P1 Space Group Research Articles

Crystal Structures and Property Measurements of Rare Earth Magnesium Thiosilicates Synthesized via Flux Crystal Growth Utilizing the Boron Chalcogen Mixture (BCM) Method

Nine new rare earth magnesium-containing thiosilicates of the formula RE3Mg0.5SiS7 (Ln = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er) were synthesized in an alkali halide flux using the boron chalcogen mixture (BCM) method. Crystals of high quality were produced, and their structures were determined by single-crystal X-ray diffraction. The compounds crystallize in the hexagonal crystal system in the P63 space group. Phase pure powders of the compounds were used for magnetic susceptibility measurements and for second-harmonic generation (SHG) measurements. Magnetic measurements indicate that Ce3Mg0.5SiS7, Sm3Mg0.5SiS7, and Dy3Mg0.5SiS7 exhibit paramagnetic behavior with a negative Weiss temperature over the 2-300 K temperature range. SHG measurements of La3Mg0.5SiS7 demonstrated SHG activity with an efficiency of 0.16 times the standard potassium dihydrogen phosphate (KDP).

Thermal expansion investigation of new langbeinite type phosphomolybdates: K2-xZr2P2-xMoxSiO12 (x = 0, 0.1, 0.2)

Members of A2(MO4)3 structure type have been identified as negative thermal expansion (NTE) materials. Specifically, tungstates (Sc2(WO4)3) and molybdates (Al2(MoO4)3) with orthorhombic structure exhibits NTE due to the transverse thermal vibration of A-O-M linkage. Langbeinite is a similar type structure consist of three-dimensional open framework with MO6 octahedral and PO4 tetrahedral interconnection. In the present work, we synthesized orthorhombic phosphomolydates of the chemical formula K2-xZr2P2-xMoxSiO12 (x = 0, 0.1, 0.2) to develop new low/zero/NTE materials with langbeinite structure. The compounds were synthesized by solution method and characterized by powder XRD, FT-IR, SEM and TG-DTA. Least square refinement method revealed that the synthesized compounds are crystallize in orthorhombic structure with P212121 space group. The characteristic stretching and bending vibrational bands of P-O, Si-O and Mo-O are observed from the FT-IR spectra. The compounds are thermally stable up to 600 °C and the effect of Mo substitution is observed from the micrographs with particle size variation. In contrary to A2(MO4)3 structure type, the average thermal expansion coefficient of K1.9Zr2Mo0.1P1.9SiO12 and K1.8Zr2Mo0.2P1.8SiO12 are found to be 8.19 and 6.89 × 10-6/ °C.

{[In2S7]8–}∞ Chain and Isolated HgS4 Planar Unit Constructed One-Dimensional Pentanary Sulfide K2Ba7HgIn4S16 Exhibiting Nonlinear-Optical Activity

Hg-based chalcogenides possess diverse structures, large nonlinear-optical (NLO) responses, and suitable birefringences, making them potentially suitable for numerous crucial criteria of practical application as infrared (IR) NLO crystals. Here, a new pentanary Hg-based sulfide K2Ba7HgIn4S16 has been discovered by a high-temperature solid-state method. It crystallizes in the orthorhombic P21212 space group, and its one-dimensional structure is constructed by {[In2S7]8-}∞ chains and isolated [HgS4]6- planar quadrilateral units located bewteeen the chains, representing a novel type of chalcogenide. K2Ba7HgIn4S16 exhibits a moderate NLO effect of 0.5 × AGS at 2.1 μm and a high laser-induced damage threshold of ∼5.8 × AGS, as well as a band gap of 2.98 eV, demonstrating that K2Ba7HgIn4S16 is a potential IR NLO material. This work enriches the structural chemistry of chalcogenides and the family of Hg-based IR NLO chalcogenides.

New Halide-Based Sodium-Ion Conductors Na3Y2Cl9 Inversely Designed by Building Block Construction.

