Biaxial nematic phases in fluids of hard board-like particles

We use density-functional theory, of the fundamental-measure type, to study the relative stability of the biaxial nematic phase, with respect to non-uniform phases such as smectic and columnar, in fluids made of hard board-like particles with sizes σ(1) > σ(2) > σ(3). A restricted-orientation (Zwanzig) approximation is adopted. Varying the ratio κ(1) = σ(1)/σ(2) while keeping κ(2) = σ(2)/σ(3), we predict phase diagrams for various values of κ(2) which include all the uniform phases: isotropic, uniaxial rod- and plate-like nematics, and biaxial nematic. In addition, spinodal instabilities of the uniform phases with respect to fluctuations of the smectic, columnar and plastic-solid types are obtained. In agreement with recent experiments, we find that the biaxial nematic phase begins to be stable for κ(2)? 2.5. Also, as predicted by previous theories and simulations on biaxial hard particles, we obtain a region of biaxiality centred at κ(1)≈κ(2) which widens as κ(2) increases. For κ(2)? 5 the region κ(2)≈κ(1) of the packing-fraction vs. κ(1) phase diagrams exhibits interesting topologies which change qualitatively with κ(2). We have found that an increasing biaxial shape anisotropy favours the formation of the biaxial nematic phase. Our study is the first to apply FMT theory to biaxial particles and, therefore, it goes beyond the second-order virial approximation. Our prediction that the phase diagram must be asymmetric in the neighbourhood of κ(1)≈κ(2) is a genuine result of the present approach, which is not accounted for by previous studies based on second-order theories.     

In situ Raman and in situ XRD analysis of PdO reduction and Pd° oxidation supported on γ-Al2O3 catalyst under different atmospheres

Reduction of Pd° and decomposition of palladium oxide supported on γ-alumina were studied at atmospheric pressure under different atmospheres (H(2), CH(4), He) over a 4 wt% Pd/Al(2)O(3) catalyst (mean palladium particle size: 5 nm with 50% of small particles of size below 5 nm). During temperature programmed tests (reduction, decomposition and oxidation) the crystal domain behaviour of the PdO/Pd° phase was evaluated by in situ Raman spectroscopy and in situ XRD analysis. Under H(2)/N(2), the reduction of small PdO particles (<5 nm) occurs at room temperature, whereas reduction of larger particles (>5 nm) starts at 100 °C and is achieved at 150 °C. Subsequent oxidation in O(2)/N(2) leads to reoxidation of small crystal domain at ambient temperature while oxidation of large particles starts at 300 °C. Under CH(4)/N(2), the small particle reduction occurs between 240 and 250 °C while large particle reduction is fast and occurs between 280 and 290 °C. Subsequent reoxidation of the catalyst reduced in CH(4)/N(2) shows that small and large particle oxidation of Pd° starts also at 300 °C. Under He, no small particle decomposition is observed probably due to strong interactions between particles and support whereas large particle reduction occurs between 700 and 750 °C. After thermal decomposition under He, the oxidation starts at 300 °C. Thus, the reduction phenomenon (small and large crystal domain) depends on the nature of the reducing agent (H(2), CH(4), He). However, whatever the reduction or decomposition treatment or the crystal domain, Pd° oxidation starts at 300 °C and is completed only at temperatures higher than 550 °C. Under lean conditions, with or without water, the palladium consists of reduced sites of palladium (Pd°, Pd(δ+) with δ < 2 or PdO(x) with x < 1) randomly distributed on palladium particles.     

Molecular association of heteronuclear vibrating square-well dumbbells in liquid-vapor phase equilibrium

