Triclinic Form Research Articles

Analysis of slip systems in protein crystals with a triclinic form using a phenomenological macro-bond method

Slip systems in triclinic hen egg-white lysozyme (Tri-HEWL) crystals, which is one of typical protein crystals, were identified by the indentation method and the surface energy estimation using phenomenological macro-bond methods.

Lithium calix[4]arenes: structural studies and use in the ring opening polymerization of cyclic esters.

We have structurally characterized a number of lithiated calix[4]arenes, where the bridge in the calix[4]arene is thia (–S–, LSH4), sulfinyl (–SO–, LSOH4), sulfonyl (–SO2–, LSO2H4), dimethyleneoxa (–CH2OCH2–, LCOCH4) or methylene (–CH2–, LH4). In the case of L4SH4, interaction with LiOtBu led to the isolation of the complex [Li8(L4S)2(THF)4]·5THF (1·5THF), whilst similar interaction of L4SOH4 led to the isolation of [Li6(L4SOH)2(THF)2]·5(THF) (2·5THF). Interestingly, the mixed sulfinyl/sulfonyl complexes [Li8(calix[4]arene(SO)(SO2)(SO1.68)2)2(THF)6]·8(THF) (3·8THF) and [Li5Na(LSO/3SO2H)2(THF)5]·7.5(THF) (4·7.5(THF) have also been characterized. Interaction of LiOtBu with LSO2H4 and LCOCH4 afforded [Li5L4SO2(OH)(THF)4]·2THF (5·2THF) and [Li6(LCOC)2(HOtBu)2]·0.78THF·1.22hexane (6·0.78THF·1.22hexane), respectively. In the case of LH4, reaction with LiOtBu in THF afforded a monoclinic polymorph [LH2Li2(thf)(OH2)2]·3THF (7·3THF) of a known triclinic form of the complex, whilst reaction of the de-butylated analogue of LH4, namely de-BuLH4, afforded a polymeric chain structure {[Li5(de-BuL)(OH)(NCMe)3]·2MeCN}n (8·2MeCN). For comparative catalytic studies, the complex [Li6(LPr)2(H2O)2]·hexane (9 hexane), where LPr2H2 = 1,3-di-n-propyloxycalix[4]areneH2, was also prepared. The molecular crystal structures of 1–9 are reported, and their ability to act as catalysts for the ring opening (co-)/polymerization (ROP) of the cyclic esters ε-caprolactone, δ-valerolactone, and rac-lactide has been investigated. In most of the cases, complex 6 outperformed the other systems, allowing for higher conversions and/or greated polymer Mn.

Crystal Structure, Hirschfeld Surface Analysis, and Absorption Spectra of a New Polymorph of Highly Symmetric Tetraphenylporphyrinato Zn(II), ZnTPP

The crystal and molecular structure of a new polymorph of four-coordinated Zn(II) tetraphenylporphyrin, with formula ZnTPP (TPP = 5,10,15,20-tetraphenyl porphyrin) has been determined from 3D X-ray diffraction data. The new polymorph crystallizes in the tetragonal space group, I4/m with cell dimensions a = 13.4206(9), c = 9.7210(16) A, V = 1750.9(3) A3, and Z = 4. The previous polymorph was crystallized in triclinic space group, P $$\bar {1}$$ . The single crystal of toluene solvate, a pseudopolymorph of tetraphenylporphinatozinc(II), ZnTPP ⋅ 2C7H8 was also crystallized in the triclinic space group, P $$\bar {1}$$ . The porphyrin cores of all the three centrosymmetric crystalline forms adopt a planar conformation which is attributed to the equivalent size of Zn2+ cations and that of porphyrin cores. In contrast to the two previous triclinic structures, which have two crystallography unique pyrrole rings, the tetragonal structure in the present form has all the pyrrole rings symmetric in nature. Further the symmetric orientations of phenyl rings about the mean N4 plane in the present form, unlike the two previous triclinic forms in which phenyl rings makes two types of dihedral angles with mean N4 plane reflects that the tetragonal structure of ZnTPP is the highly ordered geometry. All the four Zn–N bond distances in the present form are equal i.e., 2.048(2) A and is slightly longer than the average Zn–N bond distances found in the previous triclinic forms. The 3D packing of present form features sandwich type or face to face stacked layers that are bridged by a body centred molecule. The crystal packing is mainly stabilised by C–H⋅⋅⋅C and H⋅⋅⋅H intermolecular forces. Further the role and nature of various intermolecular interactions were quantitatively analysed by 3D Hirschfeld surface analysis and associated 2D fingerprint plots. The optical absorption spectra of ZnTPP and its free base analog, H2TPP have been further analysed in pure organic solvents of CH2Cl2 and CH3OH at different ionic strengths of the media and their results have been discussed in detail.

