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The impact that the anion and alkyl group has on the electronic structures and magnetic properties of four mononuclear Mn(III) complexes is explored in [Mn(salEen-Br) 2 ]Y (salEen-Br = 2-{[2-(ethylamino)ethylimino]methyl}-4-Br-phenol; Y = ClO 4 - 1 and BF 4 - ·1/3CH 2 Cl 2 2 ) and [Mn(salBzen-Br) 2 ]Y (salBzen-Br = 2-{[2-(benzylamino)ethylimino]methyl}-4-Br-phenol; Y = ClO 4 - 3 and BF 4 - 4 ). X-ray structures of [Mn(salEen-Br) 2 ]ClO 4 ·0.45C 6 H 14 1-hexane , [Mn(salEen-Br) 2 ]BF 4 ·0.33CH 2 Cl 2 ·0.15C 6 H 14 2-dcm-hexane , and 3 - 4 reveal that they crystallize in ambient conditions in the monoclinic P 2 1 / c space group. Lowering the temperature, 2-dcm-hexane uniquely exhibits a structural phase transition toward a monoclinic P 2 1 / n crystal structure determined at 100 K with the unit cell trebling in size. Remarkably, at room temperature, the axially elongated Jahn-Teller axis in 2-dcm-hexane is poorly defined but becomes clearer at low temperature after the phase transition. Magnetic susceptibility measurements of 1 - 4 reveal that only 3 and 4 show slow relaxation of magnetization with Δ eff / k B = 27.9 and 20.7 K, implying that the benzyl group is important for observing single-molecule magnet (SMM) properties. Theoretical calculations demonstrate that the alkyl group subtly influences the orbital levels and therefore very likely the observed SMM properties.

In order to bind guest molecules with exquisite selectivity, biological host molecules often employ low symmetry binding pockets. The majority of metallosupramolecular assemblies, however, rely on symmetrical ligands to form high-symmetry assemblies that enclosing similarly symmetrical cavities. Here we employ an unsymmetrical quaterpyridine ligand in combination with cobalt(II) to form a mixture of low-symmetry [M 2 L 3 ] helicates and [M 4 L 6 ] tetrahedra and their subsequent oxidation to Co(III)-containing assemblies.

Despite the use of achiral ligands, the vast majority of metallosupramolecular assemblies containing octahedral tris-bidentate metal centres show strong stereochemical communication between metal centres, generally resulting in homochiral assemblies even though they are statistically disfavoured. Here we show that when resolved stereocentres are attached to the central part of a quaterpyridine ligand, the stereochemical coupling from this centre is insufficient to disrupt the strong stereochemical communication between metal centres in both [M 2 L 3 ] helicates and [M 4 L 6 ] tetrahedra.

Coordination cages can be used for enantio- and regioselective catalysis and for the selective sensing and separation of isomeric guest molecules. Here, stereoisomers of a family of coordination cages are resolved using ultra-high-resolution cyclic ion-mobility mass spectrometry (cIM-MS). The observed ratio of diastereomers is dependent on both the metal ion and counter ion. Moreover, the point groups can be assigned through complementary NMR experiments. This method enables the identification and interrogation of the individual isomers in complex mixtures of cages which cannot be performed in solution. Furthermore, these techniques allow the stability of individual isomers within the mixture to be probed, with the T-symmetric isomers in this case shown to be more robust than the C 3 and S 4 analogues., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Molecular crystals displaying elastic flexibility have important applications in the fields of optoelectronics and nanophotonic technologies. Understanding the mechanisms by which these materials bend is critical to the design of future materials incorporating these properties. Based on the known elastic properties of bis(acetylacetonato)copper(II), a series of 14 aliphatic derivatives are synthesized and crystallized. All those which grew in a needle morphology display noticeable elasticity, with 1D chains of π-stacked molecules parallel to the long metric length of the crystal a consistent crystallographic feature. Crystallographic mapping is used to measure the mechanism of elasticity at an atomic-scale. Symmetric derivatives with ethyl and propyl side chains are found to have different mechanisms of elasticity, which are further distinguished from the previously reported mechanism of bis(acetylacetonato)copper(II). While crystals of bis(acetylacetonato)copper(II) are known to bend elastically via a molecular rotation mechanism, the elasticity of the compounds presented is facilitated by expansion of their π-stacking interactions., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)

Organic materials are promising candidates for the development of efficient sensors for many medicinal and materials science applications. Single crystals of a small molecule, 4-trifluoromethyl phenyl isothiocyanate (4CFNCS), exhibit plastic deformation when bent, twisted, or coiled. Synchrotron micro-focus X-ray diffraction mapping of the bent region of the crystal confirms the mechanism of deformation. The crystals are incorporated into a flexible piezoresistive sensor using a composite constituting PEDOT: PSS/4CFNCS, which shows an impressive performance at high-pressure ranges (sensitivity 0.08 kPa -1 above 44 kPa)., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

Coordination cages with well-defined cavities show great promise in the field of catalysis on account of their unique combination of molecular confinement effects and transition-metal redox chemistry. Here, three coordination cages are reduced from their native 16 + oxidation state to the 2 + state in the gas phase without observable structural degradation. Using this method, the reaction rate constants for each reduction step were determined, with no noticeable differences arising following either the incorporation of a C 60 -fullerene guest or alteration of the cage chemical structure. The reactivity of highly reduced cage species toward molecular oxygen is "switched-on" after a threshold number of reduction steps, which is influenced by guest molecules and the structure of cage components. These new experimental approaches provide a unique window to explore the chemistry of highly-reduced cage species that can be modulated by altering their structures and encapsulated guest species., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The radical reactions of dimethylsulfoxide (DMSO) and tetrahydrothiophene-1-oxide (THTO) with reactive oxygen species (ROS) in the presence of a nitroxide radical scavenger have been evaluated both synthetically and in analytical practice. Fenton-mediated generation of oxygen-centred radicals produced several unusual products that reflect the fragmentation and ring-opening radical mechanisms of DMSO and THTO respectively. Addition of pollution-derived ROS to DMSO/THTO nitroxide solutions produced LC-MS detectable amounts of the same products isolated from the larger-scaled Fenton reactions. For air pollution analysis, these results highlight the complexity surrounding DMSO reactivity and fragmentation, and indicate that THTO produces simpler outcomes that should facilitate analysis of the processes involved.

The interplay of many factors influences the outcomes of self-assembly reactions. Using an acetylene-appended quaterpyridine ligand we show that both the size of the metal ion and the presence of steric repulsion between the acetylene groups result in the exclusive formation of [M 2 L 3 ] helicates rather than a helicate/tetrahedron equilibrium.

Self-assembled coordination cages and metal-organic frameworks have relied extensively on symmetric ligands in their formation. Here we have prepared a relatively simple system employing an unsymmetric ligand that results in two distinct self-assembled structures, a [Fe 2 L 3 ] 4+ helicate and a [Fe 4 L 6 ] 8+ cage composed of 10 interconverting diastereomers and their enantiomers. We show that the steric profile of the ligand controls the complexity, thermodynamics and kinetics of interconversion of the system., (© 2021 Wiley-VCH GmbH.)