Compounds In Solid State Research Articles

Stoichiometric Lanthanide Compounds with Diglycolamides: A Synthetic Approach toward Understanding Rare-Earth Speciation in Solution.

A fundamental understanding of coordination chemistry across the lanthanide series is essential for explaining the chemical behavior of rare-earth metals in complex liquid-liquid extraction processes. Probing the exact bonding between the extractant and the metal is sometimes done through the synthesis of solid-state compounds that can serve as models for metal speciation in solution. In the case of diglycolamide (DGA), a commonly used neutral diamide extractant, extensive studies identify the stepwise formation of 1:1 [Ln(DGA)(H2O)6]3+, 1:2 [Ln(DGA)2(H2O)3]3+, and 1:3 [Ln(DGA)3]3+ complexes in solution. The crystallographic reports, however, exclusively show a 1:3 [Ln(DGA)3]3+ moiety in the solid state, while the structures of 1:1 and 1:2 complexes are yet to be isolated and comprehensively studied. In this work, we report the synthesis and characterization of three new families of stoichiometric N,N,N',N'-tetramethyldiglycolamide (TMDGA) compounds: [Ln(TMDGA)(H2O)5Cl]Cl2·2H2O, [Ln(TMDGA)2(H2O)3]Cl3·3H2O, and [Ln(TMDGA)3]Cl3·7H2O, where Ln = Nd, Eu, Gd, with Ln:TMDGA ratios of 1:1, 1:2, and 1:3, respectively. The compounds have been analyzed using vibrational spectroscopy (both Raman and FT-IR), as well as variable temperature fluorescence spectroscopy. A spectrophotometric titration of Eu(III) was performed to confirm the presence of the [Eu(TMDGA)n]3+ (n = 1, 2, and 3) species in solution and to compare the individual solid-state emission spectra to their respective analogues in solution.

The DFT Revelation of Optical Properties for Solid-State Anthracene Chalcone Compounds Containing Halogen Groups Modulated by a Charge Transfer Cocrystal Strategy

The DFT Revelation of Optical Properties for Solid-State Anthracene Chalcone Compounds Containing Halogen Groups Modulated by a Charge Transfer Cocrystal Strategy

A photochromic double-polyanion-type arsenotungstate

A double-polyanion-type arsenotungstate, namely [H2N(CH3)2]14H8.5[Si0.5As0.5W18O62][BaNa2{As2W19O67(H2O)}]·29H2O was prepared by self-assembly strategy of some simple raw materials, in which a Dawson-type [Si0.5As0.5W18O62]12.5− polyanion and a [BaNa2{As2W19O67(H2O)}]10− polyanion co-exist in the lattice. Two half-occupied Ba2+ ions were inserted into the pocket-shaped vacancies of {As2W19} building blocks, while two Na2+ ions served as connectors bridging adjacent units. Furthermore, dimethylamine cations play a vital role in building a hydrogen bond network with the polyoxometalate skeleton to maintain the framework of the solid-state compound 1. In addition, being characterized under the 300 W Xe-lamp, the color of compound 1 changed from light green to bluish grey after 210 s with recovery to its original color after about 14 h treating with darkness, displaying a reversible photochromism.

Designing Dual-State and Aggregation-Induced Emissive Luminogens from Lignocellulosic Biosourced Molecules.

Utilizing lignocellulosic biosourced platforms, we synthesized novel cyanostilbene (CS) derivatives featuring the 3,4-dimethoxyphenyl moiety. These derivatives were investigated for their emission properties in both solution and solid states. The two simple CS derivatives exhibit very weak luminescence in solution but significant luminescence in the solid state, indicating distinct Aggregation-Induced Emission (AIE) characteristic. Furthermore, combining these two CS units, without conjugation and with quasi perpendicular orientation, results in a Dual-State Emission (DSE) fluorophore showing luminescence both in solution and solid states. X-ray crystallography studies on the solid-state compounds reveal a structure-emission relationship, demonstrating that the colour emission correlates with the conformations adopted by the molecules in the solid state, which influence the type of stacking.