Multi-crystal data collection using synchrotron radiation as exemplified with low-symmetry crystals of Dps.

Multi-crystal data collection using synchrotron radiation was successfully applied to determine the three-dimensional structure of a triclinic crystal form of Dps from Escherichia coli at 2.0 Å resolution. The final data set was obtained by combining 261 partial diffraction data sets measured from crystals with an average size of approximately 5 µm. The most important features of diffraction data measurement and processing for low-symmetry crystals are discussed.

Concomitant polymorphic forms of 3-cyclopropyl-5-(2-hydrazinylpyridin-3-yl)-1,2,4-oxadiazole.

The dipharmacophore compound 3-cyclopropyl-5-(2-hydrazinylpyridin-3-yl)-1,2,4-oxadiazole, C10H11N5O, was studied on the assumption of its potential biological activity. Two concomitant polymorphs were obtained on crystallization from isopropanol solution and these were thoroughly studied. Identical conformations of the molecules are found in both structures despite the low difference in energy between the four possible conformers. The two polymorphs differ crucially with respect to their crystal structures. A centrosymmetric dimer formed due to both stacking interactions of the `head-to-tail' type and N-H...N(π) hydrogen bonds is the building unit in the triclinic structure. The dimeric building units form an isotropic packing. In the orthorhombic polymorphic structure, the molecules form stacking interactions of the `head-to-head' type, which results in their organization in a column as the primary basic structural motif. The formation of N-H...N(lone pair) hydrogen bonds between two neighbouring columns allows the formation of a double column as the main structural motif. The correct packing motifs in the two polymorphs could not be identified without calculations of the pairwise interaction energies. The triclinic structure has a higher density and a lower (by 0.60 kcal mol-1) lattice energy according to periodic calculations compared to the orthorhombic structure. This allows us to presume that the triclinic form of 3-cyclopropyl-5-(2-hydrazinylpyridin-3-yl)-1,2,4-oxadiazole is the more stable.

Thermochemistry of 5,10,15,20-tetraphenylporphyrin

Saturated vapor pressure of 5,10,15,20-tetraphenylporphyrin (TPP) was determined by Knudsen effusion mass spectrometry technique. The temperature dependence of the vapor pressure is described by the equation ln (p/Pa) = −(23.45 ± 0.26)⋅103/T + (37.32 ± 0.47) in the temperature range 490–615 K. The molar heat capacity measurements of TPP were performed in the temperature range 169–568 K. Quantum-chemical calculations of the structure and force field of the TPP molecule were carried out. These data were used to calculate thermodynamic functions of TPP in the solid and gas states. The enthalpy of sublimation of triclinic form of TPP was determined by the second and third laws of thermodynamics. The value ΔsH° (298.15 K) = 220 ± 12 kJ⋅mol−1 was recommended. The reaction based Feller-Peterson-Dixon approach predicts the gas phase TPP formation enthalpy ΔfH° (298.15 K) = 1004 ± 10 kJ⋅mol−1. A combination of the two last values results in the formation enthalpy of the TPP triclinic form ΔfH° (298.15 K) = 784 ± 15 kJ⋅mol−1.

Templating effect of single-layer graphene supported by an insulating substrate on the molecular orientation of lead phthalocyanine.

