Alpha,beta-unsaturated ketoximes carrying a terminal pyridine or quinoline subunit as building blocks for supramolecular syntheses

[Structure: see text]. The crystal structures of a new series of alpha,beta-unsaturated ketoximes, 8-14, carrying the terminal 4-pyridinyl, 3-pyridinyl, or 4-quinolinyl subunit have been investigated by X-ray structural analysis. The dominating intermolecular interaction in all structures, except 11, is the head-tail OH...N hydrogen bond between the oxime moiety and the nitrogen atom of the heterocyclic unit. This intermolecular interaction generates infinite chains, which are cross-linked by CH...O/N/Cl or CH...pi interactions. Compound 10 has been shown to adopt a double-helical structure in the crystalline state. Compound 11 represents the only case where the unexpected head-head NOH...N(OH) hydrogen bonds determine the crystal packing. Both hydrogen-bonding and aromatic interactions stabilize the crystal structures of 8-14.     

Solid state crystalline and liquid crystalline structure of semifluorinated 1-bromoalkane compounds

A series of semifluorinated 1-bromoalkane (SFBA) mesogens have been synthesized and characterized to better understand their solid state crystalline and liquid crystalline structures. In the solid state, the local conformation of the fluorocarbon segments becomes disordered once the fluorocarbon chain reaches a length above eight CF units. This is evident from the pronounced decrease of molar melting enthalpy. An increasing amount of helix and helix reverse conformations and increasingly disordered packing can also be observed with each addition of a fluorocarbon segment. X-ray diffraction peaks in the small angle region can be indexed by a tilted, two dimensional layered (herring bone) structure. The crystal structure is similar to a type of plastic crystal in which the amphiphilic character is clear, because the two segments of fluorocarbon and hydrocarbon are almost immiscible. Heating of F(CF2)12(CH2)10Br leads to a transition from plastic crystal to smectic B, as revealed by time-resolved XRD and FTIR analysis. At this solid-to-liquid transition temperature, conformational analysis confirmed an onset of the CH2 gauche conformation within the hexagonal lattice, most likely due to changes occurring in the hydrocarbon segment, and a sudden increase of helix defects along the fluorocarbon segment. The disordered helix rigid-rod structure of the fluorocarbon segment and its poor compatibility with the hydrocarbon segment play an important role in the crystalline solid and liquid crystalline structures.     

Deconvoluted Fourier-transform LNT-IR study of coordination copper(II) compounds with dextran derivatives

Deconvoluted Fourier-transform IR spectra, recorded at room and liquid nitrogen temperature, of polysaccharide dextran and its coordination compounds with the copper(II) ion were analyzed in order to find the most specific spectral peculiarities. This allows one to obtain information about the structure and conformation of these polymer compounds. Different influences on the system of intra-and intermolecular interactions were exhibited by analogs recrystallized from D₂O. The changes in intensity and width of the IR bands in the region 1450–1050 cm⁻¹ were related to changes in conformation and short-range interactions of the dextran. In the synthesized copper(II)-dextran complexes, the presence of water molecules was confirmed. The results of the FTIR spectroscopy study allowed one to suggest a predominant crystalline form of the copper(II)-dextran complexes. The text was submitted by the authors in English.     

On the interplay between CH...O and OH...O interactions in determining crystal packing and molecular conformation: an experimental and theoretical charge density study of the fungal secondary metabolite austdiol (C12H12O5)

