Monitoring conformational diversity in self-organised monolayers with scanning tunnelling microscopy at near atomic resolution

The evaporation of solutions of dendron-functionalised 2,2'-bipyridines on a graphite surface gives highly ordered monolayers; near atomic resolution STM imaging has allowed a detailed conformational analysis to be made.     

Preparation and structural characterisation of terpy-cored dendrimers and dendriplexes

2,2':6',2'-Terpyridine (terpy) ligands and their iron(II) and cobalt(II) complexes bearing first and second generation Frechet-type dendritic wedges have been prepared and structurally characterised. The rotational freedom within the dendritic wedge results in a great diversity in conformational space. Structural studies are reported on first generation species and their metal complexes, and the variety of inter- and intramolecular interactions which dominate the conformation of the dendrimer and the packing of the molecules (ions) in the lattice are discussed.     

Reactions of octacyanomolybdate(V) and octacyanotungstate(V) with s(2) metal-ion reducing centers

The s(2) centers, Sn(II), Ge(II), and In(i) reduce Mo(V)(CN)(8)(3-) and W(V)(CN)(8)(3-) quantitatively to the corresponding octacyanomolybdate(IV) and -tungstate(iv) anions. Reductions by In(i) proceed 10(3)-10(5) times as rapidly as those by Sn(II) and Ge(II). All reactions are triggered by a single electron oxidation, yielding a much more reactive s(1) intermediate. Reductions by Sn(II) in chloride medium proceed predominantly through the SnCl(3)(-) anion. The Ge(II)-W(CN)(8)(3-) reaction is initiated by a slow unimolecular heterolysis of the Ge(II) center, yielding very nearly linear profiles when the reductant is in excess.     

Formation of a [1 + 1] metallomacrocycle from a heterotritopic ligand containing two terpy and one bipy metal-binding domains

Reaction of the heterotritopic ligand L, which contains one bipy and two terpy metal-binding domains linked by a flexible spacer with iron(II) chloride results in the formation of a [1 + 1] metallomacrocycle.     

A rod-like polymer containing (Ru(terpy)2) units prepared by electrochemical coupling of pendant thienyl moieties

A new rod-like coordination polymer consisting of (Ru-(terpy)2) motifs bridged by bithiophene units has been prepared by electrochemical polymerisation in acidic organic medium.     

Esca studies of polyurethanes: blood platelet activation in relation to surface composition

Segmented polyurethanes (SPU) were synthesized with polyethylene oxide (PEO), polypropylene oxide, or polytetramethylene oxide as the “soft segment,” from the respective polyether diols, of which molecular weight varied from 600 to 2000. The “hard segment” was created from ethylene diamine and tolylene diisocyanate or 4,4′-diphenylmethane diisocyanate. Platelet activation was assessed using columns packed with beads coated with each of the SPU by solutions from which the solvent was subsequently evaporated. Citrated whole human blood was passed through the columns and the platelet count in aliquots leaving the columns was compared with the platelet count in blood that had not contacted the column surface. By this method the fraction of platelets retained in the column averaged for several donors, ρ, was determined. In parallel experiments, SPU surfaces formed under identical conditions by evaporation of solvent were examined by X-ray electron spectroscopy for carbon, oxygen, and nitrogen content of the surface. The carbon C_1s spectra proved to be particularly useful, when analyzed for the components with peaks respectively at 286 eV (carbon not bonded to an ether oxygen) and at 288 eV (carbon bonded to an ether oxygen). The platelet retention index ρ was found to increase nearly linearly with the ratio of the 286-eV intensity to the 288-eV intensity, and extrapolated to nearly zero for zero value of the intensity ratio, which would correspond to amorphous PEO, suggesting that if a surface were only amorphous PEO it would be remarkably inactive toward platelets. In contrast, nitrogen spectra show no systematic relationship with ρ.