Molecular aggregates are formed by heteronuclear vibrating square-well dumbbells. In a recent article [G. A. Chapela and J. Alejandre, J. Chem. Phys., 132(10), 104704 (2010)], it is shown that heteronuclear vibrating square-well dumbbells with a diameter ratio between particles of 1/2 and interacting potential ratio of 4 form micelles of different sizes and shapes which manifest themselves in both the liquid and vapor phases, up to and above the critical point. This means that micellization and phase separation are present simultaneously in this simple model. These systems present a maximum in the critical temperature when plotted against the potential well depth of the second particle ε(2). In the same publication, it was speculated that the formation of micelles was responsible for the appearance of the maximum. A thorough study on this phenomena is presented here and it is found that there is a threshold on the size of the second particle and its corresponding depth of interaction potential, where the micelles are formed. If the diameter and well depth of the second particle are small enough for the first and deep enough for the second, micelles are formed. For σ(2)/σ(1) between 0.25 and 0.65 and ε(2)/ε(1) larger than 5.7, micelles are formed up to and above the critical temperature. Outside these ranges micelles appear only at temperatures lower than the critical point. There is a strong temperature dependence on the formation and persistence of the aggregates. For the deepest wells and large enough second particles, a gel interconnected aggregate is obtained. In this work, the micelles are formed at temperatures as low as the triple point and as high as the critical point and, in some cases, persist well above it. The presence of these maxima in critical temperatures T(c) when plotted against ε(2) as follows. At lower values of ε(2), an increase of T(c) is obtained as is expected by the increase of the attractive volume as indicated by the principle of corresponding states. As ε(2) increases further, the formation of molecular aggregates produce a saturation effect of the deepening of the potential well by encapsulating the particles of the second kind inside the micelles, so the resulting T(c) represents a new poly disperse system of molecular aggregates and not the original heteronuclear vibrating square-well dumbbells. The surface tension is also analyzed for these systems, and it is shown that decreases with increasing attraction due to the formation of molecular aggregates.     

Synthesis and Crystal Structure of Carvedilol

1INTRODUCTI0NCarvedilol,1-(4-carbazolyloxy)-3-[2-methoxyphenoxy)ethylaminoj-2-propanol,isanewgblockingandvasodilatingagent"'.IthadsynthesizedbyF.Wiedemannetalt23.Howeverthereportaboutcrystalstructureofcarvedilolhasnotbeenseen.Inthispaper,wediscussthecrystalstructureofthecarvedilolsynthe-sized[2ibythereacti0nof4-(2,3-ex0xypropoxy)-carbazoleand2-(2-methoxyphe-noxy)ethylamine.Sinceknowledgeofthemolecularandcrystalstructureofcarvedil0lwasconsideredusefulforunderstandingthemechanismoftheactio…     

Hard sphere fluids at a soft repulsive wall: a comparative study using Monte Carlo and density functional methods

Hard-sphere fluids confined between parallel plates at a distance D apart are studied for a wide range of packing fractions including also the onset of crystallization, applying Monte Carlo simulation techniques and density functional theory. The walls repel the hard spheres (of diameter σ) with a Weeks-Chandler-Andersen (WCA) potential V(WCA)(z) = 4ε[(σ(w)/z)(12) - (σ(w)/z)(6) + 1/4], with range σ(w) = σ/2. We vary the strength ε over a wide range and the case of simple hard walls is also treated for comparison. By the variation of ε one can change both the surface excess packing fraction and the wall-fluid (γ(wf)) and wall-crystal (γ(wc)) surface free energies. Several different methods to extract γ(wf) and γ(wc) from Monte Carlo (MC) simulations are implemented, and their accuracy and efficiency is comparatively discussed. The density functional theory (DFT) using fundamental measure functionals is found to be quantitatively accurate over a wide range of packing fractions; small deviations between DFT and MC near the fluid to crystal transition need to be studied further. Our results on density profiles near soft walls could be useful to interpret corresponding experiments with suitable colloidal dispersions.     

Self‐assembly of nanorod/nanoparticle mixtures in polymer brushes

The aggregation behavior and phase separation of nanorod (NR)/nanoparticle (NP) nanoinclusions immersed in semiflexible polymer brushes (PBs) are investigated by using molecular dynamics simulations. A variety of phases are formed by varying the size ratio q = σ_r/σ_p, where σ_r and σ_p are the diameters of NR and NPs, respectively, and the attractive interactions ε_M between NR/NP nanoinclusions and PBs. Ordered structures of NRs surrounded by large NPs are observed for the small size ratio q, and a dispersed mixture phase appears for the moderate size ratio q at weak attractive interaction. Meanwhile, the crystallization of NRs occurs at strong attractive interaction for the large size ratio q and a main face‐centered cubic (fcc) structure combined with a small amount of hexagonal‐closed packed (hcp) structure is observed. This investigation can provide some insights into the self‐assembly of complex nanoinclusions and promise a new approach for controlling the self‐assemble behavior of NPs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 299–309     

