3D Framework Containing Cu4Br4 Cubane as Connecting Node with Strong Ferroelectricity

Ferroelectricity, Piezoelectricity, and Unprecedented Starry Ferroelastic Patterns in Organic-Inorganic (CH3C(NH2)2)3[Sb2X9] (X = Cl/Br/I) Hybrids

In this study, we present a novel class of lead-free hybrid antimony halides incorporating the acetamidinium cation, with the chemical compositions: (CH3C(NH2)2)3[Sb2Cl9] (ACA), (CH3C(NH2)2)3[Sb2Br9] (ABA), and (CH3C(NH2)2)3[Sb2I9] (AIA) . Despite their seemingly analogous chemical formulations, these compounds exhibit diverse physical characteristics, predominantly dictated by the differences in their metal-halide architectures. Indeed, the anionic frameworks of ACA and AIA are reminiscent of well-known ferroelectric materials, with ACA distinguished by its piezoelectric and ferroelastic characteristics, underpinned by a buckled honeycomb two-dimensional (2D) layers of antimony chloride. Conversely, AIA is characterized by its ferroelectric attribute, with discrete bioctahedral units forming a zero-dimensional (0D) structure. A surprising structural deviation constitutes the anionic sublattice of ABA, which amalgamates features from both ACA and AIA, yielding an unprecedented hybrid two-component (0D + 2D) anionic architecture. The ferroelectric properties of AIA have been demonstrated through pyroelectric current measurements and hysteresis loop analyses. Additionally, the noncentrosymmetric nature of ACA and AIA has been corroborated by second harmonic generation experiments. The piezoelectricity of ACA was confirmed using piezoresponse force microscopy (PFM). Furthermore, observations under a polarizing microscope revealed distinct ferroelastic properties in both ACA and ABA, characterized by well-defined and abundant star patterns previously observed only in simple oxides and alloys.

Excited-State Structural Dynamics of the Cubane-Type Metal Cluster [Cu4I4(py)4] Explored by Time-Resolved X-Ray Liquidography

Cubane-type metal clusters respond uniquely to stimuli like light and electric potential, resulting in behaviors such as crystal-to-crystal phase transitions. While structural adaptability is known to be linked to these responses, direct experimental evidence for the associated structural changes has been missing. This study addresses this gap by examining the structural dynamics of the copper(I) iodide cubane (Cu4I4(py)4, py = pyridine) upon photoexcitation using time-resolved X-ray liquidography. The results reveal: 1) 100 picoseconds (ps) after excitation, two distinct excited states-the cluster-centered triplet (3CC) state and the (metal+halide)-to-ligand charge transfer triplet (3(M/X)LCT) state-are present; 2) the 3(M/X)LCT state decays with an apparent time constant of 1.21 ns, primarily transitioning to the 3CC state, with a small fraction undergoing decay to the ground state (GS); and 3) the 3CC state eventually returns to the GS. The molecular structures, provided for these states serve as benchmarks for theoretical studies. Importantly, the 3CC structure exhibits significant distortion in the Cu4I4 core and reduced symmetry, findings that are unanticipated by previous models. This comprehensive investigation deepens the understanding of the structural transformations occurring upon photoexcitation, with a potential impact on future applications of these compounds as versatile components in photosensitive metal-organic frameworks.

Inducing piezoelectric behavior in a copper iodide cubane cluster-based metal-organic framework via linker engineering

Cu4I4 cubane-type secondary building units are reticulated with a piperazine linker at room temperature to crystallize the metal-organic frameworks (MOFs) Cu4I4(Pip)2 in a non-centrosymmetric P6222 space group. For the first time, cubane cluster type MOF's strong piezoelectric nature has been studied by switching spectroscopy piezo force microscopy (SS-PFM) and piezo force microscopy (PFM) mapping of the crystal, with piezoelectric constant (d33) ∼52.33 pm V-1, highlighting its potential for mechanical energy harvesting processes.

