CrystEngComm最新文献

The behaviour of photoexcited electrons in light-responsive coordination polymers (CPs) significantly determines their performance in fluorescence sensing, smart materials, photoelectric display and photocatalysis, and this behaviour can be skilfully manipulated by optimizing the geometric and electronic structures of the ligand field around the metal ion. To reveal the micro-environmental effect of the ligand field on the bandgap and photoexcited electrons, three semiconductive Cd(II)-based CPs have been achieved through coordination of π-conjugated 2,6-bis(2-pyrazin-2-yl)-4-(4-(tetrazol-5-yl)phenyl)pyridine (HL) and 1,3,5-benzenetricarboxylic acid (H₃BTC) with Cd(II) ion. Possessing N₃O₄ and O₆ donors, complex 1 assumed an extended triple-decker sandwich structure with a central {Cd₂(BTC)} sheet terminated up and down by planar L⁻ spacers. Two quadrangular {Cd₂(L)₂} dimers with N₄O₃ and N₄O₂ donors were propagated by doubly deprotonated HBTC²⁻ connectors to the cationic (4 4) layer of 2. The reproducible {Cd₂(L)₂} dimers with only N₄O₃ donors in 3 were extended by mirror-symmetric HBTC²⁻ linkers to a bent chain. The distinct donor combinations in the local ligand fields of Cd(II) ions dominated the bandgaps and movements of the charge-carriers. Emitting intense steel blue fluorescence, complex 1 served as a highly efficient bilirubin probe with a quenching constant up to 9.48 × 10⁴ M⁻¹ driven by photo-induced electron charge and Förster resonance energy transfer. In contrast, complex 2, with excellent separation efficiency of charge carriers, acted as a photocatalyst to completely degrade methylene blue up to 97% within 90 minutes of UV irradiation. Apparently, slight modifications of the surroundings of the ligand field by a heterodonor strategy achieved a remarkable effect on the photophysical properties of the semiconductive CPs, providing valuable hints for the construction of photosensitive CPs.

In this work, the cocrystallization of both benzotrifuroxan (BTF) and [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 4,6-dioxide (furazanotetrazine dioxide, FTDO) with [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxide (FCO), 1,5-dioxide (FCDO) and some of their nitro derivatives was investigated, focusing on the cocrystal structural features and their detonation performance. First, cocrystallization energies using crystal structure prediction (CSP) methods, identifying energetically favorable component ratios for BTF and FTDO with cinnoline oxides, were calculated. Then two novel cocrystals, the BTF–FCDO 4 (1 : 2) and the FTDO–FCDO 3 (1 : 2) compositions, were prepared and characterized by X-ray diffraction and Hirshfeld surface analysis. The primary intermolecular interactions in BTF cocrystals include dominant n(NO₂)⋯π(BTF) contacts and π-stacking motifs, and in FTDO cocrystals, hydrogen-bonded synthons. The calculated energetic parameters were 7.37 km s⁻¹ and 23.99 GPa for the FTDO (1 : 2) cocrystal, and 7.69 km s⁻¹ and 26.4 GPa for the BTF (1 : 2) cocrystal. Their cocrystals (1 : 2) with FCDOs exhibited, compared to pure parent compounds, lower detonation velocities and pressures due to high FCDOs molar content, yet still outperformed conventional energetic compounds such as 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitrobenzene (TNB).

Dihydrogen phosphate (H₂PO₄⁻) in food and the environment is one of the major concerns for human health. Over the past few years, a large number of fluorescent metal–organic frameworks (MOFs) have been studied to explore desirable methods for selective analysis because fluorescence techniques have high sensitivity and are easy to operate. Herein, a chain-based MOF derived from Tb^III clusters {[Tb₃(BTDB)₃(μ₃-OH)₃(H₂O)]·solvents}_n (JXUST-52, H₂BTDB = (benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoic acid) was successfully synthesized and structurally characterized. Single-crystal X-ray diffraction showed that three adjacent Tb^III ions were connected via carboxylate oxygen and μ₃-OH⁻, forming an infinite chain structure along the b axis. The neighbouring chains were linked by BTDB²⁻ ligands to finally form a chain-based 3D structure. JXUST-52 exhibited relatively good thermal and chemical stabilities and can specifically recognize H₂PO₄⁻ through luminescence enhancement and blue shift with a detection limit of 0.016 mM. Furthermore, the significant luminescence enhancement and blue shift under UV lamp irradiation were observable by the naked eye. The luminescence sensing mechanism is attributed to absorbance-induced enhancement between JXUST-52 and H₂PO₄⁻. In addition, lamp beads and test paper based on JXUST-52 were designed for the detection of H₂PO₄⁻ in practical application.

