Solvent-Induced Syntheses, Crystal Structures, Magnetic Properties, and Single-Crystal-to-Single-Crystal Transformation of Azido-Cu(II) Coordination Polymers with 2-Naphthoic Acid as Co-ligand

Metal-Organic Framework Flowers as a Naked-Eye Colorimetric Indicator of Trace Water

Convenient and sensitive trace water indication is of great significance in various industrial processes. Here, a flower-like metal-organic framework Cu-FMM is assembled from ultrathin nanosheets that change its coordination structure reversibly with the capture and loss of water molecules, enabling sensitive trace water naked-eye colorimetric indication ability. A recognizable black/yellow color change can be observed when the dried Cu-FMM is exposed to the atmosphere or solvent with trace water as low as RH 3% and a water content of 0.25‰ (v/v) and further enables potential trace water imaging applications. The excellent accessibility of the multi-scale pore structure of Cu-FMM contributes to a fast response time of 3.8 s with good reversibility (>100 cycles), outperforming traditional coordination polymer humidity sensors. The present study provides new inspirations for the design of sensitive and applicable naked-eye water indicator materials that are applicable to in situ and continuous monitoring in industrial processes.

[MII(H2dapsc)]-[Cr(CN)6] (M = Mn, Co) Chain and Trimer Complexes: Synthesis, Crystal Structure, Non-Covalent Interactions and Magnetic Properties

Four new heterometallic complexes combining [M^II(H₂dapsc)]²⁺ cations with the chelating H₂dapsc {2,6-diacetylpyridine-bis(semicarbazone)} Schiff base ligand and [Cr(CN)₆]^3- anion were synthesized: {[M^II(H₂dapsc)]Cr^III(CN)₆K(H₂O)_2.5(EtOH)_0.5}_n·1.2n(H₂O), M = Mn (1) and Co (2), {[Mn(H₂dapsc)]₂Cr(CN)₆(H₂O)₂}Cl·H₂O (3) and {[Co(H₂dapsc)]₂Cr(CN)₆(H₂O)₂}Cl·2EtOH·3H₂O (4). In all the compounds, M(II) centers are seven-coordinated by N₃O₂ atoms of H₂dapsc in the equatorial plane and N or O atoms of two apical -CN/water ligands. Crystals 1 and 2 are isostructural and contain infinite negatively charged chains of alternating [M^II(H₂dapsc)]²⁺ and [Cr^III(CN)₆]^3- units linked by CN-bridges. Compounds 3 and 4 consist of centrosymmetric positively charged trimers in which two [M^II(H₂dapsc)]²⁺ cations are bound through one [Cr^III(CN)₆]^3- anion. All structures are regulated by π-stacking of coplanar H₂dapsc moieties as well as by an extensive net of hydrogen bonding. Adjacent chains in 1 and 2 interact also by coordination bonds via a pair of K⁺ ions. The compounds containing Mn^II (1, 3) and Co^II (2, 4) show a significant difference in magnetic properties. The ac magnetic measurements revealed that complexes 1 and 3 behave as a spin glass and a field-induced single-molecule magnet, respectively, while 2 and 4 do not exhibit slow magnetic relaxation in zero and non-zero dc fields. The relationship between magnetic properties and non-covalent interactions in the structures 1-4 was traced.

Solvent coligands fine-tuned the structures and magnetic properties of triple-bridged 1D azido-copper(ii) coordination polymers

The structures and magnetic properties of three triple-bridged 1D azido–Cu(ii) coordination polymers are well-regulated by altering the coordinated alkanol molecules.

Ligand ratio/solvent-influenced syntheses, crystal structures, and magnetic properties of polydentate Schiff base ligand-Dy(iii) compounds with β-diketonate ligands as co-ligands

Tuning the synthesis conditions and further regulating the magnetic dynamics of single-molecule magnets (SMMs) are crucial challenges for chemists.

