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Reactions between Ln(NO3)3 and cucurbit[6]uril in HNO3 have been studied, aiming to create novel light-emitting systems. Aquanitrato complexes of lanthanides were obtained as supramolecular assemblies 1–10 with the organic macrocyclic cavitand cucurbit[6]uril. X-ray diffraction study demonstrated that these compounds have the following compositions: [{Ln(H2O)5(NO3)}2(C36H36N24O12)](NO3)4·HNO3·nH2O (Ln = Pr(1), Nd(2), Sm(3), Eu(4), Gd(5), Tb(6)) and 2[Ln(H2O)8](NO3)3·C36H36N24O12·2HNO3·mH2O (Ln = Dy(7), Ho(8), Er(9), Yb(10)). Compounds with different structures were shown to crystallize under the same synthesis conditions for the early and late lanthanides. The compounds were characterized by powder X-ray diffraction, thermogravimetric and elemental analyses, and IR spectroscopy. The magnetic property of compound 5 was also examined. The luminescent properties for compounds 1–10 were studied. The chromaticity coordinates (CIE) for compounds 1–10 were calculated. The color purity of compound 4 was found to be 96%, which is very close to that of the standard red light source. Compound 4 can be considered a potential red-emitting candidate for near-UV WLEDs. The color purity of compound 7 is very close to zero, so it is well suited for generation of white light, which further suggests its utility for W-LED applications. A cool white LED device was fabricated for the first time by combining the supramolecular coordination polymer 7 and a UV LED chip (365 nm) under a voltage of 3.0 V; the CIE, CCT and CP were (0.301, 0.325), 7228 K and 7%, respectively. [ABSTRACT FROM AUTHOR]

A series of new 8-benzyloxyisoquinoline derivatives are designed and synthesized based on the 4H-pyran chemistry. These compounds have twisted molecular conformations and loose packing modes according to their crystal structures, and thus exhibit outstanding dual-state emissions. Importantly, using cheap and easily available polymethyl methacrylate (PMMA) as the host molecule and the isoquinoline derivatives as the guest molecules, the resultant two-component doped materials show green or orange room-temperature phosphorescence (RTP) activities with delayed lifetimes of 72–106 ms, which originate from the guest molecule through the suppression of non-radiative transitions of excited triplet excitons by the rigid microenvironment provided by the PMMA polymer. This result provides a valuable reference for developing isoquinoline-based solid-state luminescent materials with dual-state emissions and RTP properties. [ABSTRACT FROM AUTHOR]

Luminescent materials used in solid-state lighting usually face the challenge of the adjustment of luminescence properties. The coordinated luminescence of two activators in luminescent materials is a good method. Herein, CaAl2Si2O8:Dy3+, CaAl2Si2O8:Eu3+, and CaAl2Si2O8:Dy3+, Eu3+ with a pure phase (CaAl2Si2O8) were synthesized in air. The X-ray diffraction patterns of the samples were measured and their crystal structures were elucidated. Under excitation at 350 nm, the yellow emission of CaAl2Si2O8:Dy3+ in the spectral range of 525–800 nm was observed due to the 4F9/2 → 6H15/2, 6H13/2, 6H11/2, and 6H9/2 transitions of Dy3+ ions. CaAl2Si2O8:Eu3+ showed red emission in the range of 550–720 nm because of the transitions 5D0 → 7F1, 7F2, 7F3, and 7F4 of Eu3+ ions when it was excited by 394 nm light. A tunable color emission of CaAl2Si2O8:Dy3+, Eu3+ from yellow to red was found when the ratio between Dy3+ and Eu3+ ions was changed. We investigated the concentration-dependent spectra and ensured the optimal Dy3+ and Eu3+ concentrations in host CaAl2Si2O8. The spectra of the samples manifested the energy transfer from Dy3+ to Eu3+ ions. The energy-level diagrams of Dy3+ and Eu3+ ions were used to analyze the luminous mechanism of the samples. The research results are beneficial to the development of other Dy3+ and Eu3+ co-doped luminescence materials. [ABSTRACT FROM AUTHOR]

The pharmaceutical cocrystal landscape of ethenzamide has been addressed during the past years with the aim of improving its physicochemical properties, mainly solubility and dissolution rate. Herein four novel ethenzamide cocrystals have been isolated by mechanochemical synthesis and thoroughly characterized by powder and single-crystal X-ray diffraction. Polyphenols have been selected as coformers based on ethenzamide synthon preference as well as their safety profile and antioxidant character. Besides crystallographic analysis, theoretical calculations have been made to evaluate the strength of intermolecular interactions and their role in crystal packing. The results evidence differences in the supramolecular architecture depending on the different polyphenolic isomers used as coformers. Finally, the physicochemical properties of the novel compounds were assessed and compared to those of ethenzamide alone. Although the solubility profile is significantly enhanced, the thermodynamic stability of the novel cocrystals in aqueous medium is restricted to 24 hours. These findings have been correlated with the crystal structure. [ABSTRACT FROM AUTHOR]

Analysis of known crystal structures of halobenzenes reveals that the 176 closest intermolecular interactions contain either edge⋯face or face⋯face approaches between aromatic rings. Most of these close approaches possess the specific geometry and symmetry of π–π stacking defined as "symthon I". A further 20 face⋯face approaches have similar geometry but exhibit only inversion symmetry, yielding a geometric definition for the new "symthon III". There are 17 examples of edge⋯face approaches that meet the previously defined symmetry and geometric requirements for "symthon II". The other close interactions are simple variants of these three symthons. Only symthon I accommodates halogen disorder and solid solutions – in this dataset exclusively in space group no. 14. The number (N) and disposition of halogen substituents influence the preferred symthons; for example edge⋯face interactions are confined to N ≤ 3. The inclusion here of halobenzenes containing more than one type of halogen completes an earlier study of unmixed halobenzenes. [ABSTRACT FROM AUTHOR]

In the field of crystallization-based chiral resolution, preferential crystallization is particularly interesting. In recent work, we showed how the simultaneous resolution of two racemic compounds can be realized through the formation of chiral conglomerate cocrystals. The crystallization of a compound as a conglomerate is a rather rare phenomenon. In this study, we decided to test the probability of multi-component conglomerate formation between two racemic compounds by cocrystallizing racemic compounds with each other. Specifically, racemic proline, mandelic acid and etiracetam were cocrystallized with 14 racemic coformers. The analysis of XRPD patterns upon grinding revealed 16 potential cocrystals, four of which have been already published. The crystal structures of all new cocrystals were determined by single crystal diffraction. The crystal structure elucidation showed 13 cocrystals were racemates and 3 were conglomerates. All conglomerates are isomorphous as they were formed between etiracetam and mandelic acid or its 2-fluoro- and 2-chloro-derivatives. Simultaneous resolution through preferential cocrystallization of racemic compounds, therefore, is limited to very specific systems. In parallel, our results did, however, highlight a striking success rate of DL -proline in the context of cocrystallization as 11 out of 14 cocrystallization experiments were successful. [ABSTRACT FROM AUTHOR]

This work reports on hybrid hexamethylenediaminium lead halide perovskites. The materials were prepared using wet synthesis and the subsequent precipitation from aqueous solution. Structural and morphological charactarization studies show their high degree of crystallinity and phase purity. The determined perovskites' structural parameters agree well with the literature reports. The recorded XPS and DRS data allowed for the first schematic representation of the perovskite band structures. The latter match well the results of DFT modeling. It is shown for the first time that the increase in the perovskite bandgaps is solely due to the increase in the anion electronegativity. Namely, as the anion electronegativity increases, the corresponding valence band energy decreases. In contrast, the electronegativity of the anions has no effect on the perovskite conduction band energies. The presented study deepens our understanding of the relationship between the crystal and electronic structures of low-dimensional hybrid halide perovskites. [ABSTRACT FROM AUTHOR]