In recent years, lead-free organic–inorganic hybrid zero-dimensional metal halides have attracted considerable attention due to their outstanding optical properties, largely attributed to the confinement of localized metal groups. We report the discovery of a newly structured [MMim]₂[CuI₃] crystal with a distinct [CuI₃]²⁻ trigonal planar structure encapsulated by inert organic [MMim]⁺ clusters. The structure, composition, and thermal stability of the crystal were analyzed using XRD and TG–DTA. The optical properties of [MMim]₂[CuI₃] crystals were both experimentally measured and theoretically calculated. These crystals exhibit intense broadband orange luminescence with pronounced Stokes shifts and a microsecond-scale fluorescence lifetime decay, primarily due to self-trapped exciton emission. Temperature-dependent fluorescence spectra were also recorded to explore the luminescence mechanism. In summary, these findings highlight the remarkable potential of lead-free [MMim]₂[CuI₃] crystals in advancing optoelectronic applications.

This work is dedicated to investigating the structural, luminescence and photocurrent characteristics of LuAG:Ce single crystalline films grown using the liquid phase epitaxy method on both LuAG and YAG substrates. The primary objective is to analyze the influence of different growth modes, namely homoepitaxial and quasi-homoepitaxial, on the structural and luminescence properties of Ce³⁺ ions in these films under ambient and high-pressure conditions. Based on the results of X-ray diffraction measurements, we can conclude that both epitaxial structures are fully relaxed. However, a slight deformation of the garnet lattices is observed, manifesting the inequality of the in-plane and out-of-plane lattice constants of substrates and films. The difference in the energy gap values between positions of 4f–5d_1,2 Ce³⁺ absorption bands (6–12 meV) and the positions of the Ce³⁺ emission band (6 meV) was observed for both LuAG:Ce films and caused by the small differences in local perturbations of garnet hosts for epitaxial structures, grown in homoepitaxial and quasi-homoepitaxial modes. The Ce³⁺ emission intensity in both LuAG:Ce films decreases with temperature in the 10–300 K range. The decay time of the Ce³⁺ luminescence in the LuAG:Ce homoepitaxially-grown film demonstrates a weak temperature dependence in the mentioned range. However, in the LuAG:Ce quasi-homoepitaxially-grown film, the decay time of the Ce³⁺ emission shows notable temperature dependences in the 10–300 K range, probably due to the formation of Ce⁴⁺–Pb²⁺ pair centers. The non-monotonical redshift of the Ce³⁺ emission band and the increase of the Ce³⁺ decay time are observed in both LuAG:Ce films under increasing external pressure from ambient to 19 GPa due to the compression and distortion of the crystal lattice. The redshift changes of the Ce³⁺ emission band on pressure are significantly more complicated for the LuAG:Ce quasi-homoepitaxially-grown film than the homoepitaxially-grown counterpart. The outcomes of this study contribute to the fundamental understanding of epitaxial growth processes and their impact on the luminescence characteristics of rare-earth-doped materials in the single crystalline film form.

Herein, we report the design and crystal growth of the network of K₂H₂mpba (1) [H₄mpba = N,N′-1,3-phenylenebis(oxamic acid)], which exhibits the quite unusual (6,12)-connected alb topology. The characterization of 1 shows the following features: (i) the presence of deprotonated H₂mpba²⁻ moieties, (ii) thermal stability up to approximately 300 °C, and (iii) H₂mpba²⁻ acting as a 12-c molecular building block (MBB) and occupying the vertices of the double six-membered ring “d6R”. These rings combine with potassium ions, which fill the vertices of a trigonal prism. A discussion is provided on the role played by the type of metal centre (Mⁿ⁺, M = Mn, Ni, Co, Cu) and countercation [tetrabutylammonium (TBA⁺) or tetraethylammonium (TEA⁺)] in a series of structurally characterized Mⁿ⁺–H₂mpba²⁻ systems described in the literature.

