Spin driven emergent antiferromagnetism and metal insulator transition in nanoscale p-Si

The entanglement of the charge, spin and orbital degrees of freedom can give rise to emergent behavior especially in thin films, surfaces and interfaces. Often, materials that exhibit those properties require large spin orbit coupling. We hypothesize that the emergent behavior can also occur due to spin, electron and phonon interactions in widely studied simple materials such as Si. That is, large intrinsic spin-orbit coupling is not an essential requirement for emergent behavior. The central hypothesis is that when one of the specimen dimensions is of the same order (or smaller) as the spin diffusion length, then non-equilibrium spin accumulation due to spin injection or spin-Hall effect (SHE) will lead to emergent phase transformations in the non-ferromagnetic semiconductors. In this experimental work, we report spin mediated emergent antiferromagnetism and metal insulator transition in a Pd (1 nm)/Ni81Fe19 (25 nm)/MgO (1 nm)/p-Si (~400 nm) thin film specimen. The spin-Hall effect in p-Si, observed through Rashba spin-orbit coupling mediated spin-Hall magnetoresistance behavior, is proposed to cause the spin accumulation and resulting emergent behavior. The phase transition is discovered from the diverging behavior in longitudinal third harmonic voltage, which is related to the thermal conductivity and heat capacity.Comment: 34 pages, Physica Status Solidi B- Physics, 201

Ni-based bimetallic heterogeneous catalysts for energy and environmental applications

Bimetallic catalysts have attracted extensive attention for a wide range of applications in energy production and environmental remediation due to their tunable chemical/physical properties. These properties are mainly governed by a number of parameters such as compositions of the bimetallic systems, their preparation method, and their morphostructure. In this regard, numerous efforts have been made to develop “designer” bimetallic catalysts with specific nanostructures and surface properties as a result of recent advances in the area of materials chemistry. The present review highlights a detailed overview of the development of nickel-based bimetallic catalysts for energy and environmental applications. Starting from a materials science perspective in order to obtain controlled morphologies and surface properties, with a focus on the fundamental understanding of these bimetallic systems to make a correlation with their catalytic behaviors, a detailed account is provided on the utilization of these systems in the catalytic reactions related to energy production and environmental remediation. We include the entire library of nickel-based bimetallic catalysts for both chemical and electrochemical processes such as catalytic reforming, dehydrogenation, hydrogenation, electrocatalysis and many other reactions

Alkenmetathese: Anwendungen in der Synthese von neuartigen metallorganischen Komplexen, und mechanistische Untersuchungen

