We report here on a new series of CO-reducing molecular catalysts based on Earth-abundant elements that are very selective for the production of formic acid in dimethylformamide (DMF)/water mixtures (Faradaic efficiency of 90 ± 10%) at moderate overpotentials (500-700 mV in DMF measured at the middle of the catalytic wave). The [CpCo(PN)I] compounds contain diphosphine ligands, PN, with two pendant amine residues that act as proton relays during CO-reduction catalysis and tune their activity. Four different PN ligands with cyclohexyl or phenyl substituents on phosphorus and benzyl or phenyl substituents on nitrogen were employed, and the compound with the most electron-donating phosphine ligand and the most basic amine functions performs best among the series, with turnover frequency >1000 s. State-of-the-art benchmarking of catalytic performances ranks this new class of cobalt-based complexes among the most promising CO-to-formic acid reducing catalysts developed to date; addressing the stability issues would allow further improvement. Mechanistic studies and density functional theory simulations confirmed the role of amine groups for stabilizing key intermediates through hydrogen bonding with water molecules during hydride transfer from the Co center to the CO molecule.

The synthesis of silicone polyesteramides was successfully performed in bulk at 70 °C via a biocatalytic route. Immobilized Candida antartica Lipase B (Novozym 435, N435) was used as catalyst under mild conditions to perform the polycondensation reaction using various feed mole ratios of diethyl adipate (DEA), 1,8-octanediol (OD), and R,ω-(diaminopropyl)polydimethylsiloxane (Si-NH 2 ). The syntheses of poly(octamethylene adipate), POA, and poly(R,ω-(diaminopropyl)polydimethylsiloxane adipamide), PSiAA, were also performed by N435 catalysis in order to compare their properties with those of silicone polyesteramides. The microstructures of all polymers were studied by 1 H NMR spectroscopy, and calculated amide/ester ratios were in agreement with the monomer feed mole ratio. Formation of amide links (DEA-SiAA units) occurs more rapidly than ester repeats (DEA-OA units). This results in copolymers that tend toward a blocklike sequence distribution. Thermal stability of the polyesteramides, evaluated by TGA both in nitrogen and in air, increases with DEA-SiAA content (up to 50 mol %). The relative amount of amide and ester units along the polymer chain strongly affects the physical aspect of the polyesteramides. High content of DEA-OA units leads to hard solid materials containing a welldeveloped high melting POA-type crystal phase, whose melting temperature changes with composition. When DEA-SiAA units are the major component, the material acquires a sticky appearance.

Synthesis and characterization of alternating poly(amide urethane)s from ε-caprolactone, diamines and diphenyl carbonate Sharma, Bhaskar; Keul, Helmut; Höcker, Hartwig; Loontjens, Ton; Benthem, Rolf van CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. AbstractThe synthesis of alternating poly(amide urethane)s 5a-d was performed in three steps using 3-caprolactone, diamines, and diphenyl carbonate as starting materials. The microstructure and nature of the end groups of the poly(amide urethane)s were determined by means of 1 H NMR spectroscopy, which reveals an alternating sequence of amide and urethane linkages in a linear chain with hydroxy and phenyl urethane end groups. The molecular weight and polydispersity of the polymers obtained (5700! M n ! 7900, 1:25! M w = M n ! 1:38) were determined by means of gel permeation chromatography. The thermal properties determined by means of DSC show that the poly(amide urethane)s 5a-d are semicrystalline materials having one or two endothermic transitions similar to the poly(amide urethane)s 10a-d prepared from 3-caprolactam, amino alcohols, and diphenyl carbonate. Thermogravimetric analysis of poly(amide urethane)s 5a-b shows a single step decomposition, while poly(amide urethane)s 10a-c decompose in two steps indicating that different degradation mechanisms are operating. q

