Molecules In Unit Cell Research Articles

Design, Synthesis, Crystal Structure and Photophysical Properties of New Oxadiazole Extended Viologen Fluorophore

Viologens (N,N'-dimethyl-4,4-bipyridinium) are advanced functional materials, found important applications in electrochromic devices, molecular machines, organic batteries, and carbohydrate oxidation catalysts in alkaline fuel. In this article, we investigated the design, synthesis and photophysical properties of N,N'-dimethyl-2,5-Bis(pyridinium)oxadiazole 4 and its precursor 2,5- Bis(pyridine)oxadiazole 2. The crystal structure and photophysical properties of viologen 4 and precursor 2 have been determined. The viologen molecule 4 crystallized in monoclinic form, space group P21/n with four molecules in unit cell. Precursor molecule 2 also crystalized in monoclinic form, space group C2/c with four molecules in unit cell. From X-rd data, we found three cations in the molecular structure of viologen molecule 4, which is unusual in viologens. In the three-dimensional molecular packing diagram of molecule 4, the three cations and iodate anions are stabilized by C···C, C···I, N···I, N···H, H···I, N—H···I and C—H···I. The dihedral angle between planes having oxadiazole and two benzene rings are 5° and 8°, suggesting the molecule 4 is a slightly strained one. The molecular structure of precursor molecule 2 stabilized by C···C and N···H short contacts between the molecules. The molecule 4 displayed strong absorbance at 315 nm and emissions between 390 - 410 nm.

Stereochemistry of tropane alkaloid of convolvine and their derivatives

Structures of alkaloid convolvine (1) isolated from Convolvulus subhirsutus and its derivatives-convolamine(N-methylconvolvine) (2) and hydrochloride of N-benzylconvolvine (3) have been determined by single crystal X-ray diffraction technique. Compounds were crystallized in monoclinic space groups having four molecules in unit cell. All compounds contain a bicyclic ring system of tropane, where piperidine rings in all case adopt chair conformation. Hydrogen atom and methyl- and benzyl-substituents located in nitrogen atom of studied compounds occupy equatorial positions. The substituent of tropane core- the veratroyloxy group containing in all compound molecules is an α-axial oriented relative to the tropane core. In crystal structures of compound 1 and 2, the molecules are located in the distance of van der Waals interactions. The H-bond between the anion Cl and the proton of the N atom is observed in the crystal of N-benzylconvolvine hydrochloride (Cl···N 3.337 Å, Cl···H 2.42 Å and Cl-H-N 175°).

Synthesis [1-(4-acetylphenyl)-3-(2-methylphenyl)]triazene: NMR, Vibrational, X-ray Crystallography Characterization with HF/DFT Studies

[1-(4-acetylphenyl)-3-(2-methylphenyl)]triazene (AMT) was synthesized by experimental methods, its chemical and spectrometric properties was studied by FT-IR, FT-Raman,1H-NMR,13C-NMR and X-ray singlecrystal diffraction methods. The obtained results showed that this structure hasorthorombic system with space group of pbca and eight molecules in unit cell. Its unit cell parameters comprise a=8.0665(2), b=8.0019(2) and c=21.5249(5). Then molecular number of [1-(4-acetylphenyl)-3-(2-methylphenyl)]triazene (AMT) structure has been studied by HF/DFT methods. However, FT-IR, FT-Raman,1H-NMR, 13C-NMR spectra were analyzed that the obtained results for vibrational spectra and amount of chemical shift correspond significantly with theoretical methods. Some structural parameters such as bonds length, bonds angle and dihedral angle were studied using theoretical and experimental methods. The parameters such as thermodynamical parameters, dipole moment, HOMO and LUMO energetic values, electrophilicity (ω), chemical potential(μ), chemical hardness(η) and max amount of electronic charge transfer (ΔNmax) are calculated for this compound in conclusion. The proposed methods were successfully applied to the determination of vibrational spectra, chemical shift amounts and structural parameters.

