α-Nickel sulfate hexahydrate crystals: relationship of growth conditions, crystal structure and properties

2019 ◽  
Vol 52 (6) ◽  
pp. 1371-1377
Author(s):  
R. R. Choudhury ◽  
R. Chitra ◽  
I. P. Makarova ◽  
V. L. Manomenova ◽  
E. B. Rudneva ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Raman Spectra ◽  
Nickel Sulfate ◽  
Detailed Comparison ◽  
Growth Conditions ◽  
Fine Tuning ◽  
Interionic Interaction ◽  
Crystal Properties ◽  
Structural Differences

Studies on α-nickel sulfate hexahydrate (NSH) crystals grown under different conditions are undertaken to investigate how changes in growth conditions affect crystal properties and whether or not there is any modification of the average crystal structure due to changes in crystallization conditions. Thermogravimetric and microhardness studies were carried out on the crystals grown from two different aqueous solutions, one of them containing an excess of sulfuric acid. Raman spectra were recorded and a single-crystal neutron diffraction investigation was conducted on both crystals. A detailed comparison between the two crystal structures and their Raman spectra showed that, although the two crystal structures are very similar, there are slight differences, such as the change in unit-cell volume, differences in the ionic structure, particularly of the sulfate ions, and changes in the hydrogen-bonding network. During solution crystal growth of a salt like NSH, varying the ionic environment around the solute ions influences the interionic interactions between them. Hence it is suggested that the above-mentioned structural differences result from a fine-tuning of the interionic interaction between the cations and anions of NSH in the solution phase. This difference is finally carried over to the crystalline phase. The resulting small crystal structure differences are enough to produce measurable changes in the thermal stability and fragility of the crystals. These differences in crystal properties can be explained on the basis of the observed structural differences between the two crystals grown under different conditions.

scholarly journals Crystal structure of the cyan fluorescent protein Cerulean-S175G

2016 ◽  
Vol 72 (7) ◽  
pp. 516-522 ◽  
Author(s):  
Sang-wook Park ◽  
Sunghyun Kang ◽  
Tae-Sung Yoon
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Conformational Changes ◽  
Fluorescent Protein ◽  
Detailed Comparison ◽  
Cyan Fluorescent Protein ◽  
Double Mutation ◽  
Aequorea Victoria ◽  
Green Fluorescent ◽  
Enhanced Cyan Fluorescent Protein

Enhanced cyan fluorescent protein (ECFP) was derived fromAequorea victoriagreen fluorescent protein (avGFP), notably with S65T/Y66W mutations. Its chromophore consists of a tripeptide comprised of Thr65, Trp66 and Gly67 (TWG) residues, while that ofavGFP consists of a Ser65, Tyr66 and Gly67 (SYG) tripeptide. Cerulean and SCFP3A were derived from ECFP-S72A/H148D (a double mutation) with additional Y145A and S175G mutations, respectively, while Cerulean-S175G has both mutations (Y145A and S175G). The crystal structures of these ECFP variants at neutral pH were reported to adopt two distinct major conformations calledECFPandCerulean. In this study, Cerulean-S175G was revealed to adopt only theCeruleanconformation, while Cerulean has been reported to adopt both theECFPand theCeruleanconformations in its crystal structures. Sharing the same S175G mutation with SCFP3A, Cerulean-S175G showed a slightly increased quantum yield, like SCFP3A, but did not adopt theECFPconformation adopted by SCFP3A. Detailed comparison of Cerulean-S175G and other ECFP variants revealed that the notable conformational changes in ECFP variants can be understood mainly in terms of the interaction between the Trp66 residue of the chromophore and residues 145–148 of β-strand 7.