The total experimental electron density rho(r), its Laplacian inverted delta(2)rho(r), the molecular dipole moment, the electrostatic potential phi(r), and the intermolecular interaction energies have been obtained from an extensive set of single-crystal X-ray diffracted intensities, collected at T = 70(1) K, for the fungal metabolite austdiol (1). The experimental results have been compared with theoretical densities from DFT calculations on the isolated molecule and with fully periodic calculations. The crystal structure of (1) consists of zigzag ribbons extended along one cell axis and formed by molecules connected by both OH...O and CH...O interactions, while in a perpendicular direction, adjacent molecules are linked by short CH...O intermolecular contacts. An extensive, quantitative study of all the intra- and intermolecular H...O interactions, based not only on geometrical criteria, but also on the topological analysis of rho(r), as well as on the evaluation of the pertinent energetics, allowed us (i) to assess the mutual role of OH...O and CH...O interactions in determining molecular conformation and crystal packing; (ii) to identify those CH...O contacts which are true hydrogen bonds (HBs); (iii) to determine the relative hydrogen bond strengths. An experimental, quantitative evidence is given that CH...O HBs are very similar to the conventional OH...O HBs, albeit generally weaker. The comparison between experimental and theoretical electric dipole moments indicates that a noticeable charge rearrangement occurs upon crystallization and shows the effects of the mutual cooperation of HBs in the crystal. The total intermolecular interaction energies and the electrostatic energy contribution obtained through different theoretical methods are reported and compared with the experimental results. It is found that the new approach proposed by Spackman, based on the use of the promolecular charge density to approximate the penetration contribution to intermolecular electrostatic energies, predicts the correct relative electrostatic interaction energies in most of the cases.     

Interaction of hydronium ion with dibenzo-18-crown-6: NMR, IR, and theoretical study

Interaction of dibenzo-18-crown-6 (DBC) with H 3O (+) (HP) in nitrobenzene- d 5 and dichloromethane- d 2 was studied by using (1)H and (13)C NMR spectra and relaxations, FTIR spectra, and quantum chemical DFT calculations. NMR shows that the DBC*HP complex is in a dynamic equilibrium with the reactants, the equilibrium constant K being 0.66 x 10 (3), 1.16 x 10 (4), and 1.03 x 10 (4) L x mol (-1) in CD 2Cl 2, nitrobenzene, and acetonitrile, respectively. The complex appears to have a C 2 v symmetry in NMR, but FTIR combined with DFT normal mode calculations suggest that such high symmetry is only apparent and due to exchange averaging of the structure. FTIR spectra as well as energy-optimized DFT calculations show that the most stable state of the complex in solution is that with three linear hydrogen bonds of HP with one CH 2-O-CH 2 and two Ar-O-Ar oxygen atoms. The structure is similar to that found in solid state but adopts a somewhat different conformation in solution. The dynamics of exchange between bound and free DBC was studied by NMR transverse relaxation. It was found to be too fast to give reproducible results when measured with the ordinary CPMG sequence or its variant DIFTRE removing residual static dipolar interaction, but it could be established by rotating-frame measurements with high intensity of the spin-lock field. The correlation time of exchange was found to be 5.6 x 10 (-6) and 3.8 x 10 (-6) s in dichloromethane and nitrobenzene, respectively. Such fast exchange can be explained by cooperative assistance of present water molecules.     

CONFORMATION AND CHAIN PACKING STRUCTURES OF POLY (ρ-PHENYLEN BENZOBISTHIAZOLE) BY MOLECULAR SIMULATION*

The conformation, the chain packing stabilization and the unit cell modeling of poly(p-phenylene benzobisthiazole) have been investigated by using molecular simulation techniquein the present work. A coupling behaviour of σ-bond rotations at either side of the pheny-lene ring or the heterocyclic ring was found surely to exceed a length of the repeat unit ofthe polymer chain. For a single chain model, the stable torsion angle of the repeat resultedat 14°. In the crystalline cell minimization, the dihedral angle along the polymer chaincould even be stabilized in various values. It therefore indicates that the intermolecularinteraction does play a considerable role for this polymer forming the conformation. Ac-cording to cohesive energies calculated for these unit cell models, the torsion angle in themost stable crystalline cell is 0°. When the chains packing together, there exist so manyenergy stable wells along the chain axis 0.35--0.36nm apart from neighbouring chains.Most of the unit cells have quite closed cohesive energies. These factors thus cause thedifficulty of forming an unique perfect crystalline structure of the polymer. The presentstudy suggested a number of reasonable unit cells, and the most stable crystalline structurefor this polymer that is monoclinic, non-primitive unit cell.     