Triazole-based Mn(II), Fe(II), Ni(II), Cu(II) and Zn(II) complexes as potential anticancer agents – Physicochemical properties, in silico predictions and in vitro activity

A series of solid-state coordination compounds of Mn(II), Fe(II), Ni(II), Cu(II) and Zn(II) with 5-((1-methyl-pyrrol-2-yl)methyl)-4-(2-chlorophenyl)-1,2,4-triazoline-3-thione as a ligand were synthesized and studied in terms of their chemical composition (elemental analysis, ICP), spectroscopic properties (FTIR) and magnetic measurements. Single crystal X-ray diffraction analysis (SC-XRD), HRMS and NMR studies were carried out to confirm the structure of the organic ligand. Its biological potential was evaluated in silico, using molecular docking studies and ADME analysis. The anticancer activity of all five metal complexes and the organic ligand were tested in vitro against A549 and HT-29 cancer cells. We found that the metal complexes in general exhibited better anticancer activity in comparison with the free ligand, with the Cu(II) complex exhibiting the highest activity against both tested cell lines.

Topology optimization of gyroid structure-based metal hydride reactor for high-performance hydrogen storage

Numerous engineering applications stand to gain substantial advantages by mitigating structural weight. While methods for optimizing continuous solids and discrete frame structures have long been available, the advent of additive manufacturing techniques has ushered in the potential for intricate geometries. In contrast, the hydrogen fuel sector confronts a pivotal challenge: the need to develop efficient hydrogen storage systems. Solid-state compounds like metal hydrides (MH) present a compelling solution among various hydrogen storage technologies thanks to their inherent safety attributes and superior hydrogen volumetric density. Nonetheless, the limitation of MH lies in its gravimetric density, impeding its application in mobility contexts. A transformative strategy addresses this limitation by seamlessly integrating the reactor tank into the vehicle's frame and chassis. This study introduces a pioneering concept—an optimally designed MH container incorporating a gyroid structure. Subsequently, this innovative design underwent rigorous analysis, employing finite element analysis (FEA) and computational fluid dynamics, assessing mechanical properties, heat transfer capabilities, and the efficiency of hydrogen charging into the MH within the structure. Using topology optimization of solid isotropic material with penalization method, a 17 % increase in the chamber volume and a concurrent reduction of the material by nearly 50 %. This profound transformation positively impacted the reactor's volumetric and gravimetric density. Despite a measurable reduction in strength, the optimized structure demonstrated resilience, successfully withstanding prescribed mechanical shear loads. Furthermore, the structure exhibited impressive rigidity, with displacement below 0.2 mm, rendering it suitable and highly competent for integration into assembly components like vehicle frames or chassis. Notably, the optimized structure exhibited a promising enhancement in hydrogen charging rate.

Supramolecular Metal Halide Complexes for High-Temperature Nonlinear Optical Switches.

Nonlinear optical (NLO) switching materials, which exhibit reversible intensity modulation in response to thermal stimuli, have found extensive applications across diverse fields including sensing, photoelectronics, and photonic applications. While significant progress has been made in solid-state NLO switching materials, these materials typically showcase their highest NLO performance near room temperature. However, this performance drastically deteriorates upon heating, primarily due to the phase transition undergone by the materials from noncentrosymmetric to centrosymmetric phase. Here, we introduce a new class of NLO switching materials, solid-state supramolecular compounds 18-Crown-6 ether@Cu2Cl4·4H2O (1·4H2O), exhibiting reversible and stable NLO switching when subjected to near-infrared (NIR) photoexcitation and/or thermal stimuli. The reversible crystal structure in response to external stimuli is attributed to the presence of a weakly coordinated bridging water molecule facilitated by hydrogen bonding/chelation interactions between the metal halide and crown-ether supramolecules. We observed an exceptionally high second-harmonic generation (SHG) signal under continuous photoexcitation, even at temperatures exceeding 110 °C. In addition, the bridging water molecules within the complex can be released and recaptured in a fully reversible manner, all without requiring excessive energy input. This feature allows for precise control of SHG signal activation and deactivation through structural transformations, resulting in a high-contrast off/on ratio, reaching values in the million-fold range.

