Viscometric and volumetric studies on binary mixtures of 1,2-dichloroethane and chlorinated methanes or their binary equimolar mixtures at 303.15 K

Excess viscosities, η^E and molar excess volumes V^E were obtained for binary mixtures of 1,2-dichloroethane and chlorinated methanes and for pseudobinary mixtures of 1,2-dichloroethane and equimolar binary mixtures from chlorinated methanes at 303.15 K. The chlorinated methanes include carbon tetrachloride, chloroform and dichloromethane. Grunberg—Nissan interaction parameter d and interaction energy for flow of activation W_vis were also presented. The relationship between the η^E's and the V^E's has been quantitively considered using Singh's equations. The excess viscosities for all the systems are negative over the entire compositions. There are specific interactions between 1,2-dichloroethane and chlorinated methanes, but the specific interactions are not strong. The interactions of 1,2-dichloroethane with chlorinated methanes decrease in the order: chloroform > dichloromethane > carbon tetrachloride. ‘Pseudochloroform’ has been defined by us for the first time as the equimolar mixture of dichloromethane and carbon tetrachloride.     

Adjusting selectivity in micellar electrokinetic capillary chromatography with 1,2-hexanediol

In this report, we introduce a new micelle modifier useful to alter selectivity in micellar electrokinetic capillary chromatography (MECC). 1,2-Hexanediol acts as a class I organic modifier in that its effects are on the sodium dodecyl sulfate (SDS) micellar rather than the surrounding aqueous phase. This characteristic allows 1,2-hexanediol to improve resolution when applied at concentrations as low as 20 mM (0.25% v/v) by altering the selectivity observed with SDS alone. The effects of 1,2-hexanediol on the critical micelle concentration of SDS, electroosmotic flow, electrophoretic mobility of the SDS micelle, and reproducibility are presented. 1,2-Hexanediol had little impact on the migration time window at concentrations below 100 mM. Changes in selectivity induced by 1,2-hexanediol for a large set of model compounds are presented. Analytes capable of forming hydrogen bonds tend to decrease their interactions with the micellar phase while nonhydrogen bonding analytes increase their interactions. The usefulness of 1,2-hexanediol was demonstrated by examining its effects on the separation of dansylated amino acids. Eighteen of twenty amino acids could be separated with a resolution greater than 1.6 within 1600 s using a combination of 1,2-hexanediol and isopropanol.     

Theoretical study on the consecutive 1,2-hydroboration and 1,1-organoboration reactions of alkyn-1-yl(vinyl)silane with borane

The detailed pathway of the consecutive 1,2-hydroboration and 1,1-organoboration reactions of alkyn-1-yl(vinyl)silane with borane were studied theoretically by DFT calculations. It is found that the 1,2-hydroboration will occur at the CC moiety when the alkynyl end is substituted, and give the anti-Markovnikov adduct as a result of steric hindrance. From the 1,2-hydroboration intermediate, the intramolecular 1,1-organoboration is a concerted asynchronous process, in which the C-Si cleavage precedes 1,2-alkyl migration, with activation energy about 25 kcal/mol. Calculations reveal the electronic property of the substituent at the alkyne end has quite limited effect on the 1,1-organoboration activation energy. The ring constrain is found to influence the weak Si-H-B interactions in the 1-silacyclopent-2-ene product most, and similar C-H-B interactions were predicted for the corresponding carbon analogues.     

Enthalpic interaction coefficients of NaI–alkanediol pairs in methanol and in water

The dissolution enthalpies of NaI in the mixtures of methanol with 1,2-alkanediols (1,2-propanediol, 1,2-butanediol, 1,2-pentanediol) and with ??,??-alkanediols (1,3-propanediol, 1,4-butanediol, 1,5-pentanediol), as well NaI in the mixtures of water with 1,3-propanediol and 1,2-pentanediol, were determined at 298.15?K. The energetic effect of interactions between the investigated alkanediols and NaI in methanol and in water was calculated using the enthalpic pair interaction coefficients (h _xy ) model. These results along with the other data concerning the NaI?Cnon-electrolyte pairs taken from our earlier reports and from the literature were analyzed with respect to the effect of the non-electrolyte properties on the variations of the h _xy values. The group contributions illustrating the interactions of NaI with selected functional groups in non-electrolyte (alkanediol and alkanol) molecules, namely: CH₂ and OH groups were calculated and discussed.     