Achromatic polarization switch using a film-compensated twisted nematic liquid crystal cell

Two liquid crystal materials, 4,4'-bis(ω-hydroxyalkoxy)-α-methylstilbenes, with butyloxy and octyloxy terminal chains and denoted HAMS-4 and HAMS-8, respectively, were synthesized. The corresponding compounds, 4,4'-bis(ω-alkoxy)-α-methylstilbenes (AMS-n) (n = 2 to 7, 9, 10 and 11), which do not hydrogen bond, were also synthesized and used to study the influence of hydrogen bonding on phase behaviour. DSC, polarizing optical microscopy and miscibility studies were used for determination of the structure and property relationships of the various liquid crystalline phases exhibited by the two homologues and the AMS-n homologues. The FTIR spectra were measured at various temperatures on going from the crystalline phase to the isotropic phase through the intermediate phases. The characteristics of the OH stretch band, the CH₂ stretching, bending and rocking progression modes, as well as the ring C C stretch and the ring skeletal vibrations were studied to elucidate the modes and geometry of the hydrogen bonding of the terminal OH group, the conformation of the terminal chains and the intermolecular interaction between the aromatic mesogenic cores in the various phases.     

Solid state self‐assembly of the single‐walled carbon nanotubes and poly(γ‐benzyl‐l‐glutamate)s with different conformations

A series of pyrenyl‐terminated poly(γ‐benzyl‐l ‐glutamate)s (py‐PBLGs) with controlled polymer molecular weight (M_W = 2.3–14.8 kg mol^?1) and molecular weight distribution (PDI = 1.17–1.55) have been prepared from 1‐pyrenemethylamine hydrochloride‐mediated ring‐opening polymerization (ROP) of γ‐benzyl‐l ‐glutamic acid based N‐carboxyanhydride (BLG‐NCA). FTIR analysis revealed that the py‐PBLG₉ was conformationally heterogeneous with 35.0% α‐helix, 55.6% β‐sheet, and 9.4% random coil conformations in the solid state, whereas the py‐PBLG₆₆ adopts 100% α‐helix conformation. Py‐PBLGs promote the dispersion of SWCNTs in organic solvents and in the PBLG solid through π–π interaction, as evidenced by the Raman spectroscopic studies. WAXD analysis revealed that the SWCNTs significantly affect the ordering of the py‐PBLG self‐assembly: the long range hexagonal packing of py‐PBLG₆₆ rods is notably enhanced by the addition of SWCNTs, whereas the lamellar packing of py‐PGLG₉ β‐sheets is weakened. In the hexagonal lattice, the SWCNTs are intercalated parallel to the py‐PBLG₆₆ rods, in contrast to the normal orientation of the SWCNTs with respect to the extended py‐PBLG₉ chains in the β‐sheets. The relative packing structure also affects the intermolecular interaction among the PBLGs: SWCNTs promote the interaction among the py‐PBLG₉ chains packed in a lamellar structure and weaken the intermolecular interaction among the py‐PBLG₆₆ columnar hexagonal array. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4489–4497     

Molecular conformation and melting behavior of alkyl/oligo(oxyethylene)/alkyl triblock position isomers: effect of the position of an oligo(oxyethylene) block

The molecular conformation and melting behavior of triblock position isomers H(CH(2))(k)(OCH(2)CH(2))(4)O(CH(2))(12)(-)(k)H (abbreviated as C(k)E(4)C(12)(-)(k)) with k = 6-11 have been studied by infrared spectroscopy and differential scanning calorimetry (DSC), with focus on the effect of the position of an oligo(oxyethylene) block in the molecule. The analysis of infrared spectra has revealed that the stable molecular form changes from a fully planar structure (gamma form) to a planar/helical/planar structure (beta form) with a change of the position of the tetrakis(oxyethylene) block from the center to the end of the molecule. The DSC measurements have shown that the melting points of the gamma-form solid decrease and the melting points of the beta-form solid increase with a shift of the tetrakis(oxyethylene) block toward the terminal of the molecule. The stabilities of the two molecular forms change over between k = 8 and 9. C(8)E(4)C(4) and C(9)E(4)C(3) exhibit contrasting conformational behavior with temperature; when the temperature is increased, the metastable beta form of C(8)E(4)C(4) transforms into the stable gamma form, while the metastable gamma form of C(9)E(4)C(3) transforms into the stable beta form. The metastable gamma form with a planar oligo(oxyethylene) block is a new finding in the present work. The experimental results of the stabilities of molecular forms are explained by the relative stabilities of partial crystal lattices formed by the alkyl and oligo(oxyethylene) blocks.     