Due to the excellent ionic conductivity and compatibility with high-voltage cathodes, halide-based superionic conductors as promising electrolytes have received widespread attention. A series of halide-based conductors, including Na3YCl6, are investigated aiming to find new solid electrolytes for sodium-ion batteries. However, Na3YCl6 with high ionic conductivity is meta-stable in thermostability while the stable phase exhibits poor ionic transport properties. In this work, we find that the coplanar formed anionic group (Y2Cl9)3- is the result of a combination of the structural features of the fast ion phase and stable phase of Na3YCl6 by systematic analysis of crystal structures. Aiming to find fast sodium-ion conductors, the three-step structure construction method using functional (Y2Cl9)3- groups as building blocks is proposed, and three new crystal structures in the composition of Na3Y2Cl9 with the space group of P63, Cc, and R32 are obtained. Na+ transport properties, thermostability, and electrochemical window of these structures with various symmetries are investigated by first-principles calculation methods. The results show that the principle to inverse design crystal structures of halides by basic blocks, e.g., anion groups and mobile cations, is proven to be effective and successful. For P63-Na3Y2Cl9 with outstanding transport properties, the simulation results indicate that its superionic behavior is attributed to the coherent diffusion connecting two directions. The synchronization of the migration pathways along the ab plane and the migration pathways along the c direction promotes the Na ion conductivity in Na3Y2Cl9. Our research will promote the understanding of the transport mechanism in halide-based electrolytes, and the structure construction method based on functional basic building blocks and special stacking modes will accelerate the inverse design of inorganic crystal structures.

Study of the Crystal Architecture, Optoelectronic Characteristics, and Nonlinear Optical Properties of 4-Amino Antipyrine Schiff Bases.

Two Schiff bases, (E)-4-((2-chlorobenzylidene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (4AAPOCB) and (E)-4-((4-chlorobenzylidene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (4AAPPCB), have been synthesized and grown as single crystals. Single-crystal X-ray diffraction analysis was employed to determine the crystal structure of the compounds, and the results suggest that the compounds crystallized into an orthorhombic crystal system having P212121 and Pbca space groups, respectively. Further, the crystallinity of the compounds was analyzed by the PXRD technique. The UV-vis-NIR spectra of the compounds demonstrate excellent transmittance in the entire visible region. The lower cutoff wavelengths of the compounds were determined to be 338 and 333 nm, respectively; additionally, optical band gaps of the compounds found were 4.60 and 4.35 eV. FTIR and NMR (1H and 13C) spectral techniques were utilized to analyze the molecular structure of the compounds. The compounds emit photoluminescence with broad emission bands with centers at 401 and 418 nm. The thermal stability and phase transitions were assessed through thermogravimetric methods. The phase transition prior to melting was indicated by the endothermic event at around 190 °C in the DTA curves of both crystals, and the same was observed in the DSC curves. The second harmonic efficiencies of the powdered compounds I and II were found to be 3.52 and 1.13 times better than that of the standard reference KDP. The 4AAPOCB and 4AAPPCB compounds showed isotropic polarizability amplitudes of 46.02 × 10-24 and 46.52 × 10-24 esu, respectively. The calculation of linear polarizability and NLO second-order polarizability (β) along with other optical parameters was performed for optimized geometries. The nonzero amplitudes of the average β values for compounds 4AAPOCB and 4AAPPCB were found to be 14.74 × 10-30 and 8.10 × 10-30 esu, respectively, which show a decent potential of the synthesized molecules for NLO applications. The calculated β amplitudes were further explained based on calculated electronic parameters like molecular electrostatic potentials, frontier molecular orbitals, molecular orbital energies, transition energies, oscillator strengths, and unit spherical representation of NLO polarizability. The current analysis emphasizes the significance of synthesized compounds as prospective candidates for optical and NLO applications through the use of experiments and quantum computations.

