A New Organic Solid State Reaction: Hydrogenation of Phenols

During the past fifteen years there has been a number of detailed studies devoted to the chemistry of organic molecular solids and made by a number of groups involving chemists and crystallographers. These workers were interested in the reactions of the organic solids subjected either to a physical agent like light or heat or to a chemical one which can be a solid, a liquid or a gas.¹     

Solid-state conformational heterogeneity of the 2,2,5,5-tetramethyl-3,4-hexandione monohydrazone: X-ray diffraction and MAS NMR experiments

The X-ray diffraction study of the 2,2,5,5-tetramethyl-3,4-hexandione mono-hydrazone 1 shows a solid solution of two screwed conformers in the crystal. In each of these conformers, the conjugated C=O and C=N double bonds have an approximately perpendicular orientation with = 101.1°(2) and –93.4°(2), respectively. AM1 theoretical calculations give the same result for the isolated molecule. The calculated rotational barrier around the central single bond of the conjugated moiety is about 45.98 kJ mol^–1 which is higher than the classical values observed for 1,3 conjugated systems (28.42 kJ mol^–1 in the 1,3-butadiene). Variable temperature ¹³C CPMAS NMR experiments show hindered rotation around the COC(CH₃)₃ tert-butyl group in the solid state. 1 crystallizes in the triclinic space group P ₁ with a = 10.106(1)Å, b = 11.698(1)Å, c = 12.313(1)Å, = 62.108(1)° = 70.517(1)° = 66.052(1), V = 1157.0(3)ų, D _calc = 1.06 with Z = 4.     

Synthesis,Spectral and Structural Studies of a Novel Semicarbazone Synthesized from Quinoline-2-Carboxaldehyde and N<Superscript>4</Superscript>-Phenyl-3-Semicarbazide

Abstract  

A new semicarbazone, HL has been synthesized from quinoline-2-carboxaldehyde and N⁴-phenyl-3-semicarbazide and structurally and spectrochemically characterized. ¹H NMR, ¹³C NMR, IR and electronic spectra of the compound are studied. The existence of keto form in the solid state is supported by the crystal structure and IR data. The compound crystallizes into an orthorhombic space group P2₁2₁2₁. Intra and intermolecular hydrogen bonding interactions facilitates unit cell packing in the crystal lattice.     

A New Relation Between the Melting Points of Organic Solids and Their Reactivity

Abstract

A new relation between the melting points of organic solids and their reactivity has been established. The relation follows √? = - k log Mp + C where ? is the thickness of the colored boundary Mp is the melting point of the organic solid and k and C are constants.     

Investigation using13C and15N CP MAS NMR of potential solid state tautomerism of some indolinones

A¹³C and¹⁵N CP MAS NMR study is reported for seven molecules and the results are compared with those previously obtained from solution NMR. The close agreement between the two sets of results show that the tautomeric equilibria found in solution and the solid state are the same for the compounds investigated. In all cases formA is found to be essentially the only one present. An X-ray diffraction study is presented for a molecule which is a model for formA.     

Crystal structures and spectroscopic characterization of chiral and racemic 4‐phenyl‐1,3‐oxazolidin‐2‐one

Crystal structures of (R)‐ and (rac)‐4‐phenyl‐1,3‐oxazolidin‐2‐one (4‐POO) have been determined by X‐ray diffraction and characterized by the solid state ¹³C NMR and IR spectra. Molecular geometries and intermolecular interactions in (R)‐ and (rac)‐4‐POO crystals are very similar to each other; 4‐POO molecules are linked via the N‐H…O intermolecular hydrogen bonds to form the chained structure. Chemical shifts of the solid state ¹³C NMR spectra are very similar to each other, whereas the ¹H spin‐lattice relaxation times (T_1H) value for (R)‐4‐POO is five times as large as that for (rac)‐4‐POO, reflecting the more restricted mobility of the (R)‐4‐POO chain. Although both crystals contain an unique molecule in the asymmetric unit, a doublet feature is observed for the C=O stretching mode in the IR spectra of (R)‐ and (rac)‐4‐POO crystals. The frequency gap of the C=O bands are correlated with the strength of the dipole‐dipole interactions between the neighboring C=O groups. © 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Crystal growth,structure and spectroscopic studies of a novel organic single crystal: L‐lysine p‐nitrophenolate monohydrate (LLNP)

A novel organic crystal, L‐lysine p‐nitrophenolate monohydrate (LLNP) has been grown successfully from an aqueous solution by the slow cooling method. Transparent single crystal of dimensions 22 × 12 × 12 mm³ has been obtained. The single crystal X‐ray diffraction has shown that LLNP belongs to the orthorhombic crystallographic system with space group P2₁2₁2₁. The functional groups and vibrational frequencies of the crystal have been identified using IR and Raman spectra. The proton and carbon configurations have been confirmed through ¹H‐NMR and ¹³C‐NMR spectra analyses. The UV‐Vis‐NIR transmittance spectrum for LLNP crystal has been recorded in the range from 200 to 2500 nm. The second harmonic generation (SHG) intensity of LLNP has been measured by powder SHG method and found to be as 4.2 times as that of KDP. The thermal properties have been studied by using thermo gravimetric (TG) and differential thermal analysis (DTA).     

