Crystal structure of Zn[Cl2Ti(C5H5)2]2·2C6H6

The structure of crystals of the composition Zn[Cl₂Ti(C₅H₅)₂]₂·2C₆H₆ has been determined from Patterson and Fourier syntheses of two projections, and refined toR = 0·117 by full-matrix three-dimensional least-squares methods. The crystals are orthorhombic:Pbcn,a = 18·45(5),b = 15·40(6),c = 11·35(3) Å,Z= 4. The complex consists of a central distorted ZnCl ₄ ^2– tetrahedron linked along the Cl—Cl edges to two distorted TiCl₂(C₅H₅)₂ ⁺ tetrahedra in such a way that their centres are nearly collinear The two C₆H₆ molecules in the formulae unit may be regarded as benzene of crystallization.     

Growth and characterization of Mn2+ doped calcium l‐tartrate crystals

Single crystals of Mn²⁺ doped calcium levo‐ tartrate tetrahydrate (CLTT) were grown by single diffusion gel growth technique in silica hydro‐gel media. The doping of Mn²⁺ was varied by mixing 0.001M, 0.005M, 0.01M, 0.05M, and 0.1M solutions of MnCl₂ with 1M CaCl₂ solution in equal volumes in the supernatant solutions. The actual amount of Mn²⁺ doping in CLTT crystals was estimated by ICP (Inductively Coupled Plasma) technique. The powder XRD of the samples suggested no significant change in the unit cell dimensions and the presence of any extra phase. The FT‐IR spectra indicated the presence of water molecule, O‐H bond, C‐O bond and carbonyl C=O bond. The EPR spectra confirmed the presence of Mn²⁺ ions in the crystals. The variation of the dielectric constant with temperature confirmed the earlier results of pure calcium tartrate crystals and indicated the ferroelectric nature of the doped crystals. As the amount of doping of Mn²⁺ increased the value of dielectric constant increased. The results are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth and characterization of Au3+ ion irradiated 2-amino-5-nitropyridinium hydrogen oxalate (2A5NPHO)

2-amino-5-nitropyridinium hydrogen oxalate (2A5NPHO) was grown using slow evaporation and bulk crystal of 2A5NPHO was harvested from Assembled Temperature Reduction (ATR) method. Cut and polished crystal was irradiated using Au³⁺ ion with various fluences. Electronic loss, nuclear energy loss and penetration depth were calculated using SRIM software. It was observed in X- ray pattern that intensity of peak was reduced. Intensity of peak decreased with increase of ion fluencies from 10¹³ ions/cm² to 10¹⁴ ions/cm². Optical properties were measured using UV-Vis spectrometer. The increase of absorption was due to excited electrons which were formed by vacancies and formation of additional defects centres. Energy band gap of irradiated crystals increased with increase of ion fluence. Energy band gap of irradiated crystals were 3.39 eV, 3.42 eV, and 3.4 eV for 10¹³ ions/cm², 5 × 10¹³ ions/cm² and 10¹⁴ ions/cm² respectively and increase of band gap was due to the increase of forbidden gap. Microhardness was calculated using Vicker's Hardness tester. Increase of microhardness in irradiation crystal was due to increase of high density lattice defects produced by Au³⁺ of 10.8 MeV. Electrical property was calculated using dielectric constant. Increase of dielectric constant was due to large polarization which caused by disorderness and rich defects in the crystalline surface. Decrease of intensity peak in fluorescence was due to transition of excited electron to intermediated energy levels from excited state which converted into vibrational energy of lattice atoms (phonon). Morphology of irradiated crystal was seen using scanning electron microscope (SEM). It was observed from the SEM image that surface of crystal was heavily damaged. It was also noticed that the thermal stability of the irradiated single crystal increased with increase of ion fluences. Impedance of irradiated crystal was measured. The bulk resistance and grain boundary resistance also were calculated.     

Crystal structure of vanadocene (η5-C5H5)2V

The crystal structure of vanadocene has been determined from counter data, and refined by full-matrix least-squares techniques. The crystals belong to the monoclinic space groupP2₁/n witha = 9.269(3),b = 8.020(3),c = 5.892(2) Å, = 91.21(3)°, andD _x = 1.37 gcm^-3 for Z = 2. The finalR value for 583 observed reflections is 0.031. The vanadium atom resides on a crystallographic center of inversion. The cyclopentadienyl groups are statistically disordered 70–30%. The average vanadium-carbon (⁵) bond distance is 2.26(2) Å.     

