Bicyclo[1.1.1]pentanes (BCPs) have emerged as isosteric replacements for mono- and para-substituted benzene rings in medicinal and materials applications, involving substitution at the BCP bridgehead (1,3-positions). BCP functionalization at the 2-position is much less straightforward and currently under intense investigation. Herein, we report a synthetic route to 2-methyl BCPs allowing for functionalization at the 1,3-positions, with the novel 2-methyl[1.1.1]propellane as a key intermediate. Next to an optimization for the synthesis of 2-Me-propellane, this work contains an investigation of its reactivity leading to 1,2-disubstituted and 1,2,3-trisubstituted BCP derivatives. Compared to nonsubstituted propellane, the synthesis of 2-methyl propellane was lower-yielding, and its ring-opening reactions proceeded in similar or lower yields, with radical-based reactions generally giving the best results. A preliminary study of selected physicochemical properties was conducted to assess the impact of the introduction of a bridge-methyl group, showing an expected increase of about 0.5 logP units and featuring lower melting points.

The present study discloses for the first time furanose structures in imines derived from 2-amino-2-deoxyaldoses, thus assessing the anomeric equilibria. In DMSO solution, imines derived from d-galactosamine, [(2R,3R,4R,5R,6R)-3-amino-6-hydroxymethyltetrahydropyran-2,4,5-triol], exist in equilibrium between α and β anomers of the corresponding pyranose and furanose forms. In parallel analogy to glycoimines existing exclusively in pyranoid structures, β-anomers are extensively favored, a bias that can now be ascribed with confidence to a genuine reverse anomeric effect. Specifically, this effect describes a conformational preference opposite to the anomeric effect, thereby implying a destabilization of the axial anomer (α-anomer) together with pure steric effects. As extensively detailed throughout this paper by experimental and computational methods, the core argument is the existence, in both α-pyranose and α-furanose imines, of an intramolecular hydrogen bond between the anomeric hydroxyl and the nitrogen atom that inhibits the exo-anomeric effect. Moreover, solvation may synergistically reinforce this inhibition of the exo-anomeric effect, thus favoring the predominance of the β-anomer.

Precise molecular control has become a highly attractive feature to develop the next generation of upconversion materials for autofluorescence-free deep tissue imaging. However, in aqueous environments, upconversion molecules are orders of magnitude dimmer than inorganic upconversion nanoparticles, thereby strongly limiting their applicability to bioimaging. By encapsulating ca. 1,900 upconversion molecules into sub-40 nm polymer nanoparticles, we show that molecular precision and nanomaterial brightness can be combined into a new type of hybrid nanomaterial. The brightness of these molecular upconversion nanoparticles (UCMol-NPs) is almost on par with widely used inorganic upconversion nanoparticles, permitting the experimental demonstration of live-cell imaging with UCMol-NPs, an important step toward advancing molecular upconversion into the application era. Fabrication, characterization, and modeling of UCMol-NPs with various sizes and loadings reveal that significant brightness enhancement is possible. This will be paramount for advancing upconversion beyond the current limits of inorganic nanoparticles and translating them into clinical applications.

One-dimensional (1D) antiferromagnetic chains are fascinating because of their exotic quantum phenomena. However, isolating large-spin S chains remains challenging as even minimal interchain interaction J ' tends to drive unwanted long-range ordering. Here, we report on the synthesis, crystal structure, magnetism, optical, and electronic properties of two isostructural metal-organic frameworks (MOFs), [M-2(mCB-L)(2)(mu(2)-H2O)(2)(DMF)(4)](n)solv (M = Co(ii) (mCB-Co) or Ni(ii) (mCB-Ni)), which feature water-bridged Co (S = 3/2) or Ni (S = 1) spin chains that are effectively separated by bulky carborane linkers (1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane, mCBLH(2)). The temperature-dependent susceptibility reveals strong antiferromagnetic interactions with significant intrachain coupling, J(Co)/k(B) = -4.65 K (mCB-Co) and J(Ni)/k(B) = -23.36 K (mCB-Ni), yet confirm the absence of long-range order down to 0.3 K due to negligible interchain interactions, as corroborated by specific heat data. This indicates extremely small J ', with J '/J < 4.7 x 10(-4) (3.7 x 10(-5)) for Co (Ni) MOFs, making these new materials nearly ideal 1D antiferromagnets. Additionally, optical band gaps were estimated via the Kubelka-Munk method, yielding an increase from 3.83 eV for mCB-Co to 4.20 eV for mCB-Ni, showcasing tunable electronic properties across the two MOFs.

