Crystal Structure of the Radical-Cation Salt (<Emphasis Type="Italic">o</Emphasis>-Me<Subscript>2</Subscript>TTF)I<Subscript>3</Subscript> with Close Intermolecular Sulfur Contacts

Abstract  The synthesis and crystal structure of the organic radical-cation salt (o-Me₂TTF)I₃ is described. The salt crystallizes in the monoclinic space group P2 ₁ /n with a = 10.927(2) ?, b = 11.904(2) ?, c = 12.660(2) ?, β = 115.174(5)°. The bond length of the central C=C bond in o-Me₂TTF is 1.401(1) ?, indicating an approximate oxidation state of +1 for the o-Me₂TTF radical cation. Graphical Abstract  The X-ray crystallographic structure of the radical cation salt (o-Me₂TTF)I₃ has been determined and its structural properties and synthetic preparation are discussed.      

Crystal Structure of a Non-Conductive Non-Stoichiometric Tetrathiafulvalenium Salt: (TTF)3(BF4)2

Abstract

(TTF)₃(BF₄)₂ crystallizes in the triclinic system, space group P1, a = 8.017(3), b = 8.601(1), c = 11.635(2) Å, α = 108.79(1), β = 100.96(2), γ = 99.09(2)°, Z = 1. The TTF entities are stacked in parallel columns arranged into parallel layers alternating with layers of BF₄ ^? anions. A TTF stack is constituted of (TTF⁺)₂ diads interspersed with TTF° monads; the TTF⁺-TTF⁺ overlap is of the ring-over-ring type while the TTF⁺-TTF⁺ overlap is of the bond-over-ring type. These features explain the low conductivity ([sgrave]_powdcr = 2 × 10^?5 Ω^?l cm^?1) of this apparently non-stoichiometric TTF salt.     

Liquid Crystalline Phases in 4-Acetyl-4′-n-Alkanoyloxy-Azobenzenes

Abstract

The preparation and melting behaviour of the homologous series of 4-acetyl-4′-n-alkanoylox-azobenzenes, CH₃-CO-C₆H₄-N?N-C₆H₄-O-CO-(CH₂) _n -CH₃, (with n ranging from zero to 16) is reported. The melting behaviour has been investigated by means of thermal microscopy and differential scanning calorimetry. The experimental results indicate for almost all the compounds the presence of solid state polymorphism and a type A smectic; for one compound a type B smectic phase is also present. Some homologs present, in addition, a nematic phase.     

Synthesis of Dysprosium Oxychloride (DyOCl)

Dysprosium oxychloride, DyOCl, was synthesized using a simple hydrolysis method with DyCl₃·6H₂O. X-ray powder diffraction (XRD) data was used to determine the crystal structure. The DyOCl compound is isostructural to the matlockite (PbFCl) crystal structure and crystallizes in the tetragonal P4/nmm (#129) space group. The crystal structure contains the alternating cationic layers of (DyO)_n and anionic layers of nCl^? along the c-axis. The structural data including unit cell, volume, and density of DyOCl were compared to other rare-earth oxychloride data from the Inorganic Crystal Structure Database (ICSD) and our previous study on TbOCl. Fourier-transform infrared spectroscopy was performed on DyOCl and peaks observed at 543 and 744 cm^?1 were attributed to Dy–O and Dy–Cl. Scanning electron microscopy analysis showed irregularly shaped crystals. Hot-stage XRD, thermogravimetry, as well as differential scanning calorimetry coupled to a gas chromatograph and a mass spectrometer (evolved gas analysis) were performed on DyCl₃·6H₂O to understand the phase transformation to DyOCl (and Dy₂O₃) as a function of temperature and time at temperature.

Graphic Abstract

DyOCl compound with the tetragonal P4/nmm space group is composed of the alternating layers of (DyO)_n and nCl^? along the c-axis.

     

Molecular and Crystal Structures of Some Fluorocymantrenes

The crystal and molecular structures of the fluorocymantrenes [(C₅H₄F)Mn(CO)₃] and [(C₅H_5?nF_n)Mn (CO)₂(PPh₃)] (n?=?1–3) have been studied. The influence of the phosphine for carbonyl substitution on the bond parameters is larger than the influence of the increasing fluorine content. In most cases the Mn?→?P vector is in a transoid position relative to the fluorine substituents, and therefore the conformational parameters of the PPh₃ propeller are in these cases very similar. The crystal structures show many intermolecular C–H?O hydrogen bonds and only very few C–H?F hydrogen bonds.

