Infrared spectra of proton transfer complexes of the cycleanine alkaloid in solid state

Proton transfer complexes obtained between the cycleanine alkaloid and hydrogen chloride, hydrogen bromide and nitric acids have been investigated by infrared spectroscopic technique between 4000 and 400 cm(-1) in KBr. The vibrational perturbations brought about by proton transfer complex formation, discussed in terms of preferred site of interaction, show that the proton of the inorganic acids is transferred to cycleanine through one of its N sites.     

Laser action and excited state absorption of chlorophyll-a

Stimulated emission of chlorophyll-a is observed in the spectral range around 670 nm. The calculated wavelength at the threshold turns out to be shifted by 20 nm towards longer wavelengths. To clarify this discrepancy, extrinsic-loss variations at the laser as well as measurements of nonlinear are carried out. The results indicate an excited singlet state absorption (σ > 10¹⁷ cm² within the range from 670 to 700 nm).     

Chemical analysis in the submillimetre spectral region with a compact solid state system

A new analytical system that uses the rotational signatures of gas phase molecules is described and demonstrated. It uses a solid state source to probe molecular systems in the millimetre and submillimetre wave range, the only region of the electromagnetic spectrum not yet used extensively for analytical purposes. It employs the FAst Scan Submillimetre Spectroscopy Technique (FASSST), which leads to an especially simple system architecture. Among the attributes of the system are generality, sensitivity, 'absolute' specificity, small size, simplicity, and the potential for very low cost. Applications to problems of analytical interest are also discussed.     

Infrared spectra and rotational isomerism of ethyl fluoroformate and ethyl propiolate

The infrared absorption spectra of ethyl fluoroformate and ethyl propiolate have been examined in the vapour, solution and solid states. For both esters evidence is found of rotational isomerism arising from internal rotation about the O-C₂H₅ bond, in close agreement with previous work on other ethyl esters.     

Solvent free reactions in the solid state: solid state metathesis

Transition Metal Chemistry -     

Infrared crystal spectra of heterocyclic compounds. II. IR spectrum of selenophene in the solid state

Infrared spectra of solid selenophene at different temperatures, have been measured using polarized radiation. Just below the freezing point the selenophene molecule has a noticeable degree of ring-rigidity, allowing for a definite location in sites of lower symmetry than the molecular one. Dichroic behaviour of IR lines in the solid state enables us to attribute the bands to the relative symmetry species and give a tentative hypothesis for the space group of the crystalline selenophene.     

Infrared spectral profiles in liquids and atom-diatom interactions

Molecular dynamics simulations of the infrared spectrum of a generic simple polar diatomic in a liquid nonpolar solvent allow to reproduce the different prototypical experimental line shapes of this kind of systems. This is feasible by using different solute-solvent anisotropic potentials at fixed thermodynamic conditions. In the limit cases, the rotation of the diatomic is explained in terms of a quasifree motion or a rotational diffusion evolution and the spectra show a doublet structure formed by P and R branches or a unique collapsed branch, respectively. When the profile contains three branches, including an intense Q branch in the vicinity of the center of the band, rotational evolution presents a particular hindering that can be understood by studying the influence on rotational spectral densities of the different time scales involved in rotational relaxation. Cancellation/enhancement effects among spectral density terms arising from intermediate and long times (0.4-1 ps) are essential to understand rotational hindering.     

Photochemical behavior of some p-styrylstilbenes and related compounds: spectral properties and photoisomerization in solution and in solid state

The spectral properties and Z,E-photoisomerizations of three 4-styrylstilbenes, a 4,4'-bis(P-methylstyryl)benzene and a 4,4'-distyrylstilbene were investigated in solution and in the solid state. Some notable features of the absorption and fluorescence spectra due to the structures and the phases (solution or solid) were observed, especially the Stokes shifts. Interesting photochemical behaviors in solution and in the solid state were also found. While the (E,Z)-4-styrylstilbenes undergo a one-way photoisomerization to their E,E-isomers with almost equal rates in solution, their quantum yields in the solid state decrease with increasing substituent size at the terminal aromatic rings. On the other hand, the 4,4'-bis(beta-methylstyryl)benzene undergoes a mutual photoisomerization in solution, but its E,Z-isomer isomerizes in a one-way manner to the E,E-isomer in the solid state. Additionally, the (Z,E,Z)-4,4'-styrylstilbene was found to undergo a one-way photoisomerization to the E,E,E-isomer via the E,E,Z-isomer in solution and the crystalline E,E,Z-isomer to the E,E,E-isomer in the solid state.     