The influence of single-layer graphene on top of a SiO2/Si surface on the orientation of nonplanar lead phthalocyanine (PbPc) molecules is studied using two-dimensional grazing incidence X-ray diffraction. The studies indicate the formation of a mixture of polymorphs, i.e., monoclinic and triclinic forms of PbPc with face-on (lying down) and edge-on (standing up) PbPc orientations, respectively. The formation of monoclinic fractions is attributed to the presence of the graphene layer directing the π interactions between the highly delocalized macrocycles. The competing interfacial van der Waals forces and molecule–molecule interactions lead to the formation of a small fraction of triclinic moieties. The nanoscale electrical characterization of the thin PbPc layer on graphene by means of conducting atomic force microscopy shows enhanced vertical conductance with interconnected conducting domains consisting of ordered monoclinic crystallites through which the charge transfer occurs via tunneling. These results show the importance of a templating layer to induce the formation of a required phase of PbPc suitable for specific device applications.

Reversible Temperature-Stimulated Single-Crystal-to-Single-Crystal Conformational Polymorph Transformation in Cadmium(II) Coordination Trimer with a Water Vapor Sorption/Desorption Potential

A crystalline cadmium(II) coordination trimer with pyridine-4-propanamide (4-propy), [Cd3Cl4(H2O)4(4-propy)6](CH3CH2COO)2, readily responds to external stimuli while preserving crystal integrity. Two polymorphic forms, Polymorph-I (triclinic form) and Polymorph-II (monoclinic form), undergo a reversible single-crystal-to-single-crystal conformational polymorph transformation upon temperature change, while the triclinic form (Polymorph-I) additionally shows substantial reversible sorption/desorption potential via two pathways, in response to stimulation by (i) elevated temperature, and (ii) reduced pressure. The elucidation of the conformational transformation via a variety of ex situ and in situ methods (SCXRD, VT-PXRD, TG/DSC and VT-IR), complemented by in-depth theoretical studies, suggested that the conformational transformation might be a process that occurs slowly and continuously over a wider temperature range, with different processes (distinctive conformational changes) taking place over different temperature intervals.

Tetrakis(2,3,5,6-tetrafluorobenzenethiolato-κS)(triphenylphosphane-κP)osmium(IV): a monoclinic polymorph

The structure of the title compound, [Os(C6HF4S)4{P(C6H5)3}], has been previously reported [Arroyo et al. (1994). J. Chem. Soc. Dalton Trans. pp. 1819–1824], in the space group P\overline{1}. We have now obtained a monoclinic polymorph for this compound, crystallized from ethanol, while the previous form was obtained from a hexane/chloroform mixture. The molecular structure is based on a trigonal–bipyramidal OsIV coordination geometry, close to that observed previously in the triclinic form.

Polymorphism and Temperature-Induced Phase Transitions of Na2CoP2O7.

Polymorphism and temperature-induced phase transitions of Na2CoP2O7 were studied by in situ neutron powder diffraction and complemented by ab initio calculations to reconcile previous reports of its three polymorphs. We show that the "blue" form prepared at 873 K exists at room temperature in the orthorhombic Pna21 (= P21cn) phase, which transforms via a first-order transition to the tetragonal form at the temperature close to room temperature (∼335 K). Just above the transition, the tetragonal form is likely incommensurately modulated with the modulation vanishing at ∼423 K. Above that temperature the phase remains in the unmodulated tetragonal state (P42/mnm) until melting at ∼900 K. Upon cooling after melting, Na2CoP2O7 crystallizes into the "rose" triclinic P1 form which persists while it cools to room temperature, apparently stabilized by the barrier of the reconstructive "rose"-"blue" transition. We also discuss the relationship between the tetragonal and orthorhombic structures, the driving forces of the orthorhombic distortion, and similarity to Na2ZnP2O7 and the melilite-type structural family.

Structural elucidation of triclinic and monoclinic SFCA-III - killing two birds with one stone.