Discovery of two-dimensional Ga2S3 monolayers for efficient photocatalytic overall water splitting to produce hydrogen

Screening unique structures are critical to developing efficient photocatalytic materials for solar-to-hydrogen conversion via hydrogen evolution reaction (HER). Here, we demonstrate the discovery of two-dimensional Ga2S3 monolayers as efficient photocatalysts. By performing screening over 30 generations of 30 populations using the universal structure predictor evolutionary xtallography method, accompanied by accessing the stabilities and matching with photocatalytic conditions for overall water splitting, we identify 7 preferable configurations from 1038 Ga2S3 monolayers. The bandgaps and overpotentials of the band edges of these monolayers are used to justify the hydrogen and oxygen evolution reactions and evaluate the solar-to-hydrogen conversion efficiencies, and alterations of Gibbs free energy in HERs and oxygen evolution reactions (OERs) are calculated to validate the thermodynamics feasibility. The maximum efficiency of 17.71% is observed for one Ga2S3 monolayer with the P1 space group, and higher efficiency of 19.58% can be boosted with a suitable strain. Moreover, the moderate alterations of the Gibbs free energy assure the HERs are achievable in thermodynamics and the OERs can proceed spontaneously in thermodynamics on the GS-1, 4, 6, and 7 monolayers, although those on the GS-2, 3, 5 monolayers need small external energies. These results indicate that the screened Ga2S3 monolayers can be used as promising candidates for sunlight photocatalytic overall water splitting to manufacture hydrogen.

Investigating on crystal structure, thermodynamic, and molecular dynamic of lead-free organic-inorganic hybrid [NH3(CH2)2NH3]ZnBr4 crystals

In this study, lead-free organic-inorganic hybrid [NH3(CH2)2NH3]ZnBr4 crystals were grown by slow evaporation and analyzed. The crystals showed orthorhombic structure with the P212121 space group, and the following lattice constants: a = 8.3818 (2) Å, b = 10.8880 (4) Å, c = 11.8175 (4) Å, and Z = 4. The crystals were stable up to 584 K, with two phase transitions at 468 K (TC1) and 503 K (TC2), as indicated by differential scanning calorimetry and differential thermal analysis. The structural environments of the atoms were analyzed by 1H and 13C NMR. On increasing the temperature, the spin-lattice relaxation time, T1ρ, decreased rapidly due to large energy transfer at high temperatures, as indicated by large thermal displacements of the 1H and 13C atoms of the cation. Additionally, the activation energy, Ea, at high and low temperatures was found to be 49.23 and 1.44 kJ/mol, respectively, for the molecular motion of 1H, and 37.93 and 2.13 kJ/mol, respectively, for that of 13C. Analyzing the physiochemical properties of [NH3(CH2)2NH3]ZnBr4 could facilitate its application in stable and environment-friendly solar cells.

Fluorination Enables Dual Ferroelectricity in Both Solid- and Liquid-Crystal Phases.

Ferroelectric materials are a special type of polar substances, including solids or liquid crystals. However, obtaining a material to be ferroelectric in both its solid crystal (SC) and liquid crystal (LC) phases is a great challenge. Moreover, although cholesteric LCs inherently possess the advantage of high fluidity, their ferroelectricity remains unknown. Here, through the reasonable H/F substitution on the fourth position of the phenyl group of the parent nonferroelectric dihydrocholesteryl benzoate, we designed ferroelectric dihydrocholesteryl 4-fluorobenzoate (4-F-BDC), which shows ferroelectricity in both SC and cholesteric LC phases. The fluorination induces a lower symmetric polar P1 space group and a new solid-to-solid phase transition in 4-F-BDC. Beneficial from fluorination, the SC and cholesteric LC phases of 4-F-BDC show clear ferroelectricity, as confirmed by well-shaped polarization-voltage hysteresis loops. The dual ferroelectricity in both SC and cholesteric LC phases of a single material was rarely found. This work offers a viable case for the exploration of the interplay between ferroelectric SC and LC phases and provides an efficient approach for designing ferroelectrics with dual ferroelectricity and cholesteric ferroelectric liquid crystals.

One-Dimensional Chiral Copper Iodide Chain-Like Structure Cu4 I4 (R/S-3-quinuclidinol)3 with Near-Unity Photoluminescence Quantum Yield and Efficient Circularly Polarized Luminescence.

