Probing Structural Perturbation in a Bent Molecular Crystal with Synchrotron Infrared Microspectroscopy and Periodic Density Functional Theory Calculations

The range of unit cell orientations generated at the kink of a bent single crystal poses unsurmountable challenges with diffraction analysis and limits the insight into the molecular-scale mechanism of bending. On a plastically bent crystal of hexachlorobenzene, it is demonstrated here that spatially resolved microfocus infrared spectroscopy using synchrotron radiation can be applied in conjunction with periodic density functional theory calculations to predict spectral changes or to extract information on structural changes that occur as a consequence of bending. The approach reproduces well the observed trends, such as the wall effects, and provides estimations of the vibrational shifts, unit cell deformations, and intramolecular parameters. Generally, expansion of the lattice induces red-shift while compression induces larger blue-shift of the characteristic ν­(C–C) and ν­(C–Cl) modes. Uniform or non-uniform expansion or contraction of the unit cell of 0.1 Å results in shifts of several cm–1, whereas deformation of the cell of 0.5° at the unique angle causes shifts of –1. Since this approach does not include parameters related to the actual stimulus by which the deformation has been induced, it can be generalized and applied to other mechanically, photochemically, or thermally bent crystals

Probing Structural Perturbation in a Bent Molecular Crystal with Synchrotron Infrared Microspectroscopy and Periodic Density Functional Theory Calculations

The range of unit cell orientations generated at the kink of a bent single crystal poses unsurmountable challenges with diffraction analysis and limits the insight into the molecular-scale mechanism of bending. On a plastically bent crystal of hexachlorobenzene, it is demonstrated here that spatially resolved microfocus infrared spectroscopy using synchrotron radiation can be applied in conjunction with periodic density functional theory calculations to predict spectral changes or to extract information on structural changes that occur as a consequence of bending. The approach reproduces well the observed trends, such as the wall effects, and provides estimations of the vibrational shifts, unit cell deformations, and intramolecular parameters. Generally, expansion of the lattice induces red-shift while compression induces larger blue-shift of the characteristic ν­(C–C) and ν­(C–Cl) modes. Uniform or non-uniform expansion or contraction of the unit cell of 0.1 Å results in shifts of several cm–1, whereas deformation of the cell of 0.5° at the unique angle causes shifts of –1. Since this approach does not include parameters related to the actual stimulus by which the deformation has been induced, it can be generalized and applied to other mechanically, photochemically, or thermally bent crystals

Probing Structural Perturbation in a Bent Molecular Crystal with Synchrotron Infrared Microspectroscopy and Periodic Density Functional Theory Calculations

The range of unit cell orientations generated at the kink of a bent single crystal poses unsurmountable challenges with diffraction analysis and limits the insight into the molecular-scale mechanism of bending. On a plastically bent crystal of hexachlorobenzene, it is demonstrated here that spatially resolved microfocus infrared spectroscopy using synchrotron radiation can be applied in conjunction with periodic density functional theory calculations to predict spectral changes or to extract information on structural changes that occur as a consequence of bending. The approach reproduces well the observed trends, such as the wall effects, and provides estimations of the vibrational shifts, unit cell deformations, and intramolecular parameters. Generally, expansion of the lattice induces red-shift while compression induces larger blue-shift of the characteristic ν­(C–C) and ν­(C–Cl) modes. Uniform or non-uniform expansion or contraction of the unit cell of 0.1 Å results in shifts of several cm^–1, whereas deformation of the cell of 0.5° at the unique angle causes shifts of <0.5 cm^–1. Since this approach does not include parameters related to the actual stimulus by which the deformation has been induced, it can be generalized and applied to other mechanically, photochemically, or thermally bent crystals

Flexibility in a Molecular Crystal Accomplished by Structural Modulation of Carbohydrate Epimers

Plastic bending of organic crystals is a well-known, yet mechanistically poorly understood phenomenon. On three structurally related epimers, derivatives of galactose, glucose, and mannose, it is demonstrated here that small changes in the molecular structure can have a profound effect on the mechanical properties. While the galactose derivative affords crystals which can be easily bent, the crystals of the derivatives of glucose and mannose are brittle and do not bend. Structural, microscopic, and mechanical evidence is provided showing that hydrogen bonding of water molecules is the key element for sliding over the slip planes in the crystal and accounts for the plastic bending

Forensic Discrimination of Drug Powder Based on Drug Mixing Condition Determined Using Micro Fourier Transform Infrared Spectroscopy