Tetrathiafulvalenes (TTFs) functionalized with groups able to increase non-covalent intermolecular interactions through either hydrogen, halogen or chalcogen bonding were investigated. For that purpose, we designed several appropriate precursors, fused dithiole-2-one/thiazoles, which under homocoupling led to symmetrically substituted TTFs or through heterocoupling to dissymmetrically substituted TTFs. The electrochemical investigations allowed the assessment of the electronic effect of these substituents on the overall donating ability of the TTFs. In addition two charge transfer salts have been prepared involving two of these TTFs with TCNQF4 as the electron acceptor, (4c)2(TCNQF4) and (4b)(TCNQF4). Furthermore the crystal structures of the neutral TTFs and of the charge transfer salts allowed us to study the stacking mode and the different non-covalent interactions taking place in the crystals, in connection with the calculated electrostatic surface potential (ESP) of the investigated molecules. All the data provide information about non-covalent bonding interactions in the solid state and about their potential contribution to direct to some extent crystallographic intermolecular organization. [ABSTRACT FROM AUTHOR]

Na3R(BO3)2 (R = La–Gd) borates, grown with Na2O–B2O3–NaF flux, crystallize in the space group P21/n. Contrary to previously published data, the peaks in the 980(La)–950(Gd) °C range are attributed to phase transition process, while the melting process occurs at about 100° higher. Another feature of thermal behavior consists of the gradual decomposition of the compound into Na3R2(BO3)3. The end member in the decomposition series is Na2R2O(BO3)2, which originates under oxygen/water atmosphere. In addition, the components of the thermal expansion tensor and the dependings of the unit-cell parameters of Na3Nd(BO3)2 on temperature were defined. A series of Pr3+, Nd3+, and Sm3+-doped Na3Gd(BO3)2 (NGB) borates were prepared from mixtures of grown crystals by solid-state synthesis, and their photoluminescence properties were studied in detail. The excitation and emission spectra of NGB: Pr3+ and NGB: Nd3+ are comparable with similar compounds, and the relative intensity reaches the maximum at 1 mol% of Pr3+, Sm3+, and 10 mol.% for Nd3+ doping. [ABSTRACT FROM AUTHOR]

The occurrence of tautomeric polymorphism in the Cambridge Structural Database (CSD) was established to be very rare in a previous study by A. J. Cruz-Cabeza and C. R. Groom (CrystEngComm, 2011, 13, 93). A decade has now elapsed and the CSD has seen a significant increase in its total number of crystal structures, useful CSD subsets have been introduced and the CSD Python API has been developed to allow for complex data mining. Given this, we wanted to revisit tautomeric polymorphs in the CSD alongside other polymorphs related by proton transfer and compare these results with those from an in-house pharmaceutical database in order to assess their prevalence and significance for pharmaceuticals. From A (amine–imine tautomeric polymorphs) to Z (zwitterionic polymorphs), here we study different types of polymorphs related by proton-transfer in the CSD, the CSD drug subset (DrugCSD), the single component drug subset of the CSD (SDrugCSD), and the GSK small molecule crystal structure database (GSD). First, we assess the potential of compounds to exist as tautomers. Whilst 51% of compounds in the CSD are capable of tautomerism, this number increases to 73% and 70% for the SDrugCSD and the GSD respectively. Tautomerism potential is, thus, more prevalent in pharmaceuticals than in common organic compounds in the CSD. Second, in mining the CSD we identify a total of 95 families of polymorphs related by proton transfer which can then be classified into six different categories depending on the type of proton transfer observed and the ionisation of species involved. The most common of such category is that of tautomeric polymorphs followed by zwitterionic polymorphs. The rarest type of proton transfer polymorphs is that of multi-zwitterionic polymorphs where two different zwitterions of the same compound are found in two different crystal structures. Overall, 3% of polymorphic compositions in the DrugCSD are found to be related by proton transfer which, although not very common, is of relevance to pharmaceuticals and drug development due to the potential impact on physical properties. Specific examples of each of the categories are discussed with calculations of lattice energies presented and consideration of ΔpKa values and likelihood of proton transfer and ionisation. [ABSTRACT FROM AUTHOR]

In this work, cobalt complexes 1 and 2 were synthesized from ligands L1 (1,2-bis(2-phenyl-2-(pyridin-2-yl)hydrazineylidene)ethane) and L2 (1,2-bis(2-(pyridin-2-yl)hydrazineylidene)ethane) in moderate yields. These complexes were characterized by UV-visible, IR and ESI-MS spectroscopic studies. The molecular structure of complex 1 was determined by X-ray crystallography. Complexes 1 and 2 were employed as catalysts for the oxidation of sp3 C–H bonds. A total of 12 substrates were investigated for the oxidation of benzylic and aliphatic sp3 C–H bonds. A reaction pathway was proposed and possible reactive intermediate species was successfully characterized by ESI-MS spectroscopic studies. [ABSTRACT FROM AUTHOR]

Hydrogen-bonded complexes are formed between two chain lengths of 4-alkoxystilbazoles and six different chlorophenols. Single crystal structure determinations were possible for four of the complexes, all of which showed a similar dimeric motif in which two chlorophenols formed a loose back-to-back dimer with a stilbazole hydrogen-bonded at either side. Two of the complexes showed similarities in their three-dimensional packing. Liquid crystal properties were found for all complexes except those containing pentachlorophenol. The phase behaviour of the longer-chain dodecyloxystilbazole complexes was dominated by the observation of the smectic A phase, while both nematic and smectic A phases were found for the octyloxy homologues. The mesophase stability was appreciably lower in these new complexes when compared with fluorophenol analogues reported previously, attributed to a reduction in anisotropy on account of the effects of the greater size of chlorine compared with fluorine. [ABSTRACT FROM AUTHOR]

Understanding the factors governing the self-assembly of organic ligands with metal ions is essential to engineering target molecular arrangements with the desired properties. Indeed, small modifications of the synthetic conditions lead to the obtention of different complexes, varying from discrete monomers to coordination polymers (CPs). Based on the potential coordinating ability of 2-furoic acid (2-FA), we prepared five Zn(II) and Cd(II) complexes to study the behavior of the furane O atom and the competitiveness of the M–O bond formation in methanol (MeOH). Reactions between M(OAc)2·2H2O (M = Zn(II), Cd(II)), 2-FA, and two p-substituted pyridine ligands (isonicotinamide (Isn) and 4-acetylpyridine (4-Acpy)) in MeOH yielded the two dimers [Zn(μ-2-FA)(2-FA)(Isn)2]2 (1) and [Cd(μ-2-FA)(2-FA)(Isn)2]2 (2), the dimeric paddle-wheel [Zn(μ-2-FA)2(4-Acpy)]2 (3), and the monomer [Cd(2-FA)2(4-Acpy)2(OH2)] (4). Their crystal structures have been studied, observing diverse coordination numbers between five and seven and diverse coordination modes of the carboxylate groups. Interestingly, the recrystallization of 4 in acetonitrile (ACN) resulted in a dissolution–recrystallization structural transformation (DRST), leading to an intricate coordination polymer (CP) with the formula {[Cd(μ-2-FA)(2-FA)(OH2)2]n[Cd(μ-2-FA)(2-FA)(4-Acpy)(OH2)]n} (5) exhibiting coordination of the furane O atom. Within this collection of arrangements, 2-FA displayed a great diversity of coordination modes that were combined and interchanged in the DRST process. Their photophysical properties in solution have been analyzed and their quantum yields calculated. Likewise, further insight into the DRST process was obtained from fluorescence measurements. From these results, a pathway for the structural transformation highlighting the crucial role of solvents has been proposed. [ABSTRACT FROM AUTHOR]

