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The reactivity of solid rubrene with potassium: competition between intercalation and molecular decomposition
摘要： We present the synthesis and characterization of the K+ intercalated rubrene (C42H28) phase, K2Rubrene (K2R) and identify the co-existence of amorphous and crystalline materials in samples where the crystalline component is phase pure. We suggest this is characteristic of many intercalated alkali metal-polyaromatic hydrocarbon (PAH) systems, including those for which superconductivity has been claimed. The systematic investigation of K-rubrene solid state reactions using both K and KH sources reveals complex competition between K intercalation and the decomposition of rubrene, producing three K-intercalated compounds, namely, K2R, K(RR*), and KxR? (where R* and R? are rubrene decomposition derivatives C42H26 and C30H20, respectively). K2R is obtained as the major phase over a wide composition range and is accompanied by the formation of amorphous by-products from the decomposition of rubrene. K(RR*) is synthesized as a single phase and KxR? is obtained only as a secondary phase to the majority K2R phase. The crystal structure of K2R was determined using high resolution powder X-ray diffraction, revealing that the structural rearrangement from pristine rubrene creates two large voids per rubrene within the molecular layers in which K+ is incorporated. K+ cations accommodated within the large voids interact strongly with the neighbouring rubrene via η6, η3 and η2 binding modes to the tetracene cores and the phenyl groups. This contrasts with other intercalated PAHs where only a single void per PAH is created and the intercalated K+ weakly interact with the host. The decomposition products of rubrene are also examined using solution NMR, highlighting the role of the breaking of C-CPhenyl bonds. For the crystalline decomposition derivative products K(RR*) and KxR?, a lack of definitive structural information with regards to R* and R? prevents the crystal structures being determined. The study illustrates the complexity in accessing solvent-free alkali metal salts of reduced PAH of the type claimed to afford superconductivity.
关键词： crystal structure,decomposition,rubrene,intercalation
更新于2025-09-23 15:21:21
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Synthesis, structure and photoluminescence properties of a three-dimensional cadmium(II) (4,5)-connected coordination network
摘要： The assembly of coordination polymers from metal ions and organic moieties is currently attracting considerable attention in crystal engineering due to their intriguing architectures and potential applications as functional materials. A new coordination polymer, namely poly[[(cid:2)2-trans-1,2-bis(pyridin-3-yl)-ethylene-(cid:3)2N:N0]bis((cid:2)4-4,40-oxydibenzoato-(cid:3)6O:O,O0:O00:O00,O000)dicadmium(II)], [Cd2(C14H8O5)2(C12H10N2)]n or [Cd2(4,40-OBB)2(3,30-BPE)]n, has been synthesized by the self-assembly of Cd(NO3)2(cid:2)4H2O, 4,40-oxydibenzoic acid (4,40-H2OBB) and trans-1,2-bis(pyridin-3-yl)ethene (3,30-BPE) under hydrothermal conditions. The title compound was structurally characterized by IR spectroscopy, elemental analysis and single-crystal X-ray diffraction analysis. Each CdII centre is coordinated by six carboxylate O atoms from four different 4,40-OBB2(cid:3) ligands and by one pyridyl N atom form a 3,30-BPE ligand. Adjacent crystallographically equivalent CdII ions are bridged by 4,40-OBB2(cid:3) ligands, affording a two-dimensional [Cd(4,40-OBB)]n net extending in the ac plane. Neighbouring [Cd(4,40-OBB)]n nets are interlinked by 3,30-BPE along the b axis to form a three-dimensional (3D) [Cd2(4,40-OBB)2(3,30-BPE)]n coordination network. In the network, each CdII centre is linked by four different 4,40-OBB2(cid:3) ligands and one 3,30-BPE ligand. Meanwhile, each 4,40-OBB2(cid:3) ligand connects four separate CdII ions. Therefore, if the 4,40-OBB2(cid:3) ligands and CdII ions are considered as 4- and 5-connecting nodes, the structure of the title compound can be simplified as a 3D (4,5)-connected binodal framework with the rare (4462)(4466) TCS topology (Pearson, 1985; Blake et al., 2011). The thermal stability and photoluminescence properties of the title compound have also been investigated.
