Surface coordination chemistry: corrosion inhibition by tetranuclear cluster formation of iron with salicylaldoxime

A tetranuclear iron cluster is the principal component of the purple coatings produced by treating a mild steel surface with a salicylaldoxime corrosion inhibitor. This was shown by comparison of the spectroscopic data with those of the cluster [{Fe(salH)(HsalH)}4 ], which was obtained from FeCl3 and salicylaldoxime (H2 salH) and has a distorted tetrahedral arrangement of Fe(III) atoms coordinated by terminal (1-) and bridging (2-) salicylaldoximate ligands (the central core of the cluster is depicted).

Molecular dynamics simulations to aid the rational design of organic friction modifiers

Molecular dynamics simulations were performed under conditions of constant volume and temperature and of constant pressure and temperature to elucidate the structure activity relationships of a series of non-ionic surfactant molecules derived from vegetable fat and employed as friction modifiers in commercial engine oils. The simulations show the extent to which intermolecular hydrogen bonding is important in determining the stability of the monolayer formed by the surfactant molecules and show that mono-alkanoyl glyceride molecules are able to pack more efficiently, forming significantly more intermolecular hydrogen bonds and occupying approximately half the volume needed by di-alkanoyl glyceride molecules. Density profiles are presented which show significant mixing of the hydrophobic tail groups and a non-polar solvent. The distribution of torsion angles in the tail groups shows that the conformation is consistent with a liquid at finite temperature rather than a crystal structure. The measured friction coefficients of equimolar solutions of the glycerides show that the efficacy as friction modifiers varies in the order mono-, di- and the tri-oleyl glyceride, which is consistent with the efficacy of film formation predicted by the molecular dynamics calculations.

Elucidating the mode of action of a corrosion inhibitor for iron

Two polymetallic iron(III) complexes 1 and 2 have been synthesised from the known corrosion inhibitor 3-(4-methylbenzoyl)-propionic acid HL1 and their crystal structures determined. Coordination geometries extracted from these structures have been used as the basis for molecular modelling onto idealised iron(III) oxide surfaces as an aid to understanding the efficacy of inhibitors of the 4-keto acid type. The proposed mode of action involves 1,3-bridging didentate coordination of the carboxylate function of L1 to two FeIII ions, hydrogen-bond formation between the 4-keto group of L1 and a bridging surface hydroxy group, as well as close packing of the aromatic end groups, which should generate a hydrophobic barrier on the surface. Adsorption isotherm experiments have been used to compare the strengths of binding of related carboxylic acids onto iron(III) oxide surfaces and indicate that the presence of the 4-keto function leads to the formation of significantly more stable surface complexes.

New Macrocyclic Ligands. IV. Dibenzo-Substituted Rings Incorporating Five Donor Atoms. X-Ray Structures of an N4O-Donor Macrocycle, Its Protonated Form, and Its Complex With Barium Perchlorate

The syntheses and characterization of four dibenzo-substituted macrocycles incorporating N5-, N4O-or N4S-donor sets are reported. The new systems extend the range of related (potentially pentadentate ) macrocyclic systems of this general structure reported previously. For the 17-membered macrocycle incorporating an N4O-donor set, X-ray structure determinations of the free ligand and its salt of type [LH]ClO4 confirm the structure of this compound predicted from physical measurements. The diperchloratobarium complex of this macrocycle is shown to have the barium nine-coordinate; the coordination sphere is composed of the N4O-donors of the macrocycle and four oxygen atoms derived from a monodentate as well as a bidentate perchlorate group and an ethanol molecule.

New Macrocyclic Ligands. II. Pendant Hydroxyethyl, Cyanoethyl and Carbamoylethyl Arm Systems Derived From O2N2-Donor Rings: the X-Ray Structure of a Pendant Hydroxyethyl Derivative

The syntheses and characterization of 12 new 14- to 17-membered macrocycles incorporating pendant hydroxyethyl cyanoethyl or carbamoylethyl groups are reported. The macrocyclic ring in each of these new ligands contains an O2N2-donor set. The X-ray structure of the di(hydroxyethyl) derivative of the 14-membered macrocycle is described.

New Macrocyclic Ligands. Synthesis of an Extensive Series of Potentially Pentadentate Ligands Containing Mixed Nitrogen, Oxygen and or Sulfur Heteroatoms. The X-Ray Structure of an O2N2S Derivative

The syntheses of 16 new 16- to 19-membered dibenzo macrocycles are reported. These rings incorporate nitrogen together with oxygen and/or sulfur heteroatoms . The X-ray structure of the 17-membered macrocycle containing an O2N2S heteroatom set is described.

Two-hour assay for lutropin during ovulation

A rapid lutropin assay with a 2-h incubation time and a second antibody/polyethylene glycol separation step is presented. Assay time is shortened by incubating at 37 degrees C and using relatively high concentrations of antibody and radioligand. The interval required for the antigen/antibody reaction varies directly with lutropin concentration, from 1 h for ovulation values to 8 h for low values. After a 2-h incubation, low concentrations have reached 80% of their equilibrium concentration. Separation of the bound fraction by use of combined second antibody/polyethylene glycol (50 g/L) gave one-third the nonspecific binding and as rapid a separation as with polyethylene glycol (180 g/L) alone. Optimal conditions for separating the immune complex were established, and separation was found to be independent of protein concentrations in urine or serum. This tested assay can detect increasing and ovulatory lutropin concentrations in urine or serum, but with some sacrifice in sensitivity.

Two-hour assay for lutropin during ovulation

A rapid lutropin assay with a 2-h incubation time and a second antibody/polyethylene glycol separation step is presented. Assay time is shortened by incubating at 37 degrees C and using relatively high concentrations of antibody and radioligand. The interval required for the antigen/antibody reaction varies directly with lutropin concentration, from 1 h for ovulation values to 8 h for low values. After a 2-h incubation, low concentrations have reached 80% of their equilibrium concentration. Separation of the bound fraction by use of combined second antibody/polyethylene glycol (50 g/L) gave one-third the nonspecific binding and as rapid a separation as with polyethylene glycol (180 g/L) alone. Optimal conditions for separating the immune complex were established, and separation was found to be independent of protein concentrations in urine or serum. This tested assay can detect increasing and ovulatory lutropin concentrations in urine or serum, but with some sacrifice in sensitivity.