The molecular structure of 3(5)-methyl-4,5(3)-trimethylenepyrazole hydrochloride and its13C and15N NMR spectroscopy

The title compound (C₇N₂H₁₀, HC1, 1/2H₂O) crystallizes in the space groupC2/c with cell parameters:a=11.651(9),b=16.309(1),c=9.167(1)Å,=94.95(3)°,Z=8, withd=1.287 g cm^–3. One of the chlorine atoms lies on a twofold axis, the second and the oxygen atom of the water molecule have disordered positions. Intermolecular interactions through hydrogen bonds are established between nitrogen atoms of the pyrazole ring and chlorine atoms or the water molecule. In this way, chains of molecules are built; these chains, through van der Waals interactions, form layers which are stacked in the a direction. The¹H,¹³C, and¹⁵N NMR (this last using the double labelled compound) have been recorded in solution and the¹³C NMR spectrum also in the solid state (CP/MAS technique). The NMR parameters ( andJ's) thus obtained are discussed using the molecular structure.     

Viscoelastic Parameters of a Side-Chain Nematic Polymer: I—Results of a Proton NMR Study

The reorientational behaviour in a static magnetic field of a nematic siloxane side-chain polymer is investigated by proton NMR. At variance with what occurs in main-chain and lyotropic nematic polymers, the return to equilibrium of a tnonodomain whose mean director has been rotated at an angle α to the field, is found to be homogeneous for all angles a between 0 and π/2. The usual nematic order parameter and the static (on the proton NMR time scale) order parameter are deduced from analysis of the equilibrium lineshapes. The twist viscosity γ₁ is deduced from the study of time dependent lineshapes following the rotations α. The temperature dependence of γ₁ is discussed in terms of the Vogel equation γ₁ = B S ^β exp(E _β/R(T - T _o}). It is not possible to discriminate between β = 1 or 2, but in both cases, the freezing temperature of the director T_o is found to be non-zero. A nematic to smectic pretransitional effect on γ₁ is observed. The information concerning the viscoelastic parameters contained in the value of the static order parameter is also discussed.     

Synthesis,characterization and X‐ray crystal structure of guanidinuim (pyridine‐2,6‐dicarboxylato)(pyridine‐2,6‐monocarboxylato) zincate(II) mono pyridine‐2,6‐dicarboxylic acid tetrahydrate

A new complex of Zinc(II) and guanidinium pyridine–2,6–dicarboxylate proton transfer compound, (GnH)₂ (pydc), was synthesized and characterized using IR, ¹H NMR and ¹³C NMR spectroscopy and single crystal X–ray diffraction. The chemical formula and space group of the resulting complex is (GnH)[Zn(pydc)(pydcH)] · (pydcH₂) · 4H₂O, P 1 where the final R value is 0.0310 for 13287 reflections collected. The [Zn(pydc)(pydcH)]^– anions and the (GnH)⁺ counter‐cations form a three‐dimensional solid‐state structure by a variety of noncovalent interactions such as ion pairing, hydrogen bonding and π–π stacking which are going to be discussed. (© 2007 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

NMR and X-ray Investigations of a Plastic Crystalline Phase in MBBA

Abstract

Wideline and high resolution NMR studies have been carried out on MBBA in its isotropic, nematic and solid phases. Isotropic and nematic phase spectra correspond to what has been reported earlier. In the solid phase, contrary to expectations, very intense narrow signals similar to signals of the isotropic phase have been observed for the first time at temperatures close to the solid ? nematic phase transition temperature. This indicates rapid reorientational or translational motion in the system. The X-ray results however confirm the existence of translational order. The results are interpreted as indicative of the existence of a plastic crystalline phase in MBBA.     

Formation of silica/epoxy hybrid network polymers

Epoxy-based inorganic–organic hybrid polymers, for use as a matrix in coatings, have been prepared from 3-glycidoxypropyltrimethoxysilane by a sol–gel process. The precursor molecule possesses both epoxy and silicon alkoxide functionality and so interlinked inorganic–organic networks can be formed. Diethylenetriamine was used to open the epoxy rings and form the organic network to an extent determined by the initial ratio of amine to epoxy groups. The materials were cured either at room temperature or with an additional heat treatment at 150 °C. Structural characterisation of the cured hybrid materials was performed using a combination of Raman, and ²⁹Si and ¹³C MAS NMR spectroscopies. These show that the formation of the two networks does not occur independently and the rate or extent of organic cross-linking has a direct effect on the extent of the inorganic network formation, and vice-versa.     

