An Efficient Strategy for Self-Assembly of DNA-Mimic Homochiral 1D Helical Cu(II) Chain from Achiral Flexible Ligand by Spontaneous Resolution

New Dimension in Magnetism and Superconductivity: 3D and Curvilinear Nanoarchitectures

Traditionally, the primary field, where curvature has been at the heart of research, is the theory of general relativity. In recent studies, however, the impact of curvilinear geometry enters various disciplines, ranging from solid-state physics over soft-matter physics, chemistry, and biology to mathematics, giving rise to a plethora of emerging domains such as curvilinear nematics, curvilinear studies of cell biology, curvilinear semiconductors, superfluidity, optics, 2D van der Waals materials, plasmonics, magnetism, and superconductivity. Here, the state of the art is summarized and prospects for future research in curvilinear solid-state systems exhibiting such fundamental cooperative phenomena as ferromagnetism, antiferromagnetism, and superconductivity are outlined. Highlighting the recent developments and current challenges in theory, fabrication, and characterization of curvilinear micro- and nanostructures, special attention is paid to perspective research directions entailing new physics and to their strong application potential. Overall, the perspective is aimed at crossing the boundaries between the magnetism and superconductivity communities and drawing attention to the conceptual aspects of how extension of structures into the third dimension and curvilinear geometry can modify existing and aid launching novel functionalities. In addition, the perspective should stimulate the development and dissemination of research and development oriented techniques to facilitate rapid transitions from laboratory demonstrations to industry-ready prototypes and eventual products.

A cobalt-based coordination polymer with a tripodal carboxylate ligand: synthese, structure and properties

A new cobalt-based coordination polymer (CP), [Co(Htatb)(1,4-bib)]·DMF (1), has been hydrothermally synthesized from CoCl2 ·6H2O, 4,4′,4′′-s-triazine-2,4,6-tribenzoic acid (H3tatb), and 1,4-bis(1-imidazoly)benzene (1,4-bib). The product has been characterized by IR spectroscopy, elemental and thermogravimetric analysis, and single-crystal X-ray diffraction. In compound 1, the Htatb ligand links three CoII ions resulting in a double-strand chain structure, further bridged through the 1,4-bib ligands to generate a 2D structure with channels. The fluorescence and cyclovoltammetry characteristics of compound 1 have also been investigated.

Homochiral metal-organic frameworks for enantioseparation

Obtaining homochiral compounds is of high importance to human health and environmental sustainability. Currently, enantioseparation is one of the most effective approaches to obtain homochiral compounds. Thanks to their controlled synthesis and high efficiency, homochiral metal-organic frameworks (HMOFs) are one of the most widely studied porous materials to enable enantioseparation. In this review, we discuss the chiral pocket model in depth as the key to unlock enantioselective separation mechanisms in HMOFs. In particular, we classify our discussion of these chiral pockets (also regarded as "molecular traps") into: (a) achiral/chiral linker based helical channels as a result of packing modality; and (b) chiral pores inherited from chiral ligands. Driven by a number of mechanisms of enantioseparation, conceptual advances have been recently made in the design of HMOFs for achieving high enantioseparation performances. Herein, these are systematically categorised and discussed. Further we elucidate various applications of HMOFs as regards enantioseparation, systematically classifying them into their use for purification and related analytical utility according to the reported examples. Last but not the least, we discuss the challenges and perspectives concerning the rational design of HMOFs and their corresponding enantioseparations.

Water-Stable Cobalt-Based MOF for Water Oxidation in Neutral Aqueous Solution: A Case of Mimicking the Photosystem II

Inspired by the highly efficient water oxidation of Mn₄CaO₅ in natural photosynthesis, development of novel artificial water oxidation catalysts (WOCs) with structure and function mimicked has inspired extensive interests. A novel 3D cobalt-based MOF (GXY-L8-Co) was synthesized for promising artificial water oxidation by employing the Co₄O₄ quasi-cubane motifs with a similar structure as the Mn₄CaO₅ as the core. The GXY-L8-Co not only shows good chemical stability in common organic solvents or water for up to 10 days but also exhibits oxygen evolution performance. It has been demonstrated that the uniform distribution of Co₄O₄ catalytic active sites confined in the MOF framework should be responsible for the good robustness and catalytic performance.