Reversible crystal-to-amorphous structural transformations and magnetic variations in single end-on azide-bridged MII (M = Mn, Ni) coordination polymers

Azide-bridged coordination polymers undergo reversible crystal-to-amorphous phase transformations during the hydration–dehydration process.

Liquid-free single-crystal to single-crystal transformations in coordination polymers

Single-crystal to single-crystal (SCSC) transformations not only can create new materials, but also provide an opportunity to explore the process of forming a chemical bond. SCSC transformations discussed in this paper are confined to transformationsviaan absolutely liquid-free mode and involve the breakage and formation of new chemical bonds.

Tuning of Exchange Coupling and Switchable Magnetization Dynamics by Displacing the Bridging Ligands Observed in Two Dimeric Manganese(III) Compounds

Two Mn(III)-based dimers, [Mn₂(bpad)₂(CH₃O)₄]_n (1) and [Mn₂(bpad)₂(pa)₂]_n·2H₂O (2) (Hbpad = N³-benzoylpyridine-2-carboxamidrazone, H₂pa = phthalic acid), have been assembled from a tridentate Schiff-base chelator and various anionic coligands. Noteworthily, compound 1 could be identified as a reaction precursor to transform to 2 in the presence of phthalic acid, resulting in a rarely structural conversion process in which the bridges between intradimer Mn(III) ions alter from methanol oxygen atom with μ₂-O mode in 1 (Mn Mn distance of 3.046 Å) to syn-anti carboxylate in 2 (Mn Mn distance of 4.043 Å), while the Mn(III) centers retain hexa-coordinated geometries with independently distorted octahedrons in two compounds. The dc magnetic determinations reveal that ferromagnetic coupling between two metal centers with J = 1.31 cm⁻¹ exists in 1, whereas 2 displays weak antiferromagnetic interactions with the coupling constant J of −0.56 cm⁻¹. Frequency-dependent ac susceptibilities in the absence of dc field for 1 suggest slow relaxation of the magnetization with an energy barrier of 13.9 K, signifying that 1 features single-molecule magnet (SMM) behavior. This work presents a rational strategy to fine-tune the magnetic interactions and further magnetization dynamics of the Mn(III)-containing dinuclear units through small structural variations driven by the ingenious chemistry.

SMM behaviour and magnetocaloric effect in heterometallic 3d–4f coordination clusters with high azide : metal ratios

We present the synthesis and characterization of heterometallic compounds with a very large azide to metal ratio and fascinating magnetic properties.

Ligand directed structural diversity and magnetism in copper(ii)–azido assemblies with isomeric aminopyridines: synthesis, structure, magnetism and theoretical studies

Ligand geometry and molar ratios play an influential role in directing the supramolecular assemblage and associated magnetic properties as described for the Cu(ii) complexes involving isomeric aminopyridines and azide.

Coligand modifications fine-tuned the structure and magnetic properties of two triple-bridged azido-Cu(ii) chain compounds exhibiting ferromagnetic ordering and slow relaxation

Two triple-bridged azido-Cu(ii) compounds with different benzoates as coligands exhibit distinct magnetic properties.

A substituent effect of phenylacetic acid coligand perturbed structures and magnetic properties observed in two triple-bridged azido-Cu(ii) chain compounds with ferromagnetic ordering and slow magnetic relaxation

Two triple-bridged azido-Cu(ii) chains exhibit distinct magnetic behaviors.

Stabilization of Cu7 clusters in azide networks: syntheses, structures and magnetic behaviour

Two new azide bridged copper(II) coordination polymer compounds, [Cu7(N3)14(C3H10N2)(C4H13N3)]n (I) and [Cu7(N3)14(C3H10N2)(C5H15N3)2]n (II) [where C3H10N2 = 1,2-diaminopropane (1,2-DAP); C4H13N3 = diethylenetriamine (DETA); C5H15N3 = N-2-aminoethyl-1,3-propanediamine (AEDAP)] were prepared by employing a room temperature diffusion technique involving three layers. Single crystal studies reveal that both compounds I and II, have similar connectivity forming Cu7 clusters through end-on (EO) bonding of the azide. The Cu7 clusters are connected through end-to-end (EE) connectivity of the azides forming three-dimensional structures. Magnetic studies confirmed the ferromagnetic interactions within the Cu7 units and revealed the occurrence of concomitant ferro- and antiferro-magnetic interactions between these clusters. As a result I behaves as a weak-ferromagnet with TC = 10 K.