The quantitative evaluation of the drug mixing condition was conducted for application in the forensic discrimination of drug powders using micro Fourier transform infrared (FT-IR) spectroscopy. Bromhexine hydrochloride (BHCl) and p-hydroxybenzoic acid (PHBA) were used as the simulated drug and additive, respectively. Equal masses of two chemicals were (1) simply mixed, (2) homogenized using agate mortar, or (3) dissolved in methanol and dried, and then (4) homogenized using agate mortar. The mixed powders dispersed on BaF2 plates were subjected to mapping analysis of micro FT-IR spectroscopy using synchrotron radiation (SR) or globar light in transmission mode with aperture sizes of 2.5 x 2.5 and 10 x 10μm2, and x–y scanning steps of 2.5 and 10 μm, respectively. The areas of the vibration bands specific to BHCl (C–N bending) and PHBA (CO stretching) were converted to the molar contents (CBHCl, CPHBA), and the relative content ratio (RCR: CPHBA/[CBHCl + CPHBA]) was used as one mixing parameter. The resulting two-dimensional distribution map provided the relative spatial localizations of the two species, and frequency histograms with a horizontal axis of RCR were plotted to evaluate the RCR distribution. The percentage frequency of the extreme value in which RCR was 0 or 1 (%EV) was used as one mixing index. After excluding the extreme values, the coefficient of variation (CV) of the RCR distribution was used as another mixing index. The differentiation among four mixing modes could be evaluated from the standpoint of %EV and CV, and the discrimination capacity by SR instrument was superior to that by globe light instrument

Ten-Membered Cyclodecatetraene Derivatives Including Two Gallium Atoms: Experimental and Theoretical Studies on Synthesis, Structures, and Their Transformations to Nine- and Five-Membered Gallacycles

The chemistry of medium-sized ring compounds, including group 13 elements, has scarcely been investigated. Herein, we report that 5,10-digallacyclodeca-1,3,6,8-tetraene derivatives Cl2Ga2C8R8 (R = Me (5a), Et (5b)) can be obtained by the reaction of GaCl3 and zirconacyclopentadiene Cp2ZrC4R4 (R = Me (2a), Et (2b), Cp: η5-C5H5) in toluene. X-ray crystal structure analysis revealed that compound 5b has a 10-membered cyclodecatetraene structure composed of two butadiene skeletons and two GaCl fragments. X-ray crystal structure analysis and IR measurement confirmed that compound 5b forms Ga2Cl2 four-membered rings via intermolecular Cl to Ga donor–acceptor interactions, which result in the formation of oligomeric chain structures in the solid state and toluene solution. The treatment of compound 5b with 2 equivalents of 4-(dimethylamino)­pyridine (DMAP) proceeded via the coordination of DMAP to the Ga center and the ring contraction to give DMAP-coordinated five-membered gallole Cl­(DMAP)­GaC4Et4 (4bDMAP). The reaction of compound 5a with 2 equivalents of MesLi (Mes: 2,4,6-Me3C6H2) in toluene to form a 9,10-digallabicyclo[4.3.1]­decatriene derivative (MesGaC8Me8)­GaMes (6a) caused ring contraction. Theoretical investigation revealed that the 10-membered ring derivative, Cl2Ga2C8H8 (GaH-10), is formed by the dimerization of two gallole molecules, ClGaC4H4 (GaH-5), via the addition of two Ga–C bonds without an energy barrier. The immediate formation of GaH-10 was attributed to the transannular electronic interaction between the expanded empty p-orbital on the Ga atom and the electron-rich sp2 carbons of the CC double bond in GaH-5. Moreover, GaH-10 and one of the isomer, nine-membered ring derivative (ClGaC8H8)­GaCl, were found to be thermodynamically more stable, as compared to GaH-5

Infrared Spectra and Hydrogen-Bond Configurations of Water Molecules at the Interface of Water-Insoluble Polymers under Humidified Conditions

Elucidating the state of interfacial water, especially the hydrogen-bond configurations, is considered to be key for a better understanding of the functions of polymers that are exhibited in the presence of water. Here, an analysis in this direction is conducted for two water-insoluble biocompatible polymers, poly­(2-methoxyethyl acrylate) and cyclic­(poly­(2-methoxyethyl acrylate)), and a non-biocompatible polymer, poly­(n-butyl acrylate), by measuring their IR spectra under humidified conditions and by carrying out theoretical calculations on model complex systems. It is found that the OH stretching bands of water are decomposed into four components, and while the higher-frequency components (with peaks at ∼3610 and ∼3540 cm–1) behave in parallel with the CO and C–O–C stretching and CH deformation bands of the polymers, the lower-frequency components (with peaks at ∼3430 and ∼3260 cm–1) become pronounced to a greater extent with increasing humidity. From the theoretical calculations, it is shown that the OH stretching frequency that is distributed from ∼3650 to ∼3200 cm–1 is correlated to the hydrogen-bond configurations and is mainly controlled by the electric field that is sensed by the vibrating H atom. By combining these observed and calculated results, the configurations of water at the interface of the polymers are discussed