PbCN2 – an elucidation of its modifications and morphologies

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Cordula Braun ◽  
Liuda Mereacre ◽  
Helmut Ehrenberg
Keyword(s):  
Crystal Structure ◽  
Ph Value ◽  
Detailed Comparison ◽  
Growth Conditions ◽  
Structural Investigations ◽  
Space Group ◽  
Structure Space ◽  
Two Phases ◽  
Centrosymmetric Structure

Abstract Concerning the crystal structure of PbCN2 there exist two different descriptions in the literature, one based on the non-centrosymmetric structure, space group Pna21, another one on the centrosymmetric one in space group Pnma. To elucidate the conditions for their appearance, comprehensive preparative and structural investigations have been conducted which proved the existence of two distinct modifications of PbCN2. A detailed comparison of the two phases is provided. The growth conditions and crystallization processes of the two PbCN2 structures are reported with focus on the influence of the pH value on the products. Depending on the growth conditions several different morphologies arise, namely PbCN2 in needle-shaped and platelet-shaped crystals, as well as pompon-shaped and lance-shaped crystals.

scholarly journals Combinatorial selection of molecular conformations and supramolecular synthons in quercetin cocrystal landscapes: a route to ternary solids

IUCrJ ◽  
2015 ◽  
Vol 2 (4) ◽  
pp. 402-408 ◽  
Author(s):  
Ritesh Dubey ◽  
Gautam R. Desiraju
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Combinatorial Library ◽  
Molecular Conformation ◽  
Fine Tuning ◽  
Experimental Conditions ◽  
Supramolecular Synthons ◽  
Molecular Conformations ◽  
Structural Space ◽  
Selection Of

The crystallization of 28 binary and ternary cocrystals of quercetin with dibasic coformers is analyzed in terms of a combinatorial selection from a solution of preferred molecular conformations and supramolecular synthons. The crystal structures are characterized by distinctive O—H...N and O—H...O based synthons and are classified as nonporous, porous and helical. Variability in molecular conformation and synthon structure led to an increase in the energetic and structural space around the crystallization event. This space is the crystal structure landscape of the compound and is explored by fine-tuning the experimental conditions of crystallization. In the landscape context, we develop a strategy for the isolation of ternary cocrystals with the use of auxiliary template molecules to reduce the molecular and supramolecular `confusion' that is inherent in a molecule like quercetin. The absence of concomitant polymorphism in this study highlights the selectivity in conformation and synthon choice from the virtual combinatorial library in solution.

Effect of solution acidity on the crystallization of polychromates in uranyl-bearing systems: synthesis and crystal structures of Rb2[(UO2)(Cr2O7)(NO3)2] and two new polymorphs of Rb2Cr3O10

2021 ◽  
Vol 236 (1-2) ◽  
pp. 11-21
Author(s):  
Evgeny V. Nazarchuk ◽  
Oleg I. Siidra ◽  
Dmitry O. Charkin ◽  
Stepan N. Kalmykov ◽  
Elena L. Kotova
Keyword(s):  
Crystal Structure ◽  
Aqueous Solutions ◽  
Crystal Structures ◽  
Hydrothermal Treatment ◽  
Ambient Conditions ◽  
Screw Axis ◽  
3D Framework ◽  
Solution Acidity

Abstract Three new rubidium polychromates, Rb2[(UO2)(Cr2O7)(NO3)2] (1), γ-Rb2Cr3O10 (2) and δ-Rb2Cr3O10 (3) were prepared by combination of hydrothermal treatment at 220 °C and evaporation of aqueous solutions under ambient conditions. Compound 1 is monoclinic, P 2 1 / c $P{2}_{1}/c$ , a = 13.6542(19), b = 19.698(3), c = 11.6984(17) Å, β = 114.326(2)°, V = 2867.0(7) Å3, R 1 = 0.040; 2 is hexagonal, P 6 3 / m $P{6}_{3}/m$ , a = 11.991(2), c = 12.828(3) Å, γ = 120°, V = 1597.3(5) Å3, R 1 = 0.031; 3 is monoclinic, P 2 1 / n $P{2}_{1}/n$ , a = 7.446(3), b = 18.194(6), c = 7.848(3) Å, β = 99.953(9)°, V = 1047.3(7) Å3, R 1 = 0.037. In the crystal structure of 1, UO8 bipyramids and NO3 groups share edges to form [(UO2)(NO3)2] species which share common corners with dichromate Cr2O7 groups producing novel type of uranyl dichromate chains [(UO2)(Cr2O7)(NO3)2]2−. In the structures of new Rb2Cr3O10 polymorphs, CrO4 tetrahedra share vertices to form Cr3O10 2− species. The trichromate groups are aligned along the 63 screw axis forming channels running in the ab plane in the structure of 2. The Rb cations reside between the channels and in their centers completing the structure. The trichromate anions are linked by the Rb+ cations into a 3D framework in the structure of 3. Effect of solution acidity on the crystallization of polychromates in uranyl-bearing systems is discussed.

