Solvent free reactions in the solid state: solid state metathesis

Transition Metal Chemistry -     

Heteronuclear NOE in the solid state

A series of small molecules and polymers was examined in order to investigate the heteronuclear NOE effect in solids. Contrary to a previously reported interpretation it was found that caution has to be used in interpreting NOE rates purely in terms of correlation times. The NOE rate of a methyl group was not solely dependent upon correlation times but also the distance (r⁻⁶) from the nearest methyl neighbour.     

Conformation-specific photochemistry in the solid state

The unsymmetrical ene-dione $\text{1b}$ exists in solution as a mixture of two conformational isomers, A and B, in rapid equilibrium. Irradiation of $\text{1b}$ in this medium leads to four products, two from each conformer. In the solid state, however, compound $\text{1b}$ adopts a single conformation (A), and photolysis of crystals of $\text{1b}$ leads to a single product. The formation of one rather than two photoproducts in this instance is attributed to a unique solid state steric effect, termed steric compression.     

Ionic conduction in the solid state

Solid state ionic conductors are important from an industrial viewpoint. A variety of such conductors have been found. In order to understand the reasons for high ionic conductivity in these solids, there have been a number of experimental, theoretical and computational studies in the literature. We provide here a survey of these investigations with focus on what is known and elaborate on issues that still remain unresolved. Conductivity depends on a number of factors such as presence of interstitial sites, ion size, temperature, crystal structure etc. We discuss the recent results from atomistic computer simulations on the dependence of conductivity in NASICONs as a function of composition, temperature, phase change and cation among others. A new potential for modelling of NASICON structure that has been proposed is also discussed. Dedicated to Prof J Gopalakrishnan on his 62nd birthday.     

Encapsulation of gases in the solid state

A hemicarcerand encapsulates, stores and releases gases in the solid state.     

The hydrogen bond in the solid state

The hydrogen bond is the most important of all directional intermolecular interactions. It is operative in determining molecular conformation, molecular aggregation, and the function of a vast number of chemical systems ranging from inorganic to biological. Research into hydrogen bonds experienced a stagnant period in the 1980s, but re-opened around 1990, and has been in rapid development since then. In terms of modern concepts, the hydrogen bond is understood as a very broad phenomenon, and it is accepted that there are open borders to other effects. There are dozens of different types of X-H.A hydrogen bonds that occur commonly in the condensed phases, and in addition there are innumerable less common ones. Dissociation energies span more than two orders of magnitude (about 0.2-40 kcal mol(-1)). Within this range, the nature of the interaction is not constant, but its electrostatic, covalent, and dispersion contributions vary in their relative weights. The hydrogen bond has broad transition regions that merge continuously with the covalent bond, the van der Waals interaction, the ionic interaction, and also the cation-pi interaction. All hydrogen bonds can be considered as incipient proton transfer reactions, and for strong hydrogen bonds, this reaction can be in a very advanced state. In this review, a coherent survey is given on all these matters.     

Nucleobase-induced supramolecular polymerization in the solid state

Supramolecular polymerization, that is, the self-assembly of polymer-like materials through the utilization of the noncovalent bond, has been a developing area of research over the last decade. In this article, we report the synthesis of nucleobase-terminated (N⁶-anisoyl-adenine and thymine) low-molecular-weight poly(tetrahydrofuran) macromonomers (<2000 g mol⁻¹). The adenine-derived supramolecular telechelic polymer self-assembled in the solid state to yield materials with film- and fiber-forming capabilities. This material was thermally reversible and exhibited a ceiling temperature, above which a drop in viscosity was observed and fibers could no longer be obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3589–3596, 2003     

Ferroelectricity in solid state chemistry

This article discusses some state-of-the-art aspects of solid state chemistry within the context of ferroelectric materials such as oxides, fluorides and oxyfluorides, whose crystalline networks include octahedra. Structural considerations make it possible to determine the origin of the ferroelectricity and to predict the existence of polar properties in new families. Crystallographic distortions of different nature lead to highly variable transition sequences. Ferroelectricity is often associated with ferroelasticity. The Curie temperature is linked to the composition and to the chemical bond. In this respect, several factors are to be considered, e.g. size, coordination and configuration of the cations, covalence of bonds, order-disorder, etc. Physical studies are very useful: first, the dielectric characteristics and their variations with temperature, frequency and electric field are typical of ferroelectrics; second, the pyroelectric, piezoelectric, electro-optical and non-linear optical properties are among the most effective. Various types of materials (single crystals, ceramics, thin films) are used nowadays in a wide range of applications. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SASferroelectricity / solid state chemistry     

The structure of glibenclamide in the solid state

The structure of glibenclamide, 5‐chloro‐N‐(2‐{4‐[(cyclohexylamino)carbonyl] aminosulfonyl}phenyl) ethyl)‐2‐methoxybenzamide, an important antidiabetic drug, has been studied both in solution and in the solid state by a combination of NMR spectroscopy and theoretical calculations. The possibility that glibenclamide suffers a tautomerization under melting to afford a desmotrope was rejected. Copyright © 2012 John Wiley & Sons, Ltd.     