Mixed-valence europium-activated phosphors are receiving attention in many fields, such as lighting, anti-counterfeiting, optical recording, encryption, and temperature sensing. However, it remains difficult to construct mixed-valence europium-activated compounds due to the reductive and oxidative synthesis conditions required to obtain Eu2+ and Eu3+ ions, respectively. Herein, mixed-valence Eu2+/Eu3+ was realized in the CaBPO5 built by rigidly connected BO4 and PO4 tetrahedrons by partial Eu3+ → Eu2+ self-reduction in the air atmosphere. Commendably, the CaBPO5:Eu2+/Eu3+ phosphor exhibits excellent ratiometric temperature sensing performance with the maximum absolute and relative sensitivity being as high as 0.184 K−1 and 3.444% K−1 with good signal discriminability, due to the high and low, respectively, temperature-dependence of Eu2+ and Eu3+ emissions. The rapid dropping intensity of Eu2+ in CaBPO5 with increasing temperature was due to the small energy gap (∼0.48 eV) between the Eu2+-5d state and the conduction band. Our work not only provides a novel thermometer candidate but also enlightens researchers to a method of effectively designing new mixed-valence metal-ion activated luminescent thermometers via selective tetrahedrally coordinated rigid crystal structure. [ABSTRACT FROM AUTHOR]

The design and development of multicomponent systems in the salt–cocrystal continuum zone (ΔpKa = −1 to 4) are considered advantageous since they can crystallize as a salt, cocrystal, or combination of both and create opportunities to select the right crystal form with desirable properties for product development. Herein, the choice of solvent, temperature, pH, and crystal environment significantly influenced the ionization state in the crystal; however, the structural features that stabilize the neutral or ionic molecular pairs were not clear, and thus further studies are necessary from a crystal engineering point of view. A new multicomponent system was envisaged between the antiviral drug famciclovir and its coformer fumaric acid (FAM–FUM), which falls in the salt–cocrystal continuum zone (with ΔpKa value of 0.81) and possesses complementary functional groups to form robust supramolecular synthons, such as acid–pyrimidine and acid–imidazole for co-crystallization. Three novel crystalline forms of famciclovir–fumaric acid were identified in our crystallization trials, including a cocrystal (FAM–FUM 2 : 2 form I), a salt (FAM–FUM 2 : 2 form II) and a salt–cocrystal continuum (FAM–FUM 1 : 0.5). The first two forms are actually polymorphs having the same drug-to-coformer stoichiometry, while the third is a different stoichiometry structure. These crystal forms were well characterized by different solid-state techniques (SCXRD, PXRD, DSC, TGA, HSM, FT-IR spectroscopy, and SS-NMR). All three structures are sustained by a similar two-point acid–pyrimidine heterosynthon but differ in their ionization state. The synthon is neutral in 2 : 2 form I, ionic in 2 : 2 form II, and adopts an intermediate state in the 1 : 0.5 crystal. Interestingly, these three forms were concomitantly crystallized in the same solvent medium, which suggests that the crystal environment/solid-state structure may play a dominant role in the ionization state of the complex rather than the experimental variables. The crystal structure analysis provided important clues on why the different structures adopted different ionization states. An auxiliary hydrogen bond was seen to stabilize the ionic synthon in FAM–FUM 2 : 2 form II, while it was absent in the neutral synthon of the FAM–FUM 2 : 2 form I. The intermediate state or partially ionic state in FAM–FUM 1 : 0.5 was stabilized by shorter hydrogen bonds compared to the neutral synthon. [ABSTRACT FROM AUTHOR]

Cocrystallization is a crystallization technique for drugs that are difficult to crystallize as single components. In this study, we found a novel cocrystal hydrate consisting of captopril (CPL), which is an amino acid-derived drug and has a thiol group, and L -proline (LPR), although a CPL–LPR cocrystal anhydrate has been previously reported. Nano-spot screening elucidated a new LF Raman spectrum for the combination of CPL and LPR due to the formation of a crystalline complex. Single crystal X-ray diffraction analysis revealed that this crystalline complex was a cocrystal hydrate with a stoichiometric ratio of 1 : 1 : 1 CPL : LPR : H2O in an asymmetric unit. Notably, the CPL–LPR cocrystal hydrate showed high hygroscopicity, and the degradation product of CPL upon a storage stability test could have resulted from the changes in the intermolecular interactions and the location of the water molecules involved in the thiolate formation in the crystal structure. The storage stability tests highlighted a higher amount of CPL degradation product in the CPL–LPR cocrystal hydrate than in the CPL crystal, potentially due to i) increased hygroscopicity, ii) decreased intermolecular interactions that contribute to CPL stabilization and iii) increased reactivity by water molecules for the crystal structure of the CPL–LPR cocrystal hydrate. Therefore, it is suggested to select a coformer with few OH groups involved in the interaction with water or low hygroscopicity to optimize the stable cocrystals of drugs. [ABSTRACT FROM AUTHOR]

Recently, great advances have been made in the mechanochromic luminescence (MCL) of organic crystals that can switch their emission colors upon exposure to mechanical stimuli. Although several polymorphic crystals and solvates have exhibited multicolor MCL properties, a further deep understanding of the relationship between crystal structures and stimuli-responsive properties is required for rationally generating multicolor-emissive polymorphic crystals and solvates from a single luminescent compound. Herein, multicolor luminescence switching has been achieved for solvates of a phenanthroimidazolylbenzothiadiazole derivative with dianisyl groups. Four types of solvates with different luminescence properties changed their emission colors upon amorphization induced by mechanical stimuli. The amorphous state was recrystallized into solvates when exposed to solvent vapors. Furthermore, the solvate containing pyridine molecules showed a bathochromic shift in emission wavelength upon exposure to acid vapor. Typical acid-responsive luminescence switching is characterized by the protonation of the basic moiety of luminescent molecules, whereas in this study, the change in luminescence color could be induced by protonating non-luminescent pyridine molecules in the solvate. The present study potentially provides useful insights for the development of smart luminescent sensors. [ABSTRACT FROM AUTHOR]

Weakly coordinating anions (WCAs) facilitate the stabilization and isolation of highly reactive and almost "naked" cations. Alkoxyaluminate-based WCAs such as [Al(OC(CF3)3)4]− ([pf]−) are widely used due to their synthetic accessibility and their high stability. However, small cations are still able to coordinate the oxygen atoms of the [pf]− anion or even to abstract an alkoxy ligand. The novel WCA [Al(OC10F15)4]− ([pfAd]−; OC10F15 = perfluoro-1-adamantoxy) is characterized by a very rigid core framework, thus indicating a higher stability towards fluoride-ion abstraction (DFT calculations) and providing hope to generate less disordered crystal structures. The [pfAd]− anion was generated by the reaction of the highly acidic alcohol perfluoro-1-adamantanol C10F15OH with LiAlH4 in o-DFB. Li[pfAd] could not be synthesized free of impurities (and still contains unreacted alcohol). Yet, starting from contaminated Li[pfAd], the very useful pure salts Ag[pfAd], [Ph3C][pfAd] and [H(OEt2)2][pfAd] could be synthesized. The salts were characterized by NMR spectroscopy, single-crystal X-ray diffraction and IR spectroscopy. Additionally, [NO][pfAd] could be synthesized containing alcohol impurities but nonetheless enabled the synthesis of the salt P9+[pfAd]−. The synthesis of Tl[pfAd] in a mixture of H2O/acetone/o-DFB demonstrated the water stability of the [pfAd]− anion. [ABSTRACT FROM AUTHOR]