Alkoxyamine re-formation reaction. Effects of the nitroxide fragment: a multiparameter analysis

A few years ago, Studer and co-workers (Macromolecules 2006, 39, 1347-1352) reported the dramatic effect of the reaction of re-formation of alkoxyamines on the fate of the nitroxide-mediated polymerization (NMP) of styrene. This prompted us to investigate more carefully the effects of the nitroxide structure on the re-formation rate constant k(c). Ten new values of k(c) were obtained for the reaction of imidozalidine nitroxide and the phenethyl radical. These values were combined with the 21 values of k(c) reported in the literature for a multiparameter analysis (log(k(c)/M(-1) s(-1)) = (10.22 ± 0.10) + (0.46 ± 0.02)E(s) + (0.41 ± 0.17)σ(I)) using the electrical Hammett constant σ(I) to describe both the stabilization and polar effects as well as the modified Taft steric constant E(s) of the nitroxide. The same analysis was performed for the k(c) values of the cross-coupling reaction of nitroxides with tert-butoxylcarbonyl-2-prop-2-yl radical (log(k(c)/M(-1) s(-1)) = (11.10 ± 0.25) + (0.57 ± 0.05)E(s) + (1.42 ± 0.18)σ(I)) and tert-butoxycarbonylethyl radical (log(k(c)/M(-1) s(-1)) = (10.23 ± 0.16) + (0.35 ± 0.03)E(s) + (0.93 ± 0.25)σ(I)). These correlations were applied for the analysis of the NMP of styrene controlled by 6π(?), 6θ(?), and 6ρ(?) using a Fischer phase diagram.     

THE CRYSTAL AND MOLECULAR STRUCTURE OF N,N''''-Di-n-BUTYL-29,30-DIMETHOXY- 13,27-DIMETHYL-6,20-DIAZA-3,9, 17,23-TETRAOXATRICYCLIC(23.3.1.1~(11 ,1S)- CYCLOTRIACONTANE-1(29),11,13,15(30),25,27-HEXENE

<正> C36H58N2O6, Mr=614.84, triclinic, Pl, a=8.730(2), b=9.560(4), c=11.320(5)A, α=68.43(3), β=89.18(3), r=86.51(3), V=877.2A3, 2=1, Dc=1.16 gcm-3, λ(MoKα)=0.7017A, μ=0.84cm-1, full matrix least-squares refinement; final R=0.080, Rw=0.050 for 1713 (I>3σ) unique reflections. The crystal is composed of discrete molecules having an approximate centre of symmetry and the nolecular packing in the crystal is determined solely by van der Walls forces. The six non-carbon atoms in the 28- membered ring are approximately coplanar. The distances of O(32)...O(42) and O(31)...O(41) are 8.718and 6.954A,and that for N(31)...N(41) 10.976A. ' '     

Influence of a depletion interaction on dynamical heterogeneity in a dense quasi-two-dimensional colloid liquid

We report the results of digital video microscopy studies of the large particle displacements in a quasi-two-dimensional binary mixture of large (L) and small (S) colloid particles with diameter ratio sigma(L)/sigma(S)=4.65, as a function of the large and small colloid particle densities. As in the case of the one-component quasi-two-dimensional colloid system, the binary mixtures exhibit structural and dynamical heterogeneity. The distribution of large particle displacements over the time scale examined provides evidence for (at least) two different mechanisms of motion, one associated with particles in locally ordered regions and the other associated with particles in locally disordered regions. When rhoL*=Npisigma(L) (2)/4A< or =0.35, the addition of small colloid particles leads to a monotonic decrease in the large particle diffusion coefficient with increasing small particle volume fraction. When rhoL* > or =0.35 the addition of small colloid particles to a dense system of large colloid particles at first leads to an increase in the large particle diffusion coefficient, which is then followed by the expected decrease of the large particle diffusion coefficient with increasing small colloid particle volume fraction. The mode coupling theory of the ideal glass transition in three-dimensional systems makes a qualitative prediction that agrees with the initial increase in the large particle diffusion coefficient with increasing small particle density. Nevertheless, because the structural and dynamical heterogeneities of the quasi-two-dimensional colloid liquid occur within the field of equilibrium states, and the fluctuations generate locally ordered domains rather than just disordered regions of higher and lower density, it is suggested that mode coupling theory does not account for all classes of relevant fluctuations in a quasi-two-dimensional liquid.     