Graphic Abstract

The influence of the phosphine for carbonyl substitution on the bond parameters of the fluorocymantrenes [(C₅H₄F)Mn(CO)₃] and [(C₅H_5?nF_n)Mn (CO)₂(PPh₃)] (n?=?1–3) is larger than the influence of the increasing fluorine content.

     

Transitions de Phase en Series Mesogenes:

The polymorphism of the di(4-alkylphenyl) and di(4-alkoxyphenyl) tetrathiafulvalene (TTF) is investigated by optical, crystallographic and calorimetric methods. All the studied derivatives are mesomorphic. The first mesophase is always a smectic G phase; the second one is a nematic N phase for short chains and a smectic C phase for long chains.

The entropies corresponding to the passage high-temperature crystalline phase C₁ → S_G and to the “melting” (C₁ → mesophases → isotropic phase I) increase with the length of the chain and with the presence of the oxygen atom in the radical.     

The Crystal and Molecular Structure of 4'-Cyanophenyl-4-n-Pentylbenzoate

The crystal and molecular structure of the title compound with the formula C₅H¹¹—C₆H₄—COO—C₆H₄—CN (CPPB) has been determined by X-ray diffraction methods. CPPB crystallizes in the monoclinic space group P2₁/n with eight molecules in a unit cell of dimensions a = 15.268(2) Å, b = 9.165(1) Å, c = 24.031(3) Å, β = 94.67(1)°. The structure has been solved by direct methods and refined to an R value of 0.070.

The CPPB molecules adopt a stretched form and are packed in an approximate parallel imbricated mode, the molecular long axes making an angle of about 5° with the crystal c axis. The molecular geometry and packing are discussed in relation to the mesomorphic behavior of CPPB.     

Synthesis and Crystal Structure of Charge-Transfer Salt (TTF)[Pt(mnt)2]

Abstract  

The synthesis and crystal structure of the title organic charge-transfer salt (TTF)[Pt(mnt)₂] (TTF = tetrathiafulvalene; mnt = cis-3,4-dimercapto-2-butenedinitrile) is described. The salt crystallizes in the P-1 space group with a = 7.9174(13) ?, b = 11.1583(18) ?, c = 11.2600(18) ?, α = 107.490(3)°, β = 91.631(3)°, and γ = 94.980(3)°. The stoichiometry between TTF and [Pt(mnt)₂] is 1:1. The structure of (TTF)[Pt(mnt)₂] consists of alternating stacks of dimerised TTF⁺ cations and dimerised [Pt(mnt)₂]⁻ anions, linked together by many kinds of short contacts and hydrogen bonds. Both the dimerised TTF⁺ cations and dimerised [Pt(mnt)₂]⁻ anions are arranged in a parallel face-to-face mode.     

Calorimetric Study of Crystalline and Liquid-Crystalline Polymorphism in the Homologues of Terephthal-bis-n-alkylaniline

The phase sequences of the homologues with n (the number of carbon atoms in the terminal alkyl chains) from 2 to 8 are obtained. At low temperatures, i) several crystalline modifications are found in each of the members with n = 4, 5, and 6 and ii) the monotropic transitions between crystal and smectic phase are observed in almost all the members. At intermediate temperature, iii) between the smectic H and C phases, the smectic F phase is found in the homologues with n ≥ = 5 by morphological observation or by a rheological method. The constancy of the temperature of the S_H(or S_F) – S_c transition with respect to “and broadening of the temperature range of S_H with increasing n in the expense of nematic phase are worthy of note. The even-odd effect of the end chain length n is observed very distinctively on the crystal melting and clearing point. Proton NMR measurement reveals a large mobility in the terminal alkyl chains in the crystal of the member with n = 6.     

Growth of Nd:Sr3Ga2Ge4O14 crystals by a modified Bridgman method

Bridgman growth of Nd:SGG (Sr₃Ga₂Ge₄O₁₄) crystals has been investigated for the first time. Pt crucible of ∅︁25mm×250mm with a seed well of ∅︁10mm×80 mm is used, and seed is SGG crystal of ∅︁10mm×50mm grown by Bridgman method in advance. The growth parameters are optimized as the furnace temperature is set to 1450∼1500°C, temperature gradient in the crystal‐melt interface is less than 25 K/cm and growth rate is less than 0.5mm/h. The Nd:SGG crystals with 25mm in diameter and 60mm in length are grown successfully from 1.5 to 8at% Nd³⁺ doped stoichiometric Sr₃Ga₂Ge₄O₁₄ melt. The distribution coefficient and concentration of Nd³⁺ in Nd:SGG crystals are obviously higher than those of Nd:YAG crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural Studies of the 1:1 Complex of <Emphasis Type="Italic">o</Emphasis>-3,4-Dimethyltetrathiafulvalene (<Emphasis Type="Italic">o</Emphasis>-Me<Subscript>2</Subscript>TTF) and 1,2,4,5-Tetracyanobenzene (TCNB)

