Ferrocene and Porphyrin Monolayers on Si(100) Surfaces: Preparation and Effect of Linker Length on Electron Transfer

The missing link : Ferrocene and porphyrin monolayers are tethered on silicon surfaces with short (see picture, left) or long (right) linkers. Electron transfer to the silicon substrate is faster for monolayers with a short linker.

     

Réduction du soufre par un sulfure et oxydation électrochimique d'un sulfure dans le diméthylsulfoxyde

Progressive addition of sodium sulphide to a sulphur solution in dimethylsulphoxide results in the formation of polysulphide ions, identical to those obtained by electrochemical reduction of sulphur in the same solvent. Conversely, electrochemical oxidation of sulphide leads to the formation of sulphur-sulphur bonds, and cyclooctasulphur S₈ is finally obtained.     

A Nearly Linear Single Hydroxo Bridge. Synthesis, Structure, and Magnetic Susceptibility of (&mgr;-Hydroxo)bis((tetraphenylporphinato)manganese(III)) Perchlorate

The synthesis, X-ray structure, and magnetic susceptibility characterization of a hydroxo-bridged complex, (&mgr;-hydroxo)bis((tetraphenylporphinato)manganese(III)) perchlorate, {[Mn-(TPP)](2)(OH)}ClO(4), are described. The complex is readily prepared by a controlled hydrolysis of monomeric diaquo(tetraphenylporphinato)manganese(III) perchlorate. Interestingly, the bridging hydroxo complex appears to be more stable than the putative &mgr;-oxo complex in halocarbon solvents. The X-ray structure determination shows a complex in which two five-coordinate manganese(III) ions are bridged by a single hydroxo ligand with an average Mn-O distance of 2.026(1) ? and a Mn-O(H)-Mn bridge angle of 160.4(8) degrees. The two porphyrin planes are nearly coplanar, and the two metal ions are separated by 3.993 ?. The average Mn-N(P) distance is 2.008(7) ?. The two manganese ions are displaced by 0.19 and 0.20 ? from their respective 24-atom mean planes. Both of the two porphyrin rings are moderately S(4) ruffled and have a near-staggered orientation (the N-Mn-Mn'-N' dihedral angle is 29.9 degrees ). The four inter-ring pairs of meso-phenyl groups of the binuclear cation are extremely crowded, with a nearly perpendicular orientation for each pair. The solid-state magnetic susceptibility was measured over the temperature range 2-300 K. The observed behavior is typical of an exchange-coupled binuclear complex. The data were fit to the total spin Hamiltonian (H(tot) = H(1) + H(2) - 2J&Svector;(1).&Svector;(2)) of a zero-field-split, high-spin d(4)-d(4) dimer in its actual crystallographic geometry, using numerical techniques. The hydroxide bridge supports a relatively strong antiferromagnetic coupling (2J = -74.0 cm(-1)) between two zero-field-split (D = -10.8 cm(-1)) manganese(III) ions. Crystal data: a = 16.807(7) ?, b = 17.061(6) ?, c = 17.191(5) ?, alpha = 85.64(3) degrees, beta = 79.75(3) degrees, gamma = 61.95(2) degrees, triclinic, space group P&onemacr;, V = 4281(3) ?(3), Z = 2, R(1) = 0.0707 for 14 802 observed data based on F(o) >/= 4.0sigma(F(o)), R(2w) = 0.2007 for 21 696 total unique data, least-squares refinement on F(2) using all data.     

Genesis

A Commentary on the paper ”Investigation of the structures of the crystalline and columnar phases of linear chain copper(II) alkanoates?, by H. Abied, D. Guillon, A. Skoulios, P. Weber, A.M. Giroud‐Godquin and J.C. Marchon. First published in Liquid Crystals, 2, 269‐279 (1987).     

Genesis

A Commentary on the paper “Investigation of the structures of the crystalline and columnar phases of linear chain copper(II) alkanoates„, by H. Abied, D. Guillon, A. Skoulios, P. Weber, A.M. Giroud-Godquin and J.C. Marchon. First published in Liquid Crystals, 2, 269-279 (1987).     

Isolement de nouveaux complexes de zinc de dipyrrométhènes formés au cours de la synthèse de la méso-tétramésitylporphyrine par la réaction de Rothemund

Three new zinc bis(dipyrromethene) complexes have been isolated in the preparation of meso-tetramesitylporphyrin by the Rothemund zinc template based condensation process.     

Nickel porphyrin nanotweezers

A strapped chiroporphyrin free base with two 8-methylene chains linking two adjacent meso-substituents was synthesized as the alpha 4 conformer; insertion of Ni(II) triggered a complete conversion to the alpha beta alpha beta complex, and demetallation totally regenerated the strapped free base in the alpha 4 conformation.