Ferroelectric epitaxial films of Pb1−xSrx TiO3 (PST) with nominal compositions of x = 0, 0.33, 0.39, and 0.43, supported by (100) SrTiO3 (STO) substrates, have been successfully grown by liquid phase epitaxy (LPE). Energy dispersive X-ray measurements performed on selected films reveal an increase in the Sr-content for each nominal increase in the growth solution. Structural and spectroscopic investigations, from X-ray diffraction and Raman spectroscopy, unveil that all of the PST films possess a tetragonal structure at room temperature, and with increasing Sr-content, the tetragonality and Curie temperature decrease accordingly with values approaching those of reference bulk compound materials. These results confirm we achieved full control of the composition, structure, and transition temperature of the ferroelectric films, by adapting the nominal composition of the LPE growth solution, performing epitaxial growth while maintaining the bulk-like properties. Finally, using piezoresponse force microscopy, various nanoscale polar domain configurations for the PST epitaxial films were disclosed. This indicates that films having a higher Sr content can have polar domain configurations compatible with different a/c and c nanodomains. This work underlines the usefulness of the LPE method for controlling tetragonal ferroelectric PST film growth, in order to tune the nanoscale polarisation landscape in films having bulk-like structures and ferroelectric transition temperatures. This opens a path to new investigations fully exploiting the combined advantages of multiple nanoscale electrical boundary configurations within bulk-like ferroelectric films. [ABSTRACT FROM AUTHOR]

In this study, the complicated solvation behaviors of arbutin were studied from both experiment investigations and theoretical calculations. Six solid forms of arbutin, namely the anhydrous form I and five solvates, were successfully obtained. The structures of form I, solvate S1, solvate S4, and solvate S5 are reported for the first time. The obtained forms of arbutin were thoroughly characterized and distinguished by PXRD, PLM, DSC, TGA, Raman, and FTIR spectroscopy techniques. It was found that solvate S4 and solvate S5 were isostructural solvates. Further, the packing arrangements and pore structures were analyzed to illustrate the formation of the isostructural solvates. Moreover, analyses of the crystal structures showed that arbutin exhibited flexible conformations in various solid forms, and there were strong correlations between the crystal lattice energy and the thermal stability of various solvates. Finally, the formation mechanism of arbutin solvates was proposed and rationalized and the conversion relationship between different solid forms was also established. [ABSTRACT FROM AUTHOR]

Based on Krivovichev information measures for crystal structures and the universal partitioning scheme for different sources of information described previously by Hornfeck, a ladder of information for crystal structures with primary motifs of different dimensionalities (0D, 1D, or 2D) is proposed. Ethanol (0D), SnIP (1D), and TlOH (2D) are discussed as examples of the introduced concept. The proposed calculation technique allows to explicitly obtain contributions of substructures of ordered structures into the information content of a structure conforming to the rule of strong additivity, thus giving a simple assessment of complexity at different hierarchical levels of organization, and takes into account partitioning contacts formed by structural units into equivalence classes, which is poorly dependent on that of the structural units themselves. The technique is a complementation to the multilevel topological analysis performed in the ToposPro program package. [ABSTRACT FROM AUTHOR]

We describe the synthesis, crystal structure and semiconducting properties of a number of hexacyanidometallates with the formula A2[MFe(CN)6]·xH2O (A = Na, K; M = Mg, Ca, Sr and Ba). All crystal structures were studied via single-crystal or powder X-ray diffraction. The unexpectedly low-symmetric structures in these ferrocyanides are described and contrasted with analogous transition-metal compounds which have been reported to be strictly or nearly cubic. The amount of crystal water in the structure for powder samples was determined by the thermogravimetric analysis (TGA), supported by IR and Raman spectroscopy. Electronic-structure calculations of K2[MgFe(CN)6] and K2[CaFe(CN)6] are compared with experimental UV-Vis measurements. The large band gaps by advanced theory indicate that the smaller experimental band gaps are due to surface effects of impurity states. Mott–Schottky curves of K2[MgFe(CN)6], K2[CaFe(CN)6] and K2[BaFe(CN)6]·3H2O exhibit positive slopes, which characterizes these compounds as n-type semiconductors. [ABSTRACT FROM AUTHOR]

Described herein are the synthesis, structure, and photophysics of the iodo-substituted cyclic trinuclear copper(I) complex, Cu3[4-I-3,5-(CF3)2Pz]3 supported by a highly-fluorinated pyrazolate in comparison with its previously reported 4-Br/4-Cl analogues. The crystal structure is stabilised by multiple supramolecular interactions of Cu3⋯I and hydrogen/halogen bonding. The photophysical properties and supramolecular interactions are investigated experimentally/computationally for all three 4-halo complexes vis-à-vis relativistic effects. [ABSTRACT FROM AUTHOR]

Shape-persistent macrocycles have been of interest for many years to researchers due to their potential in synthesis and materials chemistry. They are regarded as reasonably rigid and in many cases they are able to spontaneously aggregate forming supramolecular assemblies. The dependence of a steric hindrance located on oxygen atoms in 2,6-bis-acetylenephenolates on the structure of macrocycles obtained from these precursors by Eglinton homocoupling has been investigated. A small library of crystal structures of arylene butadiynylene species has been obtained and analyzed in detail. Our results showed that regardless of the steric hindrance usually a wide range of macrocycles is formed (starting from tetramers) even though the smaller derivatives are significantly deviated from planarity, which might result from avoiding too much strain in these macrocyclic, cross-conjugated molecules. [ABSTRACT FROM AUTHOR]

Saponification, resulting from pigment–binder interactions, is one of the most endangering phenomena affecting the appearance and stability of painted works of art. The crystallization of metal carboxylates (soaps) in paint layers is recently assumed as the most critical point for the development of undesirable changes induced by saponification, however, the factors triggering it are not fully understood. The red pigment cinnabar (HgS) has been suspected of contributing to saponification, however, the paucity of reliable reference structural data limited the experimental research of its effect at the molecular level. Within this study we synthesized mercury(II) carboxylates of the formula Hg(C16)x(C18)2−x (x = 0.0; 0.2; 0.5; 0.8; 1.0; 1.2; 1.5; 1.8; 2.0) where C16 and C18 are hexadecanoate (palmitate) and octadecanoate (stearate), respectively, and characterize them by combination of X-ray powder diffraction (XRPD) and 13C and 199Hg solid state NMR (ssNMR). For a more detailed interpretation of their structural and thermal behavior, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used. The crystal structure of the studied mercury carboxylates was described on the basis of complementary ssNMR and XRPD measurements, Rietveld refinement and DFT calculations. All the subjected compounds crystallize in a monoclinic lattice of the C2/c symmetry. Mercury atoms are arranged in a slightly distorted square antiprismatic geometry and are monodentatically bonded to carboxylate anions. The structural disorder at the aliphatic end of the stearic acid chains was detected in the mixed carboxylates. Within the paper, the structural (dis)similarity with the corresponding lead carboxylates is discussed. The synthesized and characterized mercury carboxylates were applied to describe neo-formed mercury soaps in a model experiment simulating an egg-based paint system. [ABSTRACT FROM AUTHOR]