Chapter 1 provides an overview on alkene metathesis reaction. Chapter 2 describes a mass spectrometric investigation of the activity of Hoveyda's second generation metathesis catalyst. Reduction of (CD3)2CO with NaBH4 affords 2-propanol-d6 (6-d6, 53%). Treatment of 6-d6 with HBr gives 2-bromopropane-d6 (3-d6, 63%). Subsequent O-alkylation of salicylaldehyde with 3-d6 (Cs2CO3 base) yields 2-isopropoxybenzaldehyde-d6 (4-d6, 60%). Wittig olefination of 4-d6 (Ph3PCH3+ Br−, t-BuOK) affords 2-isopropoxystyrene-d6 (1-d6, 35%). Nitration of mesitylene-d12 gives 1,3,5-trimethylnitrobenzene-d11 (12-d11, 74%). Catalytic hydrogenation of 12-d11 yields 2,4,6-trimethylaniline-d11 (7-d11, 76%). Condensation of glyoxal with 7-d11 (2 equiv) affords the diimine glyoxal-bis(2,4,6-trimethylphenylimine)-d22 (9-d22, 90%). Treatment of 9-d22 with NaBH4 gives the diamine N,N'-bis(2,4,6-trimethylphenyl)ethylenediamine-d22 dihydrochloride (10-d22, 83%). Reaction of 10-d22 with HC(OEt)3 leads to 1,3-bis(2,4,6-trimethylphenyl)imidazolinium-d22 chloride (2-d22, 84%). Reaction of Ru(=CHPh)(PCy3)2(Cl)2 (13) with 2-d22 (hexanes, t-BuOK) gives Ru(=CHPh)(H2IMes-d22)(PCy3)(Cl)2 (14-d22, 57%). Treatment of 14-d22 with 1-d6 in the presence of CuCl yields (H2IMes-d22)(Cl2)Ru=CH-o-OC6H4(i-Pr-d6) (15-d28, 85%). Mixtures of 15-d28 and its natural abundance analog 15-d0 are utilized in crossover experiments; depending upon conditions, the recovered catalyst can be either unscrambled or a 15-d0/15-d6/15-d22/15-d28 mixture. The latter is consistent with a boomerang mechanism. Chapter 3 describes the synthesis and characterization of gyroscope-like complexes with doubly trans-spanning bis(pyridine) ligands. Reactions of 2,6-NC5H3(CH2Br)2 with CH2=CHCH2MgBr (1.0 M in diethyl ether), and HO(CH2)nCH=CH2 (n = a, 1; b, 2; c, 3; d, 4) in the presence of C6H5CH2N(CH3)3+ Cl− afford alkene containing pyridines 2,6-NC5H3(CH2CH2CH=CH2)2 (21, 60%), and 2,6-NC5H3(CH2O(CH2)nCH=CH2)2 (22a-d, 45-55%), respectively. Reactions of 3,5-NC5H3(COCl)2 with HO(CH2)nCH=CH2 (n = a, 1; b, 2; c, 3; d, 4; e, 5; f, 6; g, 8) give 3,5-NC5H3(COO(CH2)nCH=CH2)2 (29a-g, 41-90%). Williamson ether syntheses involving 2,6-NC5H3Br2 and HO(CH2)nCH=CH2 (n = a, 1; b, 2) yield 2,6-NC5H3(O(CH2)nCH=CH2)2 (45-55%). Square planar complexes of most of the preceding substituted pyridines are synthesized. Reaction of [RhCl(coe)2]2 (coe = cyclooctene) with 22a gives trans-Rh(Cl)(CO)[2,6-NC5H3(CH2OCH2CH=CH2)2]2 (26%). PtCl2 is treated with 22a,b and 29a,c-g to give trans-PtCl2[2,6-NC5H3(CH2O(CH2)nCH=CH2)2]2 (trans-31a, 88%; trans-31b, 26%) and trans-PtCl2[3,5-NC5H3(COO(CH2)nCH=CH2)2]2 (trans-32a,c-g, 63-94%), respectively. Reactions of trans-(PhCN)2PdCl2 with 29e and 21 afford trans-PdCl2[3,5-NC5H3(COO(CH2)5CH=CH2)2]2 (94%) and trans-PdCl2[2,6-NC5H3(CH2CH2CH=CH2)2]2 (trans-34, 15%), respectively. Treatment of trans-31a,b and trans-32d-g with 13 and subsequent hydrogenation (Pd/C catalyst) gives the gyroscope-like complexes trans-PtCl2[2,6,2',6'-(NC5H3(CH2O(CH2)2n+2OCH2)2H3C5N)] (trans-35a,b, 10-22%) and trans-PtCl2[3,5,3',5'-(NC5H3(COO(CH2)2n+2COO)2H3C5N)] (trans-36d-g, 14-45%), respectively. The reaction of trans-34 with 13 affords trans-PdCl2[2,6,2',6'-(NC5H3((CH2)2CH=CH(CH2)2)2H3C5N)] (trans-37, 55-58%) after column chromatography. Subsequent hydrogenation (PtO2 catalyst) gives trans-PdCl2[2,6,2',6'-(NC5H3((CH2)6)2H3C5N)] (trans-38, 58-62%). The reaction of trans-32c with PhC≡CH, in the presence of CuI, affords trans-Pt(Cl)(C≡CPh)[3,5-NC5H3(COO(CH2)3CH=CH2)2]2 (trans-39c, 18%). The crystal