Chiral and Polar Duality Design of Heteroanionic Compounds: Sr18 Ge9 O5 S31 Based on [Sr3 OGeS3 ]2+ and [Sr3 SGeS3 ]2+ Groups

Chirality and polarity are the two most important and representative symmetry-dependent properties. For polar structures, all the twofold axes perpendicular to the principal axis of symmetry should be removed. For chiral structures, all the mirror-related symmetries and inversion axes should be removed. Especially for duality (polarity and chirality), all of the above symmetries should be broken and that also represents the highest-level challenge. Herein, a new symmetry-breaking strategy that employs heteroanionic groups to construct hourglass-like [Sr3 OGeS3 ]2+ and [Sr3 SGeS3 ]2+ groups to design and synthesize a new oxychalcogenide Sr18 Ge9 O5 S31 with chiral-polar duality is proposed. The presence of two enantiomers of Sr18 Ge9 O5 S31 is confirmed by the single-crystal X-ray diffraction. Its optical activity and ferroelectricity are also studied by solid-state circular dichroism spectroscopy and piezoresponse force microscopy, respectively. Further property measurements show that Sr18 Ge9 O5 S31 possesses excellent nonlinear optical properties, including the strong second harmonic generation efficiency (≈2.5 × AGS), large bandgap (3.61 eV), and wide mid-infrared transparent region (≈15.3 µm). These indicate that the unique microstructure groups of heteroanionic materials are conducive to realizing symmetry-breaking and are able to provide some inspiration for exploring the chiral-polar duality materials.

Physicochemical Properties of Organic Molecular Ferroelectric Diisopropylammonium Chloride Thin Films

We fabricated ferroelectric films of the organic molecular diisopropylammonium chloride (DIPAC) using the dip-coating technique and characterized their properties using various methods. Fourier-transform infrared, scanning electron microscopy, and X-ray diffraction analysis revealed the structural features of the films. We also performed ab-initio calculations to investigate the electronic and polar properties of the DIPAC crystal, which were found to be consistent with the experimental results. In particular, the optical band gap of the DIPAC crystal was estimated to be around 4.5 eV from the band structure total density-of-states obtained by HSE06 hybrid functional methods, in good agreement with the value derived from the Tauc plot analysis (4.05 ± 0.16 eV). The films displayed an island-like morphology on the surface and showed increasing electrical conductivity with temperature, with a calculated thermal activation energy of 2.24 ± 0.03 eV. Our findings suggest that DIPAC films could be a promising alternative to lead-based perovskites for various applications such as piezoelectric devices, optoelectronics, sensors, data storage, and microelectromechanical systems.

Electrochemical sensing of copper (II) ion in water using bi-metal oxide framework modified glassy carbon electrode

In this research, an electrochemical sensor was fabricated employing the metal-organic framework (MOF) deposited glassy carbon electrode (GCE) for the sensing copper ions in water with high sensitivity. The porous nanostructured MOF was characterized through Transmission electron microscope, scanning electron microscope and X-ray diffraction analysis. The Bi-MOF nanostructure deposited GCE (Bi-MOF/GCE) was fabricated by drop-casting a suspension of Bi-MOF in water on GCE surface. The performance of modified electrode in the presence and absence of heavy metal ions such as Cd²⁺, Hg²⁺ As³⁺, Pb²⁺ and Cu²⁺ was determined by the cyclic voltammetry in deionised water within the scan rate range of 25 and 300 mVs^-1. The Bi-MOF/GCE displayed highest anodic and cathodic peak current for Cu²⁺ ions than other metal ions, which was enhanced linearly within the scan rate range of 10-100 mV s^-1. Under the employed experimental conditions, the fabricated Bi-MOF/GCE based electrochemical sensor showed an outstanding routine in the determination of copper with a lowest sensing limit of 1 × 10^-5 M, wide linear range variation, strong interaction between metal ions and Bi-MOF. It has long-term stability and good reproducibility. The Bi-MOF/GCE electrode was successfully tested to detect Cu²⁺ in tap water with acceptable results.