Investigating the Impact of Packing and Environmental Factors on the Luminescence of Pt(N^N^N) Chromophores.

Four Pt(II)(N^N^N) compounds featuring DMSO coordination at the fourth position were synthesized. Ligands varied in terms of pyridyl central ring (hydrogen/chlorine substituent) and lateral rings (triazoles with CF3 substitution or tetrazoles). Coordination to pyridine yielded tetra-nitrogen coordinated Pt(II) complexes or Pt-functionalized polymers using commercial 4-pyridyl polyvinyl (PV) or dimethylaminopyridine. Luminescence behaviors exhibited remarkable environmental dependence. While some of the molecular compounds (tetrazole derivatives) in solid state displayed quenched luminescence, all the polymers exhibited 3MMLCT emission around 600 nm. Conversely, monomer emission was evident on poly(methyl methacrylate) or polystyrene matrices. DFT calculations were used to analyze the aggregation of the complexes both at the molecular level and coordinated to the PV polymer and their influence on the HOMO-LUMO gaps.

Highly tunable emission properties of solid-state supramolecular compounds based on Eu mixed-lanthanide complexes and cucurbit[6]uril

A supramolecular approach for emission control.

Reticular chemistry-aided effective design of new second-order nonlinear optical selenites.

Noncentrosymmetric (NCS) compounds are particularly important for modern optoelectronic technology, yet their rational structural design remains a great challenge. Herein, assisted by the idea of bottom-up reticular chemistry, seven new NCS selenites, AM3[SeO3]2[Se2O5]3 (A = K+/Rb+/Cs+; M = Al3+/Ga3+/In3+), have been successfully designed and synthesized by assembling main-group metal octahedral units and SeO3 units, to construct honeycomb layers with regular channels to accommodate a variety of cations, and using planar hexagonal shapes to orientate the groups within the network. Based on this strategy, the overall symmetry of the solid-state compounds was effectively controlled, and by modifying locally connected atoms or groups, without disrupting the overall prototypical framework, a series of iso-reticular analogues have been obtained, which greatly increases the probability of NCS structures. Three of these compounds, CsM3[SeO3]2[Se2O5]3 were characterized experimentally and theoretically. The results show that they all have moderate second harmonic generation (SHG) responses, which are as large as that of commercial KH2PO4, and wide band gaps. Our study confirms the feasibility of reticular chemistry-assisted strategy in designing nonlinear optical materials with stable frameworks and good performance.

Crystal Structure of Zwitterionic (E)-9-(((3-hydroxyphenyl)iminio)methyl)-1,2,3,5,6,7- Hexahydropyrido[3,2,1-ij]Quinolin-8-Olate

The title compound (1), C19H20N2O2, crystallized with single molecule in the asymmetric unit and is present in the zwitterionic form. The compound was synthesized from the condensation reaction of 8-hydroxyjulolidine-9-carbaldehyde and 3-aminophenol. In solid state compound adopts the keto–amine tautomeric form, with the H atom attached to the N atom, which participates in an intramolecular N—H···O hydrogen bond with an S(6) ring motif. The conformation about the C=N bond is E. The aromatic ring of the julolidine moiety is inclined to the phenol ring by 13.00 (10)°. The fused non-aromatic rings of the julolidine moiety adopts a screw-boat conformations. In the crystal, the molecules are connected by N—H···O and O—H···O hydrogen bonds, with adjacent molecules related by a 21 screw axis, generating– A–B–A–B–zigzag chains extending along [010]. Furthermore, adjacent molecules are linked by pairs of C—H···O interactions, forming a ladder-like structure propagating along the a-axis direction. Density functional theory (DFT) optimized structures at the B3LYP/6–311 G(d,p) level is compared with the experimentally determined molecular structure in the solid state.