Interactions of a fungistatic antibiotic, griseofulvin, with phospholipid monolayers used as models of biological membranes

Griseofulvin (GF) is an oral antibiotic for widely occurring superficial mycosis in man and animals caused by dermaphyte fungi; it is also used in agriculture as a fungicide. The mechanism of the biological activity of GF is poorly understood. Here, the interactions of griseofulvin with lipid membranes were studied using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), and 1,2-myristoyl-sn-glycero-3-phosphoethanolamine (DMPE) monolayers spread at the air/water interface. Surface pressure (Pi), electric surface potential (Delta V), grazing incidence X-ray diffraction (GIXD), and Brewster angle microscopy (BAM) were used for studying pure phospholipid monolayers spread on GF aqueous solutions, as well as mixed phospholipid/GF monolayers spread on pure water subphase. Moreover, phospholipase A2 (PLA2) activity toward DLPC monolayers and molecular modeling of the GF surface and lipophilic properties were used to get more insight into the mechanisms of GF-membrane interactions. The results obtained show that GF has a meaningful impact on the film properties; we propose that nonpolar interactions are by and large responsible for GF retention in the monolayers. The modification of membrane properties can be detected using both physicochemical and enzymatic methods. The results obtained may be relevant for elaborating GF preparations with increased bioavailability.     

13C CP/MAS NMR Studies of Hemoprotein Models with and without an Axial Hindered Base: (13)C Shielding Tensors and Comparison with Hemoproteins and X-ray Structural Data

13C cross-polarization magic-angle-spinning (CP/MAS) NMR spectra of several carbonmonoxide (93-99% (13)C enriched) hemoprotein models with 1,2-dimethylimidazole (1,2-diMeIm) and 1-methylimidazole (1-MeIm) as axial ligands are reported. This enables the (13)CO spinning sideband manifold to be measured and hence the principal components of the (13)CO chemical shift tensor to be obtained. Negative polar interactions in the binding pocket of the cap porphyrin model and inhibition of Fe-->CO back-donation result in a reduction in shielding anisotropy; on the contrary, positive distal polar interactions result in an increase in the shielding anisotropy and asymmetry parameter in some models. It appears that the axial hindered base 1,2-dimethylimidazole has little direct effect on the local geometry at the CO site, despite higher rates of CO desorption being observed for such complexes. This suggests that the mechanism by which steric interactions are released for the 1,2-diMeIm complexes compared to 1-MeIm complexes does not involve a significant increase in bending of the Fe-C-O unit. The asymmetry of the shielding tensor of all the heme model compounds studied is smaller than that found for horse myoglobin and rabbit hemoglobin.     

Conformational and stereoelectronic investigation in 1,2-difluoropropane: The gauche effect

The effect of attaching an additional fluorine atom at C-2 in 1-fluoropropane (FP), giving 1,2-difluoropropane (DFP), on its conformational equilibrium, is theoretically evaluated. This substitution causes critical implications on the conformer stabilities of DFP (TG, GT and GG conformations) and the steric and electrostatic interactions should favor the conformer with fluorine atoms trans. However, the gauche effect plays a major role in describing the energies balance in DFP, shifting the equilibrium towards the conformation in which the two fluorine atoms are gauche. The origin of this effect is discussed through an NBO analysis, which allows the evaluation of both classical and non-classical (hyperconjugation and bent bonds) interactions as the prevailing factors governing the conformational equilibrium of molecules containing the 1,2-difluoroethane fragment.     

高效液相色谱法对反式-1,2-二取代环丙烷类化合物的手性拆分

在ＣｈｉｒａｌｃｅｌＯＤ和ＣｈｉｒａｌｃｅｌＯＪ柱上,以各种配比的正己烷／异丙醇为洗脱剂,对１３种反式－１,２－二取代环丙烷类化合物的对映体进行了手性拆分。考察了这些外消旋物在这两种柱上的色谱行为。实验表明带芳环的反式－１,２－二取代环丙烷类化合物在ＯＤ及ＯＪ柱上的拆分能力明显地与芳环上取代基的性质和位置有关。另一方面,一些带有脂族取代基的反式－１,２－二取代环丙烷类化合物也能在这两种柱上得到拆分。     

