6,7-Dimethyl-5-phenyl-1H-thieno[2,3-e]-[1,4]diazepin-2(3H)-one

In the title molecule, C15H14N2OS, the seven-membered ring adopts a boat conformation. The carbonyl, imine and phenyl groups lie to one side of the molecule, and the thienyl ring and methylene group to the other.

A dimeric tellurastannoxane carbonate cluster, tetra-tert-butyl-di-µ3-carbonato-tetrakis-[4-(N,N-dimethylamino)phenyl]di-µ-oxo-ditelluriumditin chloroform tetrasolvate

The title compound, [Sn₂Te₂(C₄H₉)₄(CO₃)₂O₂(C₈H₁₀N)₄]·4CHCl₃ or [(p-Me₂NC₆H₄)₂TeOSn^tBu₂CO₃]₂·4CHCl₃, contains an almost planar centrosymmetric inorganic Sn₂Te₂O₈C₂ core and hypercoordinated Sn and Te atoms. The structure features four secondary intramolecular Te...O contacts.

Crystal structure of (3S*,4S*)-4-hydroxy-2-(2`-methoxyethyl)-3-phenyl-3,4-dihydroisoquinol-1(2H)-one,C18H19NO3

C₁₈H₁₉N0₃, monoclinic, P12₁/n1 (No. 14), a =8.454(6) Å,
b =13.123(3) Å, c =14.698(3) Å, ß =104.85(3)^o, V =1576.2ų,
Z =4, R_gt(F) =0.062, wR_ref(F²) =0.184, T =293 K.

An orthorhombic polymorph of dichloro-bis[4-(dimethylamino)phenyl]tellurium

Unlike the previously known monoclinic form, the orthorhombic polymorph of dichlorobis[4-(dimethylamino)phenyl]tellurium, C₁₆H₂₀C1₂N₂Te, shows secondary Te...C1 interactions.

The interplay of secondary Te···N, Te···O, Te···I and I···I interactions, Te···π contacts and π-stacking in the supramolecular structures of [{2-(4-nitrobenzylideneamino)-5-methyl}phenyl](4-methoxyphenyl)tellurium dihalides

The unsymmetrical1y substituted diorganotellurium dihalides [2-(4,4'-N0₂C₆H₄CHNC₆H₃Me]RTeX₂ (R = 4-MeOC₆H₄, X = Cl,
1a; Br, 1b; I, 1c; R =4-MeC₆H₄ ; X = Cl, 2; R =C₆H₅, X = Cl, 3) were prepared in good yields and characterized by solution and solid-state ¹²⁵Te NMR spectroscopy, IR spectroscopy and X-ray crystallography. In the solid-state, molecular structures of 1a and 1c possess scarcely observed 1,4-type intramolecular Te···N secondary interaction. Crystal packing of these compounds show an unusually rich diversity of intermolecular secondary, Te·· ·0, Te· .. \ and 1···1 interactions, Te·· ·π contacts as well as extensive
π-stacking of the organic substituents.

Methyl 3-[4-(4-nitrobenzyloxy)phenyl]propanoate

The title compound, C17H17NO5, crystallizes with two molecules (A and B) in the asymmetric unit. The conformational structures of the two molecules show small but significant differences in the dihedral angles between the two aryl rings with values of 18.8 (1)_ for molecule A and 7.5 (1)_ for molecule B. In molecule A, the propanoate group is twisted out of the plane of the benzene group [Car—Car—C—C torsion angle = _44.9 (2)_], while for molecule B, this group lies closer to the plane [Car—Car—C—C torsion angle = 8.6 (3)_]. C—H_ _ _O interactions characterize the crystalpacking interactions in this compound.

Phenyl-type and C1 stationary phases for environmentally friendlier chromatography

C1 and phenyl-type stationary phases were assessed in terms of their environmental impact on separations using as test solutes polycyclic aromatic hydrocarbons. Methanol (MeOH) and acetonitrile (ACN) mobile-phase gradients were employed. These stationary phases were examined to determine if different physical and chemical properties possessed by these surfaces decreased the organic solvent consumption, and yet maintained peak capacity. The cumulative energy demand (CED) was used to gauge the environmental impact of the separations. The separation of the polycyclic aromatic hydrocarbon test mixture using current methodologies (i.e. a C18/ACN combination) had a CED of 1.13 MJ-eq, and a peak capacity of 27 peaks (resolving 7 of 12 peak pairs with R_s>1). In comparison, a butyl phenyl stationary phase with a methanol mobile phase had a peak capacity of 26, but with a CED of 0.670 MJ-eq. Monolithic columns containing C18 and C1 phases were also tested. A monolithic C18 column with MeOH had the lowest CED at 0.675 MJ-eq, a peak capacity of 28 peaks and good resolving power (resolving ten peak pairs with R_s>1), suggesting that this is a viable option with respect to reducing environmental impact for these types of analyses.

π-Selective stationary phases: (II) Adsorption behaviour of substituted aromatic compounds on n-alkyl-phenyl stationary phases

The frontal analysis method was used to measure the adsorption isotherms of phenol, 4-chlorophenol, p-cresol, 4-methoxyphenol and caffeine on a series of columns packed with home-made alkyl-phenyl bonded silica particles. These ligands consist of a phenyl ring tethered to the silica support via a carbon chain of length ranging from 0 to 4 atoms. The adsorption isotherm models that fit best to the data account for solute–solute interactions that are likely caused by π–π interactions occurring between aromatic compounds and the phenyl group of the ligand. These interactions are the dominant factor responsible for the separation of low molecular weight aromatic compounds on these phenyl-type stationary phases. The saturation capacities depend on whether the spacer of the ligands have an even or an odd number of carbon atoms, with the even alkyl chain lengths having a greater saturation capacity than the odd alkyl chain lengths. The trends in the adsorption equilibrium constant are also significantly different for the even and the odd chain length ligands.