Chiral organic-inorganic hybrid metal halide materials have shown great potential for circularly polarized luminescence (CPL) related applications for their tunable structures and efficient emissions. Here, this work combines the highly emissive Cu4 I4 cubane cluster with chiral organic ligand R/S-3-quinuclidinol, to construct a new type of 1D Cu-I chains, namely Cu4 I4 (R/S-3-quinuclidinol)3 , crystallizing in noncentrosymmetric monoclinic P21 space group. These enantiomorphic hybrids exhibit long-term stability and show bright yellow emission with a photoluminescence quantum yield (PLQY) close to 100%. Due to the successful chirality transfer from the chiral ligands to the inorganic backbone, the enantiomers show intriguing chiroptical properties, such as circular dichroism (CD) and CPL. The CPL dissymmetry factor (glum ) is measured to be ≈4×10-3 . Time-resolved photoluminescence (PL) measurements show long averaged decay lifetime up to 10 µs. The structural details within the Cu4 I4 reveal the chiral nature of these basic building units, which are significantly different than in the achiral case. This discovery provides new structural insights for the design of high performance CPL materials and their applications in light emitting devices.

A highly selective “on–off” fluorescent sensor for detection of Fe3+ ion in protein and aqueous media: Synthesis, structural characterization, and computational studies

We describe herein the design and synthesis of a smart PGA chemosensor characterized by various techniques viz., FT-IR, UV–visible, 1H NMR, 13C NMR, Mass spectroscopy, and single crystal X-ray diffraction studies. The X-ray crystal analysis revealed that the PGA chemosensor crystallized in the orthorhombic crystal system with P212121 space group. The photophysical properties of the synthesized PGA chemosensor were examined by employing absorption and fluorescence spectral analysis. PGA revealed turn-on sensing responses towards the selective recognition of Fe3+ over other metal ions via CN isomerization processes. PGA also shows reversible effects upon the addition of EDTA. The 2:1 binding stoichiometry was calculated using Job’s plot and the value of detection limit was found to be 0.265 × 10-5 M, which is far lower than the permitted limit for drinking water according to WHO guidelines. The sensing mode of PGA towards Fe3+ was explored by employing FT-IR and 1H NMR studies. Density Functional Theory (DFT) studies, were employed which closely agreed with the experimental results. The PGA chemosensor has been successfully used to detect Fe3+ in various water samples and BSA medium. Furthermore, confocal imaging studies were examined, which supports the sensing ability of PGA for detection of Fe3+ in aqueous and protein medium.

Praziquanamine enantiomers: Crystal structure, Hirshfeld surface analysis, and quantum chemical studies

In this work, we report a microwave–assisted method to perform an acid hydrolysis using 2–6 praziquanamides as substrate to produce both praziquanamine (1) enantiomers: (R)–(–)–praziquanamine (1a) or (S)–(+)–praziquanamine (1b). This method provides very good yields and short reaction times (twenty minutes). A structural characterization of praziquanamine and its enantiomers was performed by using X–ray diffraction, spectroscopic and spectrometric techniques, thermal analysis, and powder X–ray diffraction. Computational calculations were also carried out, such as density functional theory (DFT), as it yields suitable geometries for the optimized structures. We also performed frontier molecular orbital (LUMO–HOMO) and electrostatic potential (ESP) analyses. Theoretical values were calculated for electronic transitions, vibration frequencies, and chemical shifts for nuclear magnetic resonances (NMR), and they were later compared to the experimental results. Additionally, the Hirshfeld Surface Analysis was performed to evaluate intermolecular interactions. Crystal structures of both 1a and 1b enantiomers were obtained as an orthorhombic system in the non-centrosymmetric P212121 space group. Conversely, the 1 compound crystallized as a monoclinic system in the centrosymmetric P21/n space group. The following interactions define the crystal packing: N–H···O, N–H···N, C–H···O, C–H···N, C–H···π, and π–π. They all establish an infinite one-dimensional chain. The crystal architectures of praziquanamine enantiomers may be used as resolution agents to discriminate chiral topologies.