DFT insights on structural, electronic, optical and mechanical properties of double perovskites X2FeH6 (X = Ca and Sr) for hydrogen-storage applications

Hydrogen has been delivered as a magnificent alternative clean energy source to alleviate the growing energy dilemma and the harmful consequences of traditional energy sources on the environment and the population. This one-of-a-kind energy-efficient technique involves storing hydrogen in solid-state compounds and then releasing it as needed for utilization in possible energy applications. Metal hydrides have shown to be highly effective hydrogen storage mechanisms in this setting. To improve the efficiency of hydrogen storage and release at standard temperatures and pressures, however, the use of metal hydrides with high gravimetric, poor thermodynamic stability and high kinetics is required. X2FeH6 (X = Ca and Sr) has promising promise for hydrogen-storage applications, with gravimetric hydrogen densities of 4.28 wt% and 2.54 wt% weight, respectively. We used the DFT technique inside the GGA + PBE framework to undertake the first comprehensive study of the structural, electronic, optical and mechanical properties of X2FeH6 (X = Ca and Sr). Structural properties indicate that both the compounds are thermodynamically stable. The Ca2FeH6 and Sr2FeH6 are semiconductors with an estimated indirect band gap of 1.67 eV and 1.37 eV, respectively. Dielectric constants, absorption, reflectivity, energy loss functions and refractive indices are among the optical characteristics determined by the calculations. The results of mechanical properties suggest that both of these hydrides fall within the category of brittle materials. These findings are crucial for the future development of metal hydrogen storage materials.

Synthesis of indazole-benzothiadiazole push-pull molecules as solid-state fluorescent compounds

Synthesis of indazole-benzothiadiazole push-pull molecules as solid-state fluorescent compounds

Synthesis of p-Azaquinodimethane-based Quinoidal Fluorophores.

Quinoidal π-conjugated systems are sought-after materials for semiconducting applications because of their rich optical and electronic characteristics. However, the analogous fluorescent compounds are extremely rare, with just two reports in the literature. Here, we present the design and development of a third series of quinoidal fluorophores [(2,5-diarylidene)-3,6-bis(hexyloxy)-2,5-dihydropyrazine (Q1-Q5)] that incorporates p-azaquinodimethane. The fluorophores are synthesized in a two-step synthetic approach employing Knoevenagel condensation of N,N-diacetyl-piperazine-2,5-dione with different aromatic aldehydes followed by O-alkylation in high yields. Q1-Q5 are strongly emissive, and by altering the aryl-substituents, the emission colors can be modulated from blue to orange. The compounds possess emission maxima (λem) at 475-555 nm in the solution state and 510-610 nm in the solid state, with fluorescence quantum yields of up to 60%. To the best of our knowledge, the reported systems are the first quinoidal dual-state emissive (solution- and solid-state) compounds. In trifluoroacetic acid, Q5 exhibits halochromic behavior, with a dramatic color change from yellow to blue. Furthermore, the preliminary fluorescent sensing studies demonstrated that Q5 could act as a selective turn-off fluorescence probe for electron-deficient picric acid (PA), with an emission quenching of >90% in the solution state. The thin-layer chromatography (TLC) strip sensor of Q5 was also designed to detect PA in water.

Novel 1,2,4-triazolethiol–thiophen Hybrids: Facile Synthesis, Characterization, ADMET Prediction and Molecular Docking