Growth and Characterisation of Gel-grown Lead(II)Chloride and Lead(II)Bromide Single Crystals

Single crystals of pure and doped lead(II)chloride and lead(II)bromide were grown by gel technique employing a modified two-stage chemical reaction. Methods to minimise the predomination of needle morphology during the growth of these crystals have been investigated and the results are discussed. The grown crystals were characterised by optical transmission spectrum. Undoped and monovalent cation (K⁺, Na⁺, Cu⁺, Ag⁺ and Hg⁺) doped crystals of PbCl₂ and PbBr₂ were subjected to d.c. electrical conductivity studies. Using the log σT versus T⁻¹ plot, the activation energies for the migration of anion vacancies in lead(II)halides are calculated. They are found to be less for the doped crystals than those of undoped ones.     

Growth and characterization of 2-amino-5-chlorobenzophenone (2A-5CB) single crystals

Organic nonlinear optical single crystals of 2-amino-5-chlorobenzophenone (2A-5CB) were grown in ethanol by slow solvent evaporation technique. The grown crystals were characterized by single-crystal XRD, FTIR, FT-Raman and UV–vis–NIR techniques. The UV–vis–NIR spectrum ascertains the cut-off wavelength of the sample as 390 nm. The powder second harmonic generation (SHG) technique reveals that 2A-5CB crystal has its SHG efficiency nearly three times that of KDP. The dielectric response of the sample was studied in the frequency region of 50 Hz–1 MHz at varying temperatures. The photoconductivity studies indicate that the 2A-5CB crystal exhibits negative photoconductivity. TGA–DTA studies confirm the melting point of the sample as 101.5 °C.     

Growth,Morphology, Structure and Properties of Na3BaCl5 2H2O Crystals

Single crystals of Na₃BaCl₅ 2H₂O were obtained from saturated aqueous solutions at two different temperatures (27° C and 32° C). The crystal size increases with increasing temperature. The crystals obtained were subjected to a systematic morphological, X-ray and thermal analyses. The study of as-grown crystal morphology and surface morphology of Na₃BaCl₅ 2H₂O crystals clearly indicate the requirement of a slow rate of evaporation at temperatures 27 to 28° C, moderate supersaturation in order to obtain high quality single crystals of Na₃BaCl₅ 2H₂O. The X-ray diffraction studies give the following cell parameters for the title compound: monoclinic, P21/n, a = 8.5773(9), b = 9.5502(4), c = 5.2873(3) A, β =92.069°, V = 432.8 A³, Z = 2. The study of TGA curves indicate the occurrence of dehydration process at around 200° C and not the decomposition of the compound. Similarly, the low temperature DSC study indicates a thermal anomaly at 267 K, and the high temperature DSC study (323 K to 873 K) indicates the transition from dihydrate to monohydrate and in turn anhydrous state at 454.6 K for Na₃BaCl₅ 2H₂O crystals. Thus both the TGA and DSC curves conclude that the Na₃BaCl₅ 2H₂O crystals contain two molecules of water of crystallization and its molecular formula is Na₃BaCl₅ 2H₂O.     

Crystal growth and magnetic properties of the copper coordination polymer [Cu(µ ‐C2O4)(4‐aminopyridine)2(H2O)]n

In this paper, we consider various ways of crystal growth of the polymer [Cu(µ ‐C₂O₄)(4‐aminopyridine)₂(H₂O)]_n. Single crystals of the size of 1.5×1.5×0.2 mm³ have been grown by a slow diffusion technique from solutions of the monoammine copper complex and of the mixture of potassium oxalate and aminopyridine with the stoichiometric ratio. Magnetic susceptibility and ESR measurements have been performed on single crystals large enough for investigating anisotropic properties. The susceptibility can be well described within the model of a Heisenberg antiferromagnetic spin chain. The magnetic measurements reveal a small concentration of paramagnetic moments reflecting the high quality of the single crystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of organic impurities on the surface morphology and growth mechanism of KBP crystals (C8H5O4K)