Synthesis, X-ray, Hirshfeld, and AIM Studies on Zn(II) and Cd(II) Complexes with Pyridine Ligands

The synthesis and crystal structures of three heteroleptic complexes of Zn(II) and Cd(II) with pyridine ligands (ethyl nicotinate (EtNic), N,N-diethylnicotinamide (DiEtNA), and 2-amino-5-picoline (2Ampic) are presented. The complex [Zn(EtNic)2Cl2] (1) showed a distorted tetrahedral coordination geometry with two EtNic ligand units and two chloride ions as monodentate ligands. Complexes [Zn(DiEtNA)(H2O)4(SO4)]·H2O (2) and [Cd(OAc)2(2Ampic)2] (3) had hexa-coordinated Zn(II) and Cd(II) centers. In the former, the Zn(II) was coordinated with three different monodentate ligands, which were DiEtNA, H2O, and SO42−. In 3, the Cd(II) ion was coordinated with two bidentate acetate ions and two monodentate 2Ampic ligand units. The supramolecular structures of the three complexes were elucidated using Hirshfeld analysis. In 1, the most important interactions that governed the molecular packing were O···H (15.5–15.6%), Cl···H (13.6–13.8%), Cl···C (6.3%), and C···H (10.3–10.6%) contacts. For complexes 2 and 3, the H···H, O···H, and C···H contacts dominated. Their percentages were 50.2%, 41.2%, and 7.1%, respectively, for 2 and 57.1%, 19.6%, and 15.2%, respectively, for 3. Only in complex 3, weak π-π stacking interactions between the stacked pyridines were found. The Zn(II) natural charges were calculated using the DFT method to be 0.8775, 1.0559, and 1.2193 for complexes 1–3, respectively. A predominant closed-shell character for the Zn–Cl, Zn–N, Zn–O, Cd–O, and Cd–N bonds was also concluded from an atoms in molecules (AIM) study.

Metal organic frameworks for electrochemical sensor applications: A review

Metal-organic frameworks (MOFs) are broadly known as porous coordination polymers, synthesized by metal-based nodes and organic linkers. MOFs are used in various fields like catalysis, energy storage, sensors, drug delivery etc., due to their versatile properties (tailorable pore size, high surface area, and exposed active sites). This review presents a detailed discussion of MOFs as an electrochemical sensor and their enhancement in the selectivity and sensitivity of the sensor. These sensors are used for the detection of heavy metal ions like Cd²⁺, Pb²⁺, Hg²⁺, and Cu²⁺ from groundwater. Various types of organic pollutants are also detected from the water bodies using MOFs. Furthermore, electrochemical sensing of antibiotics, phenolic compounds, and pesticides has been explored. In addition to this, there is also a detailed discussion of metal nano-particles and metal-oxide based composites which can sense various compounds like glucose, amino acids, uric acid etc. The review will be helpful for young researchers, and an inspiration to future research as challenges and future opportunities of MOF-based electrochemical sensors are also reported.

Ferroelectric Metal-Organic Framework as a Host Material for Sulfur to Alleviate the Shuttle Effect of Lithium-Sulfur Battery

Ferroelectricity has an excellent reversible polarization conversion behavior under an external electric field. Herein, we propose an interesting strategy to alleviate the shuttle effect of lithium-sulfur battery by utilizing ferroelectric metal-organic framework (FMOF) as a host material for the first time. Compared to other MOF with same structure but without ferroelectricity and commercial carbon black, the cathode based on FMOF exhibits a low capacity decay and high cycling stability. These results demonstrate that the polarization switching behaviors of FMOF under the discharge voltage of lithium-sulfur battery can effectively trap polysulfides by polar-polar interactions, decrease polysulfides shuttle and improve the electrochemical performance of lithium-sulfur battery.