A part of the system CaO-SiO2-Al2O3-Fe2O3-MgO which is of relevance to iron-ore sintering has been studied in detail. For a bulk composition corresponding to 10.45 wt% CaO, 5.49 wt% MgO, 69.15 wt% Fe2O3, 13.37 wt% Al2O3 and 1.55 wt% SiO2 synthesis runs have been performed in air in the range between 1100 and 1300°C. Products have been characterized using reflected-light microscopy, electron microprobe analysis and diffraction techniques. At 1250°C, an almost phase-pure material with composition Ca2.99Mg2.67Fe3+14.58Fe2+0.77Al4.56Si0.43O36 has been obtained. The compound corresponds to the first Si-containing representative of the M14+6nO20+8n polysomatic series of so-called SFCA phases (Silico-Ferrites of Calcium and Aluminum) with n = 2 and is denoted as SFCA-III. Single-crystal diffraction investigations using synchrotron radiation at the X06DA beamline of the Swiss Light Source revealed that the chemically homogenous sample contained both a triclinic and monoclinic polytype. Basic crystallographic data are as follows: triclinic form: a = 10.3279 (2) Å, b = 10.4340 (2) Å, c = 14.3794 (2) Å, α = 93.4888 (12)°, β = 107.3209 (14)° and γ = 109.6626 (14)°, V = 1370.49 (5) Å3, Z = 2, space group P{\overline 1}; monoclinic form: a = 10.3277 (2) Å, b = 27.0134 (4) Å, c = 10.4344 (2) Å, β = 109.668 (2)°, V = 2741.22 (9) Å3, Z = 4, space group P21/n. Structure determination of both modifications was successful using diffraction data from the same allotwinned crystal. A description of the observed polytypism within the framework of OD-theory is presented. Triclinic and monoclinic SFCA-III actually correspond to the two possible maximum degree of order structures based on OD-layers containing three spinel (S) and one pyroxene (P) modules (〈S3P〉). The existence of SFCA-III in industrial iron-ore sinters has yet to be confirmed. Polytypism is likely to occur in other SFCA-members (SFCA, SFCA-I) relevant to sintering as well, but has so far been neglected in the characterization of industrial samples. Our results shed light on this phenomenon and may therefore be also helpful for better interpretation of the powder diffraction patterns that are used for phase analysis of iron-ore sinters.

Synthesis, characterization and photophysical properties of cyclotriphosphazenes including heterocyclic rings

In the present work, new cyclotriphosphazene derivatives, {[N3P3(biph)(R)4] (biph = 2′,2″-dioxy-1′,1″-biphenyl, R = imidazolyl (5) and benzimidazolyl (7)}, were synthesized for the first time. Both of these compounds (5 and 7) were fully characterized by elemental analysis, mass spectrometry and 1H and 31P NMR spectroscopy. The crystal structures of compounds 5 and 7 were determined by single-crystal X-ray crystallography. Furthermore, a second polymorph (triclinic form) of 2,2-monospiro-(2′,2″-dioxy-1′,1″-biphenyl)-4,4,6,6-tetrachlorocyclotriphosphazene (3) was isolated during the course of our study. UV–Vis absorption and fluorescence emission properties of 3, 5 and 7 were determined in a range of different solvents.

A new crystalline form of αβ-D-lactose prepared by oven drying a concentrated aqueous solution of D-lactose.

A new crystalline form of αβ-D-lactose (C12H22O11) has been prepared by the rapid drying of an approximately 40% w/v syrup of D-lactose. Initially identified from its novel powder X-ray diffraction pattern, the monoclinic crystal structure was solved from a microcrystal recovered from the generally polycrystalline mixed-phase residue obtained at the end of the drying step. This is the second crystalline form of αβ-D-lactose to be identified and it has a high degree of structural three-dimensional similarity to the previously identified triclinic form.

The Ternary Solid State Phase Behavior of Triclinic POP, POS, and SOS and Its Relationship to CB and CBE Properties

The ternary phase behavior between 1,3-dipalmitoyl-2-oleoyl-glycerol (POP), 1-palmitoyl-2-oleoyl-3-stearoyl-glycerol (POS), and 1,3-distearoyl-2-oleoyl-glycerol (SOS) in their triclinic crystal polymorphic forms was determined. The phase behavior was studied for samples crystallized from acetone and from the melt in the β2 polymorphic form. The melting point, enthalpy of fusion, crystal structure, and solid fat content (SFC) were determined for different proportions of POP:POS:SOS and compared to cocoa butter (CB) and three enzymatically synthesized cocoa butter equivalents (CBEs). A dramatic reduction in the melting point of ternary mixtures was observed with increasing POP content. The eutectic behavior between POP:POS and POP:SOS caused melting drop with increasing POP content. A eutectic region for POP:POS was also identified at 50:50:0 (w/w/w) POP:POS:SOS, while a novel specific composition of higher melting point was identified at 40:40:20 (w/w/w) POP:POS:SOS. The polymorphism of the CBEs and CB see...