The surface morphology of the (010) face of potassium biphthalate (KBP) crystals grown from aqueous solutions under the supersaturation ranging within 0.029–0.04 has been studied by the methods of optical and electron microscopies. It was revealed that the (010) surface has polygonal growth macrohills of the dislocation nature, small hillocks developing by the mechanism of successive two-dimensional nucleation, and numerous two-dimensional nuclei. The density of small hillocks (10⁴–10⁵ cm^?2) exceeds the dislocation density in KBP crystals by one to two orders of magnitude. It is shown that at low supersaturations, the (010) face grows simultaneously by the dislocation mechanism and the mechanism of successive two-dimensional nucleation. It is also established that the tangential velocity of growth-step motion on the (010) face increases in the presence of organic impurities. This effect can be used as one of the factors increasing the growth rates of crystal faces at low impurity concentrations (the so-called catalytic effect of impurities).     

Crystal structures of 5-Bromo-2-hydroxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde,and 2-hydroxynaphthalene-1-carbaldehyde 4-(2-pyridyl) thiosemicarbazones

5-Bromo-2-hydroxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, and 2-hydroxynaphthalene-1-carbaldehyde 4-(2-pyridyl) thiosemicarbazones (I–III, respectively) were synthesized and their crystal structures were determined by X-ray diffraction. All these molecules are almost planar. The presence of bulky substituents at the terminal nitrogen atoms of these molecules does not lead to changes in the conformation of the thiosemicarbazide moiety. Depending on the nature of substituents in the phenol rings, the crystals are composed of either centrosymmetric dimers (I) or infinite chains (II and III). In the concentration range of 10^?5–10^?7 mol/L, thiosemicarbazones I–III selectively inhibit the growth of human myeloid leukemia HL60 cells.     

Hydrothermal synthesis and characterization of (N(C2H5)4)4[VMo12V2O44]

The hydrothermal reaction of a mixture of Na₂MoO₄·2H₂O, V₂O₅, pyromellitic acid (1,2,4,5‐C₆H₂(COOH)₄), (C₂H₅)₄NCl and 0,1 M H₂SO₄ for 88 h at 180°C gives blue needle‐like crystals of [V^IV₂O₂(H₂O)₂ (C₆H₂(COO)₄)] in 20% yield (based on V) and dark blue prismatic crystals of the title compound, mixed‐valance (N(C₂H₅)₄)₄[VMo₁₂V₂O₄₄], 1, in 12% yield (based on Mo). 1 was investigated by means of elemental analysis, thermogravimetry, Fourier Transform Infrared Spectroscopy and Single Crystal X‐ray Diffraction Methods. Crystal data for the compound: monoclinic space group P2₁/c (No:14), a=13.7815(12) b=13.0271(9) c= 21.189(2) Å, β= 113.909(7)°, Z=2. Although [XM₁₄O₄₂]^‐n (X=P, Si, Ge, V and M=Mo and/or V) cores have been previously determined, this is the first time that [VMo₁₂V₂O₄₄]^‐4 core is synthesized and characterized. The structural difference between 1 and these HPOMs is the coordinational geometry of the central metal atoms. The central vanadium in 1 has an octahedral coordination geometry, whereas in literature, the central V, P, Si and Ge atoms in [V₁₅O₄₂]^‐9 / [SiM₈V₆O₄₂]^‐4 / [PM₈V₆O₄₂]^‐5 / [GeM₈V₆O₄₂]^‐4 have tetrahedral coordinational geometry. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electrical Conductivity of Phenoxazine-Iodine (2:3) and Phenothiazine-Iodine (2:3) Crystals

Abstract

Single crystals of phenoxazine-iodine (2 : 3) and phenothiazine-iodine (2 : 3) salts are found to be highly conducting ([sgrave] _R.T. = 5–20 ohm^?1 cm^?1). The observed deviation from the exponential temperature dependence of the conductivities is ascribed to the degenerate semiconducting phases or alternatively to the metallic phases with impurities. However, phenoxazine-iodine and phenothiazine-iodine are perfect semiconductors below 220° K with activation energies of 0.12 eV and 0.14 eV, respectively. The absorption features related with (phenoxazine)⁺ ₂ and (phenothiazine); cations are observed in the infrared spectra of the salts.     