From Short-Bite Ligand Assembled Ribbons to Nanosized Networks in Cu(I) Coordination Polymers Built Upon Bis(benzylthio)alkanes (BzS(CH2)nSBz; n = 1-9)

With the objective to establish a correlation between the spacer distance and halide dependence on the structural features of coordination polymers (CPs) assembled by the reaction between CuX salts (X = Cl, Br, I) and dithioether ligands BzS(CH₂)_nSBz (n = 1-9; Bz = benzyl), a series of 26 compounds have been prepared and structurally investigated. A particular attention has been devoted to the design of networks with extremely long and flexible methylene spacer units between the SBz donor sites. Under identical conditions, CuI and CuBr react with BzSCH₂Bz (L1) affording respectively the one-dimensional (1D) CPs {Cu(μ₂-I)₂Cu}(μ-L1)₂]_n (CP1) and {Cu(μ₂-Br)₂Cu}(μ-L1)₂] (CP2), which incorporate Cu(μ₂-X)₂Cu rhomboids as secondary building units (SBUs). The hitherto unknown architecture of two-dimensional (2D) layers obtained with CuCl (CP3) differs from that of CP1 and CP2, which bear inorganic -Cl-Cu-Cl-Cu-Cl- chains interconnected through bridging L1 ligands, thus forming a 2D architecture. The crystallographic characterization of a 1D CP obtained by reacting CuI with 1,3-bis(benzylthio)propane (L2) reveals that [{Cu(μ₂-I)₂Cu}(μ-L2)₂]_n (CP4) contains conventional Cu₂I₂ rhomboids as SBUs. In contrast, unusual isostructural CPs [{Cu(μ₂-X)}(μ₂-L2)]_n (CP5) and (CP6) are obtained with CuX when X = Br and Cl, respectively, in which the isolated Cu atoms are bridged by a single μ₂-Br or μ₂-Cl ion giving rise to infinite [Cu(μ₂-X)Cu]_n ribbons. The crystal structure of the strongly luminescent three-dimensional (3D) polymer [{Cu₄(μ₃-I)₃(μ₄-I)(μ-L3)_1.5]_n (CP7) issued from reacting 2 equiv of CuI with BzS(CH₂)₄SBz (L3) has been redetermined. CP7 features unusual [(Cu₄I₃)(μ₄-I)]_n arrays securing the 3D connectivity. In contrast, mixing CuI with an excess of L3 provides the nonemissive material [{Cu(μ₂-I)₂Cu}(μ-L3)₂]_n (CP8). Treatment of CuBr and CuCl with L3 leads to [{Cu(μ₂-Br)₂Cu}(μ-L3)₂]_n (CP9) and the 0D complex [{Cu(μ₂-Cl)₂Cu}(μ-L3)₂] (D1), respectively. The crystallographic particularity for CP9 is the coexistence of two topological isomers within the unit cell. The first one, CP9-1D, consists of simple 1D ribbons running along the a axis of the unit cell. The second topological isomer, CP9-2D, also consists of [Cu(μ₂-Br)₂Cu] SBUs, but these are interconnected in a 2D manner forming 2D sheets placed perpendicular to the 1D ribbons. Four 2D CPs, namely, [{Cu₄(μ₃-I)₄}(μ-L4)₂]_n (CP10), [{Cu(μ₂-I)₂Cu}(μ-L4)₂]_n (CP11), [{Cu(μ₂-Br)₂Cu}(μ-L4)₂]_n (CP12), and [{Cu(μ₂-Cl)₂Cu}(μ-L4)₂]_n (CP13), stem from the self-assembly process of CuX with BzS(CH₂)₆SBz (L4). A similar series of 2D materials comprising [{Cu₄(μ₃-I)₄}(μ-L5)₂]_n (CP14), [{Cu(μ₂-I)₂Cu}(μ-L5)₂]_n (CP15), [{Cu(μ₂-Br)₂Cu}(μ-L5)₂]_n (CP16), and [{Cu(μ₂-Cl)₂Cu}(μ-L5)₂]_n (CP17) result from the coordination of BzS(CH₂)₇SBz (L5) on CuX. Ligation of CuX with the long-chain ligand BzS(CH₂)₈SBz (L6) allows for the X-ray characterization of the luminescent 2D [{Cu₄(μ₃-I)₄}(μ-L6)₂]_n (CP18) and the isostructural 1D series [{Cu(μ₂-X)₂Cu}(μ-L6)₂]_n CP19 (X = I), CP20 (X = Br) and CP21(X = Cl). Noteworthy, BzS(CH₂)₉SBz (L7) bearing a very flexible nine-atom chain generated the crystalline materials 2D [{Cu₄(μ₃-I)₄}(μ-L7)₂]_n (CP22) and the isostructural 1D series [{Cu(μ₂-X)₂Cu}(μ-L6)₂]_n CP23 (X = I), CP24 (X = Br), and CP25 (X = Cl), featuring nanometric separations between the cubane- or rhomboid-SBUs. This comparative study reveals that the outcome of the reaction of CuX with the shorter ligands BzS(CH₂)_nSBz (n = 1-4) is not predictable. However, with more flexible spacer chains BzS(CH₂)_nSBz (n = 6-9), a clear structural pattern can be established. Using a 1:1 CuX-to-ligand ratio, [{Cu(μ₂-X)₂Cu}(μ-L4-7)₂] CPs are always formed, irrespectively of L4-L7. Employing a 2:1 CuX-to-ligand ratio, only CuI is able to form networks incorporating Cu₄(μ₃-I)₄ clusters as SBUs. All attempts to construct polynuclear cluster using CuBr and CuCl failed. The materials have been furthermore analyzed by powder X-ray diffraction, Raman spectroscopy, and thermogravimetric analysis, and the photophysical properties of the emissive materials have been studied.

