Chemoselective heterogeneous iridium catalyzed hydrogenation of cinnamalaniline

Selective hydrogenation of unsaturated imines over heterogeneous catalysts is an ecologically feasible and effective way to produce commercially valuable saturated imines and unsaturated amines under mild conditions, avoiding the utilization of toxic halides. The liquid-phase hydrogenation of a model imine, cinnamalaniline, over Ir, Ru, Pd and Au catalysts was studied in polar protic (methanol, 2-propanol), polar aprotic (methyl tert-butyl ether) and non-polar aprotic (toluene) solvents at 40–80 °C under atmospheric hydrogen pressure. Different metal oxides (Al2O3, ZrO2, SiO2) and carbon composites based on carbon nitrides synthesized by pyrolysis of ethylenediamine or melamine modified by KOH, HNO3, NH4Cl or TEOS (including template KIT-6), porous carbon (samples prepared by pyrolysis of sucrose, including template KIT-6) and mesoporous carbon Sibunit were applied to study the effect of the support. Among the tested metals, iridium exhibited the most promising catalytic performance in terms of hydrogenation activity and chemoselectivity towards unsaturated amine. The use of Ir on carbon nitrides (C3N4–NH4Cl, CxNy-KIT-6) and amphoteric metal oxides (ZrO2, Al2O3) in nonpolar aprotic toluene solvent provided the best selectivity towards unsaturated amine by minimizing oligomerization. Computational studies indicate that the selective hydrogenation of the C=N group on Ir results from a favorable cinnamalaniline adsorption geometry at high surface coverage. Comparable heterogeneously catalyzed highly chemoselective hydrogenation of unsaturated imine into unsaturated amine under atmospheric hydrogen pressure and low temperatures has not been reported previously.peerReviewe

Electronic pathway in reaction centers from Rhodobacter sphaeroides and Chloroflexus aurantiacus

The reaction centers (RC) of Chloroflexus aurantiacus and Rhodobacter sphaeroidesH(M182)L mutant were investigated. Prediction for electron transfer (ET) at very low temperatures was also performed. To describe the kinetics of the C. aurantiacus RCs, the incoherent model of electron transfer was used. It was shown that the asymmetry in electronic coupling parameters must be included to explain the experiments. For the description of R. sphaeroidesH(M182)L mutant RCs, the coherent and incoherent models of electron transfer were used. These two models are discussed with regard to the observed electron transfer kinetics. It seems likely that the electron transfer asymmetry in R. sphaeroides RCs is caused mainly by the asymmetry in the free energy levels of L- and M-side cofactors. In the case of C. aurantiacus RCs, the unidirectionality of the charge separation can be caused mainly by the difference in the electronic coupling parameters in two branches