No abstract

Summary: Poly(amide urethane)s were prepared from ε‐caprolactam, amino alcohols, and diphenyl carbonate or ethylene carbonate in three steps. Polycondensation was performed either with α‐hydroxy‐ω‐O‐phenyl urethanes or with α‐hydroxy‐ω‐O‐hydroxyethyl urethanes; it was found that the reactivity at 90 °C of the first is much higher than that of the latter. For nearly equal reactivity, the temperature for the polycondensation of α‐hydroxy‐ω‐O‐hydroxyethyl urethanes had to be increased from 90 °C to 150 °C. The microstructure of the resulting poly(amide urethane)s differs by the content of urea groups in the polymer chains, which is 5% for poly(amide urethane)s prepared from α‐hydroxy‐ω‐O‐phenyl urethanes and 15% for poly(amide urethane)s prepared from α‐hydroxy‐ω‐O‐hydroxyethyl urethanes. As a consequence, the thermal properties of the poly(amide urethane)s differ slightly.Synthesis of poly(amide urethane)s.magnified imageSynthesis of poly(amide urethane)s.

This study probes the nature of noncovalent interactions, such as cation-π, metal ion-lone pair (M-LP), hydrogen bonding (HB), charge-assisted hydrogen bonding (CAHB), and π-π interactions, using energy decomposition schemes-density functional theory (DFT)-symmetry-adapted perturbation theory and reduced variational space. Among cation-π complexes, the polarization and electrostatic components are the major contributors to the interaction energy (IE) for metal ion-π complexes, while for onium ion-π complexes (NH4+, PH4+, OH3+, and SH3+) the dispersion component is prominent. For M-LP complexes, the electrostatic component contributes more to the IE except the dicationic metal ion complexes with H2 S and PH3 where the polarization component dominates. Although electrostatic component dominates for the HB and CAHB complexes, dispersion is predominant in π-π complexes.

Quantum chemical [MP2(FULL)/6-311++G-(d,p)] calculations are done on the binding of hydrated Li(+), Na(+), K(+), Mg(2+), Cu(+), and Zn(2+) metal ions with biologically relevant heteroaromatics such as imidazole and methylimidazole. The computed interaction energies are found to be in good agreement with the available experimental data. The effect of hydration on hydrogen bonding has been studied in detail and it shows that the hydrogen bond strength between H(2)O···H-N(1) substantially increases in the presence of metal ions. The present study quantifies the cooperativity between M···imidazole (M = Li(+), Na(+), K(+), Mg(2+), Cu(+), and Zn(2+)) and N(1)-H···OH(2) interactions. Topological atoms in molecules (AIM) analysis and charge analysis support the variation in hydrogen-bonding strength and the variation in M···imidazole binding strength. Effect of hydration on N(1)-H stretching frequency is studied, and it shows a clear shift in the stretching frequency after sequential hydration of metal ion as well as the N(1) of imidazole. The present study provides a detailed account on the biologically important M-histidine motif interaction with metal ions, where histidine is modeled by imidazole and methylimidazole.

Quantum chemical calculations have been performed at CCSD(T)/def2-TZVP level to investigate the strength and nature of interactions of ammonia (NH3 ), water (H2 O), and benzene (C6 H6 ) with various metal ions and validated with the available experimental results. For all the considered metal ions, a preference for C6 H6 is observed for dicationic ions whereas the monocationic ions prefer to bind with NH3 . Density Functional Theory-Symmetry Adapted Perturbation Theory (DFT-SAPT) analysis has been employed at PBE0AC/def2-TZVP level on these complexes (closed shell), to understand the various energy terms contributing to binding energy (BE). The DFT-SAPT result shows that for the metal ion complexes with H2 O electrostatic component is the major contributor to the BE whereas, for C6 H6 complexes polarization component is dominant, except in the case of alkali metal ion complexes. However, in case of NH3 complexes, electrostatic component is dominant for s-block metal ions, whereas, for the d and p-block metal ion complexes both electrostatic and polarization components are important. The geometry (M(+) -N and M(+) -O distance for NH3 and H2 O complexes respectively, and cation-π distance for C6 H6 complexes) for the alkali and alkaline earth metal ion complexes increases down the group. Natural population analysis performed on NH3 , H2 O, and C6 H6 complexes shows that the charge transfer to metal ions is higher in case of C6 H6 complexes.