Packing of molecules of poly-<Emphasis Type="Italic">p</Emphasis>-phenylenebenzo-bis-oxazole in crystalline structures: Calculation by the molecular mechanics method

The mutual packing of trans- and cis-stereoisomeric molecules of poly-p-phenylenebenzo-bisoxazole is calculated by the molecular mechanics method. By varying all intramolecular and intermolecular parameters, energetically favorable structures are found. Calculation is performed both for molecules with uniform rotational isomeric composition (only TRANS or CIS mutual orientation of heterocycles along the polymer chain) and for molecules with random alternation of rotational isomers. In ordered structures, all molecules are shown to have a flat conformation and they are packed so that their planes are shifted along and perpendicular to the direction of molecular axes. The shifts can be similar [towards one (Δ) or another (?Δ) side] and alternating (±Δ). For trans-TRANS molecules with a homogeneous rotational isomeric composition, longitudinal shifts Δ and ?Δ are not equivalent because, in one case, similar heteroatoms of neighboring molecules appear to be the most closely positioned, whereas in the other case, this is true of different heteroatoms. As a result, different types of molecular packing develop: in the first case, structures with parallel mutual orientation of molecular planes form and, in the second case, the structures are characterized by parquet arrangement. When trans-TRANS molecules are packed with an alternating longitudinal shift, the mutual packing of molecules shows the parquet pattern. At the same time, for cis-stereoisomeric molecules with homogeneous or arbitrary rotational isomeric composition, only the parquet pattern in their mutual arrangement is observed. This conclusion disagrees with experimental evidence according to which, in crystalline structures, the planes of molecules are parallel to each other. For the above structures, the packing energy calculated with allowance for the experimental values of cell parameters appears higher than that for the structures under study. The difference in energy exceeds 80 kJ/mol (per one monomer unit). The experimentally observed type of crystalline structure is assumed to be conceived even at the stage of nucleation of crystal-solvate phases.     

Preparation and properties of methoxycarbonylsulfenyl isocyanate, CH(3)OC(O)SNCO

Pure methoxycarbonylsulfenyl isocyanate, CH3OC(O)SNCO, is quantitatively prepared by the metathesis reaction between CH3OC(O)SCl and AgNCO. This novel species has been obtained in its pure form and characterized by 1H and 13C NMR, UV-vis, FTIR, and FT-Raman spectroscopy. The conformational properties of the gaseous molecule have been studied by vibrational spectroscopy and quantum chemical calculations (B3LYP and MP2 methods). The compound exhibits a conformational equilibrium at room temperature having the most stable form CS symmetry with the C=O double bond synperiplanar with respect to the S-N single bond. A second form was observed in the IR spectrum and corresponds to a conformer possessing the C-S bond antiperiplanar with respect to the N=C double bond of the isocyanate group. The structure of a single crystal of CH3OC(O)SNCO was determined by X-ray diffraction analysis at low temperature using a miniature zone melting procedure. The crystalline solid (triclinic, P1, a = 8.292(6) A, b = 9.839(7) A, c = 11.865(8) A, alpha = 67.290(2) degrees , beta = 71.5570(10) degrees , gamma = 83.4850(10) degrees and Z = 6) shows the presence of molecules having exclusively a synperiplanar conformation with respect to the three phi(CO-C=O), phi(O=C-SN), and phi(CS-N=C) dihedral angles.     