Electrical Conductivity and Thermoelectric Power of Silver Iododichromate Fast Ion Conducting Electrolytes

Fast ion conducting solid electrolytes are becoming increasingly important owing to their application in solid state ionic devices. The present work deals with the silver ion conducting x AgI – (1–x)Ag₂Cr₂O₇ electrolyte system. These electrolytes have been characterised by X-ray diffraction, electrical conductivity, electronic conductivity and thermoelectric power techniques. A high ionic conductivity of the order of 10⁻³ S/cm has been observed for the composition mol% 80 AgI–20 Ag₂Cr₂O₇, at room temperature. The electronic conductivity of this electrolyte is three orders of magnitude lower than the ionic conductivity.     

High-temperature in situB NMR study of network dynamics in boron-containing glass-forming liquids

In situ high-temperature nuclear magnetic resonance (NMR) spectroscopy can be very useful for probing changes in structure and dynamics in glass-forming liquids, and is a unique method for observing chemical exchange among structural species (e.g. BO₃–BO₄, Qⁿ–Qⁿ⁺¹, and NBO–BO) at the seconds to microseconds time scales. High-temperature ¹¹B MAS NMR line shape measurements were made at about 100 K above the glass transitions on (Na₂O)_0.3(B₂O₃)_0.7 and (Na₂O)_0.2(B₂O₃)_0.21(Al₂O₃)_0.08(SiO₂)_0.51 glass-forming liquids. BO₃ and BO₄ groups are well resolved in ¹¹B MAS NMR spectra at 14.1 T with sample spinning at 5000 Hz. At higher temperatures, partial peak coalescence occurred due to exchange of BO₃ and BO₄. Temperature effects on borate speciation were also determined by varying the fictive temperature (T_f) of glasses, where T_f estimated from differential scanning calorimetry measurements. We combined these complementary data sets to model structural exchange in the liquid state. The time scale of BO₃–BO₄ exchange from NMR data, τ_NMR, appears to be “decoupled” from that of the macroscopic shear relaxation process τ_s derived from the viscosity, however, at higher temperatures, τ_s approaches τ_NMR. The “decoupling” at lower temperature may be related to intermediate-range compositional heterogeneities, and/or fast modifier cation diffusivities which trigger “unsuccessful” network exchange events.     

Melting and Crystallization Processes of EBBA III. Microscopic Observation

Melting and crystallization processes of EBBA (N-p-ethoxybenzylidene-p'-butyl aniline) have been studied by the method of microscopic observation. A solid sample obtained by rapid cooling (cooling rate: 40 K/min) from nematic to 5°C (sample A) shows granular texture. A band like crystal grows in sample A at room temperature. A solid sample obtained by quenching (cooling rate: 13 K/s) from nematic to about - 100°C (sample B) shows cloudy texture. In the heating process sample B transforms to a more stable crystalline form which shows mosaic texture. A needle crystal grows slowly in a supercooled nematic state, then smaller needle crystals grow rapidly around the needle crystal. The formation and transformation processes of solid modifications are explained on the basis of the idea of instability of them, and schematic phase diagram of those solid forms is presented.

Keywords: EBBA, liquid crystals, nematic, solids, crystal growth, microscopic observation     

Crystal and molecular structure of [(4-picolineN-oxide)2H]+ [AuCl4]−: A diadduct revealing a short hydrogen bond

The crystal structure of the [AuCl₄]^–-stabilized hydronium ion diadduct of 4-picolineN-oxide has been determined using 1388 reflections collected on a CAD4 diffractometer. The structure was refined to anR value of 0.46. Two 4-picolineN-oxide molecules form a short hydrogen-bonded hydronium ion diadduct [H(4-picNO)₂]⁺ with an OO distance of 2.442(4) Å. The planar [AuCl₄]^– acts as a counter anion. Due to the nonbonding packing interactions, the Au(III) ion appears to be in an unusual six-coordinate distorted octahedral environment in the solid state. The changes in the N=O distance, the shifts in the infrared absorptions, and the downfield NMR chemical shifts for the bridged protons are explained in terms of inductive effects of the substituents on the pyridineN-oxide ring.     