Crystal engineering of photochromic diarylethene single crystals

Photochromic performance of diarylethene single crystals was controlled by crystal engineering using non-covalent aromatic-aromatic interactions as the directional intermolecular force. A diarylethene derivative with two pentafluorophenyl groups, 1,2-bis(2-methyl-5-pentafluorophenyl-3-thienyl)perfluorocyclopentene (1a), formed stoichiometric co-crystals with benzene (Bz) and naphthalene (Np) by aryl-perfluoroaryl interactions. Face-to-face pi-stacking interactions between the pentafluorophenyl groups of 1a and the aromatic molecules are responsible for 2:1 and 1:1 stoichiometric compositions in 1a/Bz and 1a/Np co-crystals, respectively. The diarylethene underwent thermally stable and photoreversible photochromic reactions in a homo-crystal of 1a and co-crystals 1a/Bz and 1a/Np. The absorption spectra of the photogenerated closed-ring isomers varied depending on the conformation of the diarylethene molecules packed in the crystals. The diarylethene 1a also formed 1:1 stoichiometric co-crystals with different kinds of diarylethenes, 1,2-bis(2-ethyl-5-phenyl-3-thienyl)perfluorocyclopentene (2a) and 1,2-bis[2-methyl-5-(1-naphthyl)-3-thienyl]perfluorocyclopentene (3a). Both co-crystals 1a/2a and 1a/3a showed photochromism. Although 1a, 2a, and 3a underwent efficient photocyclization reactions in their homo-crystals, highly selective photocyclization reactions of 2a or 3a were observed in the co-crystals. The selective reactions were confirmed by HPLC and X-ray crystallography. Excited energy transfers from 1a to 2a and from 1a to 3a are considered to occur and cause the selective reactions.     

Electrostatic contributions to indole-lipid interactions

The role of electrostatic forces in indole-lipid interactions was studied by (1)H and (2)H NMR in ether- and ester-linked phospholipid bilayers with incorporated indole. Indole-ring-current-induced (1)H NMR chemical shifts of lipid resonances in bilayers of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, 1,2-dioleoyl-sn-glycero-3-phosphocholine, 1,2-di-O-octadecenyl-sn-glycero-3-phosphocholine, and 1,2-di-O-octadecenyl-sn-glycero-3-phosphomethanol show a bimodal indole distribution, with indole residing at the upper hydrocarbon chain/glycerol region of the lipid and near the choline group, when present. (2)H NMR of indole-d(7)-incorporated lipid bilayers reveals that the former site is occupied by about two-thirds of the indole, which adopts a distinct preferred orientation with respect to the bilayer normal. The results suggest that the upper hydrocarbon chain/glycerol location is dictated by many factors, including interactions with the electric charges and dipoles, van der Waals interactions, entropic contributions, and hydrogen bonding. Indole diffusion rates are higher in lipids with ester bonds and lower in choline-containing lipids, suggesting that interactions between indole and carbonyl groups are of minor importance for lipid-indole association and that cation-pi interactions with choline drive the second indole location. Nuclear Overhauser effect spectroscopy cross-relaxation rates suggest a 30-ns lifetime for indole-lipid associations. These results may have important implications for sidedness and structural transitions in tryptophan-rich membrane proteins.     

Cooperativity in alkane-1,2- and 1,3-polyols: NMR,QTAIM, and IQA study of O─H…OH and C─H…OH bonding interactions

Proton nuclear magnetic resonance chemical shifts and atom–atom interaction energies for alkanepolyols with 1,2-diol and 1,3-diol repeat units, and for their 1:1 pyridine complexes, are computed by density functional theory calculations. In the 1,3-polyols, based on a tG'Gg' repeat unit, the only important intramolecular hydrogen bonding interactions are O─H^…OH. By quantum theory of atoms in molecules analysis of the electron density, unstable bond and ring critical points are found for such interactions in 1,2-polyols with tG'g repeat units, from butane-1,2,3,4-tetrol onwards and in their pyridine complexes from propane-1,2,3-triol onwards. Several features (OH proton shifts and charges, and interaction energies computed by the interacting quantum atoms approach) are used to monitor the dependence of cooperativity on chain length: This is much less regular in 1,2-polyols than in 1,3-polyols and by most criteria has a higher damping factor. Well defined C─H^…OH interactions are found in butane-1,2,3,4-tetrol and higher members of the 1,2-polyol series, as well as in their pyridine complexes: There is no evidence for cooperativity with O─H^…OH bonding. For the 1,2-polyols, there is a tenuous empirical relationship between the existence of a bond critical point for O─H^…OH hydrogen bonding and the interaction energies of competing exchange channels, but the primary/secondary ratio is always less than unity.     