Synthesis, spectral and solid state characterization of a new bioactive hydrazine bridged cyclic diphosphonium compound

The facile preparation of a racemic hydrazine bridged diphosphonium compound possessing a ring system analogous to bicyclo[3.3.2]decane is reported. Although the reaction yield is low, the structure of the compound, which possesses an eight-membered ring, two phosphonium cationic centers, a biimino bridge, molecular chirality and two fused aromatic rings locked into roughly perpendicular planes is unusual. The compound displays substantial biological activity in the brine shrimp test and cleaves plasmid DNA.     

Infrared spectral characteristics of noncyclic carbonylureas

Noncyclic diacylimides (noncyclic carbonylureas) have NH frequencies higher than cyclic diacylimides. In solid state spectra, two bands at 3240-3220 cm⁻¹ and 3140-3120 cm⁻¹, and in chloroform spectra, one band at 3480-3380 cm⁻¹ appear consistently in all compounds under discussion. Consequently, these bands could be considered as characteristic of noncyclic diacylimides, and furthermore, the occurrence of several weak bands in the region 3300–3100 cm⁻¹ along with regular NH bands may be considered as characteristic of noncyclic diacylimides. By contrast, cyclic diacylimides in the solid state show two widely separated carbonyl bands in the 1790-1720 cm⁻¹ and 1710-1670 cm⁻¹ regions, whereas in noncyclic diacylimides these bands appear as one strong band at 1670-1660 cm⁻¹ with a weak shoulder at 1690-1680 cm⁻¹. Furthermore, the compounds behave like secondary amides, as there appear amide I, II and III bands regularly. The amide II band seems to be characteristic of noncyclic diacylimides, as the band is missing in cyclic diacylimides.     

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.     

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.     

The molecular structure of 4-piperidinemethanol in gas,solutions, and solid state: spectral and theoretical investigations

Structural Chemistry - FT-IR (4000–400 cm) spectra of gaseous, solid 4-piperidinemethanol, and its solutions in tetrachloromethane and dichloromethane and Raman spectrum...     

Encapsulation of gases in the solid state

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

Infrared heat aided solid state synthesis of pyrroles from 1,4‐diketones and ammonium acetate

A facile amination of 1,4‐diketones with ammonium acetate has been achieved by mechanochemical grinding assisted by infrared irradiation in the presence of silica gel. The wastes are reduced and the energy resources saved. J. Heterocyclic Chem., (2012).     

Structure and dynamics of L-selenomethionine in the solid state

L-selenomethionine 1 crystallizes in P2(1) space group with two molecules in the asymmetric unit. Solid-state NMR spectroscopy is used for searching of structure and dynamics of 1 in the crystal lattice. The distinct molecular motion of side chains for A and B molecules of 1 is apparent from measurements of relaxation parameters (1H 1rho, 13C T1) and analysis of CSA data (2D-PASS experiment). The 13C delta(ii) and 77Se delta(ii) parameters are correlated with theoretical shielding parameters obtained by means DFT GIAO calculations. Attempt to explain the mechanism of phase transition of crystals of 1 at 313K is presented.     

Infrared spectroscopy of the solid phases of ammonia

Thin films of solid ammonia (NH(3) and ND(3)) have been characterized using low temperature (25-110 K) Fourier-transform infrared (FTIR) spectroscopy, and the three solid phase (amorphous, metastable, and crystalline) spectra are reported. This work has been motivated by confusion in the literature about the metastable and crystalline phases as a result of an early erroneous report by Staats and Morgan [(J. Chem. Phys. 31, 553 (1959)]. Although the crystalline phase has subsequently been reported correctly, the metastable phase has not been described in the literature in detail. The unique characteristics of the metastable phase, reported here for the first time, include multiple peaks in the nu(2) and nu(3) regions and peak intensities that are dependent on the deposition temperature. This behavior may be the result of (a) preferential molecular orientations in the solid, or (b) exciton splitting due to different crystal shapes in the solid. The amorphous and metastable phases of deuterated ammonia are also reported for the first time.