structures of trans-31a, trans-35a, trans-35b, trans-36e, and trans-38 are determined and analyzed. Chapter 4 describes an NMR study of the reactivity of Grubbs' first and second generation metathesis catalysts with alkene-containing pyridines and rhenium complexes. Sequential treatment of (R)-(η5-C5H5)Re(NO)(PPh3)(CH3) ((R)-40) with Ph3C+ PF6– and CH2=CHCH2MgBr (1.0 M in diethyl ether) affords the butenyl complex (R)-(η5-C5H5)Re(NO)(PPh3)(CH2CH2CH=CH2) ((R)-45, 50% after recrystallization). Analogous treatment of (R)-40 with Ph3C+ PF6– and CH2=CHCH2CH2MgBr (0.5 M in THF) gives the pentenyl rhenium complex (R)-(η5-C5H5)Re(NO)(PPh3)(CH2CH2CH2CH=CH2) ((R)-46, 45% after column chromatography). Equimolar quantities of the alkene-containing rhenium complexes (R)-43, (R)-45, and (R)-46, and alkene-containing pyridines 22a, 25b, and 29g are combined with 13 or Ru(=CHPh)(H2IMes)(PCy3)(Cl)2. The reactions are monitored by low temperature NMR. The reaction of (R)-45 (2 equiv) with 13 yields (η5-C5H5)Re(NO)(PPh3)(CH2)2(CH=)Ru(PCy3)2(Cl)2 (49%) in ≥ 90% purity, as assayed by 31P{1H} NMR. The crystal structure of (R)-46 is determined and analyzed.Kapitel 1 liefert einen Überblick über die Alkenmetathese-Reaktion. Kapitel 2 beschreibt die Aktivität des Hoveyda-Metathese-Katalysators der zweiten Generation mit Hilfe von massenspektrometrischen Untersuchungen. Reduktion von (CD3)2CO mit NaBH4 liefert 2-Propanol-d6 (6-d6, 53%). Reaktion von 6-d6 mit HBr ergibt 2-Brompropan-d6 (3-d6, 63%). Anschließende O-Alkylierung von Salicylaldehyd mit 3-d6 (Base Cs2CO3) führt zu 2-Isopropoxybenzaldehyd-d6 (4-d6, 60%). Wittig-Reaktion von 4-d6 (Ph3PCH3+ Br−, t-BuOK) liefert 2-Isopropoxystyrol-d6 (1-d6, 35%). Nitrierung von Mesitylen-d12 ergibt 1,3,5-Trimethylnitrobenzol-d11 (12-d11, 74%). Katalytische Hydrierung von 12-d11 führt zu 2,4,6-Trimethylanilin-d11 (7-d11, 76%). Kondensation von Glyoxal mit 7-d11 (2 äquiv) liefert das Diimin Glyoxal-bis(2,4,6-trimethylphenylimin)-d22 (9-d22, 90%). Reaktion von 9-d22 mit NaBH4 ergibt das Diamin N,N'-Bis(2,4,6-trimethylphenyl)ethylendiamin-d22 dihydrochlorid (10-d22, 83%). Reaktion von 10-d22 mit HC(OEt)3 führt zu 1,3-Bis(2,4,6-trimethylphenyl)imidazolinium-d22 chlorid (2-d22, 84%). Reaktion von Ru(=CHPh)(PCy3)2(Cl)2 (13) mit 2-d22 (Hexan, t-BuOK) ergibt Ru(=CHPh)(H2IMes-d22)(PCy3)(Cl)2 (14-d22, 57%). Behandlung von 14-d22 mit 1-d6 in Gegenwart von CuCl liefert (H2IMes-d22)(Cl2)Ru=CH-o-OC6H4(i-Pr-d6) (15-d28, 85%). Gemische von 15-d28 und sein natürliches Analogon 15-d0 werden in "Crossover-Experimenten" eingesetzt; abhängig von den Reaktionsbedingungen kann der Katalysator rein oder als Mischung 15-d0/15-d6/15-d22/15-d28 zurückgewonnen werden. Letzteres steht mit einem Bumerang-Mechanismus im Einklang. Kapitel 3 beschreibt die Synthese und Charakterisierung von gyroskopähnlichen Molekülen mit zweifach trans-ständigen Bispyridin-Liganden. Reaktionen von 2,6-NC5H3(CH2Br)2 mit CH2=CHCH2MgBr (1.0 M in Diethylether), und HO(CH2)nCH=CH2 (n = a, 1; b, 2; c, 3; d, 4) in Gegenwart von C6H5CH2N(CH3)3+ Cl− liefern die alkenhaltigen Pyridine 2,6-NC5H3(CH2CH2CH=CH2)2 (21, 60%), bzw. 2,6-NC5H3(CH2O(CH2)nCH=CH2)2 (22a-d, 45-55%). Reaktionen von 3,5-NC5H3(COCl)2 mit HO(CH2)nCH=CH2 (n = a, 1; b, 2; c, 3; d, 4; e, 5; f, 6; g, 8) ergeben 3,5-NC5H3(COO(CH2)nCH=CH2)2 (29a-g, 41-90%). Williamson Ether Synthesen von 2,6-NC5H3Br2 und HO(CH2)nCH=CH2 (n = a, 1; b, 2) ergeben 2,6-NC5H3(O(CH2)nCH=CH2)2 (45-55%). Quadratisch-planare Komplexe von einigen der beschriebenen substituierten Pyridine werden synthetisiert. Reaktion