This article describes the synthesis of four new co-crystals obtained via cross-crystallisation of 2- and 4-mercaptopyridines with thiourea and trithiocyanuric acid and examines their crystal structures. The resulting structures are the first four reported co-crystals of mercaptopyridines. In one case, the synthesis resulted in the production of a ternary co-crystal of unexpected composition instead of the desired product and the correct co-crystal needed to be obtained under dark room conditions; interestingly, when separated from solution, all four co-crystal samples were fully light resistant. The crystal state of the four co-crystals is stabilized by several N–H⋯S type hydrogen bonds. Additionally, in the case of thiourea co-crystals, additional short contacts of S⋯S type are also observed. This relatively complicated network of intermolecular interactions is fully characterized herein. [ABSTRACT FROM AUTHOR]

A bibliographic and literature-based analysis of the impact of the Cambridge Structural Database (CSD) and the papers associated with crystal structures in the CSD has been undertaken. The analysis shows the broad impact of the CSD in the chemical sciences and also highlights how areas where the CSD has impact have changed over time. In addition, we note the changing nature of crystallography as a science, observing how crystal structures are now impactful. A brief illustration of some more unusual contributions to the CSD and publications using the CSD is also presented. [ABSTRACT FROM AUTHOR]

The majority of the fabrication procedures of lanthanide-doped materials involve thermal treatment that often results in crystallite regrowth, stabilizing the specific crystal structure and resulting in luminescence enhancement. The efficiency and intensity of up-conversion luminescence are closely related to the structure and synthesis process of the materials. Herein, well-crystallized and pure tetragonal NaY(MoO4)2 microcrystals with a uniform octahedral shape have been successfully synthesized via an environmentally friendly hydrothermal method, followed by annealing treatment. The phases, structures, morphologies, and compositions of the synthesized products annealed at 500–1000 °C remain unchanged, indicating high thermal stability. Furthermore, the NaY(MoO4)2:Yb3+/Er3+ microcrystals exhibit strong green emission when irradiated using infrared (980 nm) or ultraviolet (378 nm) wavelengths. Upon 980 nm excitation, up to 37-fold luminescence enhancement is achieved when the samples are annealed at about 700 °C. Interestingly, the high colour purity of the strong green emission is not only independent of the dopant concentration and heat treatment temperature, but it is also independent of the excitation conditions, including power and wavelength, and this makes it particularly suitable as a green safety signal light and luminescent security ink in paintings. As-prepared safety inks with NaY(MoO4)2:Yb3+/Er3+ microcrystals were used for visual fingerprint recognition printed on A4 paper with three-level fingerprint security features, significantly increasing the difficulty of illegal imitation and enhancing the levels of anti-counterfeiting. [ABSTRACT FROM AUTHOR]

Explaining the intensification of upconversion luminescence (UCL) from a single phase NIR-upconverting (UC) crystal due to non-lanthanide dopant insertion appears challenging in the absence of proper mechanistic investigation. In this paper, through extensive synchrotron based X-ray probing, we made an attempt to understand the variations in the structural attributes of UC crystals generated through non-lanthanide ion doping. The structures of the NaYF4/Yb3+/M3+ (M3+ = Er3+/Tm3+) UC crystals doped with different Li+ concentrations were primarily investigated using Rietveld refinement analysis from synchrotron X-ray diffraction (SXRD) and supported with absorption data (XAFS), where necessary. The structural investigation was also supported by TEM, HRTEM, XANES, FT-IR and Raman spectroscopy. Rietveld analysis revealed that all the generated Li+ doped NaYF4 crystals belong to the P6 space group. Most of the Li+ ions were found to be localized in octahedral voids and lattice positions, simultaneously, in the P6 crystal structures. The overall study showed that the change in the UCL intensity behavior with Li+ incorporation could not be predicted from the lattice parameters, morphology or the particle size variation. A detailed XAFS study rather suggested the possible existence of local lattice disorder, which was found to be reflected in terms of lattice strain obtained from Williamson--Hall analysis, irrespective of the activator ions. The remarkable coherence between the variation trends of UCL intensity and lattice strain indicated that the perturbation of the local symmetry field is in some way connected with the local disorder that may not always manifest through average structural attributes like lattice parameters. [ABSTRACT FROM AUTHOR]

Disordered crystals have garnered increasing attention as new laser materials because of their broad emission bandwidths. This paper reports a novel Yb-doped strontium yttrium phosphate (Yb:YSr3(PO4)3) crystal with a disordered structure, as well as its crystal growth, structure, spectral properties, and laser performance. The crystal structure (cubic, 4¯3m point group) was refined using the Rietveld method. The absorption cross-section and fluorescence lifetime were determined to be 1.31 × 10−20 cm2 at 976 nm and 1267 μs, respectively. The stimulated emission cross-section was 1.04 × 10−20 cm2 at 1013 nm, with an emission bandwidth of 55 nm. In addition, continuous-wave laser operation was realized using the Yb:YSr3(PO4)3 crystal with different output coupler transmissions, where the obtained maximum output power and slope efficiency were 1.3 W and 61%, respectively. A dual-wavelength regime with wavelengths centered at 1039 nm and 1047 nm (Δν = 2.2 THz) was achieved under certain conditions; thus, this crystal is expected to be employed for developing terahertz sources. In addition, the laser can operate at multiple wavelengths, ranging from 1023 to 1050 nm. The results indicate that the Yb:YSr3(PO4)3 crystal with a disordered structure may be a promising multi-wavelength laser crystal. [ABSTRACT FROM AUTHOR]

Peptidases are regulated by latency and inhibitors, as well as compatibilization and cofactors. Ulilysin from Methanosarcina acetivorans, also called lysargiNase, is an archaeal metallopeptidase (MP) that is biosynthesized as a zymogen with a 60-residue N-terminal prosegment (PS). In the presence of calcium, it self-activates to yield the mature enzyme, which specifically cleaves before basic residues and thus complements trypsin in proteomics workflows. Here, we obtained a low-resolution crystal structure of proulilysin, in which 28 protomers arranged as 14 dimers form a continuous double helix of 544 Å pitch that parallels cell axis b of the crystal. The PS includes two α-helices and obstructs the active-site cleft of the catalytic domain (CD) by traversing it in the opposite orientation of a substrate, and a cysteine blocks the catalytic zinc according to a "cysteine-switch mechanism". Moreover, the PS interacts through its first helix with an "S-loop" of the CD, which acts as an "activation segment" that lacks one of two essential calcium cations. Upon PS removal during maturation, the S-loop adopts its competent conformation and binds the second calcium ion. Next, we found that in addition to general MP inhibitors, ulilysin was competitively and reversibly inhibited by 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF; Ki = 4 μM). This is a compound that normally forms an irreversible covalent complex with serine peptidases but does not inhibit MPs. A high-resolution crystal structure of the complex revealed that the inhibitor penetrates the specificity pocket of ulilysin. A primary amine of the inhibitor salt-bridges an aspartate at the pocket bottom, thus mimicking the basic side chain of substrates. In contrast, the sulfonyl fluoride warhead is not involved and the catalytic zinc ion is freely accessible. Thus, the usage of inhibitor cocktails of peptidases, which typically contain AEBSF at ∼25-fold higher concentrations than the determined Ki, should be avoided when working with ulilysin. Finally, the structure of the complex, which occurred as a crystallographic dimer recurring in previous mature ulilysin structures, unveiled an N-terminal product fragment that delineated the non-primed side of the cleft. These results complement prior structures of ulilysin with primed-side product fragments and inhibitors. [ABSTRACT FROM AUTHOR]