关键词： coordination polymer,crystal engineering,crystal structure,photoluminescence properties,TCS network,cadmium(II),topology
更新于2025-09-23 15:21:01
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Tricolor luminescence switching by thermal and mechanical stimuli in the crystal polymorphs of pyridyl substituted fluorene
摘要： Stimuli-responsive organic luminescence switching materials have attracted much attention for a decade. Most of the reported examples display a reversible two-color luminescence switching, multicolor switched materials remain extremely lacking due to the un-designability of this kind of smart materials. Herein, we reported a simple organic molecule, 4,4'-(9,9-dimethyl-9H-fluorene-2,7-diyl)dipyridine (MFDP), which exhibited three different crystal polymorphs (V-MFDP, B-MFDP and G-MFDP) with different luminescent colors. Furthermore, the three crystal polymorphs showed a reversible tricolor fluorescent switching from violet to blue and to green upon physical stimuli. The single-crystal structures of the three polymorphs were obtained, and the results indicate that, the stimuli response properties of the three polymorphs come from the different stacking modes induced by intermolecular interactions. The competition between weak π?π stacking and weak hydrogen bonding is the main reason for the the phase transformations among the three crystal polymorphs.
关键词： Fluorene,π–π Stacking,Crystal Structure,Luminescence Switching,Stimuli-response
更新于2025-09-23 15:21:01
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A polyoxometalate-based metal–organic polyhedron constructed from a {V <sub/>5</sub> O <sub/>9</sub> Cl} building unit with rhombicuboctahedral geometry
摘要： The design and construction of metal–organic polyhedra has received much attention by chemists due to the intriguing diversity of architectures and topologies that can be achieved. There are several crucial factors which should be considered for the construction of metal–organic polyhedra, such as the starting materials, reaction time and temperature, solvent and suitable organic ligands. Recently, polyoxometalates (POMs), serving as secondary building units to construct POM-based metal–organic polyhedra, have been the subject of much interest. The title compound, dodecakis(dimethylammonium) octakis(μ-benzene-1,3,5-tricarboxylato)hexa-μ-chlorido-tetracosa-μ-oxido-triacontaoxidotriacontavanadium, (NH2Me2)12[(V5O9Cl)6(C9H3O6)8], was synthesized successfully by self-assembly of VOCl3 and benzene-1,3,5-tricarboxylic acid under solvothermal conditions. The title polyhedron has an rdo topology when the {V5O9Cl} building unit and the benzene-1,3,5-tricarboxylate (BTC3?) ligand were simplified into 4-connected and 3-connected vertices. Interestingly, when the {V5O9Cl} building unit and the BTC3? ligand are considered as quadrangular and triangular faces, the structure displays rhombicuboctahedral geometry with an outer diameter of 21.88 ?. The packing of the polyhedra produces a circular channel with a diameter of 8.2 ?. The title compound was characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, thermogravimetric analysis and powder X-ray diffraction.
关键词： POV,crystal structure,SQUEEZE,nanoball,rhombicuboctahedron,MOP,molecular polyhedra,nanocage,topological analysis,metal–organic polyhedron,circular channel,polyoxometalate
更新于2025-09-23 15:21:01
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Crystal structure, vibrational spectra, optical properties and density functional theory approach of a picrate salt based on substituted triphenylphosphinium
摘要： A new organic crystal, [BzTPP][PIC](1) ([BzTPP]+ = benzyl triphenylphosphinium, [PIC]- = picrate), has been grown by slow evaporation solution growth technique. Single crystal XRD reveals that it belongs to monoclinic system with P21/c. The two neighboring [BzTPP]+ cations from a dimer through C-H···π interaction while anions stack into a columnar structure through N···O, O···O and π···π interaction. The anions and cations form a column structure alternately in ···AC-AC-AC-AC··· sequence through C-H···O hydrogen bonds. The experimental vibrational bands (IR and Raman) have been discussed and assigned based on DFT calculations. The HOMO-LUMO energy gap explains the charge transfer interactions in the molecule. The thermal stability of the hybrid crystal was analyzed by TG-TDA-MS technique and revealed that the title crystal was stable up to 290 °C. The fluorescence spectra reveal three main emission peaks at 295, 388 and 543 nm upon excitation at 250 nm in solid state at room temperature. The energy of weak interactions in the molecule and nonlinear optical properties were studies using DFT calculations.