Morphological effects in liquid phase epitaxy (The C8H5O4K-C8H5O4Rb-H2O system)

The results of the complex study of the morphology and defect state of the crystals of the isomorphous potassium acid phthalate-rubidium acid phthalate (KAP-RbAP) series formed in aqueous solutions are presented. The crystals are characterized by heteroepitaxial porous and solid textures formed as a result of the exchange reaction between the crystals and solution. The interaction of the KAP and RbAP crystals with saturated RbAP and KAP aqueous solutions is studied both in situ and in vitro under optical and atomic force microscopes. The results obtained are used to create a theoretical model of formation of characteristic morphological textures in liquid phase epitaxy, including their formation from the aqueous solutions of the respective salts.     

Synthesis and structure of (η5-C5H5)2Hf(η1-NC4H4)2

The crystal structure of (⁵-C₅H₅)₂Hf(¹-NC₄H₄)₂ has been determined from X-ray data measured by counter methods. The title compound is isostructural with (⁵-C₅H₅)₂Zr(¹-NC₄H₄)₂, and crystallizes in the monoclinic space groupP2₁/c (C _2h ⁵ , No. 14) with unit cell constantsa=9.605(3),b=8.174(3),c=19.487(4) Å, =90.85(3)°, andZ=4 forD _c=1.91 gcm^–3. Full-matrix least-squares refinement gave a finalR value of 0.068 for 2154 independent observed reflections. The two cyclopentadienyl rings are ⁵-coordinated to the hafnium atom at an average Hf-C(⁵–) distance of 2.51(1) Å. The Hf-N-centroid (-pyrrolyl) angles average 166°.     

A Unique Example of a Co-crystal of [Co(AMTTO)2(H2O)2](NO3)2 and [Co(AMTTO)2(CH3CN)2](NO3)2 (AMTTO = 4-amino-5-methyl-1,2,4-triazol-3(2H)-thione)

A co-crystal of cobalt(II) complexes, Co(AMTTO)₂(CH₃CN)₂]²⁺(NO₃)₂. [Co(AMTTO)₂(H₂O)₂]²⁺(NO₃)₂, compound (1) was isolated from the reaction of Co(NO₃)₂?6H₂O and 4-amino-3-mercapto-6-methyl-5-oxo-1,2,4-triazine (AMTTO) in acetonitrile as solvent. Isolated crystals were characterized by elemental analyses, IR spectroscopy as well as X-ray diffraction studies. Crystal data for 1 at 95 K revealed a monoclinic space group P2₁/n, a?=?11.7903(5), b?=?12.1279(5), c?=?14.1443(6) Å, β?=?99.244(4)°, Z?=?2, R₁?=?0.0339. Compound 1 consists of two co-crystallized Co(II) complexes [Co(AMTTO)₂(CH₃CN)₂]²⁺ and [Co(AMTTO)₂(H₂O)₂]²⁺ and four nitrate counter anions In both complexes, cobalt(II) ions are in an octahedral arrangement. Two S, N bidentate AMTTO ligands are coordinated to both Co(II) ions. The coordination sphere of Co1 is completed by two acetonitrile molecules, and these positions are occupied by water molecules for Co2.

Graphic Abstract

A co-crystal of cobalt(II) compound was isolated from the reaction of Co(NO₃)₂?6H₂O and 4-amino-3-mercapto-6-methyl-5-oxo-1,2,4-triazine in acetonitrile as solvent.

     

Growth of (Perylene)2 [Pd(mnt)2] crystals

The conditions for the growth of (Perylene)₂ [Pd(mnt)₂] crystals either by chemical oxidation and electrochemical routes are described. The electrocrystallisation is limited by close proximity of the oxidation potentials of the perylene donor and [Pd(mnt)₂]^? anion, and depending on the experimental conditions different morphologies can be obtained. (Per)₂ [Pd(mnt)₂] crystals obtained by elecrocrystallisation were found to be mainly of the β-polymorph with properties comparable to the Cu, Ni and Pt analogues previously described at variance with those obtained by chemical oxidation which are mainly of the α-polymorph .     