共聚物/表面活性剂体系微观与宏观粘度

高分子与表面活性剂的相互作用，无论从基础研究还是应用研究均很有意义＊．表面活性剂和高分子相互作用往往可以使高分子链的的象变化，例如通过生成分子缔合复合作问（associatedcomPleX），改变高分子链的静电相互作用，可引起高分子链的舒展和卷曲．另一方面，高分子也影响表面活性剂的物理化学性质．例如，溶液表面张力、粘度、电导、表现临界胶束浓度（＊＊C）和聚集数（＊叫等物理参数。‘］．在实用方面，在高分子和表面活性剂相互作用的复合体中，表面活性剂分子排列接近生物膜结构，可作为模拟生物酶催化的模型体系问．由超高分…     

Structure,conformation, and motions of polytetrahydrofuran (PTHF) in the hexagonal form of the PTHF-urea inclusion compound

Combination of differential scanning calorimetry, x-ray diffraction, Fourier transform infrared, and C-13 nuclear magnetic resonance observations made on the crystalline inclusion compound (IC) formed between polytetrahydrofuran (PTHF) and urea (U), together with their comparison to identical observations performed on bulk semicrystalline samples of PTHF, have permitted an analysis of the conformations, motions, and environments available to PTHF chains in both solid-state phases. The isolated PTHF chains occupying the narrow channels of the PTHF-U-IC are highly extended, though small rotational deviations averaging 24° from the nearly all trans, planar zig zag conformation of bulk crystalline PTHF chains produce some significant differences in their behaviors. PTHF chains in PTHF-U-IC possess much greater mobility than bulk crystalline PTHF chains as evidenced by C-13 spin lattice relaxation times, T₁, 50 times shorter (1.5 s) than observed for bulk crystalline PTHF chains (75 s). FTIR observations are consistent with very little specific interaction between guest PTHF chains and host urea matrix molecules and result in similar spectra for bulk and IC PTHF, except for the presence of the CH₂ rocking vibration band at 745 cm^?1 observed for bulk PTHF. The absence of this band in the IC PTHF can be understood by considering the symmetry of the all trans, planar zig zag conformation of bulk crystalline PTHF chains, which prevents the CH₂ rocking mode from coupling with skeletal stretching and bending modes as occurs in the nonplanar, helical PTHF chains in PTHF-U-IC. © 1995 John Wiley & Sons, Inc.     

A class of nonplanar conjugated compounds with aggregation-induced emission: structural and optical properties of 2,5-diphenyl-1,4-distyrylbenzene derivatives with all cis double bonds

We have studied the structural and optical properties of four 2,5-diphenyl-1,4-distyrylbenzene derivatives with all cis double bonds. These compounds belong to a class of nonplanar conjugated compounds possessing a typical Aggregation-Induced Emission (AIE) property that has no emission in solution but intense emission in crystal. The four molecules are packed in different stacking modes with different intermolecular interactions, resulting in different crystalline state photoluminescence (PL) efficiency. The torsional molecular configuration increases the intermolecular distances effectively in the crystalline state, which decreases the difference of the optical properties from the frozen isolated molecules to the crystalline state. The Stokes shifts of these compounds are very large and the PL spectra have only one broad emission band with poor structure, due to the relatively large configuration difference between the ground state and the first singlet excited state, and the abundant vibration energy levels of the torsional molecule with changeable conformation.     

Study of the effect of hydrogen bonding on the phase behaviour of p-nitro azobenzene derivatives with hydrophilic tails

The infrared spectra of N-n-(4-nitrophenyl)azophenyloxyalkyldiethanolamines (Cn) are examined in the range of 4000-400cm-1 at different temperatures and the assignment of the fundamental vibrations given. Based on (1) the localization of the broad absorption band at 3456cm-1, and (2) attribution of the associated OH bands centred at 1410-1390, 1100, and 650-634cm-1 to, respectively deltaOH deformation, nuC-O stretching and gammaOH out-of-plane bending, intermolecular hydrogen bonding between OH groups in the crystalline, liquid crystalline and isotropic states is proposed. By considering the results of FTIR, WAXD and DSC measurements, the molecular arrangment of C10 in its smectic A phase as consisting of hydrogen bonding and strong interaction between dipolar groups (NO2) is proposed. This may explain the high stability and high orientational ordering property of Cn compounds in the liquid crystalline state compared with that of n-bromo-1-[4-(4-nitrophenyl)azophenyl] oxyalkanes (Bn).     