关键词： Substituted benzyl triphenylphosphinium picrate,Optical properties,vibrational spectra,Crystal structure,DFT calculations
更新于2025-09-23 15:21:01
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Crystal structure and ferroelectric polarization of tetragonal (Bi <sub/>1/2</sub> Na <sub/>1/2</sub> )TiO <sub/>3</sub> –12BaTiO <sub/>3</sub>
摘要： We have investigated the crystal structure and ferroelectric polarization of (Bi1/2Na1/2)TiO3–12%BaTiO3 by high-resolution neutron powder di?raction Rietveld analysis and density-functional theory calculations. It is revealed that the sample has a ferroelectric distortion in tetragonal P4mm symmetry along with a large tetragonality c/a of 1.022. The A- and B-site atoms exhibit a cooperative o?-center displacement along the polar c-axis, which results in a large spontaneous polarization of 54 μC/cm2.
关键词： crystal structure,neutron powder diffraction,tetragonal (Bi1/2Na1/2)TiO3–12BaTiO3,density-functional theory,ferroelectric polarization
更新于2025-09-23 15:21:01
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Sm <sub/>3</sub> O <sub/>2</sub> Sm[SeO <sub/>3</sub> ] <sub/>4</sub> and Sm <sub/>3</sub> O <sub/>2</sub> Cl[SeO <sub/>3</sub> ] <sub/>2</sub> : A Monoclinic Form of Samarium Oxide Oxoselenate(IV) and a Samarium Oxide Chloride Oxoselenate(IV) both with <sup>1</sup><sub/>∞</sub> {[O <sub/>2</sub> Sm <sub/>3</sub> ] <sup>5+</sup> } Chains
摘要： Appropriate mixtures of Sm2O3 and SeO2 with various chloride fluxes yielded single crystals of Sm3O2Sm[SeO3]4 (monoclinic, P21/n; a = 1497.89(8), b = 556.61(3), c = 1639.63(9) pm, β = 91.054(3)° with Z = 8 for Sm2Se2O7) or Sm3O2Cl[SeO3]2 (orthorhombic, Pnma; a = 565.82(4), b = 1457.14(9), c = 1145.23(7) pm and Z = 4). In contrast to the known tetragonal form of Sm2Se2O7, the monoclinic one exhibits four crystallographically different Sm3+ and Se4+ cations. Nonetheless [OSm4]10+ tetrahedra are connected by trans-oriented edges to single chains 1(cid:2){[OSm4/2]4+} like in tetragonal Sm2O[SeO3]2. The monoclinic form, however, displays double chains 1(cid:2){[O2Sm3]5+} of edge-linked [OSm4]10+ tetrahedra, which are also present in the samarium(III) oxide chloride oxoselenate(IV) Sm3O2Cl[SeO3]2. Both tetragonal Sm2O[SeO3]2 and monoclinic Sm3O2Sm[SeO3]4 with the empirical formula Sm2Se2O7 as well as Sm3O2Cl[SeO3]2 contain empty channels in their crystal structures, apt to accommodate the lone-pair electrons at the Se4+ cations. These are residing in isolated ψ1-tetrahedral [SeO3]2(cid:3) anions. Non-selenium bonded oxide anions (and if necessary chloride anions in the case of Sm3O2Cl[SeO3]2) take care of the charge balance. The much higher density (Dx = 6.207 g·cm–3) of the tetragonal form (P42/ncm; a = 1077.03(8), c = 526.38(4) pm) indicates the new monoclinic modification of Sm2Se2O7 (Dx = 5.546 g·cm–3) as high-temperature phase, which is confirmed by its synthesis under fast quenching conditions.