The introduction of added '3-dimensionality' through late-stage functionalisation of extended (hetero)aromatic systems is a powerful synthetic approach. The abundance of starting materials and cross-coupling methodologies to access the precursors allows for highly diverse products. Subsequent selective partial reduction can alter the core structure in a manner of interest to medicinal chemists. Herein, we describe the precise, partial reduction of multicyclic heteroaromatic systems using a simple heterogeneous catalyst. The approach can be extended to introduce deuterium (again at late-stage). Excellent yields can be obtained using simple reaction conditions. The introduction of added '3-dimensionality' through late-stage functionalisation is a powerful synthetic approach to biologically significant moieties. Herein, a hydrogenative, regioselective dearomatisation of extended (hetero)aromatic systems is described, using a simple Pd catalyst at atmospheric hydrogen pressure. Deuteration is also demonstrated and some initial mechanistic insights are revealed.+ image

The reverse anomeric effect is usually associated with the equatorial preference of nitrogen substituents at the anomeric center. Once postulated as another anomeric effect with explanations ranging from electrostatic interactions to delocalization effects, it is now firmly considered to be essentially steric in nature. Through an extensive research on aryl imines from 2-amino-2-deoxyaldoses, spanning nearly two decades, we realized that such substances often show an anomalous anomeric behavior that cannot easily be rationalized on the basis of purely steric grounds. The apparent preference, or stabilization, of the β-anomer takes place to an extent that not only neutralizes but also overcomes the normal anomeric effect. Calculations indicate that there is no stereoelectronic effect opposing the anomeric effect, resulting from the repulsion between electron lone pairs on the imine nitrogen and the endocyclic oxygen. Such data and compelling structural evidence unravel why the exoanomeric effect is largely inhibited. We are now confident, as witnessed by 2-iminoaldoses, that elimination of the exo-anomeric effect in the α-anomer is due to the formation of an intramolecular hydrogen bond between the anomeric hydroxyl and the iminic nitrogen, thereby accounting for a true electronic effect. In addition, discrete solvation may help justify the observed preference for the β-anomer.

A series of tin(II) triflate phosphine oxide complexes has been prepared from the reaction of Sn(OTf)2 (OTf- = [O3SCF3]-) with various ratios of OPPh3, OPMe3 or dppmO2 (dppmO2 = Ph2(O)PCH2P(O)Ph2). The complexes [Sn(OPPh3)n][OTf]2 (n = 2, 3 or 4), [Sn(OPMe3)n][OTf]2 (n = 2 or 3) and [Sn(dppmO2)n][OTf]2 (n = 1 or 2) have been isolated in moderate to good yields. Selected germanium(II) and lead(II) analogues have been made for comparison, namely [Ge(OPPh3)n][OTf]2 (n = 2 or 3) and [Pb(OPR3)4][OTf]2 (R = Me, Ph). The effect of changing the weakly coordinating OTf- anion for the non-coordinating [BArF]- anion was investigated through anion metathesis, furnishing the complexes [Sn(OPPh3)n][BArF]2 (n = 3 or 4) and [Ge(OPPh3)3][BArF]2. The isolated solids were characterised by 1H, 19F{1H}, 31P{1H} and IR spectroscopy and microanalysis. Crystal structures were obtained for all complexes except [Ge(OPPh3)2][OTf]2 and [Sn(OPPh3)3][BArF]2, allowing comparisons of the structural features of these divalent group 14 complexes down the group and as a function of coordination number, ligand sterics and electronics. Thirteen heavy group 14 phosphine oxide complexes were synthesised. This work shows that the solid-state structures of these compounds depend on ligand type, metal and counter anion. image