Spectroscopic study of α- and β-phase isotactic polypropylene and of atactic polypropylene in solution

Raman spectroscopy is used to investigate the conformation and packing of isotactic crystalline α-phase polypropylene compared with lower-order β-phase isotactic polypropylene and to study the solution behavior of atactic polypropylene. The high-frequency region of the spectrum is analyzed in light of a normal-mode calculation that takes into account the methyl-group vibrations. This region is sensitive to both chain conformation and packing, and because of the high intensity of the methyl and methylene high-frequency stretching modes, it can be used to probe small changes in intermolecular or intramolecular order. Differences in the thermal behavior between the two solid isotactic polypropylene samples are explained interms of packing defects which exist in the β-phase form. In the solution study, we demonstrate that, for molecules in which bands sensitive to intermolecular interactions exist, as is the case of the methyl and methylene vibrations of polypropylene, spectroscopic techniques can be used to estimate the minimum overlap concentration.     

Study of the effect of hydrogen bonding on the phase behaviour of p-nitro azobenzene derivatives with hydrophilic tails

The infrared spectra of N-n-(4-nitrophenyl)azophenyloxyalkyldiethanolamines (Cn) are examined in the range of 4000-400cm-1 at different temperatures and the assignment of the fundamental vibrations given. Based on (1) the localization of the broad absorption band at 3456cm-1, and (2) attribution of the associated OH bands centred at 1410-1390, 1100, and 650-634cm-1 to, respectively deltaOH deformation, nuC-O stretching and gammaOH out-of-plane bending, intermolecular hydrogen bonding between OH groups in the crystalline, liquid crystalline and isotropic states is proposed. By considering the results of FTIR, WAXD and DSC measurements, the molecular arrangment of C10 in its smectic A phase as consisting of hydrogen bonding and strong interaction between dipolar groups (NO2) is proposed. This may explain the high stability and high orientational ordering property of Cn compounds in the liquid crystalline state compared with that of n-bromo-1-[4-(4-nitrophenyl)azophenyl] oxyalkanes (Bn).     

Structural and spectral perspectives of a novel thiosemicarbazone synthesized from di-2-pyridyl ketone and 4-phenyl-3-thiosemicarbazide

A new thiosemicarbazone, HL is synthesized from di-2-pyridyl ketone and 4-phenyl-3-thiosemicarbazide and structurally and spectrochemically characterized. 1H NMR, 13C NMR, COSY, HMQC and IR spectra of the compound are studied and the proton magnetic resonance spectrum reveals some unprecedented observations. The thione form is predominant in the solid state, as supported by the crystal structure and IR data, while a thiol-thione equilibrium is proposed in the solution state by NMR studies. The compound crystallizes into a monoclinic lattice with space group C2/c and the ZE conformation is exhibited by the thiosemicarbazone. Intra- and intermolecular hydrogen-bonding interactions give rise to a two-dimensional packing in the crystal lattice.     

Conformational Polymorphism in N‐(4′‐methoxyphenyl)‐ 3‐bromothiobenzamide

Three conformational polymorphs of N‐(4′‐methoxyphenyl)‐3‐bromothiobenzamide, yellow α, orange β, and yellow γ, have been identified by single‐crystal X‐ray diffraction. The properties and structure of the polymorphs were examined with FT Raman, FTIR (ATR), and UV/Vis spectroscopy, as well as differential scanning calorimetry. Computational data on rotational barriers in the isolated gas‐phase molecule indicate that the molecular conformation found in the α form is energetically preferred, but only by around 2 kJ mol^?1 over the γ conformation. The planar molecular structure found in the β form is destabilized by 10–14 kJ mol^?1, depending on the calculation method. However, experimental evidence suggests that the β polymorph is the most stable crystalline phase at room temperature. This is attributed to the relative planarity of this structure, which allows more and stronger intermolecular interactions, that is, more energetically effective packing. Calculated electronic‐absorption maxima were in agreement with experimental spectra.     

Structure-fluorescence relationships in pyrrole appended o-carborane crystalline materials

Based on three rationally designed pyrrole-appended o-carborane derivatives, we present that fluorescence properties of crystalline materials are highly dependent on intermolecular interaction and steric hinderance. Though the three molecules are similar in structure, single crystals of the three compounds showed obvious difference in molecular stacking and fluorescence behavior. Systematic studies indicate that fluorescence quantum yields, thermo-response as well as mechano-response are highly ...