Photocyclization of 2,4,6-triethylbenzophenones in the solid state

Photocyclization of 2,4,6-triethylbenzophenones (TEBPs) into (E)- or (Z)-benzocyclobutenols ((E)- or (Z)-CBs) is E-selective in solution. By contrast, upon solid-state photolysis, TEBP-3,4-diCl and especially TEBP-4-t-Bu gave (Z)-CB relative to (E)-CB with a much higher proportion than that in solution. For TEBP-4-t-Bu, the most major product in the solid state is an indanol derivative (Inol) (E/Z/Inol=1:3.9:10.3 at 9% conversion). On the basis of the X-ray crystallographic analysis, Inol and (Z)-CB are both topochemical products. Notably, the relative proportion of (E)-CB increased with increased conversion, namely with increased disruption of the crystal lattice. The DFT calculation of highly hindered 2,6-diisopropylbenzophenone (DIBP) was also conducted. These results in conjunction with the previous results on 2,4,6-triisopropylbenzophenones (TIBPs) indicate that CB is formed either via trans-enol followed by its conrotatory ring-closure (paths a and d) or through direct cyclization of biradical (BR) (path b) as shown in Scheme 1. Normally the former route is faster. However, in the crystalline state or in the case of sterically hindered phenyl ketones, path b tends to be adopted.     

Molecular structure of decamethylgermanocene in the solid state

The low temperature X-ray structure analysis of decamethylgermanocene reveals two independent molecules in the unit cell, both of which have a bent sandwich structure with angles between the planes of the two C₅Me₅ rings of 31.26(0.09)° and 31.55(0.10)°, respectively. The perpendicular germanium to ring distances are 220 pm, corresponding to Ge-C bond lengths ranging from 240 to 266 pm.     

Packing behavior of benzoylterryleneimide in the solid state

The packing behavior of benzoylterryleneimide was determined by X-ray powder and electron diffraction. The latter was applied to a material solidified from a solution after spreading it onto a water surface. By this procedure various nonequilibrium structures were prepared: crystalline lamellae are embedded in a structure of lower order, the texture of which looks similar to a texture seen in rigid liquid-crystalline polymers. The transition between both regimes is gradual. X-ray diffraction was applied to an annealed crystalline powder. The crystalline packing of the dark-blue compound can be described by a monoclinic unit cell with lattice parameters a?=?11.25?Å, b?=?10.93?Å, c?=?27.78?Å, β?=?91.0°, ρ?=?1.38?g/cm³ and Z?=?4?at ambient temperature. In order to enable optimum space-filling, the molecules are arranged parallel two by two with the planes of the aromatic ring systems 3.47?Å apart in centrosymmetrical relation and shifted longitudinally so that the diisopropylphenyl group of one molecule fits into the cavity at the carbonyl oxygen of the adjacent molecule.     

Thermal polymerization of acrylamide in the solid state

The role of imperfections in thermal polymerization of acrylamide in the solid state was studied. The polymer yield and the degree of polymerization are highly dependent on the particle size and on the pressure to which the monomer is subjected prior to polymerization reaction. There is an enhancement in the rate of polymerization in air unlike in the case of radiation-induced polymerization. Thermal polymerization of acrylamide in pelletized form results in the formation of water-soluble linear polymer and water-insoluble cross-linked product with the evolution of ammonia. The activation energy (E) values obtained in the present investigation reveal that basically there are two processes taking place, one with E = 34–36 kcal/mole, corresponding to the initiation process, and the other with E = 19 ± 3 kcal/more for the propagation process.     

Photolysis of zinc azide in the solid state

The photolysis of anhydrous zinc azide prepared by (1) dehydration of Zn(N₃)₂·2H₂O and (2) precipitation by acetone from aqueous solution, under the action of high pressure mercury arc is reported here. The pressure of nitrogen developed during photolysis under steady-state conditions at constant intensity is a linear function of t^1/2 in both the samples. The rate of photolysis is a linear function of intensity at constant temperature. A detailed analysis of the dark rate suggests that the dependence on t^1/2 should be due to the diffusion of nitrogen from the reaction site to the surface of the solid azide. An appropriate mathematical analysis is presented. The linear dependence of the rate of photolysis on the intensity of irradiation is interpreted in terms of the reaction of a trapped exciton with an adjacent azide ion. Absence of any detectable photoconduction in the wavelength range of the irradiating radiation suggests that excitons are the most probable reactive species. The sample of zinc azide obtained by the first method decomposes faster than the other under identical conditions, and has a slightly lower energy of activation of 1.4 kcal/mole compared to 1.75 kcal/mole for the second. These differences are discussed in terms of the defect concentrations of the two azide samples.     

Radiation-induced polymerization of tetraoxane in the solid state

The radiation-induced polymerization of tetraoxane in the solid state has been investigated in air and in vacuo. The polymerization rate was higher in air than in vacuo, whereas the molecular weight of the polymer obtained at high conversion in air was considerably lower than in vacuo. A large decrease in the molecular weight with increasing polymer yield observed in air may be explained mainly by degradation during polymerization.     

Theoretical study of the alpha-cyclodextrin dimer

The molecular structure, stabilization energy, and thermodynamic properties of the plausible modes of the interaction for the three possible alpha-cyclodextrin (alpha-CD) dimers (head-to-head, tail-to-tail, and head-to-tail) with a water cluster were obtained using quantum chemical methods for the first time. Nine distinct spatial arrangements were investigated. The head-to-head mode of interaction with water is preferred by more than 10 kcal.mol(-1) (BLYP/6-31G(d,p)//PM3 Gibbs free energy difference value at room temperature) in relation to the next stable structure, with a water dimer structure placed inside each cavity and cyclic water tetramers surrounding each tail end. The inter alpha-CD hydrogen bonds play a major role to stabilize the dimeric structures, with no water tetramer being found between the two alpha-CD subunits for the preferred global minimum structure. Therefore, a theoretical model aimed to describe the behavior of alpha-CD dimer, or their inclusion complexes, in the aqueous media should take into account this preference for binding of the water molecules.