scholarly journals Crystal Chemical Relations in the Shchurovskyite Family: Synthesis and Crystal Structures of K2Cu[Cu3O]2(PO4)4 and K2.35Cu0.825[Cu3O]2(PO4)4

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 807
Author(s):  
Ilya V. Kornyakov ◽  
Sergey V. Krivovichev
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structural Complexity ◽  
Crystal Chemical ◽  
X Ray Diffraction ◽  
Complexity Measures ◽  
X Ray ◽  
The Family ◽  
Similarities And Differences ◽  
Related Compounds

Single crystals of two novel shchurovskyite-related compounds, K2Cu[Cu3O]2(PO4)4 (1) and K2.35Cu0.825[Cu3O]2(PO4)4 (2), were synthesized by crystallization from gaseous phase and structurally characterized using single-crystal X-ray diffraction analysis. The crystal structures of both compounds are based upon similar Cu-based layers, formed by rods of the [O2Cu6] dimers of oxocentered (OCu4) tetrahedra. The topologies of the layers show both similarities and differences from the shchurovskyite-type layers. The layers are connected in different fashions via additional Cu atoms located in the interlayer, in contrast to shchurovskyite, where the layers are linked by Ca2+ cations. The structures of the shchurovskyite family are characterized using information-based structural complexity measures, which demonstrate that the crystal structure of 1 is the simplest one, whereas that of 2 is the most complex in the family.

scholarly journals Spotlight on Alkali Metals: The Structural Chemistry of Alkali Metal Thallides

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1013
Author(s):  
Stefanie Gärtner
Keyword(s):  
Crystal Structure ◽  
Alkali Metal ◽  
Crystal Structures ◽  
Alkali Metals ◽  
Valence Electron ◽  
Oxidation States ◽  
Valence Electron Concentration ◽  
Base Metals ◽  
Charge Balancing

Alkali metal thallides go back to the investigative works of Eduard Zintl about base metals in negative oxidation states. In 1932, he described the crystal structure of NaTl as the first representative for this class of compounds. Since then, a bunch of versatile crystal structures has been reported for thallium as electronegative element in intermetallic solid state compounds. For combinations of thallium with alkali metals as electropositive counterparts, a broad range of different unique structure types has been observed. Interestingly, various thallium substructures at the same or very similar valence electron concentration (VEC) are obtained. This in return emphasizes that the role of the alkali metals on structure formation goes far beyond ancillary filling atoms, which are present only due to charge balancing reasons. In this review, the alkali metals are in focus and the local surroundings of the latter are discussed in terms of their crystallographic sites in the corresponding crystal structures.

Über einige Beziehungen zwischhen Kristallstrukturen

1956 ◽  
Vol 11 (11) ◽  
pp. 920-934b
Author(s):  
Konrad Schubert
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Spatial Correlation ◽  
Chemical Elements ◽  
Electron Gas ◽  
Lattice Constants ◽  
Hexagonal Close Packed ◽  
Binary Compounds ◽  
Atomic Radii ◽  
Insight Into

In determining structures we use physical propositions in order to find a likely crystal structure. The same propositions are of value for the ordering of known structures into a natural system. The atomic radii form such a proposition. Another proposition is contained in the spatial correlation of electrons in the electron gas. The question is, whether this correlation is of influence on the crystal structure or not. To gain a first insight into this question, it is useful to know whether the crystal structures are physically compatible with a certain spatial correlation of electrons. Some qualitative rules are given to assess the physical possibility of a spatial correlation of electrons in a crystal structure. For the crystal structures of some chemical elements proposals for electron correlation are given. These proposals account for rationalities existing between some lattice constants, e. g. the axial ratios of the hexagonal close packed structures of Co and Zn. The proposals are also applicable to some binary compounds. With regard to these commensurabilities, it seems possible that the examination of the spatial correlation of electrons may lead to a better understanding of the crystal-chemical empiry.

Sign in / Sign up

Export Citation Format

Share Document