Water and the relationship to the crystal structure stability of azithromycin

This study investigated the solid-state physical stabilities of azithromycin dihydrate (AZM-DH), thermally prepared anhydrate and hemihydrate modifications. Programmed thermal treatment of AZM-DH in DSC yielded the formation of anhydrate amorphs (I, II), crystalline AZM anhydrate and hemihydrate phases. The formation of the anhydrate amorphs, I and II, respectively, involved different transformation pathways of solid–liquid–solid (melting and supercooling) and solid–solid (378 K for 24 h.). Both amorph phases exhibit hygroscopic behaviour, producing non-stoichiometric hydrates, with extent of moisture absorption increasing with increased storage humidity (0–96% RH/313 K). TG analysis after controlled storage (4 days at 96% RH/313 K) detected absorbed waters of hydration up to 5.9 and 5.3% for amorphs I and II, respectively. The crystal anhydrate and hemihydrate phases were hygroscopic and readily converted to the stoichiometric dihydrate form, which was compositionally stable in RH ranges from 11 to 96% at 313 K. Solubility studies, performed in distilled water at 310 K, showed an at least 1.5 fold solubility improvement for both amorph forms relative to crystalline AZM-DH, but with some evidence of solvent-mediated phase transformation after 20 min. Structural characterization by single-crystal XRD concluded that thermally stimulated amorphization required energy to disrupt intermolecular hydrogen bond interactions by bridging water molecules in addition to hydrogen bond interactions between neighbouring AZM molecules in unit cell.

Sol–gel synthesis, crystal structure, and characterization of Y x Bi2+x Cd4−3x O7 (0.05 ≤ x ≤ 0.35) nano-oxides

Synthesis of the Bi2+x Y x Cd4−3x O7 (D1–D4: x = 0.05, 0.15, 0.25, and 0.35) nano-oxides was performed by sol–gel method via nitrate–citrate route. Analysis of the powder X-ray diffraction patterns shows a tetragonal unit cell with lattice parameters: a = 9.6874, 9.6919, 9.6909, and 9.6890 A, c = 5.9091, 5.4276, 5.4271, and 5.4268 A, respectively, in D1–D4, with space group P42/mcm and Z = 2 (number of molecules in unit cell). Average crystallite sizes determined by Scherrer’s relation are found to be in the range 53–83, 40–68, 23–85, and 51–88 nm in D1–D4, respectively, that shows the nanoparticles formation in the samples. On Rietveld refinement, the agreement factors are lowered to R p = 0.97, 0.97, 0.97, and 0.97; R wp = 0.98, 0.98, 0.98, and 0.98; and R exp = 0.001, 0.001, 0.002, and 0.002 in samples D1–D4, respectively. The calculated bond lengths in D1–D4 are as follows: Cd1–O1: 2.4348, 2.4359, 2.4361, and 2.4373 A; Bi2–O3: 2.3238, 2.3258, 2.3260, and 2.3272 A; and Bi3–O1: 2.2270, 2.2289, 2.2290, and 2.2302 A, respectively. The plane-wave density functional theory calculations on the unit cell crystal structure of D1–D4 show that the high density of states (DOS) of valence band located at −7.0 to 0.0 eV is due to the Y 4s, 4p; Bi 6s, 6p; Cd 4s, 4p; and O 2s, 2p orbitals. The DOS of conduction band located at ~0.0 to 2.2 eV is due to Y 4s, 4p; Bi 6s, 6p; Cd 4s, 4p; and O 2p orbitals. The optical absorbance spectra of the samples D1–D4 show the broad band of ~290 nm, which is commonly assigned to the Bi+3 (5d 10) 1S0 → 3P1 electronic transitions .