The synthesis of novel phosphine palladium PEPPSI and dimer complexes bearing RuPhos, SPhos and XPhos phosphines is reported. The crystal structures of XPhos Pd PEPPSI with pyridine, SPhos Pd PEPPSI with 3-chloropyridine as throw-away ligands and the RuPhos palladium dimer were obtained and compared with previously reported congeners. The catalytic activity of these novel complexes was examined via a C–N coupling reaction involving 4-chloroanisole and morpholine. RuPhos complex 2b proved most active, leading to 97% yield with a low (0.2 mol%) catalyst loading, while phosphine palladium dimers showed significantly lower catalytic activity. However, the addition of 3-pentanone as an activator/stabilizer significantly improved the yields of phosphine dimers and PEPPSI complexes when the reactions were performed in THF. [ABSTRACT FROM AUTHOR]

Mononuclear oxovanadium(V) complexes [V(O)XL (1: X = Ot-Bu, 2: X = Cl)] [H2L: 2,2′-methylene bis(4,6-di-tert-butylphenol)(4′-tert-butyl-6′-(1-adamantyl)phenol)] directed towards asymmetric catalysis have been synthesised as racemic compounds using an unsymmetric and achiral phenolic bidentate ligand (H2L), and NMR and UV-vis absorption spectroscopies, single-crystal X-ray diffraction, and IR spectroscopy revealed their racemic chiral-at-vanadium structures in solution and in the crystal. In addition, theoretical calculations revealed that the HOMO–LUMO energy gap is smaller for unsymmetric ligands, which promotes d-orbital splitting of the metal centre. [ABSTRACT FROM AUTHOR]

We report the synthesis of single crystals of the quaternary sulfide, BaCeCuS3, for the first time by heating a polycrystalline sample of BaCeCuS3 with an excess of KCl flux inside a vacuum-sealed fused silica tube. The crystal structure of the compound is determined by a single-crystal X-ray diffraction study which shows that it crystallizes in the primitive orthorhombic crystal system (space group: Pnma) with cell constants of a = 10.6740(13) Å, b = 4.1200(6) Å, and c = 13.409(2) Å. The structure is best described as a pseudo-two-dimensional structure where tetrahedral CuS4 and octahedral CeS6 units serve as the main building blocks. The polyanionic layers in the structure are separated by the presence of electropositive Ba2+ cations. The optical absorption study on the polycrystalline sample of BaCeCuS3 shows a semiconducting nature with a direct bandgap of 1.8(2) eV consistent with the green color of the sample. The temperature-dependent thermal conductivity (ktot) measurements on the polycrystalline BaCeCuS3 sample reveal an extremely low value of ktot (0.32 W m−1 K−1) at 773 K. DFT calculations were carried out to obtain the electronic structure of the title compound. Our theoretical studies predict a high value of the thermoelectric figure of merit (>1) for BaCeCuS3 by optimization of the charge carriers. To also explore a practical application of BaCeCuS3, a liquid junction solar cell was fabricated: TiO2/CdS/BaCeCuS3/Sn2−/S2−/MWCNTs@Ni, and the cell delivered an efficiency enhanced by ∼45% compared to the one without the sulfide. The performance improvement is affected by the hole conducting properties of BaCeCuS3, which allows facile hole transfer from CdS to the polysulfide, increases the charge separation, and hence increases the efficiency. [ABSTRACT FROM AUTHOR]

Single crystals of Fe[SeO4]OH have been synthesized by hydrothermal treatment. The Fe[SeO4]OH structure was investigated using the superspace approach. It is shown that the structure belongs to a family of compounds including kieserite-like and pauflerite-like structure types. All these structures consist of topologically identical layers interconnected either by a mirror plane (m) or by an inversion centre (1¯). The sequence of these local elements of symmetry, m and 1¯, determines each member of the family. We used the (3 + 1)-dimension superspace group Pnam(00γ)000 applied to an average structure to be able to reproduce known polytypes and predict new ordered and partially or completely disordered structures in the R[MO4]Z structural family. [ABSTRACT FROM AUTHOR]

A series of new heteroleptic copper(I) complexes [Cu(N^N)(P^P)][BF4] (1–6), where N^N is a pyrazole-substituted 2,2′-bipyridine (5-(1H-pyrazol-4-yl)-2,2′-bipyridine (5-pzbpy, L1), 4,4′-di(1H-pyrazol-4-yl)-2,2′-bipyridine (4,4′-pz2bpy, L2), 5,5′-di(1H-pyrazol-4-yl)-2,2′-bipyridine (5,5′-pz2bpy, L3), and 3,8-di(1H-pyrazol-4-yl)-1,10-phenanthroline (3,8-pz2phen, L4)) and P^P is either oxybis(2,1-phenylene)bis(diphenylphosphane) (POP) or 1,3-bis(diphenylphosphanyl)propane (dppp), were successfully prepared and investigated. The crystal structures of 1, 2, 3 and 6 were determined by single X-ray diffraction. The novel copper(I) complexes 1, 2 and 3 show turn-on emission sensing for halogen ions. The fluorescence enhancement of the copper(I) complexes increases in the order of F− < I− < Br− < Cl−, and the differences in fluorescence intensity could be easily distinguished with the naked eye under UV light illumination. The 1H NMR titration indicated that the interaction involves hydrogen-bond formation between the halide (Cl−, Br− and I−) and the acidic H of the pyrazole group, with N–H deprotonation occurring at increasing F− concentrations. The result was further confirmed by carrying out theoretical calculations. [ABSTRACT FROM AUTHOR]

The entanglement of cyclic polymers is an open issue. Cyclic poly(ε-caprolactone)s (PCLs) with a number-average molar mass (Mn) ranging from 8 to 37 kg mol−1 were synthesized using a protocol without linear precursors to avoid the influence of linear contaminants. The crystallization and melting behaviors of the synthesized unconcatenated and unknotted cyclic PCLs were investigated by DSC, POM and X-ray. The DSC and POM characterized crystallization behaviors of the cyclic PCLs showed that the half-time of crystallization and spherulite growth rate related to the molecular weights. The rheological results showed that the critical molecular weight of cyclic PCLs is 11 kg mol−1, which is about two times that of the linear PCLs. The coupling effect of ring topology and entanglement leads to the maximum crystallization rate and minimum lamellar thickness at the medium molecular weight. In situ simultaneous SAXS/WAXS probe in heating was performed on the samples after isothermal crystallization, and the results indicated that the ring topology did not change the crystal of PCL, but the evolution of nano-scale crystalline structure is different from that of the linear PCLs. The evolution of metastable crystalline structure of cyclic PCLs is discussed based on the SAXS results, and the entanglements were found to reduce the rate of structural evolution. [ABSTRACT FROM AUTHOR]

At multianvil high-pressure/high-temperature conditions of 10 GPa and 1273 K, the first ternary tungsten tellurate WTe2O7 is formed, starting from a stoichiometric mixture of WO3 and TeO2. The compound crystallizes triclinic in a hitherto unknown crystal structure type with the space group P1¯; (no. 2), and was refined from single-crystal X-ray diffractometer data: a = 538.3(1), b = 687.5(1), c = 802.3(1) pm, α = 72.4(1)°, β = 85.7(1)°, γ = 68.1(1)°, wR2 = 0.0323, GooF = 1.048, 3157 F2 values, and 106 variables. The main motifs of the crystal structure are pairs of edge-linked [WO6]6− octahedra and fourfold oxygen-coordinated Te4+ atoms. The oxidation state of W6+ and Te4+ was further verified by measuring the characteristic binding energy values for the W 4f and the Te 3d core levels via X-ray photoelectron spectroscopy (XPS). In addition, DFT calculations of the structure, the associated electron localisation functions (ELF) and vibrational spectra have been carried out. The theoretical data clearly demonstrates the impact of the residual electron density located at the Te4+ ions, which can be directly interpreted as the presence of lone electron pairs within the solid structure. [ABSTRACT FROM AUTHOR]