A new semiconducting 1D Cu(i)–Cu(ii) mixed-valence coordination polymer with Cu(ii) dimethylpiperidine–dithiocarbamate and a tetranuclear Cu(i)–Br cluster unit

A new 1D semiconducting mixed-valence Cu(i)–Cu(ii) coordination polymer was synthesized and characterized using impedance measurements.

An unusual 32-membered copper(ii) metallomacrocube based on a Cu4O3X cubic core: photocatalytic, electrocatalytic, and magnetic properties

The first Cu₃₂ cluster featuring a multi-cubane (Cu₄O₃X) structure exhibited excellent catalytic performance in the degradation of organic pollutant rhodamine B, good electrocatalytic activity for nitrite reduction, and strong antiferromagnetic interactions.

Self-assembly patterns of steroid-based all-organic ferroelectrics: valuable insights from the single-crystals derived from an organogel and solution

We report herein the first example of a single-crystal grown from a steroid-based organogel matrix.

A novel pentacoordinated cadmium compound: catena-poly[benzyltriethylammonium [[chloridocadmate(II)]-di-μ-chlorido]]

The structure of the title one-dimensional ABX3-type organic-inorganic hybrid complex, {(C13H22N)[CdCl3]}n, consists of benzyltriethylammonium cations and one-dimensional anionic {[CdCl3](-)}n chains, in which the Cd(II) centres are in an unusual two-layer five-coordinated arrangement. The Cd(II) atom is pentacoordinated by four bridging and one terminal chloride ligand, forming a slightly distorted trigonal bipyramidal ClCd(μ-Cl)4 arrangement. The trigonal bipyramid is linked by two opposite shared faces, giving rise to a zigzag linear anionic {[CdCl3](-)}n chain. The benzyltriethylammonium cations are located in the inter-space of the inorganic network. There are C-H···Cl hydrogen bonds present and these play a crucial role in linking the organic cations and inorganic layers, and also help assemble the components into a three-dimensional network.

Poly[bis(4-chloropyridinium) tetra-μ2-chlorido-tetrachloridotrimercurate(II)]

The structure of the title compound, {(C(5)H(5)ClN)(2)[Hg(3)Cl(8)]}(n), consists of 4-chloropyridinium cations and one-dimensional [Hg(3)Cl(8)](2-) anion chains. There are two coordination environments for Hg(II) in the inorganic chain. The first is a distorted tetrahedral geometry made up of an HgCl(2) unit with two Cl(-) anion bridges, while the second is an octahedral coordination geometry consisting of an HgCl(2) unit and four chloride-anion bridges. This gives rise to a novel three-layer centrosymmetric polymer. Finally, the three-dimensional network comes about through the many C-H···Cl and N-H···Cl hydrogen bonds that link the organic and inorganic layers.