Curvilinear One-Dimensional Antiferromagnets

Antiferromagnets host exotic quasiparticles, support high frequency excitations and are key enablers of the prospective spintronic and spin-orbitronic technologies. Here, we propose a concept of a curvilinear antiferromagnetism where material responses can be tailored by a geometrical curvature without the need to adjust material parameters. We show that an intrinsically achiral one-dimensional (1D) curvilinear antiferromagnet behaves as a chiral helimagnet with geometrically tunable Dzyaloshinskii-Moriya interaction (DMI) and orientation of the Néel vector. The curvature-induced DMI results in the hybridization of spin wave modes and enables a geometrically driven local minimum of the low-frequency branch. This positions curvilinear 1D antiferromagnets as a novel platform for the realization of geometrically tunable chiral antiferromagnets for antiferromagnetic spin-orbitronics and fundamental discoveries in the formation of coherent magnon condensates in the momentum space.

Elucidation of the Structure of a Thiol Functionalized Cu-tmpa Complex Anchored to Gold via a Self-Assembled Monolayer

The structure of the copper complex of the 6-((1-butanethiol)oxy)-tris(2-pyridylmethyl)amine ligand (Cu-tmpa-O(CH₂)₄SH) anchored to a gold surface has been investigated. To enable covalent attachment of the complex to the gold surface, a heteromolecular self-assembled monolayer (SAM) of butanethiol and a thiol-substituted tmpa ligand was used. Subsequent formation of the immobilized copper complex by cyclic voltammetry in the presence of Cu(OTf)₂ resulted in the formation of the anchored Cu-tmpa-O(CH₂)₄SH system which, according to scanning electron microscopy and X-ray diffraction, did not contain any accumulated copper nanoparticles or crystalline copper material. Electrochemical investigation of the heterogenized system barely showed any redox activity and lacked the typical Cu^II/I redox couple in contrast to the homogeneous complex in solution. The difference between the heterogenized system and the homogeneous complex was confirmed by X-ray photoelectron spectroscopy; the XPS spectrum did not show any satellite features of a Cu^II species but instead showed the presence of a Cu^I ion in a ∼2:3 ratio to nitrogen and a ∼2:7 ratio to sulfur. The +I oxidation state of the copper species was confirmed by the edge position in the X-ray absorption near-edge structure (XANES) region of the X-ray absorption spectrum. These results show that upon immobilization of Cu-tmpa-O(CH₂)₄SH, the resulting structure is not identical to the homogeneous Cu^II-tmpa complex. Upon anchoring, a novel Cu^I species is formed instead. This illustrates the importance of a thorough characterization of heterogenized molecular systems before drawing any conclusions regarding the structure–function relationships.

Both the oxidation state and the structure of the Cu^II complex of tris(2-pyridylmethyl)amine (Cu-tmpa) change upon anchoring it to a gold surface via a self-assembled monolayer. It was shown by XPS and XANES that a Cu^I species is formed upon anchoring instead in which each tmpa ligand contains roughly two to three copper ions.

{Ni4} Cubanes from enantiomerically pure 2-(1-hydroxyethyl)pyridine ligands: supramolecular chirality

Homometallic {NiII4} cubane-like clusters with a rare chiral core have been prepared via the employment of enantiomerically pure 2-(1-hydroxyethyl)pyridine (Hmpm). Comparison with the achiral cubanes derived from the related 2-pyridinemethanol (Hpym) ligand reveals drastic structural changes as a consequence of the transfer of chirality from the ligands to the whole structure. Their magnetic properties have been related to the structural features of their cubane-type cores.

Structure, DFT Calculations, and Magnetic Characterization of Coordination Polymers of Bridged Dicyanamido-Metal(II) Complexes

Three coordination polymers of metal(II)-dicyanamido (dca) complexes with 4-methoxypyridine-N-oxide (4-MOP-NO); namely, catena-[Co(µ1,5-dca)2(4-MOP-NO)2] (1), catena-[Mn(µ1,5-dca)2(4-MOP-NO)2] (2), catena-[Cd(µ1,5-dca)2(4-MOP-NO)2] (3), and the mononuclear [Cu(κ1dca)2(4-MOP-NO)2] (4), were synthesized in this research. The complexes were analyzed by single crystal X-ray diffraction as well as spectroscopic methods (UV/vis, IR). The polymeric 1-D chains in complexes 1–3 were achieved by the doubly µ1,5-bridging dca ligands and the O-donor atoms of two axial 4-MOP-NO molecules in trans configuration around the distorted M(II) octahedral. On the other hand, the two “trans-axial” pyridine-N-oxide molecules in complexes 2 and 3 display opposite orientation (s-trans). The DFT (density functional theory) computational studies on the complexes 1–3 were consistent with the experimentally observed crystal structures. Compounds 1 and 2 display weak antiferromagnetic coupling between metal ions (J = −10.8 for 1 and −0.35 for 2).