The cavity inside fullerene C 60 provides a highly symmetric and inert environment for housing atoms and small molecules. Here we report the encapsulation of formaldehyde inside C 60 by molecular surgery, yielding the supermolecular complex CH 2 O@C 60 , despite the 4.4 Å van der Waals length of CH 2 O exceeding the 3.7 Å internal diameter of C 60 . The presence of CH 2 O significantly reduces the cage HOMO-LUMO gap. Nuclear spin-spin couplings are observed between the fullerene host and the formaldehyde guest. The rapid spin-lattice relaxation of the formaldehyde 13 C nuclei is attributed to a dominant spin-rotation mechanism. Despite being squeezed so tightly, the encapsulated formaldehyde molecules rotate freely about their long axes even at cryogenic temperatures, allowing observation of the ortho-to-para spin isomer conversion by infrared spectroscopy. The particle in a box nature of the system is demonstrated by the observation of two quantised translational modes in the cryogenic THz spectra.

We report a de novo enantioselective synthesis of 2,3,4-trideoxy-2,2,3,3,4,4-hexafluoro-d-glycero-hexopyranose (hexafluorinated d-glucose), an iconic polar hydrophobic glycomimetic. The 12-step synthesis features robust and reproducible chemistry and was achieved by incorporating an asymmetric dihydroxylation step to install the stereogenic center with excellent enantioselectivity (95:5 er). Virtual enantiopurity (>99.5% ee) was further reached using a simple crystallization procedure and the absolute confirmation was ascertained by X-ray analysis. The synthetic route also allowed access to the novel hexafluorinated heptose derivative 2,3,4-trideoxy-2,2,3,3,4,4-hexafluoro-l-threo-heptopyranose.

This paper explores and revisits in detail the formation and characterization of sugar-based aminonitriles, whose ultimate origin can be traced to the interaction of biomolecules with cyanide. Although the synthesis and spectroscopic data of 2-amino-aldononitriles were reported long ago, there are both contradictory and confusing results among the published data. We have now addressed this concern through an exhaustive structural elucidation of acylated 2-amino- and 2-alkyl(aryl)amino-2-deoxyaldonitriles using mass spectrometry and FT-IR, FT–Raman, and NMR spectroscopies. Several structures could be unambiguously determined through single-crystal X-ray diffraction, which allowed us to correct other misassignments. Moreover, this study unveils how steric and electronic effects influence the acylation outcome of the amino, (alkyl, aryl)amino, or acetamido group at C-2. The chirality at the latter, which was assigned tentatively through optical rotation correlation, and hence the preferential threo stereochemistry generated during the cyanohydrin synthesis of 2-amino-2-deoxy aldononitriles have now been established with confidence.

Multi‐metallic multivariate (MTV) rare earth (RE) metal−organic frameworks (MOFs) are of interest for the development of multifunctional materials, however examples with more than three RE cations are rare and obstructed by compositional segregation during synthesis. Herein, this work demonstrates the synthesis of a multi‐metallic MTV RE MOF incorporating two, four, six, or eight different RE ions with different sizes and in nearly equimolar amounts and no compositional segregation. The MOFs are formed by a combination of RE cations (La, Ce, Eu, Gd, Tb, Dy, Y, and Yb) and a 1,7‐di(4‐carboxyphenyl)‐1,7‐dicarba‐ closo ‐dodecaborane ( m CB‐L) linker. The steric bulkiness and acidity of m CB‐L is crucial for the incorporation of different size RE ions into the MOF structure. Demonstration of the incorporation of all RE cations is performed via compositional and structural characterization. The more complex MTV MOF, including all eight RE ions ( m CB‐8RE), are also characterized using optical, thermal, and magnetic techniques. Element‐selective X‐ray absorption spectroscopy and X‐ray Magnetic Circular Dichroism measurements allow us to characterize spectroscopically each of the eight RE ions and determine their magnetic moments. This work paves the way for the investigation of MTV MOFs with the possibility to combine RE ions à la carte for diverse applications.