Site-selective imination of an anthracenone sensor: selective fluorescence detection of barium(II)

Site-selective imination of anthraquinone-based macrocyclic crown ethers using titanium tetrachloride as the catalyst yields imines where only the external carbonyl group of the anthraquinone forms Schiff-bases. The following aromatic amines yield monomeric compounds (aniline, 4-nitroaniline, 4-pyrrolaniline, and 1,3-phenylenediamine). Reaction of 2 equiv of the macrocyclic anthraquinone host with 1,2- and 1,4-phenylenediamine yields dimeric imine compounds. The 1,2-diimino host acts as a luminescence sensor, exhibiting enhanced selectivity for Ba(II) ion. Spectroscopic data indicate that two barium ions coordinate to the sensor. Due to E/Z isomerization of the imine, the monomeric complexes are nonluminescent. Restricted rotation about the 1,2 oriented C═N groups or other noncovalent/coordinate-covalent interactions acting between neighboring crown ether rings may inhibit E/Z isomerization in this example, which is different from current examples that employ coordination of a metal cation with a chelating imine nitrogen atom to suppress E/Z isomerization and activate luminescence. The 1,4-diimino adduct, where the crown rings remain widely separated, remains nonluminescent.     

Filler-polymer interactions in filled polybutadiene compounds

Bound rubber in a filled rubber compound is formed by physical adsorption and chemisorption between the rubber and filler. Polybutadiene (PB) is composed of three components of 1,2-, cis-1,4-, and trans-1,4-units. Filler-polymer interactions in PB compounds filled with carbon black or silica were studied by analyzing microstructures of the bound rubbers with pyrolysis-gas chromatography. Differences in the filler-polymer interactions of the 1,2-, cis-1,4-, and trans-1,4-units were investigated. The filler-polymer interaction of the 1,2-unit is stronger than those of the cis-1,4- and trans-1,4-units. The interaction of the 1,2-unit with silica is stronger than with carbon black. Bound rubber content is decreased by treatment with ammonia. Change of the bound rubber composition after the ammonia treatment was also studied.     

Structural Study on Four co-Crystals of N-Containing Heteroaromatics with Iodofluorobenzene

N-Containing heteroaromatics 1,2,4,5-tetra(pyridin-3-yl)benzene[1,2,4,5-T(3-PY)B] and 1,2,4,5-tetra-(pyridin-4-yl)benzene[1,2,4,5-T(4-PY)B] were each co-crystallized with 1,2-diiodo-tetrafluoro-benzene(1,2-DITFB), or 1,4-diiodo-tetrafluoro-benzene(1,4-DITFB), respectively, generating four co-crystals, namely, (1,2-DITFB)₄·[1,2,4,5-T(3-PY)B](1), (1,2-DITFB)₄·[1,2,4,5-T(4-PY)B](2), (1,4-DITFB)₂·[1,2,4,5-T(3-PY)B]·CHCl₃(3), and (1,4-DITFB)·[1,2,4,5-T(4-PY)B]·2CHCl₃(4). This study takes aim at providing an insight into the relative importance of fundamental solid state halogen bonding interactions(i.e., halogen…N, halogen…halogen, and halogen…π) in systems. The effects of the donor and acceptor on supramolecular assembly and the crystal structure determined interactions were discussed. The N…I halogen bonds are the main directing interactions responsible for the observed structures. In compounds 1 and 2, the donors exhibited lower-than-expected supramolecular connectivity. In spite of this, co-crystal 2 exhibits polymeric structures consisting of infinite one-dimensional(1D) double-zigzag chains of alternating electron donor and acceptor. The basic structure of co-crystals 3 and 4 is also infinite 1D chain. Therefore, the 1D halogen bonded supramolecular assemblies can be obtained by matching the appropriate donor and acceptor.     

Rubidium-mediated birch-type reduction of 1,2-diphenylbenzene in tetrahydrofuran

The reaction of 1,2-diphenylbenzene with rubidium metal in THF yields extremely sensitive and pyrophoric [η(5)-{1,2-diphenyl-2,5-cyclohexadienyl}rubidium](∞) (1). Compound 1 characterizes a possible intermediate in a Birch-type reaction and represents a very rare example of a fully characterized organorubidium complex as well as an open main-group metal pentadienide as part of a six-membered ring. In the solid state the rubidium atoms interact with the cyclohexadienyl moiety, whereas the coordination sphere of the soft cation is additionally stabilized exclusively by several metal π-arene interactions despite the presence of strongly coordinating donors. The bonding situation was elucidated by MP2/def2-TZVPP calculations including population analysis.     