2-Chloro-anilinium perchlorate

In the crystal of the title compound, C(6)H(7)ClN(+)·ClO(4) (-), a layer-like structure parallel to the bc plane is formed through N-H⋯O hydrogen bonds between the cations and anions. These layers are connected by weak C-H⋯O inter-actions, forming a three-dimensional network.

2-Hy-droxy-pyridinium p-toluene-sulfonate

In the title molecular salt, C(5)H(6)NO(+)·C(7)H(7)O(3)S(-), the cations and anions are connected by N-H⋯O and O-H⋯O hydrogen bonds, forming [100] chains.

Bis(2-methyl-piperidinium) naphthalene-1,5-disulfonate

In the structure of the title mol-ecular salt, 2C(6)H(14)N(+)·C(10)H(6)O(6)S(2) (2-), the asymmetric unit consists of one 2-methyl-piperidinium cation and one-half of a naphthalene-1,5-disulfonate anion; the anion lies across a centre of symmetry. In the crystal, the cations and anions are linked through N-H⋯O hydrogen bonds, forming a two-dimensional network.

3-Methyl-piperidinium bromide

In the crystal structure of the title molecular salt, C₆H₁₄N⁺·Br⁻, N—H⋯Br hydrogen bonds link the cations and anions to form a one-dimensional network.

1H-Pyrazol-2-ium hydrogen oxalate

In the title compound, C(3)H(5)N(2) (+)·C(2)HO(4) (-), the anions form centrosymmetric dimers through cyclic O-H⋯O hydrogen-bonding associations [graph set R(2) (2)(10)]. These dimers are then linked through a cyclic R(4) (2)(10) N-H⋯O hydrogen-bonding association involving two cations and the carboxyl O-atom acceptors of separate anions, giving chain structures extending across the (111) plane.

Tetra-kis(4-chloro-anilinium) hexa-chlorido-stannate(IV) dichloride

The asymmetric unit of the title compound, (C₆H₇ClN)₄[SnCl₆]Cl₂, comprises two 4-chloro­anilinium cations, half of an [SnCl₆]²⁻ anion and a Cl⁻ anion. The Sn^IV atom, located on a special position on a twofold rotation axis, exhibits an octa­hedral environment. In the crystal, mol­ecules are linked by N—H⋯Cl hydrogen bonds between the 4-chloro­anilinium cations, [SnCl₆]²⁻ anions and Cl⁻ anions.

Tris(2-methylpiperidinium) tetrachloridoferrate dichloride

The asymmetric unit of the title salt, (C₆H₁₄N)₃[FeCl₄]Cl₂, consists of a tetra­hedral tetra­chloro­ferrate anion, three independent 2-methyl­piperidinium cations and two chloride ions. All the piperidine rings adopt chair conformations. In the crystal, the organic cations and the free chloride anions are linked into chains parallel to the a axis by N—H⋯Cl hydrogen bonds.

Guanidinium bromide–18-crown-6 (2/1)

In the title compound, 2CH₆N₃⁺·2Br⁻·C₁₂H₂₄O₆, the 18-crown-6 mol­ecule lies about an inversion center, whereas the guanidinium cation and bromide anion are in general positions. The guanidinium cations link with the bromide anions and the crown ether mol­ecules via N—H⋯O and N—H⋯Br hydrogen bonds, thus forming a three-dimensional network.

(4-Aza-1-azoniabicyclo-[2.2.2]octane-κN(4))trichloridocobalt(II)

In the title compound, [CoCl(3)(C(6)H(13)N(2))], the tetra-hedrally coordinated Co(II) ion has Co-Cl distances ranging from 2.2220 (11) to 2.2449 (9) Å and a Co-N distance of 2.056 (2) Å. In the crystal, N-H⋯Cl hydrogen bonds link mol-ecules into chains in [010]. Weak C-H⋯Cl inter-actions stabilize further the crystal packing.