Nonadiabatic dynamics of O(1D) + N2(X1Σg+) → O(3P) + N2(X1Σg+) on three coupled potential surfaces: symmetry, Coriolis, spin-orbit, and Renner-Teller effects

We present the spin-orbit (SO) and Renner-Teller (RT) quantum dynamics of the spin-forbidden quenching O((1)D) + N(2)(X(1)Σ(g)(+)) → O((3)P) + N(2)(X(1)Σ(g)(+)) on the N(2)O X(1)A', ?(3)A", and b(3)A' coupled PESs. We use the permutation-inversion symmetry, propagate coupled-channel (CC) real wavepackets, and compute initial-state-resolved probabilities and cross sections σ(j(0)) for the ground vibrational and the first two rotational states of N(2), j(0) = 0 and 1. Labeling symmetry angular states by j and K, we report selection rules for j and for the minimum K value associated with any electronic state, showing that ?(3)A" is uncoupled in the centrifugal-sudden (CS) approximation at j(0) = 0. The dynamics is resonance-dominated, the probabilities are larger at low K, σ(j(0)) decrease with the collision energy and increase with j(0), and the CS σ(0) is lower than the CC one. The nonadiabatic interactions play different roles on the quenching dynamics, because the X(1)A'-b(3)A' SO effects are those most important while the ?(3)A"-b(3)A' RT ones are negligible.     

Synthesis of tailored core-brush polymer particles via a living radical polymerization and architecture of colloidal crystals

Narrow disperse core-brush polymer nanoparticles (BP) were synthesized by grafting from photo-induced atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate (HEMA) from N,N-diethyldithiocarbamate (DC) groups of core-shell particle surface. We constructed colloidal crystals of these particles by depositing on glass substrate. By variation of the particle size, the brilliant color could be varied throughout the visible spectrum. We locked also permanently such colloidal crystals by cross-linking of poly(2-hydroxyethyl methacrylate) (PHEMA) brush phases with glutaraldehyde. The peak wavelength (λ(max)) in the reflection spectra agreed well with the bandgap position for light incident on the (1 1 1) face of face-centered cubic (fcc) lattice according to Bragg's law.     

String formation and demixing in monolayers of dipolar colloidal mixtures

Employing hypernetted chain (HNC) integral equations and a stability analysis we investigate the structure and phase behavior of bidisperse mixtures of dipolar hard spheres with different size ratios s=σ(S)/σ(L) confined to a plane. The dipole moments of the particles are perfectly ordered along an in-plane direction, yielding anisotropic interactions favoring chain formation. Exploring a range of size ratios and compositions, our study predicts a complex interplay between aggregation phenomena, on the one hand, and volume phase transitions, on the other hand. In dilute, strongly asymmetric systems (s = 0.5), our HNC analysis indicates chain formation of the large particles, while the small particles act as a weakly correlated background. According to our fluctuation analysis, this aggregation behavior results in combined condensation-demixing transitions, with a trend towards pure demixing when the concentration of the large particles, c(L), becomes small. In dense systems, the most interesting results are found for intermediate size ratios, s ~ 0.7-0.8. Here we find signatures of a concentration-driven transition from pure chains of large particles (large c(L)) to mixed chains with alternating order of large and small particles (small c(L)). The two regimes are separated by a characteristic "jump" in the HNC non-solution line.     

Synthesis and Crystal Structure of exo-4-（3,4-Dichlorophenyl）-8-ethyl-3,3a,4,5,8, 12d-hexahydro-2H-furo[3,2-c]indolo[3,2-f]quinoline

The title compound exo-4-(3,4-dichlorophenyl)-8-ethyl-3,3a,4,5,8,12d-hexahydro-2H-furo[3,2-c]indolo[3,2-f]quinoline (C25H22Cl2N2O, Mr = 437.35) was synthesized and crystallized. The crystal belongs to tetragonal, space group I4(1)/a with a = 17.4903(3), b = 17.4903(3), c = 28.3403(5) , Z = 16, V = 8669.6(3) 3, Dc = 1.340 g·cm-3, μ(MoKɑ) = 0.319 mm-1, F(000) = 3648, R = 0.0429 and wR = 0.711 for 2714 observed reflections I > 2σ(I). X-ray analysis reveals that atoms C(1), C(2), C(3), C(4), C(5) and N(1) on the new pyridine ring are slightly distorted, forming a distorted boat conformation.     