von [RhCl(coe)2]2 (coe = Cycloocten) mit 22a ergibt trans-Rh(Cl)(CO)[2,6-NC5H3(CH2OCH2CH=CH2)2]2 (26%). PtCl2 wird mit 22a,b und 29a,c-g versetzt und führt zu trans-PtCl2[2,6-NC5H3(CH2O(CH2)nCH=CH2)2]2 (trans-31a, 88%; trans-31b, 26%), bzw. trans-PtCl2[3,5-NC5H3(COO(CH2)nCH=CH2)2]2 (trans-32a,c-g, 63-94%). Rektionen von trans-(PhCN)2PdCl2 mit 29e und 21 ergeben trans-PdCl2[3,5-NC5H3(COO(CH2)5CH=CH2)2]2 (94%) bzw. trans-PdCl2[2,6-NC5H3(CH2CH2CH=CH2)2]2 (trans-34, 15%). Behandlung von trans-31a,b und trans-32d-g mit 13 und anschließende Hydrierung (Katalysator Pd/C) ergibt die gyroskopähnlichen Komplexe trans-PtCl2[2,6,2',6'-(NC5H3(CH2O(CH2)2n+2OCH2)2H3C5N)] (trans-35a,b, 10-22%), bzw. trans-PtCl2[3,5,3',5'-(NC5H3(COO(CH2)2n+2COO)2H3C5N)] (trans-36d-g, 14-45%). Die Reaktion von trans-34 mit 13 liefert nach säulenchromatographischer Reinigung trans-PdCl2[2,6,2',6'-(NC5H3((CH2)2CH=CH(CH2)2)2H3C5N)] (trans-37, 55-58%). Anschließende Hydrierung (Katalysator PtO2) ergibt trans-PdCl2[2,6,2',6'-(NC5H3((CH2)6)2H3C5N)] (trans-38, 58-62%). Die Reaktion von trans-32c mit PhC≡CH, in Gegenwart von CuI, liefert trans-Pt(Cl)(C≡CPh)[3,5-NC5H3(COO(CH2)3CH=CH2)2]2 (trans-39c, 18%). Die Kristallstrukturen von trans-31a, trans-35a, trans-35b, trans-36e, und trans-38 wurden bestimmt und analysiert. Kapitel 4 beschreibt die Reaktivität der Grubbs-Metathese-Katalysatoren der ersten und zweiten Generation mit alkenhaltigen Pyridinen und Rhenium-Komplexen mit Hilfe von NMR Studien. Behandlung von (R)-(η5-C5H5)Re(NO)(PPh3)(CH3) ((R)-40) mit Ph3C+ PF6– und CH2=CHCH2MgBr (1.0 M in Diethylether) liefert nach Umkristallisation den Butenyl-Rheniumkomplex (R)-(η5-C5H5)Re(NO)(PPh3)(CH2CH2CH=CH2) ((R)-45, 50%). Analoge Behandlung von (R)-40 mit Ph3C+ PF6– und CH2=CHCH2CH2MgBr (0.5 M in THF) ergibt nach säulenchromatographischer Reinigung den Pentenyl-Rheniumkomplex (R)-(η5-C5H5)Re(NO)(PPh3)(CH2CH2CH2CH=CH2) ((R)-46, 45%). Äquimolare Mengen der alkenhaltigen Rhenium-Komplexe (R)-43, (R)-45, und (R)-46, und alkenhaltige Pyridine 22a, 25b, und 29g werden mit 13 oder Ru(=CHPh)(H2IMes)(PCy3)(Cl)2 versetzt. Die Reaktionen werden mit Hilfe von Tieftemperatur-NMR-Messungen verfolgt. Die Reaktion von (R)-45 (2 äquiv) mit 13 liefert (η5-C5H5)Re(NO)(PPh3)(CH2)2(CH=)Ru(PCy3)2(Cl)2 (49%) in ≥ 90% Reinheit, bestimmt durch 31P{1H}-NMR-Spektroskopie. Die Kristallstruktur von (R)-46 wurde bestimmt und analysiert

Deep Eutectic Solvents: Alternative Solvents for Biomass-Based Waste Valorization

Innovative technologies can transform what are now considered “waste streams” into feedstocks for a range of products. Indeed, the use of biomass as a source of biopolymers and chemicals currently has a consolidated economic dimension, with well-developed and regulated markets, in which the evaluation of the manufacturing processes relies on specific criteria such as purity and yield, and respects defined regulatory parameters for the process safety. In this context, ionic liquids and deep eutectic solvents have been proposed as environmentally friendly solvents for applications related to biomass waste valorization. This mini-review draws attention to some recent advancements in the use of a series of new-solvent technologies, with an emphasis on deep eutectic solvents (DESs) as key players in the development of new processes for biomass waste valorization. This work aims to highlight the role and importance of DESs in the following three strategic areas: chitin recovery from biomass and isolation of valuable chemicals and biofuels from biomass waste streams