Investigation on the molecular, electronic, biological and spectroscopic properties of a novel cobalt complex: An intuition from an experimental and computational perspective

The preparation, spectroscopic, biological and electrical characterization, in addition of the X-ray crystal structure investigation of a novel tree-dimensional compound [C6H16N2 Co(NCS)4] is reported. The synthetized compound crystallizes in the P212121 space group. The structure is made up of layers of cobalt (II) bridged by terminally bound thiocyanate-N ligand achieving distorted MN4 tetrahedron surroundings around the metal center. The main source of the distortion of the ideal tetrahedron is due to the geometrical constraints issued from the occurrence of piperazinium ligand, the values of the N–Co–N bond angles covering the range 101.64(11)–116.81(12)°.The vibrational modes of the functional groups were investigated using FT-IR measurements. Hirshfeld surface analysis was performed to investigate the short contacts and hydrogen bonds in the compound. In addition of the study of the photoluminescent behavior which reveals a high optical property. Explorations of impedance spectroscopy on [C6H16N2 Co(NCS)4] reveal fascinating electrical behavior which reveals that the Co complex component can be used as an electronic chip and under certain conditions, this semiconductor have the ability to act either as a conductor which can be a considered as a pure element. The thermal analysis was used to confirm the crystal thermal stability. Finally, the compound’s antioxidant activity and the molecular docking were occurred which suggest that the Cobalt complex acts as a COX-2 inhibitor Agent.

Discovering the Solid-State Secrets of Lorlatinib by NMR Crystallography: To Hydrogen Bond or not to Hydrogen Bond

Lorlatinib is an active pharmaceutical ingredient (API) used in the treatment of lung cancer. Here, an NMR crystallography analysis is presented whereby the single-crystal X-ray diffraction structure (CSD: 2205098) determination is complemented by multinuclear (1H, 13C, 14/15N, 19F) magic-angle spinning (MAS) solid-state NMR and gauge-including projector augmented wave (GIPAW) calculation of NMR chemical shifts. Lorlatinib crystallises in the P21 space group, with two distinct molecules in the asymmetric unit cell, Z′ = 2. Three of the four NH2 hydrogen atoms form intermolecular hydrogen bonds, N30-H…N15 between the two distinct molecules and N30-H…O2 between two equivalent molecules. This is reflected in one of the NH21H chemical shifts being significantly lower, 4.0 ppm compared to 7.0 ppm. Two-dimensional 1H–13C, 14N-1H and 1H (double-quantum, DQ)-1H (single-quantum, SQ) MAS NMR spectra are presented. The 1H resonances are assigned and specific HH proximities corresponding to the observed DQ peaks are identified. The resolution enhancement at a 1H Larmor frequency of 1 GHz as compared to 500 or 600 MHz is demonstrated.

The synthesis, structure and photoluminescence of new (C8H18N)2CdCl4 crystals

Organic-inorganic hybrid new (C8H18N)2CdCl4 single crystals were grown using a solution method, with its important physical properties, including in structure, phase purity, thermal analysis, absorption and diffuse reflectance spectra, and photoluminescence characteristic were systematically studied. (C8H18N)2CdCl4 belongs to orthorhombic P212121 space group with zero-dimensional non-centrosymmetric structure. A high phase purity was confirmed by PXRD, FT-IR and Raman spectra, and a melting point of 120°C was determined by simultaneous thermal analysis. An absorption cut-off edge of 230 nm and optical band gap of 5.52 eV were determined, with high transmittance range of 300-1900 nm was detected. More importantly, a wide photoluminescence spectra covering visible range were observed, indicating a potential applications of (C8H18N)2CdCl4 in white light luminescence. This work can supply an important guiding significance for searching new zero-dimensional hybrid d10-based metal halides with tetrahedron framework with nontoxic, high stability and some fascinating properties, especially those with white light luminescence performance.