Synthesis and Crystal Structure of (E)-2-(1-(2-Hydroxy-4-methoxyphenyl)ethylideneamino)-3-(4-hydroxyphenyl)methyl Propionate

(E)-2-(1-(2-Hydroxy-4-methoxyphenyl)ethylideneamino)-3-(4-hydroxyphenyl)methyl propionate (C22H27O6N, Mr = 401.45) has been synthesized by a condensation reaction of paeonol with tyrosin methyl ester hydrochloride, and its structure was determined by IR, NMR, HR MS and X-ray single-crystal diffraction. The crystal belongs to the monoclinic system, space group P21/c, with a = 11.91291(15), b = 9.49947(12), c = 19.8727(3) , β = 106.1104(15)°, V = 2160.60(5)3, Z = 4, Dc = 1.234 g/cm3, μ = 0.739 mm-1, F(000) = 856, R = 0.0466 and wR = 0.1461 for 3859 observed reflections with (Ⅰ> 2σ(Ⅰ)). In the crystal structure, the title compound is constructed by a centrosymmetric dimmer unit composed of a pair of π-π stacking enantiomers, and such units are linked by intermolecular O(5)-H(5)…O(1) and intramolecular N(1)-H(1)…O(1) hydrogen bonds.     

Exploitation of an additional hydrophobic pocket of σ1 receptors: late-stage diverse modifications of spirocyclic thiophenes by C-H bond functionalization

The hypothesis that the σ(1) receptor will tolerate an additional aryl moiety in position 1 of the spirocyclic system was based on spirocyclic pyrazole derivatives, pharmacophore models of σ(1) receptor ligands and DFT calculations. The strategy of introducing the aryl residue at the final step of the synthesis allowed the preparation of a large set of diverse ligands for the exploitation of the hydrophobic pocket of the σ(1) receptor protein. The catalyst system PdCl(2)/2,2'-bipyridyl/Ag(2)CO(3) is able to introduce various aryl groups onto the α-positions of spirocyclic thiophene derivatives 5 and 6 to afford the target aryl-appended spirocyclic thiophenes 3 and 4. Although the σ(1) affinity of the 1-phenyl substituted spirocyclic thiophenes 3a and 4a is slightly reduced compared with the σ(1) affinity of the non-arylated compounds 5 and 6, both compounds represent very potent σ(1) receptor ligands (3a: K(i) = 4.5 nM; 4a: K(i) = 1.0 nM). This result indicates that an aryl moiety in position 1 is well tolerated by the σ(1) receptor protein. The substitution pattern of the additional phenyl moiety has only weak effects on the σ(1) affinity. Even ligands 3f and 4h with extended naphthyl residue show high σ(1) affinity. However, decrease of σ(1) affinity by extension of the π-system to a biphenylyl substituent (4j: K(i) = 30 nM) indicates that the biphenylyl residue is too large for the primary hydrophobic binding pocket of the σ(1) receptor.     

Synthesis and Crystal Structure of N-[(3aR,4R,4aR,5aS,6S,6aS)-1,3-Dioxooctahydro-4,6-ethenocyclopropa[f]lisoindol-2(1H)-yl]-3-(trifluoromethyl)phenylmethanimine

