Thermoresponsive copolymers of ethylene oxide and N,N-diethyl glycidyl amine: polyether polyelectrolytes and PEGylated gold nanoparticle formation.

The synthesis of diblock as well as gradient copolymers of N,N-diethyl glycidyl amine (DEGA) with ethylene oxide (EO) via anionic ring-opening polymerization is presented. The polymers exhibit low polydispersities (≤1.13) and molecular weights in the range of 3300-10 200 g mol(-1) . In PEG-co-PDEGA copolymers, incorporation of 4%-29% DEGA results in tailorable cloud point temperatures in aqueous solution and melting points depending on DEGA content. mPEG-b-PDEGA block copolymers can be quaternized to generate cationic double-hydrophilic polyelectrolyte copolymers with polyether backbone. Furthermore, mPEG-b-PDEGA has been used as dual reducing and capping agent for gold nanoparticle synthesis.

Synthesis and characterization of iron(II) complexes with tetradentate diiminodiphosphine or diaminodiphosphine ligands as precatalysts for the hydrogenation of acetophenone.

Six complexes of the type trans-[Fe(NCMe)2(P-N-N-P)]X2 (X = BF4(-), B{Ar(f)}4(-)) (Ar(f) = 3,5-(CF3)2C6H3) containing diiminodiphosphine ligands and the complexes trans-[Fe(NCMe)2(P-NH-NH-P)][BF4]2 with a diaminodiphosphine ligand were obtained by the reaction of Fe(II) salts with achiral and chiral P-N-N-P or P-NH-NH-P ligands, respectively, in acetonitrile at ambient temperature. The P-N-N-P ligands are derived from reaction of ortho-diphenylphosphinobenzaldehyde with the diamines 1,2-ethylenediamine, 1,3-propylenediamine, (S,S)-1,2-disopropyl-1,2-diaminoethane, and (R,R)-1,2-diphenyl-1,2-diaminoethane. Some complexes could also be obtained for the first time in a one-pot template synthesis under mild reaction conditions. Single crystal X-ray diffraction studies of the complexes revealed a trans distorted octahedral structure around the iron. The iPr or Ph substituents on the diamine were found to be axial in the five-membered Fe-N-CHR-CHR-N- ring of the chiral P-N-N-P ligands. A steric clash between the imine hydrogen and the substituent probably determines this stereochemistry. The diaminodiphosphine complex has longer Fe-N and Fe-P bonds than the analogous diiminodiphosphine complex. The new iron compounds were used as precatalysts for the hydrogenation of acetophenone. The complexes without axial substituents on the diamine had moderate catalytic activity while that with axial Ph substituents had low activity but fair (61%) enantioselectivity for the asymmetric hydrogenation of acetophenone. The fact that the diaminodiphosphine complex has a slightly higher activity than the corresponding diiminodiphosphine complex suggests that hydrogenation of the imine groups in the P-N-N-P ligand may be important for catalyst activation. Evidence is provided, including the first density-functional theory calculations on iron-catalyzed outer-sphere ketone hydrogenation, that the mechanism is similar to that of ruthenium analogues.

Microfluidic continuous flow synthesis of rod-shaped gold and silver nanocrystals.

We present a continuous flow synthesis of gold and silver nanorods allowing tailored design of particles with desired shapes and online monitoring of particle growth.