π-Selective stationary phases: (III) Influence of the propyl phenyl ligand density on the aromatic and methylene selectivity of aromatic compounds in reversed phase liquid chromatography

The retention characteristics of phenyl type stationary phases for reversed phase high performance liquid chromatography are still largely unknown. This paper explores the retention process of these types of stationary phases by examining the retention behaviour of linear PAHs and n-alkylbenzenes on a series of propyl phenyl stationary phases that have changes in their ligand density (1.23, 1.31, 1.97, 2.50 μmol m⁻²). The aromatic and methylene selectivities increased with increasing ligand density until a point where a plateau was observed, overall the propyl phenyl phases had a higher degree of aromatic selectivity than methylene selectivity indicating that these columns are suitable for separations involving aromatic compounds. Also, retention characteristics relating to the size of the solute molecule were observed to be influenced by the ligand density. It is likely that the changing retention characteristics are caused by the different topologies of the stationary phases at different ligand densities. At high ligand densities, the partition coefficient became constant.

π-Selective stationary phases: (I) Influence of the spacer chain length of phenyl type phases on the aromatic and methylene selectivity of aromatic compounds in reversed phase high performance liquid chromatography

Phenyl type stationary phases of increasing spacer chain length (phenyl, methyl phenyl, ethyl phenyl, propyl phenyl and butyl phenyl, with 0–4 carbon atoms in the spacer chain, respectively) were synthesised and packed in house to determine the impact that the spacer chain length has on the retention process. Two trends in the aromatic selectivity, q_aromatic, were observed, depending on whether the number of carbon atoms in the spacer chain is even or odd. Linear log k′ vs ϕ plots were obtained for each stationary phase and the S coefficient was determined from the gradient of these plots. For the phenyl type phases, the S vs n_c plots of the retention factors of linear polycyclic aromatic hydrocarbons vs the number of rings exhibit a distinct discontinuity that between 3 and 4 rings, which increases with increasing spacer chain length for even phases but decreases for odd phases. Accordingly, we suggest that the retention factors depend differently on the number of carbon atoms in the spacer chain depending on whether this number is even or odd and that this effect is caused by different orientations of the aromatic ring relative to the silica surface.

Effects of π-π interactions on the separation of PAHs on phenyl-type stationary phases

Phenyl‐type stationary phase surfaces are useful for the separation of highly aromatic compounds because of the extensive intermolecular forces between the π‐electron systems. For this reason, we studied the retention behaviour and selectivity of polycyclic aromatic hydrocarbons (PAHs) on Synergi polar‐RP and Cosmosil 5PBB chromatography columns using methanol/water, acetonitrile/water, benzene spiked (0.5%) methanol/water, and benzene spiked (0.5%) acetonitrile/water mobile phases. These four solvent systems were employed because π‐π. interactions between the aromatic solute (i.e., PAH) and the aromatic stationary phase should be inhibited in mobile phases that are also π electron rich, and hence a competitor for the analyte. Our results showed that the acetonitrile mobile phases were substantially stronger eluents than the methanol mobile phases, which was consistent with the premise that retention of aromatic compounds is sensitive to π‐π. interactions. Aside from changes in absolute retention, selectivity of the PAHs was also generally greater in methanol rather than acetonitrile mobile phases because the methanol did not attenuate the π‐π. bonding interactions between the PAH and the stationary phase; but, despite this, the retention behaviour of the Synergi polar‐RP column was similar to that observed on C₁₈ columns. The excessive retention times of the Cosmosil 5PBB column were decreased dramatically when acetonitrile was used as the mobile phase; however, selectivity between structural isomers was lost.

The corrosion inhibition of aluminium alloy 7075-T651 with cerium and Mischmetal di phenyl phosphate

Previous studies have shown that cerium diphenyl phosphate (Cedpp) 3 is a very effective inhibitor of corrosion of aluminium alloys in chloride solutions. This paper describes the results of further studies using electrochemical and constant immersion corrosion tests to compare the effectiveness of Ce(dpp) 3 and Mischmetal diphenyl phosphate Mm(dpp) 3 as inhibitors of corrosion pitting on AA7075-T651 aluminium alloy. The results shows that both Ce(dpp) 3 and Mm(dpp) 3 are excellent inhibitors of pitting corrosion of this alloy in very aggressive environments of continuously aerated 0.1M and 1.0M sodium chloride (NaCl) solutions. Polarisation tests indicate that these compounds act as a cathodic inhibitors by reducing the rate of the oxygen reduction reaction, which results in a decreased corrosion current density and a separation of the corrosion potential from the pitting potential. This inhibition is thought to be due to the formation of a surface film consisting of rare earth metal oxide, aluminium oxide and a cerium-aluminium organo-phosphate complex. Surface analysis data from scanning electron microscopy and X-ray Energy Dispersive Spectroscopy show the complex nature of this protective film. This work further develops our understanding about the mechanisms through which these complex films form, and how inhibition occurs in the presence of these compounds.

1-[4-Chloro-3-(trifluoromethyl)phenyl]-4-phenyl-1H-1,2,3-triazole

In the title compound, C(15)H(9)ClF(3)N(3), the phenyl and chloro-trifluoro-methyl benzene rings are twisted with respect to the planar triazole group, making dihedral angles of 21.29 (12) and 32.19 (11)°, respectively. In the crystal, the mol-ecules pack in a head-to-tail arrangement along the a axis with closest inter-centroid distances between the triazole rings of 3.7372 (12) Å.