关键词： Chlorides,Lone-pair activity,Oxoselenates(IV),Oxides,Crystal structure,Samarium
更新于2025-09-23 15:21:01
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Structural, spectral and nonlinear optical analysis of Bis(2-methyllactato)borate tetrahydrate: a new nonlinear optical crystal for laser applications
摘要： A new nonlinear optical crystal, ‘Bis(2-methyllactato)borate tetrahydrate’ (BMBT) has been crystallized by slowly evaporating the solvent. It crystallizes in the space group P21212. Sharp peaks present in powder XRD profile reveals the good crystallinity. Its transmission bandwidth (220 nm – 1100 nm) suggest that it can be used to generate UV radiation upto 220 nm and also in optoelectronic applications. Vibrations of functional groups (B-O, CH3, CO) associated with the crystal structure have been identified through FTIR and FT-Raman spectral studies. OH stretching vibrations have been observed near 3000 cm-1 clearly endorses the existence of water molecule in the BMBT structure. The chemical shifts observed in 1H and 13C NMR spectral results establishes the molecular structure of BMBT crystal. Second harmonic generation (SHG) efficiency is obtained as 0.9 times of KDP. The third order nonlinear susceptibility (χ3), nonlinear refractive index (n2) and nonlinear absorption co-efficient (β) were found using Z-scan technique. χ3 of title crystal is found to be 4.16 X10-5 esu. The existence of SHG efficiency and the enhanced χ3 value are due to the hydrogen bonded intermolecular interactions present in the BMBT crystal structure. The observed results suggest that BMBT can be used in Q-switching, mode locking and optical sensors like night vision devices.
关键词： Crystal structure,Z-scan analysis,crystal growth,NMR spectroscopy,second harmonic generation
更新于2025-09-23 15:19:57
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Evaluation of the optical absorption/emission spectral behavior of the Cd1-xDyxSe quantum dots synthesized via cation exchange approach
摘要： Cd1-xDyxSe nanocrystalline quantum dots were synthesized via cation exchange approach for the first time. The as-synthesized Cd1-xDyxSe nanocrystals showed a cubic phase at all Dy ion contents. The formed nanoparticles of the as-synthesized Cd1-xDyxSe nanocrystals were spherical like shape and their diameters increased from 2.1–7.3 nm with increasing the amount of Dy ions. The doping of CdSe with Dy atoms comprises a read shift of the optical absorption spectral curves. Therefore, a decrease of the optical band gap from 2.58 eV to 2.15 eV owing to the increase of Dy atoms took place. The partial substitute of the Cd atoms by Dy atoms instigated remarkable enhancing of the of luminescent intensities by eight order of magnitudes, made the PL peaks more sharper by four orders and achieved enlargement of the quantum yield to reach to value of 93 %. A decrease of the Stokes shift due to the doping by the Dy atoms was reasoned to the passivation of the defects. The enlargement of luminescence intensity, the creation of narrow emission band and the high quantum yield value empowered the as-synthesized Cd1-xDyxSe nanocrystals to be employed as laser materials for the manufacturing of multicolor laser diodes.
关键词： Absorption,Crystal structure,Quantum yield,Quantum dots,Luminescence
更新于2025-09-23 15:19:57
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Temperature-Controlled Fragmentation and Ripening: Synthesis of ZnSe Nanorods with Variable Dimensions and Crystal Structure Starting from Ultrathin ZnSe Nanowires
摘要： Heavy-metal-free semiconductor nanomaterials have attracted attention because of their importance in both fundamental research and commercial applications. In particular, polarized ?uorescence emission in one-dimensional (1D) semiconductors makes them highly attractive as display materials. Herein, we developed a novel colloidal synthesis approach toward 1D ZnSe nanostructures with controlled size and crystal structure, which we call “temperature-controlled fragmentation and ripening”. First, ultrathin ZnSe nanowires (NWs) with a length of 50?200 nm and diameter of ～1.1 nm were synthesized. ZnSe nanorods (NRs) have been obtained through the fragmentation of these NWs in a controlled step while keeping the same diameter, and the length of the ?nal ZnSe NRs has been tuned in the range of 10?20 nm by moderating the heating procedure. Using a higher temperature for fragmentation allowed us to break down the ZnSe NWs to shorter ZnSe NRs, whereas controlling the ?nal growth temperature of the ZnSe NRs in a subsequent ripening stage allowed us to obtain them in either cubic zinc blende (ZB; at 220 °C) or hexagonal wurtzite (WZ; at 240 °C) crystal structures. This set of growth processes ?ipping from bottom-up to top-down to form ZnSe NRs with controlled length and selection of the ?nal crystal structure (either hexagonal WZ or cubic ZB) provides a novel growth mechanism to synthesize 1D semiconductor nanostructures.
关键词： nanorods,ripening,nanowires,temperature-controlled fragmentation,ZnSe,crystal structure
更新于2025-09-23 15:19:57