Polymorphic modifications of a 1H-pyrrolo[3,2,1-ij]quinoline-5-carboxamide possessing strong diuretic properties.

6-Hydroxy-N-(4-methoxyphenyl)-4-oxo-2,4-dihydro-1H-pyrrolo[3,2,1-ij]quinoline-5-carboxamide, C19H16N2O4, possesses strong diuretic properties and can be used as a new hypertension remedy. Two polymorphic modifications of this compound have been found, namely the triclinic polymorph (space group P-1), with one molecule in the asymmetric unit, and the monoclinic polymorph (space group P21/n), with two molecules in asymmetric unit. An analysis of the pairwise interaction energies between the molecules in the crystal phase revealed differences in the crystal packing. The triclinic form has only one level of organization, namely a chain/column, while the monoclinic form has two levels of organization, with a chain/column as the primary basic structural motif and a layer as the secondary basic structural motif.

Two polymorphs of 2-(prop-2-yn-1-yl-oxy)naphthalene-1,4-dione: solvent-dependent crystallization.

The title compound, C13H8O3, crystallizes in two polymorphs, namely the monoclinic (space group P21/c) and triclinic (space group Pī) forms, obtained from N,N-di-methyl-formamide and isopropyl alcohol solutions, respectively. The mol-ecular structures and conformations in the two forms are essentially the same as each other. The naphtho-quinone ring systems are essentially planar with r.m.s. deviations of 0.015 and 0.029 Å for the monoclinic and triclinic forms, respectively. The O-propargyl groups are coplanar with the naphtho-quinone units with r.m.s deviations ranging from 0.04 to 0.09 Å. In the monoclinic crystal, mol-ecules are linked via pairs of C-H⋯O hydrogen bonds, forming a tape structure running along [120]. The tapes are further linked by a C-H⋯π inter-action into a layer parallel to the ab plane. Adjacent layers are linked by another C-H⋯π inter-action. In the triclinic crystal, mol-ecules are linked via C-H⋯O and π-π inter-actions, forming a layer parallel to the ab plane. Adjacent layers are linked by a C-H⋯π inter-action.

Supramolecular association in the triclinic (Z′=1) and monoclinic (Z′=4) polymorphs of 4-(4-acetylphenyl)piperazin-1-ium 2-amino-4-nitrobenzoate

Abstract Crystallography reveals two polymorphs for the salt [4-(4-acetylphenyl)piperazin-1-ium][2-amino-4-nitrobenzoate], a monoclinic form (2; modelled as P21/n with Z′=4) formed directly from the reaction mixture, and a triclinic form (1; Z′=1) isolated from recrystallisation. Relatively minor differences are noted in the conformations of the anions and of the cations, mainly relating to the twist of, respectively, the carboxylate groups and piperazin-1-ium rings with respect to the phenyl rings they are connected to. The key feature of the packing of both forms is the formation of charge-assisted ammonium-N–H···O (carboxylate) hydrogen bonds which lead to cyclic 12-membered {···HNH ···OCO}2 synthons in the case of 1 but, supramolecular chains in 2. The three-dimensional architecture in the crystal of 1 is further stabilised by amine-N–H···O (nitro) and amine-N–H···O (acetyl) hydrogen bonds, leading to double-layers in the bc-plane, which are linked along the a-axis by methylene-C–H···O (carboxylate) and π-stacking interactions. The combination of ammonium-N–H···O (carboxylate) and amine-N–H···O (carboxylate, acetyl) hydrogen bonds consolidate the three-dimensional packing in the crystal of 2. The greater crystal density, packing efficiency and calculated lattice energy for 1 compared with 2, suggest the former to be the thermodynamically most stable crystal. An analysis of the Hirshfeld surfaces for 1 and 2 reveal distinctive features that differentiate between the constituents of the two forms and between the ions comprising the asymmetric unit of 2.