Synthesis, growth, structural, spectral, thermal and microhardness studies of a new hydrogen bonded organic nonlinear optical material: L–valinium p–toluenesulfonate monohydrate (LVPT)

A new organic hydrogen bonded material, L-valinium p-toluenesulfonate monohydrate (LVPT), was synthesized and grown as a single crystal by slow evaporation solution growth technique with the dimension of 29 × 7 × 4 mm3. A good X-ray quality single crystal was selected from the grown crop and used for single crystal diffraction study. It reveals that the compound crystallized in a non-centrosymmetric monoclinic space group P21 with two set of molecules in unit cell. The plane of the carboxyl group of the cation is making dihedral angle of 85.4(1)° with the plane of the aromatic ring of the anion. The crystal packing features intricate three dimensional hydrogen bonding network through chain and ring motifs. These hydrogen bonded motifs are observed at x = 0 or 1 and aromatic rings of the cations are stacked at x = 1/2 leading to alternate hydrophilic and hydrophobic layers, respectively, along a-axis of the unit cell. Fourier transform infrared (FTIR) and Raman (FT-Raman) spectral studies have been performed to identify the functional groups. The optical transmittance and the lower cutoff wavelength of the LVPT have been identified by UV–Vis absorption studies. Second harmonic generation test using a laser with wavelength of 1064 nm confirms the nonlinear optical efficiency of the sample as 1.5 greater than KDP. The thermal and mechanical properties of the sample were examined by TG/DTA and Vicker's microhardness tests, respectively. Further, the solid state properties were calculated and found to be better than the known nonlinear optical material KDP.

The chemical bond properties and ferroelectricity studies of SrBi4Ti4O15

Spontaneous polarization as the most immediate parameter in ferroelectricity is always an emphasis in ferroelectric research. Some ferroelectric microscopic theory such as Berry-phase method and first principles calculation are used to study the spontaneous polarization of perovskite type ferroelectrics. SrBi4Ti4O15 is a typical bismuth layered structure ferroelectric, the complexity of its crystal structure makes the ferroelectric research more difficult. This study, from the perspective of chemical bond, analyzes the relationship between the chemical bond properties and the spontaneous polarization, and further explores the atomic bonding state in ferroelectric crystal and its impact on ferroelectricity.By starting from the crystal structure data of SrBi4Ti4O15, the atomic local cluster structure including bond length, atomic coordination situation and the number of atoms in a crystal structure unit are obtained by the atomic environment calculation (AEC). Calculation results show that there are 13 atomic local cluster structures in SrBi4Ti4O15. Then combined with the crystal decomposition method, the SrBi4Ti4O15crystal is decomposed into 38 pseudo-binary crystals, and each pseudo-binary crystal corresponds to a chemical bond. Accordding to the dielectric theory of chemical bond that used in binary crystal, chemical bond properties such as the number of effective valence electron, the effective valence electron density and the bond ionicity are calculated. Through improvement of the bond dipole moment model, the relationship among bond dipole moment, bond properties, and bond parameter is established, and the bond dipole moment of each bond in SrBi4Ti4O15 is calculated.The spontaneous polarization of an ferroelectric can be approximated as the superposition of the spontaneous polarization of various chemical bonds in the crystal, where the spontaneous polarization of chemical bond is due to the bond dipole moment. Based on the traditional polarization theory, the spontaneous polarization can be expressed as the average bond dipole moment per unit volume, and considering the number of molecules in unit cell (Z) and the atomic site occupation factor (SOF), the correlation between bond dipole moment and spontaneous polarization of the bismuth layered ferroelectrics is established. On the basis of this, the calculated spontaneous polarization along a axis in the ferroelectric SrBi4Ti4O15 is 28.03 C/cm2.This study simplifies the complex crystal research by AEC and crystal decomposition method, and studies the ferroelectricity of the bismuth layered ferroelectrics from the viewpoint of chemical bond. The bond dipole moment as the bridge in this study for connecting spontaneous polarization with chemical bond properties, which is a new micro study method in macro-properties of bismuth layered ferroelectrics. Based on this method, the spontaneous polarization of other relevant ferroelectrics such as orthogonal SrBi2Ta2O9, orthogonal Bi4Ti3O12, and tetragonal SrBi4Ti4O15 are calculated, all the results are in good agreement with the experimental values and other theoretically calculated values.