We present a comprehensive experimental study of the crystal structure of calcium vanadate (Ca3V2O8) under systematic temperature and pressure conditions. The temperature evolution (4–1173 K) of the Ca3V2O8 structural properties is investigated at ambient pressure. The pressure evolution (0–13.8 GPa) of the Ca3V2O8 structural properties is investigated at ambient temperature. Across all pressures and temperatures used in the present work, the Ca3V2O8 crystal structure was determined by Rietveld refinement of powder X-ray diffraction data. The experimental high-pressure data are also supported by density-functional theory calculations. According to the high-pressure results, Ca3V2O8 undergoes a pressure-induced structural phase transition at a pressure of 9.8(1) GPa from the ambient pressure trigonal structure (space group R3c) to a monoclinic structure (space group Cc). The experimentally determined bulk moduli of the trigonal and monoclinic phases are, respectively, B0 = 69(2) GPa and 105(12) GPa. The trigonal to monoclinic phase transition appears to be prompted by non-hydrostatic conditions. Whilst the trigonal and monoclincic space groups show a group/subgroup relationship, the discontinuity in the volume per formula unit observed at the transition indicates a first order phase transition. According to the high-temperature results, the trigonal Ca3V2O8 structure persists over the entire range of studied temperatures. The pressure-volume equation of state, axial compressibilities, Debye temperature (264(2) K), and thermal expansion coefficients are all determined for the trigonal Ca3V2O8 structure. [ABSTRACT FROM AUTHOR]

The crystal structure of substituted formamidine salts has been modeled on the basis of a combination of quantum chemistry methods and atom–atom potentials. Based on the new author's method (MICCM) for calculating the enthalpies of formation of salts, which is based on the model of a cocrystal consisting of a mixture of cations and anions and a "quasi-salt" of the neutral components of the salt itself, the formation enthalpy is calculated as the average between the enthalpies of formation of these two structural components for salts various formamidines and the contributions of the corresponding cations to the calculation scheme are given. The results are in good agreement with the experimental data obtained by combustion calorimetry. [ABSTRACT FROM AUTHOR]

Active pharmaceutical ingredients (APIs) and selected coformers were studied in crystalline self-environment, in selected co-crystal structures, and gas phase. To obtain comparable geometries from experimental crystal structures, we rely on fast quantum mechanical GFN2-XTB molecule-in-cluster optimizations. Optimized crystal structures are first analysed in terms of molecule-pair interaction energies, by subdividing a cluster generated from asymmetric unit content through space-group symmetry into pairs of molecules. Accurate energies are then obtained by single-point molecular orbital (MO/MO) two layer "ONIOM" energy partitioning, comparing the same molecules in different crystal environments. Clusters approximate the local environment of a crystal structure for ONIOM. The pre-processor program BAERLAUCH (Acta. Cryst. A 2012) was used to set up all cluster computations. Solid-state computations using dispersion-corrected density functional theory provide reference results. ONIOM partitioned energies shed light on the driving force of co-crystal formation, with the energy gain from the complementarity of molecule-pair wavefunctions in such structures being the main driving force. It follows that improving prediction of co-crystal structure formation beyond current approaches, e.g. COSMO-RS excess enthalpies, statistics from structural databases or full crystal structure prediction is possible by finding complementary molecule-pairs through conformational sampling, as ultimately exemplified. [ABSTRACT FROM AUTHOR]

Accurate and efficient computation of relative energies of molecular crystal polymorphs is of central importance for solid-state pharmaceuticals and in other technologically relevant fields. In recent years, dispersion-corrected density-functional theory (DFT) has emerged as the pre-eminent energy ranking method for crystal structure prediction (CSP). However, planewave implementations of these methods are hindered by poor scaling for large unit cells and are limited to semi-local functionals that suffer from delocalisation error. In this work, we demonstrate that a recent implementation of the exchange-hole dipole moment (XDM) dispersion correction in the Fritz Haber Institute ab initio materials simulation (FHI-aims) package provides excellent performance for the energy ranking step of CSP. Thanks to its use of highly optimized numerical atom-centred orbitals, FHI-aims provides effectively linear scaling with system size and allows efficient use of hybrid density functionals with minimal basis-set incompleteness errors. We assess the performance of this methodology for the 26 compounds that formed the first 6 CSP blind tests. The hybrid results show significant improvements for 4/26 compounds, where delocalisation error affects the quality of predicted crystal energy landscapes. [ABSTRACT FROM AUTHOR]

Using a dicarboxylic acid, [1,1′-biphenyl]-4,4′-dicarboxylic acid (H2L1) and an exobidentate ligand, (1E,1′E)-N,N′-(1,4-phenylene)bis(1-(pyridin-4-yl)methanimine) (L2), two 3D interpenetrated networks, {[Zn3(L1)3(L2)]·9H2O}n (Zn-MOF) and {[Co3(L1)3(L2)(DMF)]·0.5DMF}n (Co-MOF), have been prepared in good yields. The crystal structure analysis of Zn-MOF and Co-MOF revealed that both have a 3D pillared-layer structure based on pinwheel trinuclear metal–carboxylate clusters as secondary building units (SBUs). Furthermore, the structures also exhibited three-fold interpenetration. Although the overall networks in Zn-MOF and Co-MOF showed significant resemblances, there are marked differences in their crystal structures, which are associated with the coordination environment of the metal centre and the binding modes of the carboxylates. Gas adsorption studies (N2 at 77 K and 1 bar) indicated that Co-MOF is more porous than Zn-MOF. Magnetic measurements on Co-MOF indicate a significant antiferromagnetic interaction (45 K to 303 K) between trimeric Co(II) S = 3/2 spins through syn–syn carboxylato bridges. Both MOFs were studied for the Lewis acid catalyzed Knoevenagel condensation reactions between benzaldehydes and malononitrile with an active methylene group, where Zn-MOF was found to be a better catalyst than Co-MOF. This was supported by the Monte Carlo simulations indicating the better substrate binding ability of Zn-MOF than Co-MOF. [ABSTRACT FROM AUTHOR]

The current study shows that Schiff base HL, (Z)-2,4-dibromo-6-(((piperidin-2-ylmethyl)imino)methyl)phenol, can be used successfully as a selective chemosensor for Zn(II) and Ni(II) among several competing cations in purely aqueous and semi-aqueous media. Under UV light in methanol–water (9 : 1) HEPES buffer, the receptor gives its response by changing its color to cyan color in the presence of Zn(II) and to bluish cyan color in the presence of Ni(II). Surprisingly, the chemosensor can only reliably identify Zn(II) in a hundred percent aqueous medium by changing its color to light yellow. UV and fluorescence studies in both aqueous and semi-aqueous media are used to further investigate this Zn(II) and Ni(II) recognition phenomenon. The high values of the host–guest binding constants, obtained by electronic and fluorescence titration, ensure that a strong bond exists between HL and Ni(II)/Zn(II). As anticipated, two highly luminescent mononuclear, crystalline compounds, complexes 1 and 2, have been developed by a separate reaction of HL and Zn(II)/Ni(II), and the high luminous properties are due to the occurrence of Chelation Enhanced Fluorescence (CHEF). According to the single crystal structure, the asymmetric units of both complexes consist of two deprotonated chemosensor units and one Zn(II)/Ni(II), leading to the formation of an octahedral complex. For Ni(II) and Zn(II) sensing, the predicted LOD is in the nanomolar range. Both complexes 1 and 2 are fluorescence active and studies to check their ATP detection ability, but intriguingly, only complex 2 is capable of detecting ATP in a fully aqueous solution. Finally, the live cell imaging study validates the two sensors' biosensing functionality. [ABSTRACT FROM AUTHOR]