Three cobalt-based coordination polymers with tripodal carboxylate and imidazole-containing ligands: syntheses, structures, properties and DFT studies

The tripodal carboxylate ligand can be employed in Co(ii) salt/imidazole-containing ligand systems to generate 1D chain, 2D layer, and 2D to 3D network, and the fluorescence properties of 1–3 and magnetic behavior of 1 and 2 have been investigated.

Low-dimensional compounds containing cyanido groups. Part XXXV. Structure, spectral, thermal and magnetic properties of a binuclear CuII-biquinoline complex with bridging and terminal dicyanamide ligands

From the system CuCl₂-biq-NaN(CN)₂ (biq is 2,2'-biquinoline), the binuclear molecular complex bis(μ-dicyanamido-κ²N¹:N⁵)bis[(2,2'-biquinoline-κ²N,N')(dicyanamido-κN¹)copper(II)], [Cu₂(C₂N₃)₄(C₁₈H₁₂N₂)₂] or [Cu₂(biq)₂(dca)₂(μ_1,5-dca)₂] (1) [dca is dicyanamide, N(CN)₂^-] was isolated and characterized by crystal structure analysis, and spectral, thermal and magnetic measurements. IR spectroscopy confirmed the presence of the biq and dca ligands in 1. Its solid-state structure consists of discrete centrosymmetric binuclear copper(II) units with double end-to-end dca bridges. Each Cu^II atom is in a distorted square-pyramidal environment with the equatorial plane formed by two nitrile N atoms from bridging dca groups, one of the two N atoms of the chelate biq molecule and one nitrile N atom from a terminal dca ligand, whereas the second biq N atom occupies the axial position. Thermal decomposition of 1 in an air atmosphere proceeds gradually, with copper(I) cyanide being the final decomposition product. Magnetic measurements revealed the formation of alternating spin chains and a relatively strong exchange interaction within the binuclear units was also confirmed by Broken Symmetry DFT (density functional theory) calculations.

Organic core-shell-shaped micro/nanoparticles from twisted macrocycles in Schiff base reaction

A series of organic core–shell-shaped micro/nanoparticles from twisted enantiomeric macrocycles could be obtained in Schiff base reaction with high yield at room temperature.

Functional self-assemblies derived from noncovalent interactions such as lipid vesicles and DNA chiral double helices are a typical feature of natural life activity. Because of this phenomenon, a self-assembly approach for various functional organic particles is a desirable objective in supramolecular chemistry. Here, we report the discovery of enantiomeric conformers from a twisted macrocyclic host (MH), which was obtained from an achiral precursor by Schiff base reaction. Further studies suggest that a series of unexpected and stable core–shell-based organic micro/nanospheres can be directly precipitated from a simple reaction solution with high yield. A single-crystal X-ray diffraction analysis of MH revealed that the unusual C–H···π interaction triggered self-assembly of the enantiomeric forms in the solid state plays an important role in the formation of the core–shell-shaped organic particles.

Low-dimensional compounds containing cyanido groups. Part XXXIV. Structure, spectral and magnetic properties of the first complex with pyridylbenzimidazole and nonlinear pseudohalide anion

From the system CuCl2 – pbi – NaN(CN)2 −, polymeric [CuCl(μ1,5-dca)(pbi)]n·nH2O (1) complex (dca=dicyanamide, pbi=2-(2-pyridyl)benzimidazole) was isolated and characterized by structure analysis, spectral and magnetic measurements. Infrared spectroscopy confirmed the presence of pbi, dca and water molecules in 1. Its solid-state structure is formed by infinite chains running along the b axis. In the chain, the Cu(II) atom is penta-coordinated by two nitrogen atoms of chelate pbi ligand, by two nitrile nitrogen atoms of bridging μ1,5-dca and by chloride ligand which occupies the apical position of tetragonal pyramid around the Cu(II) atom. Asymmetric unit is supplemented by one molecule of solvated water, which along with chlorine atom serves as acceptors in intermolecular hydrogen bonds and along with π–π interactions create a 3D supramolecular structure. Magnetic measurements revealed the presence of a weak ferromagnetic exchange interaction J/kB =0.11 K.