In the present contribution, novel 1,2,4-triazolethiol–thiophene hybrids, namely 4-ethyl-5-(thiophen-2-yl)-4H-1,2,4-triazole-3-thiol (1) and 4-phenyl-5-(thiophen-2-yl)-4H-1,2,4-triazole-3-thiol (2), which were readily fabricated from addition of isothiocyanatoethane or isothiocyanatobenzene, respectively, to thiophene-2-carbohydrazide followed by addition a KOH solution to provoke the cyclization to the 1,2,4-triazole ring. The formation of compounds 1 and 2 was firmly confirmed by the means of elemental analysis, IR, 1H and 13C{1H} NMR spectroscopy. The DFT-based computations in gas phase were additionally applied to shed light on the structure and electronic features of the title compounds. Theoretical calculations revealed that for both molecules their corresponding thione derivatives, namely 4-ethyl-5-(thiophen-2-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (1') and 4-phenyl-5-(thiophen-2-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (2'), are 15.00 and 11.96 kcal/mol, respectively, more energetically favorable in gas phase. However, a comparison of the experimental and calculated IR and NMR spectra testify to the thiol tautomers of compounds 1 and 2 for both compounds in solid state and in DMSO-d 6. The chemical activity of 1 and 2 was estimated by reactivity descriptors and MEP surface. ADMET properties of the reported compounds were predicted in silico using online services. Potential inhibition of a series of the tick-borne encephalitis (TBE) proteins by compounds 1 and 2 was studied using molecular docking, which, in turn, allowed to reveal the ligand efficiency scores for the resulting protein–ligand complexes. It was established that compound 1 exhibits the best activity against the tick-borne encephalitis virus Serine protease NS3, while compound 2 is preferable for the RNA-stimulated ATPase activity of tick-borne encephalitis virus helicase.

Three-Dimensional Noncovalent Interaction Network within [NpO2Cl4]2- Coordination Compounds: Influence on Thermochemical and Vibrational Properties.

Noncovalent interactions (NCIs) can influence the stability and chemical properties of pentavalent and hexavalent actinyl (AnO2+/2+) compounds. In this work, the impact of NCIs (actinyl-hydrogen and actinyl-cation interactions) on the enthalpy of formation (ΔHf) and vibrational features was evaluated using Np(VI) tetrachloro compounds as the model system. We calculated the ΔHf values of these solid-state compounds through density functional theory+ thermodynamics (DFT+ T) and validated the results against experimental ΔHf values obtained through isothermal acid calorimetry. Three structural descriptors were evaluated to develop predictors for ΔHf, finding a strong link between ΔHf and hydrogen bond energy (EHtotal) for neptunyl-hydrogen interactions and total electrostatic attraction energy (Eelectrostatictotal) for neptunyl-cation interactions. Finally, we used Raman spectroscopy together with bond order analysis to probe Np=O bond perturbation due to NCIs. Our results showed a strong correlation between the degree of NCIs by axial oxygen and red-shifting of Np=O symmetrical stretch (ν1) wavenumbers and quantitatively demonstrated that NCIs can weaken the Np=O bond. These properties were then compared to those of related U(VI) and Np(V) phases to evaluate the effects of subtle differences in the NCIs and overall properties. In general, the outcomes of our study demonstrated the role of NCIs in stabilizing actinyl solid materials, which consequently governs their thermochemical behaviors and vibrational signatures.

Growth and characterization of a new inorganic metal-halide crystal structure, InPb2Cl5.

A new solid-state inorganic compound, indium dilead penta-chloride, InPb2Cl5, was synthesized by melting InCl and PbCl2 in a vacuum-sealed quartz ampoule. The ampoule was heated to 793 K and then slowly cooled to room temperature to induce crystallization of InPb2Cl5. InPb2Cl5 crystallizes in the monoclinic crystal system adopting a space group of type P21/c, which is isostructural with other metal halides such as RbPb2Cl5, KPb2Cl5 and TlPb2Cl5. The bulk InPb2Cl5 exhibits a metallic black/grey colour, allowing it to be separated from white/yellow PbCl2 crystals. Due to the incongruent nature of the compound, the pure bulk InPb2Cl5 was not obtained. The black/grey InPb2Cl5 crystals were characterized by powder and single-crystal X-ray diffraction. InPbCl3 was also explored, however the growth was unsuccessful.

Zintl Phases: From Curiosities to Impactful Materials.