A new polymorph of 5-nitrobenzo[c][1,2,5]thiadiazole, polymorph II, has been discovered. This polymorph is obtained by crystallization from solutions containing Cu(II) ions, which inhibit the formation of the already known polymorph I. The packings of the two polymorphs (actual crystal structures) are compared between each other and also with seven virtual polymorphs generated from the crystal structures of similar compounds retrieved from the CSD and optimized by ab initio calculations with periodic boundary conditions. The comparison is based on the analysis of the synthons present in the different crystal structures, and on calculated lattice energy and density. For the specific case examined, our analysis suggests that among crystal structures containing a given synthon, or a given combination of synthons, only the one with the lowest Ulat is observed; crystal structures with slightly higher Ulat (within 2 kcal mol−1) can be observed, but they must be based on different synthons. [ABSTRACT FROM AUTHOR]

A new hydrazone ligand, HL [(1-methylimidazol-2-yl)methylene]isonicotinohydrazide, has been synthesized and characterized by several spectroscopic methods. The ligand (HL) was then utilized for the preparation of two new complexes, namely, [Zn(L)2]·2H2O (complex 1) and [Zn(H2L)Cl3]·H2O (complex 2). The crystal structures of these complexes have been established by single-crystal X-ray analysis. The non-covalent interactions and supramolecular assemblies observed in the crystal packing of both complexes have been described focusing on π⋯π (for 1) and O⋯π–hole (for 2) interactions along with various hydrogen bonding interactions. A DFT study has been carried out to analyse their non-covalent interactions with rationalization using molecular electrostatic potential (MEP) surfaces and the combined QTAIM/NCI plot computational tools. In addition, the in vitro biological activities of the synthesized ligand (HL) and the water-soluble complex 2 were evaluated against Escherichia coli and Staphylococcus aureus. [ABSTRACT FROM AUTHOR]

The pure phase syntheses of three novel organic charge transfer complexes, obtained by combining the polyaromatic hydrocarbon triphenylene with 7,7,8,8-tetracyanoquinodimethane (TCNQ) and its fluorinated derivatives, are reported together with their crystal structures determined by 3D electron diffraction. The degree of charge transfer is estimated via examining intramolecular vibrational mode displacements between neutral TCNQFn and its complexes with triphenylene using infrared spectroscopy. The direct optical band gaps of 1.87, 1.76 and 1.70 eV for triphenylene–TCNQFn (n = 0, 2, 4) respectively, are determined via diffuse reflectance spectroscopy. The application of advanced structure determination techniques in combination with spectroscopic methods has allowed us to shed light on compelling charge transfer systems and to gain indications for the design of improved electrical organic conductors. [ABSTRACT FROM AUTHOR]

A series of twelve selenourea compounds with fluorinated fragments were synthesized and characterized. The influence of fluorine atoms in the chemical shift of the 77Se NMR was studied. The more fluorine atoms in the structure produced a downfield shift of the 77Se signal, indicating a higher π-acidity character in the N-heterocycle. The relative position of the fluorine atom also affects the chemical shift of the 77Se. It can be seen that a fluorine atom at 3-position, following by 4- and 2-position, respectively, produced a higher downfield shift. Interestingly, the opposite effect was observed for the –CF3 group. The crystal structure of six selenourea compounds revelead that the predominant interactions were three: Se⋯H, F⋯F and F⋯H. The latter was corroborated by Hirshfeld surface analysis and 2D dimensional fingerprint plots of each crystal structure. [ABSTRACT FROM AUTHOR]

Sm3+-doped and Sm3+/Eu3+ co-doped CaTiO3 phosphor samples were synthesized by solid-state reaction method and characterized using XRD, FE-SEM, FTIR, XPS, UV visible absorption, and photoluminescence techniques. All the compounds showed a crystalline structure with an orthorhombic phase and Pnma(62) space group. The diffuse reflectance spectra showed an absorption band due to the host along with peaks for Sm3+ and Eu3+ ions. The photoluminescence emission spectra of Sm3+-doped CaTiO3 phosphor showed orange-red and deep red emissions on excitation with 407 nm in which the peak at 599 nm was of maximum intensity. Similarly, Eu3+ ions showed a maximum intensity peak at 613 nm on excitation with 398 nm wavelength. The Sm3+/Eu3+ co-doped CaTiO3 phosphor showed an energy transfer from Sm3+ to Eu3+ ions on excitation with 407 nm and the nature of interaction between them was found to be dipole–dipole type. The CIE color coordinates and the correlated color temperature (CCT) calculations of the phosphors were performed, which showed an orange-red color emission useful for LED applications. The lifetime of Sm3+ ions decreases in the presence of Eu3+ ions and this was due to energy transfer from Sm3+ to Eu3+ ions. The temperature-dependent PL spectra of the phosphors showed thermal quenching behaviour. The activation energy of CaTiO3:2Sm3+, CaTiO3:2.5Eu3+, and CaTiO3:2Sm3+/2.5Eu3+ phosphors were found to be 0.27, 0.22, and 0.17 eV, respectively. [ABSTRACT FROM AUTHOR]

Herein we report on the preparation, spectroscopic and thermal characterization, structural study, and magnetic investigation of a new heterobimetallic coordination polymer (CP) of formula {[Na(H2O)2][Cu2(bpca)2(CO3)(HCO3)]}n (1) [Hbpca = bis(2-pyridylcarbonyl)amide], which was isolated through the fixation of aerial carbon dioxide by the preformed [Cu(bpca)]+ complex in basic water/DMSO solvent mixtures. Compound 1 is made up of neutral heterobimetallic zigzag chains growing parallel to the crystallographic c axis where carbonate, bicarbonate, and bpca anions act as bridges with regular alternation of a pair of [Cu(bpca)]+ units and one [Na(H2O)2]+ fragment. The two crystallographically independent copper(II) ions (Cu1 and Cu2) are five-coordinate in somewhat distorted square pyramidal surroundings with three nitrogen atoms from the bpca ligand and either one bicarbonate-oxygen (Cu1) or a carbonate-oxygen (Cu2) in the basal plane and a shared carbonate-oxygen atom (Cu1 and Cu2) in the apical position. Each sodium(I) ion is also five-coordinate in a distorted trigonal bipyramidal environment, with two oxygen atoms from a bpca ligand and a water molecule building the trigonal plane and a bicarbonate-oxygen and another water molecule in the axial sites. The intrachain copper–copper separation across the bridging carbonate is 4.109(1) Å. The cryomagnetic study of 1 reveals the occurrence of a weak ferromagnetic interaction between the copper(II) ions through the bridging carbonate [J = +0.17(4) cm−1, the spin Hamiltonian being defined as H = −J S Cu1· S Cu2]. Density functional theory (DFT) calculations on the [{Cu(bpca)}2(μ-CO3)] fragment of 1 in the gas phase and solid state were used to estimate the magnetic coupling constant (J = +0.42 cm−1) and to describe the electronic structure and magnetic topology of the system. [ABSTRACT FROM AUTHOR]