Filler–polymer interactions in both silica and carbon black‐filled styrene–butadiene rubber compounds

Bound rubber in a filled rubber compound is formed by physical adsorption and chemisorption between the rubber and the filler. Styrene–butadiene rubber (SBR) is composed of four components of styrene, cis‐1,4‐, trans‐1,4‐, and 1,2‐units. Filler–polymer interactions in both silica and carbon black‐filled SBR compounds were studied by analyzing microstructures of the bound rubbers with pyrolysis‐gas chromatography. Differences in the filler–polymer interactions of the styrene, cis‐1,4‐, trans‐1,4‐, and 1,2‐units were investigated. The filler–polymer interactions of the butadiene units were found to be stronger than that of the styrene unit. The interactions of the cis‐1,4‐ and trans‐1,4‐units were stronger with carbon black than with silica, whereas the 1,2‐unit interacted more strongly with silica than with carbon black. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 439–445, 2001     

Physicochemical and interfacial investigation of lipid/polymer particle assemblies

A model study was investigated to develop colloidal supramolecular assemblies consisting of particles coated with lipid layers. The interactions between monodisperse sulfate-charged poly(styrene) submicrometer particles and zwitterionic/cationic lipid vesicles composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-3-trimethylammonium propane were considered. The influence of relevant experimental parameters on the final associations was examined by quasi-elastic light scattering to point out some new phenomena occurring in these colloidal systems. The major role of electrostatic interactions as driving forces to control the organization between cationic lipids and oppositely charged poly(styrene) particles was clearly evident, whereas this influence was less pronounced when considering the zwitterionic lipids. The characterization of these original complex assemblies was completed by a thorough study of the surface modification. The combination of zeta potential measurements, X-ray photoelectron spectroscopy analyses, and microscopy observations proved that the envisioned model can really correspond to polymer particles surrounded by lipids.     

Crystal Structure and Magnetic Property of 2-(Imidazo[1,2-a]pyri-din-2-yl)-2-oxoacetic Acid and Its Perchlorate

We herein report two crystals based on 2-(imidazo[1,2-a]pyridin-2-yl)-2-oxoacetic acid radical and its perchlorate, and investigate the relationship between magnetic properties and crystal stacking structures or supramolecular interactions. 2-(Imidazo[1,2-a]pyridin-2-yl)-2-oxoacetic acid radical in two crystals mainly exist as diamagnetic dimer formed via short atomic contacts or supramolecular interactions (hydrogen bonds, anion-π or lonepair-π interactions), leading to low magnetic susceptibilities. 2-(Imidazo[1,2-a]pyridin-2-yl)-2-oxoacetic acid radical crystal exhibits quasi-one-dimensional columnar stacking chain and weak antiferromagnetism. However, its perchlorate crystal possesses one-dimensional doublestranded chain structure assembled through double hydrogen bonds and anion-π interactions, and reveals weak ferromagnetism.     

Supported phospholipid membrane interactions with 1-butyl-3-methylimidazolium chloride

Quartz crystal microbalance with dissipation measurements were conducted for a 98/2 mole ratio of 1,2-dielaidoylphosphocholine (DEPC) and 1,2-dimyristoylphosphoglycerol (DMPG) on silica, gold, and a self-assembled monolayer of 11-mercapto-1-undecanol (11MU) and 11-mercaptoundecanoic acid (11MUA) at 50 mol % each. This study demonstrates that vesicles composed of DEPC and DMPG at 98 and 2 mol %, respectively, formed a supported bilayer with unruptured vesicles present when adsorbed onto the self-assembled monolayer. Also, the partially formed supported bilayer apparently deadsorbed in the presence of 1-butyl-3-methylimidazolium chloride, suggesting that surface-bilayer interactions are weaker on a hydrophilic modified gold surface composed of 50/50 11MU/11MUA than the surface-bilayer interactions on silica.     

Voltammetric behavior of 1,2-dihydroxyanthraquinones attached to glassy carbon electrodes and their surface complexation with copper

The adsorption behavior of 1,2-dihydroxyanthraquinones on electrochemically treated GC electrodes has been analyzed on the basis of the Frumkin adsorption isotherm allowing for long-range interactions between adsorbed species. Their slow-scan voltammetric response corresponded with a voltammetric theory for reversible surface reactions accompanied by intermolecular interactions. The negative interaction parameter obtained indicated a repulsive interaction between the surface-confined species, which bound Cu²⁺ firmly at weakly acidic pHs. Although 1,2-dihydroxyanthraquinones behave normally as a bidentate ligand, the surface-immobilized species formed only a 1:1 complex with Cu(II), probably because of motional restraints imposed on them. The 1,2-dihydroxy groups of the ligand chelated a partially hydrolyzed copper(II) species, their oxidation thus being depressed. Surface-bound copper underwent a two-electron redox reaction repetitively without being released from the surface.