Ten-Membered Cyclodecatetraene Derivatives Including Two Gallium Atoms: Experimental and Theoretical Studies on Synthesis, Structures, and Their Transformations to Nine- and Five-Membered Gallacycles

The chemistry of medium-sized ring compounds, including group 13 elements, has scarcely been investigated. Herein, we report that 5,10-digallacyclodeca-1,3,6,8-tetraene derivatives Cl2Ga2C8R8 (R = Me (5a), Et (5b)) can be obtained by the reaction of GaCl3 and zirconacyclopentadiene Cp2ZrC4R4 (R = Me (2a), Et (2b), Cp: η5-C5H5) in toluene. X-ray crystal structure analysis revealed that compound 5b has a 10-membered cyclodecatetraene structure composed of two butadiene skeletons and two GaCl fragments. X-ray crystal structure analysis and IR measurement confirmed that compound 5b forms Ga2Cl2 four-membered rings via intermolecular Cl to Ga donor–acceptor interactions, which result in the formation of oligomeric chain structures in the solid state and toluene solution. The treatment of compound 5b with 2 equivalents of 4-(dimethylamino)­pyridine (DMAP) proceeded via the coordination of DMAP to the Ga center and the ring contraction to give DMAP-coordinated five-membered gallole Cl­(DMAP)­GaC4Et4 (4bDMAP). The reaction of compound 5a with 2 equivalents of MesLi (Mes: 2,4,6-Me3C6H2) in toluene to form a 9,10-digallabicyclo[4.3.1]­decatriene derivative (MesGaC8Me8)­GaMes (6a) caused ring contraction. Theoretical investigation revealed that the 10-membered ring derivative, Cl2Ga2C8H8 (GaH-10), is formed by the dimerization of two gallole molecules, ClGaC4H4 (GaH-5), via the addition of two Ga–C bonds without an energy barrier. The immediate formation of GaH-10 was attributed to the transannular electronic interaction between the expanded empty p-orbital on the Ga atom and the electron-rich sp2 carbons of the CC double bond in GaH-5. Moreover, GaH-10 and one of the isomer, nine-membered ring derivative (ClGaC8H8)­GaCl, were found to be thermodynamically more stable, as compared to GaH-5

Electronic State of a Conducting Single Molecule Magnet Based on Mn-salen Type and Ni-Dithiolene Complexes

The electrochemical oxidation of an acetone solution containing [MnIII (5-MeOsaltmen)(H2O)]2(PF6)2 (5-MeOsaltmen2– = N,N′-(1,1,2,2-tetramethylethylene)bis(5-methoxysalicylideneiminate)) and (NBu4)[Ni(dmit)2] (dmit2– = 2-thioxo-1,3-dithiole-4,5-dithiolate) afforded a hybrid material, [Mn(5-MeOsaltmen)(acetone)]2[Ni(dmit)2]6 (1), in which [Mn2]2+ single-molecule magnets (SMMs) with an ST = 4 ground state and [Ni(dmit)2]n− molecules in a charge-ordered state (n = 0 or 1) are assembled in a layer-by-layer structure. Compound 1 crystallizes in the triclinic space group P1̅ with an inversion center at the midpoint of the Mn···Mn dimer. The [Mn2]2+ unit has a typical nonplanar Mn(III) dimeric core and is structurally consistent with previously reported [Mn2] SMMs. The six [Ni(dmit)2]n− (n = 0 or 1) units have a square-planar coordination geometry, and the charge ordering among them was assigned on the basis of ν(CC) in IR reflectance spectra (1386, 1356, 1327, and 1296 cm–1). The [Mn2]2+ SMM and [Ni(dmit)2]n− units aggregate independently to form hybrid frames. Electronic conductivity measurements revealed that 1 behaved as a semiconductor (ρrt = 2.1 × 10–1 Ω·cm–1, Ea = 97 meV) at ambient pressure and as an insulator at 1.7 GPa (ρ1.7GPa = 4.5 Ω·cm–1, Ea = 76 meV). Magnetic measurements indicated that the [Mn2]2+ units in 1 behaved as ST = 4 SMMs at low temperatures