Low molecular weight organogelators derived from threefold symmetric tricarbamates

A group of new low molecular weight organogelators based on threefold symmetric tricarbamate were synthesized and characterized. The tricarbamates with long alkyl chains were able to gelate a wide range of polar and nonpolar organic solvents such as acetonitrile and cyclohexane, generally at concentrations lower than 20 g/L. The best organogel formation was obtained using a threefold symmetric tricarbamate in n-dodecane, in which a sufficiently transparent gel was formed at the critical gelation concentration 1 g/L. Intermolecular hydrogen bonding by the tricarbamate in a nonpolar solvent benzene-d₆ was indicated by ¹H NMR spectra. Its maximum UV absorption was 11 nm higher in chloroform than in n-dodecane, and this red shift indicated increased conjugation between the benzene core and the carbamate substituents, which confirmed a change in its conformation from nonpolar to polar solvent. The self-assembling behavior of the tricarbamate in dilute solutions was investigated by TEM. Fiber-like networks were observed in a large range of solution concentrations.     

A cis-IrL(CO) group responds to increasing steric bulk of L by M-L stretching,not M-C-O tilting or bending

The crystal structures of [Ir(2-R-bq)(PPh(3))(2)(H)(CO)](+) (bq = benzoquinolinato; R = H, i-Pr, t-Bu) show that steric interference caused by contact between the bulky pendant R groups of the bq and the C of the cis-CO is relieved by Ir-N bond stretching in the Irbq system and bending of the trans-Ph(3)P-Ir-PPh(3) groups, rather than by tilting or bending of the CO. Ir-CO is therefore more rigid than the Ir-N and Ir-P bonds. The Ir-N stretching is aided by the presence of a high trans effect H trans to N.     

d + α Scattering from 12 to 17 MeV

A previous phase-shift analysis of the d + α system had indicated that the solution obtained might not describe the backward-angle tensor analyzing powers very well above about 10 MeV. We have measured differential cross sections and all four analyzing powers A_y, A_xx, A_yy and A_xz at deuteron bombarding energies of 12, 14, 15 and 17 MeV, with some emphasis on the backward-angle region. The discrepancy with the previous phase-shift analysis was confirmed, and we have studied the changes in the phase parameters necessary to improve the fit to our new measurements.     

Steric interactions between finite objects and end-grafted polymer chains: a two-dimensional mean-field analysis

We examine the usefulness of a two-dimensional self-consistent mean-field theory for predicting polymer-induced forces between a finite object and a surface. The predictions are compared with scaling results for the compression of a single, end-grafted chain by a disk and for the compression of a brush with an athermal wall. For the former, the mean-field predictions agree with scaling theory and, in addition, provide the necessary prefactor in the scaling expressions for the Helmholtz potential and force of compression. For the brush, the mean-field results agree with the Alexander-de Gennes scaling result at moderate compressions and also provide an analytical expression for the force without any unknown parameters. We also use the mean-field theory to examine the interaction of a model bacterium with a planar substrate and show that steric interactions due to a single polymer chain alone can dominate van der Waals attraction under typical practical conditions and thus prevent bacterial adhesion to the surface.     

Linear 6,6'-biazulenyl framework featuring isocyanide termini: synthesis, structure, redox behavior, complexation, and self-assembly on Au(111)

The key step in accessing the title species (5), the first nonbenzenoid diisocyanobiaryl, involved an unexpected homocoupling of a 6-bromoazulene derivative. The reversible 2e(-) reduction of 5 was addressed electrochemically and computationally. The shifts in energies of the S(0)→S(1) and S(0)→S(2) transitions for a series of related 6,6'-biazulenyl derivatives correlate with the e(-)-donating/-withdrawing strength of their 2,2'-substituents but follow opposite trends. Species 5 adsorbs end-on (η(1)) to the Au(111) surface via one of its -NC groups to form a 2-nm-thick film. In addition, bimetallic coordination of 5's -NC termini can be readily achieved.     

Synthesis of 2-(N-Benzylpyrrolyl)-benzimidazoles Using Polyphosphoric Acid Prompted Cyclocondensation

Synthesis of a series of 2-substituted benzimidazoles was carried out for screening anti-inflammatory activities. 2-(N-benzylpyrrolyl)-benzimidazoles 9a-k were synthesized from N-benzyl-2-pyrrole carboxylic acids 8a-d and 4-substituted-1,2-phenylenediamines by cyclocondensation utilizing polyphosphoric acid (PPA) as condensing agent. The N-benzyl-2-pyrrole carboxylic acids were prepared by standard method of N-benzylation of 2-pyrrole carboxylate using NaH/DMF and appropriately substituted benzyl halides followed by alkaline hydrolysis.     

Synthesis and Crystal Structure of Bis-(N,N′-dibenzylethane-1,2-diamine) cobalt(II) acetate

Abstract  

Bis-(N,N′-dibenzylethane-1,2-diamine) cobalt(II) acetate has been synthesized and the crystal structure determined. The compound crystallizes in the space group P2₁/c, a = 8.3212(6) ?, b = 11.8774(8) ?, c = 17.3643(12) ?, β = 98.1850(10)°, V = 1698.7(2) ?³, Z = 2. The complex occupies a crystallographic inversion center. The cobalt is in a distorted octahedral environment likely due to steric influences of the acetate groups.     

Modulation of amyloid-β aggregation by metal complexes with a dual binding mode and their delivery across the blood–brain barrier using focused ultrasound

One of the key hallmarks of Alzheimer''s disease is the aggregation of the amyloid-β peptide to form fibrils. Consequently, there has been great interest in studying molecules that can disrupt amyloid-β aggregation. While a handful of molecules have been shown to inhibit amyloid-β aggregation in vitro, there remains a lack of in vivo data reported due to their inability to cross the blood–brain barrier. Here, we investigate a series of new metal complexes for their ability to inhibit amyloid-β aggregation in vitro. We demonstrate that octahedral cobalt complexes with polyaromatic ligands have high inhibitory activity thanks to their dual binding mode involving π–π stacking and metal coordination to amyloid-β (confirmed via a range of spectroscopic and biophysical techniques). In addition to their high activity, these complexes are not cytotoxic to human neuroblastoma cells. Finally, we report for the first time that these metal complexes can be safely delivered across the blood–brain barrier to specific locations in the brains of mice using focused ultrasound.

We report a series of non-toxic cobalt(iii) complexes which inhibit Aβ peptide aggregation in vitro; these complexes can be safely delivered across the blood–brain barrier in mice using focused ultrasound.