Development and Box–Behnken design optimization of a green extraction method natural deep eutectic solvent-based for phenolic compounds from barley malt rootlets

In recent years, attention has been turned finding new sources of phenolic compounds, antioxidant molecules, main by-products from the agri-food chain like barley malt rootlets (BMRs). Traditionally, phenolic compounds are extracted from food matrices using different procedures, for example, solid–liquid, liquid–liquid, or solid-phase extraction techniques employing organic solvents. With the advent of green chemistry, attention has been paid to the search for green, nontoxic, inexpensive, and nonflammable solvents and the natural deep eutectic solvents (NADESs) respect these characteristics. The aim of this project was to develop and optimize an environmentally friendly, inexpensive, and rapid extraction method for phenolic compounds from BMRs using natural DESs as extractive solvents. Several natural DESs were tested as extractive solvents and, among them, the best results in terms of total phenolic content were obtained using a choline chloride-malic acid (1:2 molar ratio)-based mixture. Box–Behnken experimental design guaranteed the extraction of 9.51 ± 0.83 gallic acid equivalent/g of BMRs, under the following optimal extraction conditions: 1:21 solid-to-liquid ratio, 80°C as extraction temperature, 43 min as the time of extraction, and 29% as a percentage of added water in the NADESs. Phenolic acids and flavonoids were detected in the BMRs extract through HPLC-PDA/MS analysis.     

Das Wissen um Unterschiede in den kognitiven Strukturen von Schülerinnen und Schülern als Erklärung von Unterrichtsbeiträgen

It is reported about a longitudinal study run at the Institute of Cognitive Mathematics of the University of Osnabrueck, in which pupils’ verbal and text productions from mathematics lessons at a grammar school are analysed by means of cognitive theoretical methods. First of all, a teaching scene from an instruction to probability calculus and further text productions from an introductory lesson about exponential functions are analysed, in which five pupils take part whose cognitive structures have been assessed and classified in individual examinations. The characteristics brought out according to these teaching scenes indicate different ideas and thinking processes of the pupils. The second part shows that the pupils’ behaviour described is not only to be regarded in isolation but it can also be found in longitudinal examinations and can therefore be considered as a stable, typical characteristic. These results lead to consequences for the planning and design of mathematics lessons based on a well-founded theory of cognition.     

Die Kristallstrukturen der Cyanidofluoridoborate K[BFx(CN)4–x], x = 0–4

The crystal structure of K[BF₃(CN)] (Pbcn (Nr. 60) with a = 13.3486(15) b = 6.5239(7) c = 10.0085(11) Å, and eight formula units per unit cell) has been determined and the one of K[BF₂(CN)₂] was confirmed and improved. The different networks in the complete series of borates K[BF_x(CN)_4–x], x = 0–4 are compared and discussed.     

Dimorphic ErAgSn and TmAgSn – High‐Pressure and High‐Temperature Driven Phase Transitions

The stannides ErAgSn and TmAgSn have been investigated under high‐temperature (HT) and high‐pressure (HP) conditions in order to investigate their structural chemistry. ErAgSn and TmAgSn are dimorphic: normal‐pressure (NP) ErAgSn and HT‐TmAgSn crystallize into the NdPtSb type structure, P6₃mc, a = 466.3(1), c = 729.0(2) pm for NP‐ErAgSn and a = 465.4(1), c = 726.6(2) pm for HT‐TmAgSn. NP‐ErAgSn was obtained via arc‐melting of the elements and subsequent annealing at 970 K, while HT‐TmAgSn crystallized directly from the melt by rapidly quenching the arc‐melted sample. HT‐TmAgSn transforms to the ZrNiAl type low‐temperature modification upon annealing at 970 K. The high‐pressure (HP) modification of ErAgSn was synthesized under multianvil high‐pressure (11.5 GPa) high‐temperature (1420 K) conditions from NP‐ErAgSn: ZrNiAl type, , a = 728.7(2), c = 445.6(1) pm. The silver and tin atoms in NP‐ErAgSn and HT‐TmAgSn build up two‐dimensional, puckered [Ag₃Sn₃] networks (277 pm intralayer Ag–Sn distance in NP‐ErAgSn) that are charge‐balanced and separated by the erbium and thulium atoms. The fourth neighbor in the adjacent layer has a longer Ag–Sn distance of 298 pm. The [AgSn] network in HP‐ErAgSn is three‐dimensional. Each silver atom has four tin neighbors (281–285 pm Ag–Sn). The [AgSn] network leaves distorted hexagonal channels, which are filled with the erbium atoms. The crystal chemistry of the three phases is discussed.     