New potential high energy density compounds: Oxadiaziridine derivatives

The -CN, -N3, -NF2, -NH2, -NHNO2, -NO2, and -ONO2 derivatives of oxadiaziridine were studied using B3LYP/6-311G** level of density functional theory. The gas phase heats of formation of oxadiaziridine derivatives were calculated by isodesmic reaction. All these compounds have high and positive heats of formation due to strain energies of small ring. Detonation properties were calculated via Kamlet-Jacobes equations and specific impulse. The effects of substituent groups on detonation performance were discussed. The impact sensitivity was estimated according to the “available free space per molecule in unit cell” and “energy gaps” methods. The similar conclusions were given by two different methods. The effects of substituents on impact sensitivity were discussed. According to the given estimations of detonation performance and sensitivity, some oxadiaziridine derivatives may be considered promising high energies materials.

Polymorphism and solvates of flecainide base

Flecainide base is pharmaceutically active substance used for production of flecainide acetate which is known in market as Tambacor, Almarytm, Apocard, Ecrinal or Flecaine. It is determined that flecainide base forms four polymorphic forms abbreviated as Ib, IIb, IIIb and IVb. Flecainide base form Ib is thermodynamically stable form at laboratory temperature while form IIIb is stable at higher temperatures. Flecainide form Ib absorbs water in its structure between layers and forms non-stoichiometric hydrate. Flecainide base binds with organic solvents and form monosolvates. Flecainide base form Ib crystallizes in orthorhombic crystals with lattice parameters a = 27.88 Å, b = 13.78 Å, c = 9.98 Å and two independent molecules in unit cell (Z′ = 2; Z = 8). Molecule arrangement in flecainide base form Ib structure is not dense and it forms a channel-type structure, where molecules of water and alcohols are placed.

Density function theory study on energetic nitro-triaziridine derivatives

The series of nitro-triaziridines had been studied as high-energy density compounds at B3LYP/6-311G** and MP2/6-311G** levels by means of density functional theory. The heats of formation (HOFs), bond dissociation energies, and detonation performance had been calculated in detail. It was found that all nitro-triaziridines have high position HOFs, and electron-withdrawing of nitro, the steric hindrance, and abundant N–N bond had positive effect with increasing values of HOFs. The thermodynamic stability is estimated by bond dissociation energy and available free space per molecule in unit cell. The detonation performance had been estimated via Kamlet–Jacobs equation and relative specific, However, two different consequences were obtained for detonation performance. Hence, for nitro-triaziridines derivatives, we assumed that a large number of extra oxygen was produced in combustion reaction or explosive reaction, which was negative for the energy released. Therefore, the oxygen balance must be considered for designing high-energy compounds. We also assumed that the Kamlet–Jacobs equation may not be applicable for the compounds, which was constituted of only oxygen, hydrogen, and nitrogen elements.

Microwave Induced Synthesis And Characterization Of Semiconducting 2-thiophenecarboxaldehyde Metal Complexes

The coordination complexes of Co(II), Ni(II) and Cu(II) derived from 2-thiophenecarboxylidene-3-chloro-4-fluoroaniline (TCC) and 2-thiophenecarboxylidene-4-fluoroaniline (TCF) have been synthesized by conventional as well as microwave methods. These compounds have been characterized by elemental analysis, FT-IR, FAB-mass, molar conductance, electronic spectra, ESR, thermal, magnetic susceptibility, electrical conductivity and XRD analysis. The complexes are coloured and stable in air. Analytical data revealed that all the complexes exhibited 1:2 (metal:ligand) ratio with the coordination 4 or 6. FAB-mass and thermal data show degradation pattern of the complexes. The thermal behavior of metal complexes shows that the hydrated complexes loses water molecules of hydration in the first step; followed by decomposition of ligand molecules in the subsequent steps. The crystal system, lattice parameter, unit cell volume and number of molecules in unit cell in the lattice of complexes have been determined by XRD analysis. XRD patterns indicate crystalline nature for the complexes. The solid state electrical conductivity of the metal complexes has also been measured. Solid state electrical conductivity studies reflect semiconducting nature of the complexes.