A unusual two-dimensional azido-Cu(ii) network with benzoate derivative as a co-ligand exhibiting ferromagnetic order and slow magnetic relaxation

A 2D layer-like Cu(ii) compound with multiple-bridges of azido, carboxylate and hydroxyl ligands, featuring strong ferromagnetic coupling and slow magnetic relaxation.

A new cobalt(II)-containing coordination polymer composed of dinuclear metal units: synthesis, crystal structure, and magnetic properties with DFT calculations

A new Co(II)-based compound with a 3-phenyl-5-(pyridin-4-yl)-1,2,4-triazole (4-Hppt) and isophthalic acid (H2ip) mixed ligand, [Co(4-Hppt)2(ip)] (1), has been synthesized and structurally and magnetically characterized. The structure of compound 1 consists of one-dimensional coordination chains based on the Co2 units bridged by dual carboxylate groups, where the pyridyl nitrogen atoms in 4-Hppt ligands are located in the axial coordination sites of the octahedral Co(II) nodes. Magnetic investigation suggests that the magnetic coupling derived from the dinuclear Co(II) ions is a moderately antiferromagnetic exchange in the title compound. Moreover, DFT calculations have been performed on the compound to offer a qualitatively theoretical explanation of the magnetic behavior.

A mononuclear cobalt(III) 3-(2-pyridyl)-5-phenyl-1,2,4-triazolato complex: hydrothermal synthesis, crystal structure, thermostability, and DFT calculations

Starting with 1H -3-phenyl-5-(pyridin-2-yl)-1,2,4-triazole (1-Hppt), a Co(III) complex, [Co(ppt)3] (1), has been synthesized by reaction with CoF3 under hydrothermal conditions and characterized by its infrared spectrum and elemental analysis. The structure was determined by single-crystal and powder X-ray diffraction. Density functional theory (DFT) was employed to determine the optimized geometry and preferred conformation of the free ligand. A supramolecular network is formed via π–π stacking interactions. The conformation and geometry of the ligands correspond with the calculated results.

12-Metal 36-membered ring based WV–CoIIlayers showing spin-glass behavior

Two cyano-bridged bimetallic W^V–Co^IIlayers were synthesized, which contain 12 metal 36 membered rings and present spin-glass behavior.

Bis(4-pyridyl)mercury – a new linear tecton in crystal engineering: coordination polymers and co-crystallization processes

Three new coordination polymers have been obtained using bis(4-pyridyl)mercury (py₂Hg) as a spacer: [Cu(Hmea)₂(py₂Hg)](ClO₄)₂·2(py₂Hg) (1), [Cu₂(pa)₂(py₂Hg)(ClO₄)₂]·0.5(py₂Hg)·H₂O (2), and [Cu₂(pa)₂(py₂Hg)₂](BF₄)₂ (3) (Hmea = monoethanolamine; Hpa = propanolamine).

Solvent-controlled formation of four Ni(ii) coordination polymers based on a flexible bis(imidazole) ligand: syntheses, structural diversification, properties

Four new isomeric Ni(ii) coordination polymers with different architectures and properties were successfully synthesized by tuning the solvent media.

In situ solvent and counteranion-induced synthesis, structural characterization and photoluminescence properties of Pb-based MOFs

With solvents or counteranions as the only variable, three novel photoluminescent Pb-based metal–organic frameworks were obtained under the similar synthetic procedures.