Chiral and achiral 1D copper(ii) coordination polymers based on glycolato and chelating aromatic diamine ligands

New chiral and achiral 1D coordination polymers based on glycolato and chelating aromatic diamine ligands.

Selective chiral symmetry breaking and luminescence sensing of a Zn(ii) metal–organic framework

The non-random handedness excess is observed in a chiral metal–organic framework [(CH₃)₂NH₂]₅[Zn_1.5(Zn₃O)(TATAT)₂]·9DMF·17H₂O (1, 1P ≫ 1M) without any chiral sources.

Chiral metal–organic frameworks constructed from four-fold helical chain SBUs for enantioselective recognition of α-hydroxy/amino acids

Three chiral 3D metal–carboxylate frameworks have been successfully synthesized, featuring four-fold helical metal chains as SBUs. Co-MOFs could recognize enantio-selectively α-hydroxy/amino acids by the change of CD signals.

Composite cluster-organic frameworks based on polyoxometalates and copper/cobalt–oxygen clusters

The first two cluster organic frameworks based on Anderson-type polyoxometalates and copper/cobalt-oxo cluster secondary building units have been successfully made under solvothermal conditions.

pH-Dependent structural diversity of a 2-pyridinemethanol Cu complex and its relatively strong magnetic exchange coupling via hydrogen bonding

The diversity of the self-assembled structures of a Cu complex via hydrogen bonding, including a square planar unit, is reported. The Cu complex forms two self-assembled structures by hydrogen bonding, depending on the acidity of the recrystallization conditions. A linear chain structure can be produced under acidic conditions, and a three-dimensional network structure is observed under basic conditions. The linear chain structure is constructed from intermolecular sharing of a hydrogen atom between two 2-pyridinemethanolate units, with an OO distance of 2.412(1) Å and an O-H-O bond angle of 170(3)°. The linear chain structure exhibits relatively strong magnetic coupling (J = -9.91(2) cm^-1) via hydrogen bonding between Cu atoms; this coupling was also confirmed by electron spin resonance experiments. Thermochromic behavior was also observed for the complex.

Supramolecular Double-Helix Formation by Diastereoisomeric Conformations of Configurationally Enantiomeric Macrocycles

Solid-state superstructures, resulting from assemblies programmed by homochirality, are attracting considerable attention. In addition, artificial double-helical architectures are being investigated, especially in relation to the ways in which homochiral small molecules can be induced to yield helical forms as a result of chiral induction. Herein, we report the highly specific self-assembly upon crystallization of a double-helical superstructure from an enantiopure macrocyclic dimer which adopts two diastereoisomeric conformations in a molar ratio of 1.5:1 in dimethyl sulfoxide. These two conformational diastereoisomers self-organize-and self-sort-in the crystalline phase in equimolar proportions to form two single-handed helices which are complementary to each other, giving rise to the assembly of a double helix that is stabilized by intermolecular [C-H···O] and π-π stacking interactions. The observed self-sorting phenomenon occurs on going from a mixed-solvent system containing two equilibrating conformational diastereoisomers, presumably present in unequal molar proportions, into the solid state. The diastereoisomeric conformations are captured upon crystallization in a 1:1 molar ratio in the double-helical superstructure, whose handedness is dictated by the choice of the enantiomeric macrocyclic dimer. The interconversion of the two conformational diastereoisomers derived from each configurationally enantiomeric macrocycle was investigated in CD₃SOCD₃ solution by variable-temperature ¹H NMR spectroscopy (VT NMR) and circular dichroism (VT CD). The merging of the resonances for the protons corresponding to the two diastereoisomers at a range of coalescence temperatures in the VT NMR spectra and occurrence of the isosbestic points in the VT CD spectra indicate that the two diastereoisomers are interconverting slowly in solution on the ¹H NMR time scale but rapidly on the laboratory time scale. To the best of our knowledge, the self-assembly of such solid-state superstructures from two conformational diastereoisomers of a homochiral macrocycle is a rare, if not unique, occurrence.