The Combination of 4‐Hydroxythiazoles with Azaheterocycles: Efficient Bidentate Ligands for Novel Ruthenium Complexes

Herein the syntheses of three novel ligands, in which an azaheterocycle is connected with a thiazole subunit: 4‐methoxy‐5‐methyl‐2‐pyridine‐2‐yl‐1,3‐thiazole ( 1 ), 4‐methoxy‐5‐methyl‐2‐pyrimidine‐2‐yl‐1,3‐thiazole ( 2 ) and 4‐methoxy‐5‐phenyl‐2‐pyridine‐2‐yl‐1,3‐thiazole ( 3 ) are reported. Because these ligands are cyclic versions of 1,4‐diazadienes, they offer good prerequisites for the synthesis of metal complexes and were employed as chelating ligands. Three novel heteroleptic cationic complexes of the type Ru(bpy)₂( L ), with bpy = 2,2′‐bipyridine were successfully synthesised. The Ru^II complexes as well as the ligands were characterised by means of mass spectrometry, NMR, UV/Vis and IR spectroscopy and elemental analysis. Furthermore, an X‐ray structure of Ru(bpy)₂ 2 (PF₆), as far as we know the first example where a thiazole is directly connected to a Ru^II core, is presented in this paper.     

New Ionic Liquid Compounds Based on Tantalum Pentachloride TaCl5: Synthesis,Structural, and Spectroscopic Elucidation of the (μ‐Oxido)‐Chloridotantalates(V) [BMPy][TaCl6], [BMPy]4[(TaCl6)2(Ta2OCl10)], and [EMIm]2[Ta2OCl10]

1‐Butyl‐4‐methylpyridinium hexachloridotantalate(V), [BMPy][TaCl₆] ( 1 ), tetrakis(1‐butyl‐4‐methylpyridinium) bis(hexachloridotantalate(V) (μ‐oxido)‐decachloridotantalate(V), [BMPy]₄[(TaCl₆)₂(Ta₂OCl₁₀)] ( 2 ), and bis(1‐ethyl‐3‐methylimidazolium)‐(μ‐oxido)‐decachloridoditantalate(V), [EMIm]₂[Ta₂OCl₁₀] ( 3 ) were synthesized and characterized by single‐crystal X‐ray diffraction and vibrational spectroscopy. Compounds 1 and 3 crystallize in the monoclinic space group P2₁/c (no. 14), whereas compound 2 crystallizes in the triclinic space group P (no. 2). All compounds are built up by the mentioned bulky organic cations and octahedral [TaCl₆]^– respective linear [Ta₂OCl₁₀]^2– anions. Coulomb interactions are dominant between the ionic species. FT‐IR and FT‐Raman spectra were recorded and interpreted, especially with respect to the inorganic species [TaCl₆]^– (O_h) and [Ta₂OCl₁₀]^2– (C_i symmetry, approximately D_4h). The melting temperatures of compounds 1 – 3 are given.     

Dehydropolymerisation of Methylamine Borane and an N-Substituted Primary Amine Borane Using a PNP Fe Catalyst

Dehydropolymerisation of methylamine borane (H₃B⋅NMeH₂) using the well-known iron amido complex [(PNP)Fe(H)(CO)] (PNP=N(CH₂CH₂PiPr₂)₂) ( 1 ) gives poly(aminoborane)s by a chain-growth mechanism. In toluene, rapid dehydrogenation of H₃B⋅NMeH₂ following first-order behaviour as a limiting case of a more general underlying Michaelis–Menten kinetics is observed, forming aminoborane H₂B=NMeH, which selectively couples to give high-molecular-weight poly(aminoborane)s (H₂BNMeH)_n and only traces of borazine (HBNMe)₃ by depolymerisation after full conversion. Based on a series of comparative experiments using structurally related Fe catalysts and dimethylamine borane (H₃B⋅NMe₂H) polymer formation is proposed to occur by nucleophilic chain growth as reported earlier computationally and experimentally. A silyl functionalised primary borane H₃B⋅N(CH₂SiMe₃)H₂ was studied in homo- and co-dehydropolymerisation reactions to give the first examples for Si containing poly(aminoborane)s.