The synthesis of new compounds and crystal structures remains an important research endeavor in pursuing technologically relevant materials. The Zintl concept is a guidepost for the design of new functional solid-state compounds. Zintl phases are named in recognition of Eduard Zintl, a German chemist who first studied a subgroup of intermetallics prepared with electropositive metals combined with main-group metalloids from groups 13-15 in the 1930s. Unlike intermetallic compounds, where metallic bonding is the norm, Zintl phases exhibit a combination of ionic and covalent bonding and are typically semiconductors. Zintl phases provide a palette for iso- and aliovalent substitutions that can each contribute uniquely to the properties. Zintl electron-counting rules can be employed to interrogate a structure type and develop a foundation of structure-property relationships. Employing substitutional chemistry allows for the rational design of new Zintl compounds with technological properties, such as magnetoelectronics, thermoelectricity, and other energy storage and conversion capabilities. Discovering new structure types and compositions through this approach is also possible. The background on the strength and innovation of the Zintl concept and a few highlights of Zintl phases with promising thermoelectric properties in the context of structural and electronic design will be provided.

(μ3 -F)(BrF5 )3 ]- - An Unprecedented Molecular Fluoridobromate(V) Anion in Cs[Br3 F16

The reaction of Cs[BrF6 ] with BrF5 gave the compound Cs[Br3 F16 ] with the unprecedented propeller-shaped, C3 -symmetric [(μ3 -F)(BrF5 )3 ]- anion. All other currently known fluoridobromates(V) contain only octahedral [BrF6 ]- anions, which, unlike the related [IF6 ]- anions, never exhibited stereochemical activity of the lone pair on the Br atoms. Despite the same coordination number of six for the Br atom in the [BrF6 ]- and [(μ3 -F)(BrF5 )3 ]- anions, the longer μ3 -F-Br bonds provide additional space, allowing the lone pairs on the Br atoms to become stereochemically active. Cs[Br3 F16 ] was characterized by single-crystal X-ray diffraction, Raman spectroscopy, and quantum-chemical calculations for both the solid-state compound and the isolated anion at 0 K. Intrinsic bond orbital calculations show that the μ3 -F-Br bond is essentially ionic in nature and also underpin the stereochemical activity of the lone pairs of the Br(V) atoms.

The Zintl Concept Applied to Intergrowth Structures: Electron‐Hole Matching, Stacking Preferences, and Chemical Pressures in Pd5InAs

AbstractEnumerating the potential stacking sequences of layers is a fundamental way to account for the structure diversity of solid state compounds. In many cases, these stacking variations represent polymorphs with only small energetic differences. Here, we examine a compound for which the preferred stacking pattern instead reveals key aspects about its chemical bonding: Pd5InAs. Its structure is based on the intergrowth of slabs of the AuCu3 and PtHg2 (or alternatively, fluorite) structure types. Two basic stacking arrangements are available to this compound, represented by the Pd5TlAs and HoCoGa5 structure types. DFT total energy calculations reveal that the former outcompetes the latter by a staggering 0.65 eV/formula unit. Through a combination of DFT‐reversed approximation Molecular Orbital (DFT‐raMO) and DFT‐Chemical Pressure (DFT‐CP) analysis we trace this preference to two factors. First, with DFT‐raMO analysis, we derive a Zintl‐like bonding scheme of Pd5InAs. This scheme, along with the inspection of selected crystal orbitals, is then connected to preferred stacking through the coordination environments of the Pd atoms at the interface between the Pd−In and Pd−As layers. In the hypothetical HoCoGa5‐type and observed Pd5InAs‐type structures, different Pd coordination environments arise at the interfaces. The hypothetical structure features square planar PdIn2As2 units, in each of which the same 4d‐orbital serves in the Pd sublattice's role as both Lewis acid (for interactions with the As) and Lewis base (for interactions with the In). In the observed structure, tetrahedral PdIn2As2 units occur instead, so that these contradictory roles are distributed to separate 4d‐orbitals, leading to more effective bonding. DFT‐CP analysis illustrates that this driving force for the Pd5TlAs‐type arrangement is supplemented by a favorable alignment of the packing tensions in the parent structures. Altogether, the resulting picture demonstrates how the reaction of simple intermetallic structures to form intergrowths can be guided by recognizable chemical interactions.