This work demonstrates a large area process for atomically thin 2D semiconductors to unlock the technological upscale required for their commercial uptake. The new atomic layer deposition (ALD) and conversion technique yields large area performance uniformity and tunability. Like graphene, 2D Transition Metal Dichalcogenides (TMDCs) are prone to upscaling challenges limiting their commercial uptake. They are challenging to grow uniformly on large substrates and to transfer on alternative substrates while they often lack in large area electrical performance uniformity. The scalable ALD process of this work enables uniform growth of 2D TMDCs on large area with independent control of layer thickness, stoichiometry and crystallinity while allowing chemical free transfers to application substrates. Field effect transistors (FETs) fabricated on flexible substrates using the process present a field effect mobility of up to 55 cm 2 /Vs, subthreshold slope down to 80 mV/dec and on/off ratios of 10 7 . In addition, non-volatile memory transistors using ferroelectric FETs (FeFETs) operating at ±5 V with on/off ratio of 10 7 and a memory window of 3.25 V are demonstrated. These FeFETs demonstrate state-of-the-art performance with multiple state switching, suitable for one-transistor non-volatile memory and for synaptic transistors revealing the applicability of the process to flexible neuromorphic applications.

One-pot processes which facilitate a number of tandem reactions, represent an environmentally friendly approach to building molecular complexity.

This paper thoroughly explores the formation of Schiff bases derived from salicylaldehydes and a conformationally restricted amino alcohol (1-amino-2-indanol), as well as the generation of 1,3-oxazolidines, a key heterocyclic core present in numerous bioactive compounds. We provide enough evidences, both experimental-including crystallographic analyses and DFT-based calculations on imine/enamine tautomerism in the solid state and solution. In the course of imine formation, a pentacyclic oxazolidine–oxazine structure could be isolated with complete stereocontrol, whose configuration has been determined by merging theory and experiment. Mechanistic studies reveal that, although oxazolidines can be obtained under kinetic conditions, the prevalence of imines obeys to thermodynamic control as they are the most stable structures. The stereochemical outcome of imine cyclization under acylating conditions leads to formation of 2,4-trans-oxazolidines.

Mn-catalysed C–H activation has emerged as a useful sustainable methodology for the formation of new C–C bonds. To date most of the protocols are described in organic solvents. Water as solvent, on the other hand, would be highly advantageous, but is often incompatible with organometallic chemistry. Herein, we describe the C–H activation of indoles using an unmodified, commercially available manganese catalyst in water. Two types of valuable allyl groups can be added and a good substrate scope is described. Substitution at the C-3 group is tolerated, allowing access to medicinally important frameworks, and the reaction works on a gram scale. Finally, harnessing the tolerance of water as the reaction medium, D2O can be used as an inexpensive source of deuterium for the C-2 labelling of indoles.