Environmental-friendly alternatives to the commercial scintillator CdWO₄, which contains the toxic element Cd, are highly desired. As potential candidates, in this work, the scintillation characteristics of Nb:YTaO₄ transparent single-crystals grown from melt by the floating-zone technique are studied. It is found that the broad UV luminescence of YTaO₄ can be turned into a broad visible one by the partial substitution of Ta with only 2% Nb. Therefore, Nb incorporation promotes a better spectral matching to Si-photodiode detectors while the high stopping power of YTaO₄ is kept, being close to that of commercial CdWO₄. The scintillation properties of pure YTaO₄, with a light yield of 15 900 ph MeV⁻¹ and an afterglow of 0.008% after 40 ms, are comparable to those of CdWO₄. The light yield weighed with a Si-photodiode reaches maximum values for 0.5 & 1% Nb:YTaO₄ crystals. An improvement in optical properties is expected by the growth of higher quality crystals by a flux-technique in the future.

Ag(0)_x–Mn₃O₄ nanocomposite layers have been obtained under “mild” chemical conditions at room temperature by treating the surface of a solution of a mixture of AgNO₃ and Mn(NO₃)₂ salts with ammonia gas. These layers consist of microglobules with a unique jellyfish-like morphology. The size and shape of these microglobules, as well as the density of their arrangement at the solution–air interface, are determined by the time of treatment with ammonia gas. Their comprehensive study was carried out by FESEM, TEM, HRTEM, SAED, XRD, and EDX methods and Raman and FT-IR spectroscopies. A hypothetical model is proposed to explain the formation of jellyfish-like microglobules. It was found that layers of these microglobules can be used as SERS substrates, allowing a signal amplification factor of 10⁷ times to be achieved.

Coordination compounds of L-carnosine (H₂car) have been the subject of much research, as they have potential therapeutic applications due to their antioxidant and anti-inflammatory properties. This paper analyzes the coordination possibilities of L-carnosine in reactions with copper(II) under different conditions. Three solvates (1–3) of copper(II) coordination compounds with car ligands were prepared, their molecular and crystal structures determined, and their interconversion conditions described. The Cu(II) ion coordination polyhedron is square-pyramidal, with water/methanol molecules in apical positions [Cu₂(car)₂(solv)₂] (solv = water or methanol). All three compounds consist of discrete dimers in which two car ligands coordinate two Cu(II) ions. The methanol solvates transform to the most stable compound, [Cu₂(car)₂(H₂O)₂]·2H₂O, upon exposure to moist air. Upon heating, this compound loses both coordinated and solvent water molecules, and the copper coordination changes to square-planar, yet the dimer is stable up to 200 °C. When cooled in moist air, it readily converts to the original compound [Cu₂(car)₂(H₂O)₂]·2H₂O. An exhaustive temperature-dependent structural and spectroscopic solid-state analysis indicates the robustness and reactivity of the activated dimer without coordinated molecules (coordinatively unsaturated sites, CUS). Preliminary results indicate that the generation of CUS requires heating after which the pyridine-based linkers can be introduced by prolonged milling using polar aprotic dimethylformamide as a liquid. These findings present potential routes for utilizing the activated dimer in creating novel compounds.

AlN crystals have attracted wide attention because of their excellent optoelectronic properties. However, the huge growth difficulty limits their large-scale application; thus, the main challenge is how to reduce the thermal stress between the AlN seeds and the tungsten holder. The massive thermal stress will lead to the increase of dislocation density and cracks, which seriously affect the quality of AlN crystals. Therefore, this work investigates the relationship between the thickness of the adhesive layer and the thermal stress by combining theory and experiment. The thickness of the adhesive layer was inversely proportional to the thermal stress at the seed in the range of 0.1–0.8 mm, while positively proportional in the range of 0.8–1 mm. The distribution of the threading edge dislocations (TEDs) and threading spiral dislocations (TSDs) is closely correlated with the thermal stress distribution. As a result, when the thickness of the adhesive layer is 0.8 mm, it can release the thermal stress of AlN seeds most effectively to below 10⁶ Pa and reduce the probability of crystal cracking. This work provides a new direction for the quality optimization of AlN crystals and the expansion growth.