The crystal structure of the title compound (C19H15F3N2O2, Mr= 360.33) was determined by single-crystal X-ray diffraction. The crystal belongs to triclinic, space group P(1), with a = 6.5604(7), b = 13.9614(16), c = 18.1790(18) (A), α = 102.749(7),β = 97.542(6), γ = 94.355(4)°, V= 1600.5(3) (A)3, Z = 4, Dc = 1.495 g/cm3, λ(MoKα) = 0.71070, F(000) = 744, μ(MoKα) = 0.122mm-1, R = 0.0434 and wR = 0.1051. A total of 7590 unique reflections were collected, of which 5429 with |F|2 ≥ 2σ|F|2 were observed. The two cyclohexene rings in the molecule adopt boat-boat conformations with the deviations of ring atoms C(9) and C10 from the C(5)/C(6)/C(7)/C(8) plane (Ⅰ) by 1.1204 (0.0023) and 1.1132 (0.0023) (A), respectively, whereas from the C(2)/C(3)/C(5)/C(8)plane (Ⅱ) by 1.1627 (0.0022) and 1.1818 (0.0021) (A), respectively. In the cyclopropane and lactam rings, atoms C(11) and N(1) point towards the double bond of C(9)-C(10) and the dihedral angle between the ring plane (Ⅲ) containing C(1), C(2), C(3) and C(4) and plane (Ⅳ) consisting of C(6),C(7) and C(11) is 55.76 (0.07)°. The dihedral angles between planes Ⅳ and Ⅰ and Ⅱ and Ⅲ are 63.58 (0.07)° and 58.10 (0.06)°, respectively. The dihedral angle between the benzene ring C(13)～C(18) and plane Ⅳ is 42.41 (0.06)°.     

Synthesis and Crystal Structure of N-[1-(4-Chlorophenyl)- 1,4-dihydro-4-oxe-6-methylpyridazine-3-carbonyl]- N'-benzoylhydrazine

1 INTRODUCTION Pyridazinone derivatives represent one of the most active classes of compounds possessing a wide spectrum of biological activity. It was widely used in pharmaceuticals and agrochemicals[1, 2]. Rohm Haas Company had reported that pyridazinones exhibit useful plant growth regulating effects [3,4]. It was also reported that diacylhydrazines exhibit excellent insecticides [5~7]. In view of these facts, it was contemplated to synthesize compounds con- taining both pyridazinone …     

钙稀土氟碳酸盐矿物中体衍交生结构的电子显微镜研究

用高分辨电子显微术研究了四川西昌地区钙稀氟碳酸盐矿物中的体衍生复合多晶体超微结构特征，直观地揭示了该类矿物非均匀结构的复杂性。研究表明，该矿物体是由钙稀土氟碳酸盐矿物系列中不同组分的氟碳铈矿与直氟碳钙铈矿结构单元层沿ｃ轴方向无序堆垛而成。     

Synthesis,Characterization and X-ray Crystal Structure of N,N＇-Bis（4-nitrophenylcarba-mothioyl）-isophthalamide·DMF

A new crystal of N,N'-bis(4-nitrophenylcarbamothioyl)isophthalamide DMF solva-te has been prepared at room temperature and characterized by elemental analysis and IR,MS,1H NMR spectra and X-ray single-crystal determination.The complex crystallizes in monoclinic,space group P21/c with a = 11.2093(12),b = 22.081(2),c = 13.9640(15) ,β= 112.128(2)°,V = 3201.8(6) 3,C28H30N8O8S2,Mr = 670.72,Dc = 1.391 Mg/m3,Z = 4,μ= 0.228 mm-1,F(000) = 1400,the final R = 0.0483 and wR = 0.1411(I > 2σ(I)).The molecular packing in the crystal is the result of N-H…O hydrogen bonding.     

Syntheses and Characterization of Two Novel Mo（W）/Cu/S Dodecanuclear Clusters with Triple Incomplete Cubane-like Structure

The self-assembly reactions of [MOS3]^2- （M = W, Mo） with CuS2COCH3 in DMF produced two novel dodecanuclear Mo（W）/Cu/S heterometallic clusters, [Et4N]4[{MOS3}3Cu6S2- （CuS2COCH3）3]·H2O （1： M = W; 2： M = Mo）. Cluster 1 crystallizes in hexagonal, space group P-62c with a = 16.5612（3）, b = 16.5612（3）, c = 16.4660（5）A, Z = 2, V = 3911.13（16）A^3, Dc = 1.935 g/cm^3, μ（MoKα） = 7.269 mm^-1, F（000） = 2192, the final R = 0.0289 and wR = 0.0789 for 2425 observed reflections （I 〉 2σ（I））. Cluster 2 is isomorphous to 1 with similar crystal parameters. X-ray analysis reveals that both clusters consist of three incomplete cubane-like cluster units {MOS3Cu3S2COCH3}, which are linked together by two μ3-S atoms.