Local structure of LuBO3 prepared via sol-gel process and its transformation with temperature: B-NMR and L-edge XAS studies

The present work deals with the temperature effect on the stability range of LuBO₃ prepared by sol-gel synthesis. Structural modifications from vaterite to calcite form versus the thermal treatments have been measured by X-ray diffraction and infrared spectroscopy. Several samples derived from the xerogel annealed at 400, 800 and 1200 °C were studied by ¹¹B solid state NMR and at the lutetium L_I-L_III edges by X-ray absorption spectroscopy to determine the local atomic arrangement around the rare earth and the boron ions. The predominance of BO₄ groups and the eightfold coordination of lutetium atoms in the LuBO₃ xerogel in samples treated up to 800 °C indicate an evolution of the xerogel to vaterite form after thermal treatment instead of the expected calcite form as established for samples prepared by solid state reaction.     

In situ high temperature 27Al NMR study of structure and dynamics in a calcium aluminosilicate glass and melt

The temperature dependence (25–1400 °C) of ²⁷Al NMR spectra and spin–lattice relaxation time constants T₁ have been studied for a calcium aluminosilicate (43.1CaO–12.5Al₂O₃–44.4SiO₂) glass and melt using an in situ high temperature probe, and the glass has been characterized by ambient temperature, high field MAS NMR. The peak positions and the line widths show a consistent behavior as motional averaging of the quadrupolar satellites increases with increasing temperature. The rate of decrease with temperature of T₁ drastically increases near the glass transition temperature T_g, which suggests a change in NMR relaxation process from vibrational to translational motions. Above the T₁ minimum (≈1200 °C), NMR correlation times obtained from T₁ are in good agreement with shear relaxation times estimated from viscosity, suggesting that microscopic nuclear spin relaxation is controlled by the same dynamics as macroscopic structural relaxation, and thus that atomic-scale motion is closely related to macroscopic viscous flow.     

The structures of some iminium salts. Crystal structures and13C NMR studies of 3-aryl-2-propenylideniminium salts

The X-ray crystal structures ofE-N, N-dimethyl-3-phenyl-2-propenylideniminium perchlorate,1, andE-N, N-dimethyl-3-(p-methoxyphenyl)-2-propenylideniminium perchlorate,2, have been determined.E-N,N-dimethyl-3-phenyl-2-propenylideniminium perchlorate, (C₁₁H₁₄N⁺)(ClO₄ ^–),1, is orthorhombic:Pmcn (No. 62)a=6.595(1),b=18,288(4),c=10.216(2) Å,Z=4.E-N, N-dimethyl-3-(p-methoxyphenyl)-2-propenylideniminium perchlorate, (C₁₂H₁₆NO⁺)(ClO₄ ^–),2, is triclinic:P1 (No. 2) with cell dimensionsa=6.862(1),b=9.830(2),c=13.376(3) Å,=119.05(1),=114.99(2), =90.79(2)°, andZ=2. Data for both crystals were collected with the use of MoK radiation and a Syntex P2₁ diffractometer. The crystal structures were solved by standard methods and refined toR ₁=0.0688,R ₂=0.0772 for1 andR ₁=0.0790 andR ₂=0.0757 for 2 based on 869 and 1765 independent reflections, respectively. The bond distances are consistent with a highly localized structure with the positive charge situated principally in the iminium moiety. The¹³C NMR spectra of these salts were obtained on the crystalline solids by CPMAS methods. Since the^13C chemical shifts of the salts were very similar, in both solution and solid states, it was concluded that the structures of the salts were comparable in both phases and were analogous.     

Phase Transition and Phase Diagram of Anion Radical Salts of [(C6H5)3PCH3]+ [(C6H5)3AsCH3]+ ×(TCNO)− 2 (0 ≤×≤ 1)

Abstract

Much attention has been paid to the solid anion radical salts of 7,7,8,8-tetracyanoquinodimethane (TCNQ), because of their prominent electronic properties.^1–4 In particular, the salts containing mixed cations represented by [(C₆H₅)₃PCH₃]⁺ _1–x [(C₆H₅)₃AsCH₃]⁺ _× (TCNQ)^? ₂, (0 ≤×≤ 1), are known to undergo phase transitions at 1 atm pressure in the solid state.^1–4 The phase transition of pure methyltriphenylphosphonium salt, (x = 0.00), takes place at 315.7 K. Heat-capacity measurements of this phase transition have been made by Kosaki et al. ³ The transition has thus been found to be of the first order. The enthalpy and the total entropy change associated with the phase transition were experimentally determined to be 485.18 cal/mol and 1.7206 cal/deg.mol, respectively. For the solid solutions, it was found that the transition temperature (T_c ) is increased, while the magnitude of the heat of transition (δH) is decreased, progressively with an increase in the composition parameter (x) and that pure methyltriphenylarsonium salt, (x = 1.00), has no such phase transition up to the decomposition temperature of about 480 K at 1 atm pressure.^1–3 Figure 1 shows the experimental relation between T _c and x, together with the relation between δH and x.⁴ In the present paper, we attempted to explain thermodynamically the phase diagram of Figure 1 for the solid solutions of those TCNQ anion radical salts.