Growth parameters and investigations on the structural, optical, mechanical, thermal and electrical properties of an l-proline guanidine carbonate single crystal

Single crystal of l-proline guanidine carbonate (LPGC) was grown by adapting most important method of slow evaporation technique by using double distilled water as a solvent at room temperature. Single crystal X-ray diffraction determined that the crystal structure of LPGC as orthorhombic non-centro symmetric system with the P212121 space group and the lattice parameters are confirmed to be a = 8.3580(4) Å, b = 10.3479(4) Å, c = 15.1833(5) Å, α = β = γ = 90°, Volume V = 1313.17(9) A3. The diffraction pattern of powder X-ray diffraction describes the factors of the crystallinity nature and the purity of the LPGC crystal. The optical absorption spectrum of LPGC crystal has been recorded and the linear optical constants such as the absorption coefficient (α), Energy band gap (Eg), extinction coefficient (K), refractive index (n) and Urbach energy (Eu) have been calculated. The active functional groups of the grown crystal were identified and confirmed by Fourier transform infrared spectroscopic study (FTIR) and Fourier transform Raman spectroscopy (FT-RAMAN). The thermal behavior and the thermal stability of the crystal were investigated by the thermogravimetric-differential thermal analysis (TG-DTA). Vickers micro hardness test was carried out to determine the mechanical stability and the hardness parameters of the crystals such as stiffness constant (C11), yield strength (σy), hardness number (Hv) and work hardening coefficient (n). The luminescence activity of the grown crystal was determined by the photoluminescence (PL) spectroscopy. The dielectric properties of the LPGC crystal were analyzed at various temperature and frequency. The presence of active chemical compounds in LPGC crystal was confirmed by energy dispersive analysis (EDAX). The Z-scan analysis of the grown crystal determines the Q-switching behavior of the grown LPGC crystal.

3-(dimethylamino)dibenzothiophene (3-DMADBT): Synthesis, characterization, crystallographic study, Quantum chemical calculations, Hirshfeld surface analysis and FT-IR spectroscopy

The 3-(dimethylamino) dibenzothiophene (3-DMADBT) has been synthesized and characterized by X-ray single crystals diffraction (XRD), FT-IR, 1H NMR, Elemental analysis, and Melting point determination. The density functional (B3LYP) and Hartree-Fock (HF) methods with a 6–31 G (d,p) level were established to calculate the parameters of molecular geometry, normal mode frequencies and the related vibrational assignments, and 1H chemical shift values for gage-including atomic orbitals (GIAO) of 3-DMADBT in its ground state. Potential energy distribution (PED) analyses were used to assign vibrations. The tested chemical crystallizes in an orthorhombic crystal structure with a space group of P212121 and unit cell dimensions of a = 6.0750 (5) Å, b = 8.9566 (6) Å, c = 21.2622 (11) Å, and V = 1156.90 (14) Å3. The calculated data shows that optimized geometries can accurately reproduce the crystal structure. The experimental results accord well with the theoretical vibrational frequencies and chemical shift values from 1H NMR. Furthermore, the compound's Mulliken charge distribution and molecular electrostatic potential maps (MEP) have been developed. The energy gap (∆E), electron affinity (A), ionization potential (I), chemical potential (µ), global hardness (η), and global electrophilicity (w) are all calculated using the HOMO-LUMO analysis. In addition, the Hirshfeld surface analysis is used to determine interactions in the crystal structure.

A fluorene based imine compound: Structural characterization, DNA binding properties and fluorescence sensor properties towards metal ions

In the course of this work, a new fluorene-based Schiff base compound (SB) from the condensation reaction 2-aminofluorene and 4-(diethylamino)salicylaldehyde was synthesized and its structure was characterized by FTIR, 1H/13C NMR spectroscopies and elemental analysis. Crystal structure of the synthesized compound (SB) was determined single crystal X-ray diffraction study. Crystal structure of the compound was solved in monoclinic unit cell and P21 space group. The molecule shows phenol-imine intramolecular hydrogen bond and molecules are connected by CH····π interactions. The Schiff base compound was then screened for its DNA binding properties by using UV–vis absorption, fluorescence and viscosity studies. All DNA binding data showed that the compound interacts with FSdsDNA via intercalation. The intrinsic DNA binding constant of the compound from UV–vis spectral data was 3.00×104 M−1 which is significantly lower than ethidium bromide (an intercalating agent). The compound was further investigated for colorimetric sensing of metal ions. Colorimetric sensor properties of the compound towards Fe(III), Pb(II), Zn(II), Cu(II), Al(III), Hg(II), Co(II), Mn(II) and Ni(II) ions were investigated in solution. The compound showed selective sensing properties for Cu(II) under 365 nm light. Jobs variation study indicated that the Cu(II) to receptor ratio was 2:1.