Microwave synthesis and spectral, thermal and antimicrobial activities of some novel transition metal complexes with tridentate Schiff base ligands

Some novel Schiff base metal complexes of Cr(III), Co(II), Ni(II) and Cu(II) derived from 2-[(5-bromo-2-hydroxybenzylidene)amino]pyridin-3-ol (BSAP) and {5-chloro-2-[(2-hydroxynaphthylidene)amino]phenyl}-phenylmethanone (HNAC) were synthesized by conventional as well as microwave methods. These compounds were characterized by elemental analysis, FT-IR, FAB-mass, molar conductance, electronic spectra, ESR, magnetic susceptibility, thermal, cyclic voltammetry, electrical conductivity and XRD analyses. Analytical data revealed that all the complexes exhibited 1:1 (metal:ligand) ratio with coordination number 4 or 6. IR data showed that the ligand coordinates with the metal ions in a tridentate manner. FAB-mass and thermal data showed degradation pattern of the complexes. The thermal behaviour of metal complexes showed that the hydrated complexes lose water molecules of hydration in the first step; followed by decomposition of ligand molecules in the subsequent steps. The crystal system, lattice parameter, unit cell volume and number of molecules in unit cell in the lattice of complexes were determined by XRD analysis. XRD patterns indicate crystalline nature for the complexes. The solid state electrical conductivity of the metal complexes was also measured. Solid state electrical conductivity studies reflect semiconducting nature of the complexes. The Schiff base and metal complexes displayed a good activity against the Gram-positive bacteria; Staphylococcus aureus and Gram-negative bacteria; Escherichia coli and fungi Aspergillus niger and Candida albicans. The antimicrobial results also indicate that the metal complexes displayed better antimicrobial activity as compared to the Schiff bases.

Application of terahertz spectroscopy and molecular modeling in isomers investigation: Glucose and fructose

Terahertz spectra of glucose and fructose have been measured by terahertz time-domain spectroscopy (THz-TDS) at room temperature. Because they have the same molecular formula, the differences of the THz spectra can be attributed to their molecular structures and the arrangement of molecules in unit cell. In this paper, gaseous-state theory has been employed to simulate the isolated molecule of these two isomers. The results indicate that experimental THz spectral features (0.5–4.0THz) of glucose and fructose arise from the mixture of intramolecular and intermolecular modes, involving hydrogen bonds and covalent bonds, and with the intermolecular modes dominating.

Low temperature Raman and DFT study of creatinine

The Raman spectra of creatinine powder in the wavenumber region of 500–3500 cm−1 have been recorded as a function of temperature ranging from 293 K to 83 K and different clusters of creatinine were optimized with DFT method to determine hydrogen bonding network in crystalline creatinine. The accurate vibrational assignment of all vibrational bands of creatinine has been done on the basis of the calculated vibrational spectra and the potential energy distribution. The calculated Raman spectra of hydrogen bonded tetramer cluster matches nicely with the experimentally observed spectra confirming four molecules in unit cell as reported by crystallographic data. In addition signature of dimer, which is just half of the tetramer, has also been observed. The bands associated with CH3, CH2, ν(CO), ν(CN) and ν(CH) have been given more focus to see the behavior of hydrogen bond network with temperature. The analysis of these bands reveals that a gradual change (increase/decrease) in linewidth and peak position occurs with temperature as a consequence of the anharmonic coupling of internal modes with phonon mode and intermolecular interaction. The behavior of hydrogen bond network on cooling has been explained in terms of contraction of unit cell.

