cage-escape yield. For LMCT excited states, this reductive electron transfer is vectorial and may be a general advantage of Fe(III) photosensitizers. In-depth time-resolved spectroscopic methods, including transient absorption characterization from the ultraviolet to the infrared regions, provided a quantitative description of the catalytic mechanism with associated rate constants and yields.

The identification of reaction mechanisms unique to the iron, ruthenium, and iridium PS represents progress towards the long-sought goal of utilizing earth-abundant, first-row transition metals for emerging energy and environmental applications.

: Non-covalent interactions are important for directing protein folding across multiple intermediates and can even provide access to multiple stable structures with different properties and functions. Herein, we describe an approach for mimicking this behavior in the self-assembly of metal–organic cages. Two ligands, the bend angles of which are controlled by non-covalent interactions and one ligand lacking the above-mentioned interactions, were synthesized and used for self-assembly with Pd 2 + . As these weak interactions are easily broken, the bend angles have a controlled flexibility giving access to M 2 ( L1 ) 4 , M 6 ( L2 ) 12 , and M 12 ( L2 ) 24 cages. By controlling the self-as-sembly conditions this process can be directed in a stepwise fashion. Additionally, the multiple endohedral hydro-gen-bonding sites on the ligand were found to play a role in the binding and discrimination of neutral guests. to multiple M n L 2 n ( n = 2, 6 and 12) metal–organic cages. The shape of these ligands is stabilized by non-covalent interactions. This bestows a rigidity that allows access to the larger structures, while at the same time permitting a moderate degree of flexibility so that the bend angle can adapt to both the M 6 L 12 and M 12 L 24 cages. While the self-assembly of ligand L2 eventually gives an M 12 L 24 cage ( & 120 8 ), the narrower bend angle ( & 97 8 ) in the M 6 L 12 structure can allow for stronger intraligand non-covalent interactions. This can potentially stabilize it as a kinetic intermediate and allow for the unique step-wise self-assembly observed. Preliminary studies with Pd 2 ( L1 ) 4 showed the potential for interaction and discrimination of charge-neutral guests in highly polar solvents. This can be potentially interesting for applications in catalysis. Studies aimed at increasing the interaction with guests and fine-tuning the cage environments are underway and will be reported in due course.

As metalloproteins exemplify, the chemical and physical properties of metal centers depend not only on their first but also on their second coordination sphere. Installing arrays of functional groups around the first coordination sphere of synthetic metal complexes is thus highly desirable, but it remains a challenging objective. Here we introduce a novel approach to produce tailored second coordination spheres. We used bioinspired artificial architectures based on aromatic oligoamide foldamers to construct a rigid, modular and well-defined environment around a metal complex. Specifically, aza-aromatic monomers having a tethered [2Fe-2S] cluster have been synthesized and incorporated in conical helical foldamer sequences. Exploiting the modularity and predictability of aromatic oligoamide structures allowed for the straightforward design of a conical architecture able to sequester the metal complex in a confined environment. Even though no direct metal complex-foldamer interactions were purposely designed in this first generation model, crystallography, NMR and IR spectroscopy concurred to show that the aromatic oligoamide backbone alters the structure and fluxional processes of the metal cluster.

Non-covalent interactions are important for directing protein folding across multiple intermediates and can even provide access to multiple stable structures with different properties and functions. Herein, we describe an approach for mimicking this behavior in the self-assembly of metal-organic cages. Two ligands, the bend angles of which are controlled by non-covalent interactions and one ligand lacking the above-mentioned interactions, were synthesized and used for self-assembly with Pd2+. As these weak interactions are easily broken, the bend angles have a controlled flexibility giving access to M-2(L1)(4), M-6(L2)(12), and M-12(L2)(24)cages. By controlling the self-assembly conditions this process can be directed in a stepwise fashion. Additionally, the multiple endohedral hydrogen-bonding sites on the ligand were found to play a role in the binding and discrimination of neutral guests.