Abstract  

The synthesis and crystal structure of the 1:1 complex o-Me₂TTF-TCNB is reported. The complex crystallizes in the triclinic space group P-1 with a = 6.920(1) ?, b = 7.928(2) ?, c = 17.453(4) ?, α = 100.53(3)°, β = 99.66(3)°, and γ = 97.32(3)°. The bond length of the central C=C bond in o-Me₂TTF is 1.342(2) ?, indicating a neutral state for the o-Me₂TTF donor.     

Growth and Characterization of Na2CaGe6O14 Single Crystals

Transparent, crack-free Na₂CaGe₆O₁₄ (NCG) single crystals were successfully grown using the Czcchralski technique. The largest crystal had 30 mm in total length and 18 mm in maximal diameter. Best crystal quality was achieved under low temperature gradient arrangement. The crystal structure of NCG has been refined from single crystal X-ray diffraction data. Some piezoelectric properties of NCG are reported.     

Atomic force microscopy studies on surface morphologies of CdHg(SCN)4 crystals grown in solutions containing excessive amount of Cd(II) cations

Surface morphologies of CdHg(SCN)₄ (CMTC) crystals grown from solutions with excessive amount of Cd(II) cations (5%, 20% and 50% in molar ratio) have been investigated by atomic force microscopy (AFM). [Cd(SCN)_n]^2‐n (n ≤ 4) complex anions formed by addition of excessive Cd(II) cations in the solutions have been found to act either as growth units or impurities during CMTC crystal growth. On the prismatic faces, incorporation of [Cd(SCN)_n]^2‐n (n ≤ 4) complex anions as growth units leads to the formation of well‐oriented protuberance trains at the step fronts, named as “locally anisotropic crystal growth”. These protuberances become fewer, less distinct and nearly disappeared with the increase of excessive Cd(II) cations in the solutions. The pyramidal face, however, varies from regular 2D nucleation growth at a low concentration of Cd(II) to much rougher growth surfaces at high concentrations, exhibiting typical surface morphologies where crystal growth is completely inhibited by impurities. Observations in this experiment provide a new picture of crystal growth.     

Measurement of the An isotropic Refractive Indices of Polybenzylglutamate Liquid Crystals. Molecular Factors and Dispersion

The ordinary and extraordinary refractive indices have been measured for lyotropic liquid crystal solutions of poly-γ-benzyl-L-glutamate. The onset of the liquid crystal formation is noted as an abrupt jump in the sample birefringence in the biphasic region. The concentration dependence is otherwise unremarkable. The polymer is found to add a small, anisotropic increment to the refractivity of the supporting solvent. Both n _o and n _e can thus be measured in an ordinary Abbé refractometer for the low refractive solvents common to these liquid crystal solutions. The optical birefringence does not depend significantly on polymer molecular weight. Data is also included for the wavelength dependence (dispersion) of n _o, n _e, and Δn.     

Crystal structures of gold,silver, and sodium chalcogenides: Sphenoidal interpretation

The crystal structures of 13 chalcogenides of Na, Au(I), and Ag(I) in the Na_{2 − n} (Au,Ag) _n (S,Se,Te) series, where 0 ≤ n ≤ 2, are interpreted from unified positions based on the sphenoidal representation. Its essence is in the consideration of the entire crystal space (with packing X atoms in the framework of close-packing, body-centered, or hybrid schemes) as a set of elementary space units (sphenoids). Unified one-dimensional associates of sphenoids, the so-called basic rods, with sets of possible atomic positions in them are selected for all structures. The mutual effect of the dimensional and stoichiometric ratios of all components on the features of filling rod positions is analyzed. New possibilities in the crystallochemical and crystal-geometry analysis of inorganic compounds whose structures are characterized by a relatively uniform distribution of atoms are demonstrated by the example of chalcogenides.     