Microwave Synthesis, Spectral, Thermal and Antimicrobial Studies of Some Co(II), Ni(II) and Cu(II) Complexes Containing 2‐Aminothiazole Moiety

Some new Schiff base metal complexes of Co(II), Ni(II) and Cu(II) derived from 4‐chlorobenzylidene‐2‐aminothiazole (CAT) and 2‐nitrobenzylidene‐2‐aminothiazole (NAT) have been synthesized by conventional as well as microwave methods. These compounds have been characterized by elemental analysis, FT‐IR, FAB‐mass, molar conductance, electronic spectra, ESR, magnetic susceptibility, thermal, electrical conductivity and XRD analysis. The complexes are coloured and stable in air. Analytical data revealed that all the complexes exhibited 1:2 (metal:ligand) ratio with coordination number 4 or 6. FAB‐mass and thermal data show degradation pattern of the complexes. The thermal behavior of metal complexes shows that the hydrated complexes loses water molecules of hydration in the first step; followed by decomposition of ligand molecules in the subsequent steps. The crystal system, lattice parameter, unit cell volume and number of molecules in unit cell in the lattice of complexes have been determined by XRD analysis. XRD patterns indicate crystalline nature for the complexes. The solid state electrical conductivity of the metal complexes has also been measured. Solid state electrical conductivity studies reflect semiconducting nature of the complexes. The Schiff base and metal complexes show a good activity against the Gram‐positive bacteria; Staphylococcus aureus and Gram‐negative bacteria; Escherichia coli and fungi Aspergillus niger and Candida albicans.

Structural and vibrational characteristics of amphiphilic phosphonate salts

► We reported X-ray studies of NH 4 C 10 H 21 PO 3 H and enH 2 C 10 H 21 PO 3 ·1.5H 2 O. ► Strong hydrogen bonds generate the layered structures. ► The vibrational spectra of phosphonate salts are discussed. 1-Decylphosphonic acid ( 1 ), ammonium 1-decylphosphonate (NH 4 C 10 H 21 PO 3 H) ( 2 ), ethylenediaminium 1-decylphosphonate 1,5 hydrate (enH 2 C 10 H 21 PO 3 ·1.5H 2 O) ( 3 ) and calcium 1-decylphosphonate (Ca(C 10 H 21 PO 3 H) 2 ) ( 4 ) were prepared and characterized by IR and Raman spectroscopy. The structures of 2 and 3 were determined by single crystal X-ray diffraction analysis. Compound 2 crystallizes in the P 1 ¯ space group of triclinic system with two molecules in the asymmetric unit cell whereas compound 3 crystallizes in C 2/ c space group of monoclinic system with four molecules in the unit cell and both exhibit layered supramolecular structures generated by ionic interaction, H-bonding and alkyl chain interdigitation in the case of 3 . The FT-IR and Raman spectra have been assigned in the range 4000–500 cm −1 for all compounds, and reveal the trans conformation of alkane chain in all compounds.

Accurate Molecular Crystal Lattice Energies from a Fragment QM/MM Approach with On-the-Fly Ab Initio Force Field Parametrization.

We combine quantum and classical mechanics in a fragment-based many-body interaction model to predict organic molecular crystal lattice energies. Individual molecules in the central unit cell and their short-range pairwise interactions are modeled quantum mechanically, while long-range pairwise and many-body interactions are approximated classically. The classical contributions are evaluated using an accurate ab initio force field that is constructed on-the-fly from quantum mechanical calculations on the individual molecules in the unit cell. The force field parameters include ab initio distributed multipole moments, distributed polarizabilities, and isotropic two- and three-body atomic dispersion coefficients. This QM/MM fragment model reproduces full periodic MP2 lattice energies to within a couple kJ/mol at substantially reduced cost. When high-level electronic structure methods are coupled with the ab initio force field, molecular crystal lattice energies are predicted to within 2 kJ/mol of their experimental values for six of the seven crystals examined here. Finally, Axilrod-Teller-Muto three-body dispersion energy plays a nontrivial role in several of the molecular crystals studied here.