Through a combination of X-ray and neutron total scattering and Empirical Potential Structure Refinement (EPSR) we explore the prenucleation structures of saturated aqueous magnesium sulfate. The atomistic model we present reveals a system characterised by isolated octahedral aquo magnesium species Mg(H2O)(6), magnesium sulfate pairs (Mg(H2O)(5)SO4) and extended clusters built from corner-sharing MgO6 and SO4 polyhedra. Many of these features are directly observed in the crystal structures of the known solid form hydrates, including isolated polyhedra, corner sharing chains and rings, and it is only for the extended 3D polyhedral networks of the lower hydrates (mono- & di-) that no proto structures are observed in 2M solution. Looking at the average first solvation shell of the sulfate anion we see a complex and flexible environment that commonly includes water molecules brought into proximity by a coordinated hydrated magnesium. What emerges is a high probability that 10 water molecules will be observed in a combined tetrahedral/octahedral arrangement with a further 7 taking up more dispersed positions giving an average coordination of 17. The tendency for ions to aggregate into clusters allows areas of bulk water to exist that exhibit subtle differences in structure to that of pure water.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The removal of organophosphorus (OP) herbicides from water has been studied using adsorptive removal, chemical oxidation, electrooxidation, enzymatic degradation, and photodegradation. The OP herbicide glyphosate (GP) is one of the most used herbicides worldwide, leading to excess GP in wastewater and soil. GP is commonly broken down in environmental conditions to compounds such as aminomethylphosphonic acid (AMPA) or sarcosine, with AMPA having a longer half-life and similar toxicity to GP. Metal-organic frameworks (MOFs) are excellent materials for purifying OP herbicides from water due to their ability to combine adsorption and photoactivity within one material. Herein, we report the use of a robust Zr-based MOF with a meta-carborane carboxylate ligand (mCB-MOF-2) to examine the adsorption and photodegradation of GP. The maximum adsorption capacity of mCB-MOF-2 for GP was determined to be 11.4 mmol/g. Non-covalent intermolecular forces between the carborane-based ligand and GP within the micropores of mCB-MOF-2 are thought to be responsible for strong binding affinity and capture of GP. After 24 h of irradiation with ultraviolet-visible (UV-vis) light, mCB-MOF-2 selectively converts 69% of GP to sarcosine and orthophosphate, following the C-P lyase enzymatic pathway and biomimetically photodegrading GP. Circumventing the production of AMPA is desirable, as it has a longer half-life and similar toxicity to GP. The exceptional adsorption capacity of GP by mCB-MOF-2 and its biomimetic photodegradation to non-toxic sarcosine make it a promising material for removing OP herbicides from water.

This paper documents and reinvestigates the solid-state and crystal structures of 4,4'-azobis-4-cyanopentanoic acid (ACPA), a water-soluble azobis-nitrile of immense utility as a radical initiator in living polymerizations and a labile mechanophore that can be embedded within long polymer chains to undergo selective scission under mechanical activation. Surprisingly, for such applications, both the commercially available reagent and their derivatives are used as "single initiators" when this azonitrile is actually a mixture of stereoisomers. Although the racemate and meso compounds were identified more than half a century ago and their enantiomers were separated by classical resolution, there have been confusing narratives dealing with their characterization, the existence of a conglomeratic phase, and fractional crystallization. Our results report on the X-ray crystal structures of all stereoisomers for the first time, along with further details on enantiodiscrimination and the always intriguing arguments accounting for the stability of homochiral versus heterochiral crystal aggregates. To this end, metadynamic (MTD) simulations on stereoisomer molecular aggregates were performed to capture the incipient nucleation events at the picosecond time scale. This analysis sheds light on the driving homochiral aggregation of ACPA enantiomers.

The reaction of 2,6-diformyl-4-methylphenyl disulfide with [Ni(tn)3]Cl2 (tn = 1,3-diaminopropane), in methanol and in the presence of NaBPh4 resulted in the isolation of [Ni2(L1)](DMF)2(BPh4)2 (I), (L1 = 15,95-dimethyl-3,7,11,15-tetraaza-1,9(1,3)-dibenzenacyclohexadecaphane-2,7,10,15-tetraene-12,92-bis(thiolate). This reaction represents a 2-electron solvent assisted reduction of the disulfide bond to form two thiolate ligands where methanol is converted to formaldehyde and the two nickel centres remained in the + 2 oxidation state. The crystal structure of I showed the two nickel(II) atoms are bridged by two thiolates in a binuclear Ni2S2 core inside of a macrocyclic framework. The IR spectrum showed a band at 1625 cm-1, assigned to the imine nu(C --N) stretch of the macrocyclic ligand, and bands at 734, 706 cm-1, are assigned to the tetraphenylborate counter ions. This is the first example of solvent assisted S-S bond cleavage being used to prepare a dicompartmental macrocyclic complex.