Molecular and crystal structure of 4-alkoxybenzoic acids: Design of the mesogenic phase

The crystal and molecular structures of 4-alkoxybenzoic acids C _n H_{2n + 1}-O-C₆H₄-COOH, n = 4–12, which are nematic (n = 4–6) or smectic-nematic (n = 7–12) mesogenes, are studied. No direct relationship between the molecular geometry and mesogenic properties is found. All the crystal structures contain dimers formed by pairs of O…H-O hydrogen bonds between carboxyl groups. Crystals belonging to the group of smectic-nematic liquid crystals (SNLC) are built of separate regions, namely, loosely packed aliphatic regions and closely packed aromatic regions with significant π-stacking interactions. Loose aliphatic regions occur in crystals belonging to the group of nematic liquid crystals (NLC); however, they are surrounded by dense aromatic regions and do not run throughout the crystal. In NLC, π-stacking interactions are far weaker than in SNLC. At the early stage of melting of SNLC crystals, structurized associates due to both π-stacking interactions and hydrogen bonds are retained in the melt (smectic phase), whereas, upon further heating, only hydrogen-bonded associates are left (nematic phase). In the course of melting of NLC, only hydrogen-bonded dimers are retained in the melt (nematic phase).     

Specific structural features of copper(II) complexonates with nitrilotriacetate anions: A review

The specific structural features of copper(II) complexes with nitrilotriacetate anions (H_n Nta, n = 0?2) are considered with due regard for the original results and data available in the literature. The structural features and the degree of distortion of copper coordination polyhedra (such as a (4 + 1) elongated square pyramid, a trigonal bipyramid, a (4 + 2) symmetric elongated tetragonal bipyramid, and a (4 + 1 + 1) asymmetric elongated tetragonal bipyramid) are discussed. Criteria for identification of five-vertex copper(II) polyhedra of the general formula Cu(H_n Nta)X (n = 0?2; X = Cl, Br, N, O) are proposed for the cases of a distorted square pyramid, a distorted trigonal bipyramid, and a polyhedron intermediate between them. The modes of coordination of H_n Nta ^{3 ? n} ligands with a mctal arc described in terms of crystal chemical formulas.     

Mesophase design: II. Molecular structure and crystal packing of 4-alkyloxycyanobiphenyls

A joint analysis of the molecular geometry and crystal packings of the members of a homologous series of 4-alkyloxycyanobiphenyl C _n H_{2n + 1}-O-C₆H₄-C₆H₄-CN with n = 5–12 does not reveal a direct relationship between the molecular geometry and mesogenic properties of these compounds. The crystal packings of all of them are built from alternating loose aliphatic and dense aromatic regions. The closely packed aromatic regions of crystals exhibit weak intermolecular directed interactions of different natures which are responsible for the occurrence of the mesophase. The type of mesophase depends on the number s of structure-forming elements, the ratio of their energies (if s > 1), and the melting temperature of the compound. A graph system is used to describe the crystal packings and the mesophase. It is shown that, although the mesophase graph is similar to the crystal graph, they may differ somewhat, because some symmetric limitations (for example, lattice) on the molecular associate structure are removed in the melt.     

Physical Property of New Liquid Crystal Materials and Mixture Design for Active Matrix LCD

Abstract

We studied the physical properties of three series of new fluorinated liquid crystal components and prepared some mixtures by using these components. Decahydronaphthalenes have low Δn with relatively high T _NI. Naphthalenes and Tetrahydronaphthalenes have large Δ? and variety range of Δn (0.08–0.21). Moreover, we have revealed that the fluoro- substituent at C-1 position for the naphthalene and the tetrahydronaphthalene ring has effects to increase T _NI and to reduce γ₁ with good solubility. Then, we have designed some LC mixtures for AM-LCD having good performance with 4V-driving, quick response, high birefringence, low birefringence, wide temperature range and low driving voltage.     

Polymorphic–polytypic transition induced in crystals by interaction of spirals and 2D growth mechanisms

The relationship between crystal polymorphism and polytypism can be revealed by surface patterns through the interlacing of the growth spirals. Simple high-symmetry structures as SiC, ZnS, CdI2 and more complex low-symmetry layered structures as n-paraffins, n-alcohols and micas are concerned with polymorphic–polytypic transition. In this paper, we will show for the first time, through in situ AFM observations and X-ray diffractometry, that a protein polymorph (P2₁2₁2₁α-amylase) locally changes, during growth, to a monoclinic P2₁ polytype, thanks to the screw dislocation activity. The interplay between spiral steps and 2D nuclei of the polytypes coexisting in the same crystalline individual allows to foresee the consequences on the crystal quality. The discussion is extended to other mineral and biological molecules and a new general rule is proposed to explain the interactions between surface patterns and the bulk crystal structure.