New Insights into the β Polymorphism of 1,3-Palmitoyl-stearoyl-2-oleoyl Glycerol

In this communication, we report on the discovery of two new triclinic crystal polymorphic forms (β3 and β2) of 1,3-palmitoyl-stearoyl-2-oleoyl glycerol (POS), the most abundant triacylglycerol molecular species in cocoa butter. Three distinct triclinic crystal forms were crystallized from acetone and were found to have melting points of 32.9 °C (β3), 33.8 °C (β2), and 38.7 °C (β1), and enthalpies of fusion of 141.5 kJ/mol (β3), 147.9 kJ/mol (β2), and 158.5 kJ/mol (β1). All crystal forms had a similar long spacing (d001 = 64.1, 63.5, and 63.9 A for β3, β2, and β1, respectively) but displayed distinctly different wide-angle scattering patterns, i.e., short-spacings. In this communication, we clarify the 60-year-old confusion related to the polymorphism of POS, a key component responsible for the mechanical and thermal properties, and ultimately quality, of chocolate.

Synthesis Conditions on the Nature of GdBO3 Phase Formed

AbstractPresent study has been carried out to develop a facile synthetic methodology for preparing single phase monoclinic and triclinic forms of GdBO3, a potential phosphor material. This is achieved by varying annealing temperatures and annealing steps. Detailed structural studies, using X‐ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopic techniques confirmed that, Gd3+‐boric acid complexes formed initially at low temperatures (300 °C or less) get converted to monoclinic and triclinic forms of GdBO3 depending upon annealing temperatures, annealing steps and heating rates. Multiple steps with slow heating rates (∼3 °C/min) lead to the formation of single phase triclinic form of GdBO3. Two step heating with relatively faster heating rates (5 °C/min and above) results in single phase monoclinic GdBO3. FTIR and Raman studies also confirmed that boron exists only as BO4 structural units (in the form of B3O93− rings) in monoclinic GdBO3 and as BO3 structural units in triclinic GdBO3. Luminescence studies carried out with Eu3+ as a probe species confirmed more covalent nature around Eu3+/Gd3+ ions with improved red colour emission from triclinic form of GdBO3 compared to the monoclinic form.

Development of ternary solid dispersions with hydrophilic polymer and surface adsorbent for improving dissolution rate of carbamazepine

In this study solid dispersions of carbamazepine in the hydrophilic Kollidon® VA64 polymer, adsorbed onto Neusilin® UFL2 adsorption carrier have been employed to improve carbamazepine dissolution rate. In order to evaluate effects of changing in the proportions of all solid dispersion components on carbamazepine dissolution rate, D-optimal mixture experimental design was used in the formulation development. From all prepared solid dispersion formulations, significantly faster carbamazepine dissolution was observed compared to pure drug. Ternary solid dispersions containing carbamazepine, Kollidon® VA64 and Neusilin® UFL2 showed superior dissolution performances over binary ones, containing only carbamazepine and Neusilin® UFL2. Proportion of Kollidon® VA64 showed the most profound effect on the amount of carbamazepine dissolved after 10 and 30 min, whereby these parameters increase upon increasing in Kollidon® VA64 concentrations up to the middle values in the studied range of Kollidon® VA64 concentrations. Physicochemical characterization of the selected samples using differential scanning calorimetry, FT-IR spectroscopy, powder X-ray diffraction and polarizing light microscopy showed polymorphic transition of carbamazepine from more thermodynamically stable monoclinic form (form III) to less thermodynamically stable triclinic form (form I) in the case of ternary, but not of binary solid dispersion formulations. This polymorphic transition can be one of the factors responsible for improving of carbamazepine dissolution rate from studied solid dispersions. Ternary solid dispersions prepared with Kollidon® VA64 hydrophilic polymer and Neusilin® UFL2 adsorption carrier resulted in significantly improvement of carbamazepine dissolution rate, but formation of metastable polymorphic form of carbamazepine requires particular care to be taken in ensuring product long term stability.