Self-Assembly of Two Isomorphous Thiocyanate Complexes of Co(II) and Ni(II) with 3-Hydroxypicolinamide

The synthesis, thermal and spectral characterization, and crystal structure of isomorphous thiocyanate cobalt(II) and nickel(II) complexes with 3-hydroxypicolinamide (3-OHpia), [M(C6H6N2O2)2(NCS)2]·2H2O, are reported. The metal(II) ions are chelated by two cis-oriented 3-OHpia and two thiocyanate ligands in distorted octahedral geometry. The distortion within the coordination sphere is mainly imposed by formation of the chelate rings. The compounds crystallize in monoclinic space group P2/c with two symmetrically independent molecules and a = 14.4945(2) A, b = 8.5906(1) A, c = 16.3865(3) A, β = 105.987(2)°, Z = 4 (1) and a = 14.4927(5) A, b = 8.5912(3) A, c = 16.2712(6) A, β = 105.740(4)°, Z = 4 (2). Commonly observed supramolecular amide synthons are not robust enough to accommodate thiocyanate ions and H2O molecules. But instead, neutral complexes are linked through hydrogen bonds leading to two different hydrogen bonding ribbon motifs involving amide moieties and H2O molecules [C(8)R 2 2 (12) along c axis] and amide moieties and thiocyanate ions [C(8)R 2 2 (16) along b axis] for symmetrically related molecules labelled as 1 [Co1 (1) and Ni1 (2)] and 2 [Co2 (1) and Ni2 (2)], respectively. Isomorphous cobalt(II) and nickel(II) complexes with 3-hydroxypicolinamide [Co(NCS)2(3-OHpia)2] and [Ni(NCS)2(3-OHpia)2], crystallize with two symmetrically independent molecules in unit cell. The amide–amide interactions are not robust enough to accommodate usually disruptive thiocyanate ions and H2O molecule, but instead two different hydrogen bonding ribbon motifs involving amide groups are found, C(8)R 2 2 (12) and C(8)R 2 2 (16).

Structural study on few co-crystals and a salt of quinoline derivatives having amide bond

The N-[2-(4-Methoxy-phenyl)-ethyl]-2-(quinolin-8-yloxy)-acetamide forms 1:1 co-crystals with aromatic diols namely 1,4-dihydroxybenzene, 1,5-dihydroxynaphthalene. In the later case co-crystal is formed in hydrated form. The hydrated form of co-crystal with 1,5-naphthalenediol has two symmetry independent host molecules in its unit cell, whereas such phenomenon in the co-crystal 1,4-dihydroxybenzene is not observed. The crystal structure of perchloric acid salt of (Quinolin-8-ylamino)-acetic acid is determined and this salt also shows two symmetry independent parent molecules in unit cell.

X-ray diffuse scattering from protein crystals caused by the lattice defects

Introduction Recent high resolution (better than 1A) X-ray protein crystallographic analysis requires high quality protein crystals. High quality crystals in turn produce a highresolution diffraction data set. In protein crystallography the quality of the crystal is usually defined as follows: an often-used alternative criterion is whether the crystal produces a high resolution Bragg reflection data set or not. One possible explanation of the quality of protein crystals is whether the protein molecules are orientationally ordered within the unit cell. In that case, the overall B-factor obtained by the Wilson plot technique [1] becomes a good measure of the quality of the protein crystals. As a matter of the fact, we have already made such a proposal and we have proved that the overall B-factors obtained from Wilson plots correlate much better with the quality of the crystals experimentally [1]. In other words, the quality of the protein crystals is discussed by the degree of the disorder of the protein molecules in the unit cell. Generally in X-ray diffraction phenomena it is well known that the disorder of molecules in unit cells provides diffuse scattering under a Bragg reflection profile. In the past such a diffuse scattering from a protein crystal has been often observed and this phenomenon has been discussed from the view point of molecular dynamics. We do not deny that one part of the diffuse scattering is the contribution of molecular dynamics, but we think that the main part is one of the disorder of molecules, incompleteness of crystals. The diffraction pattern on the imaging plate observed at 77K shows very distinctive diffuse scattering under Bragg reflections, which do not depend on temperature. We tried to measure the accurate profile of diffuse scattering in order to analyze the relation between the crystal quality and the molecular disorder.