Optical properties of non‐centrosymmetric mixed crystals K2(La1‐x Cex)(NO3)5 · 2 H2O (x = 0.0 – 1.0)

Large single crystals of optical quality of the non‐centrosymmetric orthorhombic potassium rare earth nitrate mixed crystals K₂(La_1–x Ce_x)(NO₃)₅ · 2 H₂O were grown at 38 °C from diluted HNO₃. For crystals with x = 0.0, 0.19, 0.38 and 0.66 refractive indices and their dispersion were determined with an error less than 1 · 10^–4 in the wavelength range 0.404 – 1.083 μm by the prism method. Phase matching conditions for collinear SHG frequency conversion were analysed in detail, including calculation of the effective nonlinear optical susceptibility. By an appropriate choice of the fraction x of cerium the mixed crystals K₂(La_1–x Ce_x)(NO₃)₅ · 2 H₂O allow an adjustment of non‐critical type I phase matching conditions to a desired wavelength of the fundamental wave within the range 1.055(4) – 1.107(6) μm. Non‐critical type II phase matching can be tuned in the wavelength range 0.949(2) – 0.931(2) μm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal Growth,Thermal and Linear Optical Properties of the Non‐Centrosymmetric Hydrated Tetraborates Na2[B4O5(OH)4] . 3H2O (Tincalconite) and K2[B4O5(OH)4] . 2H2O

Large single crystals of the non‐centrosymmetric hydrated tetraborates Na₂[B₄O₅(OH)₄] . 3H₂O (Tincalconite) (point group 32) and K₂[B₄O₅(OH)₄] . 2H₂O(point group 222) were grown from aqueous solutions and the linear optical properties (refractive indices between 365 nm and 1530 nm and unpolarized absorption spectra) as a basis for nonlinear optical investigations were determined. The uniaxial positive sodium salt is not phase matchable; in the orthorhombic potassium compound type I phase matching is possible in the near infrared region. Thermal investigations indicate a phase transition at ≈285 K for Na₂[B₄O₅(OH)₄] . 3H₂O.     

Tracing of dislocations in ammonium hydrogen tartrate single crystals

Sparingly soluble ammonium hydrogen tartrate (AHT) crystals are grown by the gel method, derived from the diffusion of ammonium chloride into the set gel containing tartaric acid. Crystals up to 23 × 5 × 3 mm³ in size are grown at room temperature. AHT crystals are cleaved along (010) planes and the cleavage surfaces are studied by using multiple beam interferometry. The interferograms have revealed that the cleavages are quite flat. An attempt is made to trace the trajectory of dislocations of isolated as well as matched pairs of (010) cleavages of AHT when etched in a mixture of formic acid and methyl alcohol (2:1) and 1.0 M SrCl₂ solutions. Optical and transmission electron micrographs of dislocations show oblique, parallel and continuous line characteristics. Rows of equally spaced dislocation pits are observed and the implications of this are discussed.     

Crystal and molecular structure of (η5-C5H5)Ta(η2-C2H4)Cl2(PMe2Ph)2, a sterically crowded molecule which exhibits a distorted η5-coordination mode of the cyclopentadienyl ligand

The X-ray structure determination of (⁵-C₅H₅)Ta(²-C₂H₄)Cl₂(PMe₂Ph)₂ has revealed that the compound crystallizes in the orthorhombic space groupFdd2 witha=21.098(9),b=29.848(9),c=7.694(3) Å, andD _c=1.70g cm^–3 forZ=8. Least-squares refinement based on 893 independent observed reflections resulted in a finalR value of 0.026. The molecule resides on a crystallographic two-fold axis, with disordered ethylene and cyclopentadienyl groups. The Ta-Cl and Ta-P separations are 2.473(4) and 2.649(3) Å, respectively. Since the two carbon atoms of the ethylene molecule are indistinguishable from two of the cyclopentadienyl carbon atoms, the Ta-C bond lengths are 2.37(1) and 2.39(2) Å for the ethylene and for two of the cyclopentadienyl carbon atoms. The other three Ta-C(cyclopentadienyl) distances are much longer: 2.54(3), 2.54(3), and 2.62(3) Å. In order to achieve 18e ^– at the tantalum atom, the cyclopentadienyl ligand must be viewed in an ⁵-bonding mode. The variation of the Ta-C lengths is thus considered to be steric in origin. The carbon atoms of the C⁵H ₅ ^– group are planar to 0.03 Å.