Study of the magnetic properties of Mg, Gd, and Co doped maghemite (γ-Fe2O3) nanoparticles prepared by sol–gel

The γ-Fe2O3 magnetic nanoparticles, prepared by sol gel route, were doped with Magnesium (Mg), Gadolinium (Gd), and Cobalt (Co) oxides to enhance their magnetic properties. The X-ray diffraction, of the prepared samples, show that all samples crystallized under cubic structure with P4332 space group. The morphological properties of our nanopowders were studied with TEM investigations. The average nanoparticle sizes were distributed between 15 and 23 nm for both the pure and the doped samples. The magnetization as a function of temperature and magnetic field were measured to study the effect of the doping elements on the magnetic properties. The results show that the highest magnetization (MH) of our nanoparticles increases especially with increasing Mg, Gd and Co concentration It is also observed that cobalt doping increases the magnetic coercivity by increasing the value of the coercivity field (Hc) and remanence magnetisation (Mr), which can be used in magnetic recording devices.

PH-Driven Polymorphic Behaviour of the Third PDZ Domain of PSD95: The Role of Electrostatic Interactions

The PDZ domains are modular domains that recognise short linear C-terminal sequences in proteins that organise the formation of complex multi-component assemblies. We have crystallised the third PDZ domain of the neuronal postsynaptic density-95 protein (PSD95-PDZ3) at mildly acidic pH conditions and obtained up to four polymorphs. Thus, below pH 4.0, the protein crystallised into prism-shaped crystals that belonged to the trigonal space group P3112. In contrast, above this pH value, the crystals’ shape changes to long needles belonging to the monoclinic P21 and two different orthorhombic packings of the P212121 space group. In addition, all the polymorphs share the main crystallographic interface, where the sidechain of the Asp332 imitates the binding of the C-terminal moiety to the canonical binding motif. Furthermore, we have analysed how changes in the ionisation state of some specific residues might be critical for crystallising the different polymorphs. The analysis of these polymorphs provides clues on the relevance of specific protein-protein interactions in protein crystallisation. However, these structures allow dissecting those electrostatic interactions that play a role in the conformation adopted by some residues and the extra-domain components upon binding C-terminal sequences.

Spin-crossover in [Fe(Quinazoline)2][Fe(CN)5NO]. Evidence of its framework flexibility

The titled material shows a thermally induced spin-crossover (SCO) in the 75–150 K temperature region, with a narrow hysteresis of about 3 K. The recorded DSC data show a similar small hysteresis. Such behavior suggests that its framework has high flexibility, making possible the reversible spin transition on the sample cooling and warming, with slight kinetic effects. The crystal structure of this material was solved and refined from powder XRD patterns, complemented with information from IR, Raman, TG, and Mössbauer data. It crystallizes with a monoclinic unit cell in the P21 space group. Its framework is formed by stacked [Fe(Quinazoline)2][Fe(CN)5NO] layers. The organic molecule occupies the axial coordination sites for the iron atom linked to the N ends of equatorial CN ligands. In the interlayer region, organic ligands from adjacent layers remain coupled through weak dipolar and dispersive forces and a π⋅⋅⋅π interaction. Such relatively weak forces between adjacent layers explain the high framework flexibility inferred from the magnetic and DSC data. The crystal structure for the low temperature (low spin) phase was obtained by periodic DFT calculations using the VASP package. The results herein discussed contribute to understanding the role of the solid framework flexibility on the spin-crossover behavior in Hofmann-like 2D coordination polymers.