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The tricyclic azepino[1,2-a]indole acetates 7, readily accessible by visible-light-driven catalytic photooxygenation of cyclohepta[b]indoles 1, are convenient precursors to novel and uncommon cyclic C,N-diacyliminium ions 3. We report here the first Lewis acid-catalyzed C-C bond forming reactions of these species with TMSCN and silyl enol ethers as nucleophiles and utilizing TIPSOTf as well as Sc(OTf)3 as catalysts. Employing Sc(OTf)3/pybox complexes as a chiral catalyst system, regio- and enantioselective asymmetric alkylations with silyl enol ethers were achieved.

Electrophilic aromatic substitution (EAS) can provide a straightforward approach to the efficient synthesis of functionalized complex aromatic molecules. In general, Lewis acids serve as a beneficial stimulus for the formation of a Wheland complex, the intermediate in the classical S

Single-celled green algae within the Trebouxiophyceae (Chlorophyta) are typical components of terrestrial habitats, which often exhibit harsh environmental conditions for these microorganisms. This study provides a detailed overview of the ecophysiological, biochemical, and ultrastructural traits of an alga living on tree bark. The alga was isolated from a cypress tree in the Botanical Garden of Innsbruck (Austria) and identified by morphology and molecular phylogeny as Diplosphaera chodatii. Transmission electron microscopy after high-pressure freezing (HPF) showed an excellent preservation of the ultrastructure. The cell wall was bilayered with a smooth inner layer and an outer layer of polysaccharides with a fuzzy hair-like appearance that could possibly act as cell-cell adhesion mechanism and hence as a structural precursor supporting biofilm formation together with the mucilage observed occasionally. The photosynthetic-irradiance curves of D. chodatii indicated low light requirements without photoinhibition at high photon flux densities (1580 μmol photons m−2 s−1) supported by growth rate measurements. D. chodatii showed a high desiccation tolerance, as 85% of its initial value was recovered after controlled desiccation at a relative humidity of ~10%. The alga contained the low molecular weight carbohydrates sucrose and sorbitol, which probably act as protective compounds against desiccation. In addition, a new but chemically not elucidated mycosporine-like amino acid was detected with a molecular mass of 332 g mol−1 and an absorption maximum of 324 nm. The presented data provide various traits which contribute to a better understanding of the adaptive mechanisms of D. chodatii to terrestrial habitats.

Within the second funding period of the SPP 1708 “Material Synthesis near Room Temperature”,which started in 2017, we were able to synthesize novel anionic species utilizing Ionic Liquids (ILs) both, as reaction media and reactant. ILs, bearing the decomposable and non‐innocent methyl carbonate anion [CO3Me]−, served as starting material and enabled facile access to pseudohalide salts by reaction with Me3Si−X (X=CN, N3, OCN, SCN). Starting with the synthesized Room temperature Ionic Liquid (RT‐IL) [nBu3MeN][B(OMe)3(CN)], we were able to crystallize the double salt [nBu3MeN]2[B(OMe)3(CN)](CN). Furthermore, we studied the reaction of [WCC]SCN and [WCC]CN (WCC=weakly coordinating cation) with their corresponding protic acids HX (X=SCN, CN), which resulted in formation of [H(NCS)2]− and the temperature labile solvate anions [CN(HCN)n]− (n=2, 3). In addition, the highly labile anionic HCN solvates were obtained from [PPN]X ([PPN]=μ‐nitridobis(triphenylphosphonium), X=N3, OCN, SCN and OCP) and HCN. Crystals of [PPN][X(HCN)3] (X=N3, OCN) and [PPN][SCN(HCN)2] were obtained when the crystallization was carried out at low temperatures. Interestingly, reaction of [PPN]OCP with HCN was noticed, which led to the formation of [P(CN)2]−, crystallizing as HCN disolvate [PPN][P(CN⋅HCN)2]. Furthermore, we were able to isolate the novel cyanido(halido) silicate dianions of the type [SiCl0.78(CN)5.22]2− and [SiF(CN)5]2− and the hexa‐substituted [Si(CN)6]2− by temperature controlled halide/cyanide exchange reactions. By facile neutralization reactions with the non‐innocent cation of [Et3HN]2[Si(CN)6] with MOH (M=Li, K), Li2[Si(CN)6] ⋅ 2 H2O and K2[Si(CN)6] were obtained, which form three dimensional coordination polymers. From salt metathesis processes of M2[Si(CN)6] with different imidazolium bromides, we were able to isolate new imidazolium salts and the ionic liquid [BMIm]2[Si(CN)6]. When reacting [Mes(nBu)Im]2[Si(CN)6] with an excess of the strong Lewis acid B(C6F5)3, the voluminous adduct anion {Si[CN⋅B(C6F5)3]6}2− was obtained., The reaction of ionic liquids (ILs) with methylcarbonate anions like [R3MeE][CO3Me] (E=N: R=Et, nPr, nBu; E=P, R=Ph) with Me3Si−X (X=CN, N3, OCN, SCN) or H2SiF6 led to quantitative formation of pseudohalide salts [R3MeE]X or fluorosilicates, e. g. [R3MeN]2[SiF6]. From these precursors, novel anionic species like [B(OMe)3(CN)]− or cyanido(halido)silicates of the type [SiCl0.78(CN)5.22]2−, [SiF(CN)5]2− and [Si(CN)6]2− were obtained. Functionalization of the hexacyanidosilicate with the Lewis acid B(C6F5)3 led to the voluminous WCA {Si[CN⋅B(C6F5)3]6}2−. Beside [H(NCS)2]−, highly labile solvate anions of the type [X(HCN)2]− (X=CN, SCN), [X(HCN)3]− (X=CN, N3, OCN) and [P(CN⋅HCN)2]− were obtained from IL‐like mixtures, when starting from [WCC]X ([WCC]=[Ph4P], [PPN]) and neat HCN.

The photo-isomerization of an isolable five-membered singlet biradical based on C, N, and P ([TerNP]2CNDmp, 2a) selectively afforded a closed-shell housane-type isomer (3a) by forming a transannular P-P bond. In the dark, the housane-type species re-isomerized to the biradical, resulting in a fully reversible overall process. In the present study, the influence of tBuNC on the thermal reverse reaction was investigated: the isonitrile acted as a catalyst, thus allowing control over the thermal reaction rate. Moreover, tBuNC also reacted with the biradical to form an adduct species ([TerNP]2CNDmp·CNtBu, 4a), which can be regarded as the resting state of the system. The reactive species 2a and 3a could be re-generated in situ by irradiation with red light. The results of this study extend our understanding of this new class of molecular switches.

Attempts have been made to prepare salts with the labile tris(trimethylsilyl)chalconium ions, [(Me3Si)3E]+ (E=O, S), by reacting [Me3Si‐H‐SiMe3][B(C6F5)4] and Me3Si[CB] (CB−=carborate=[CHB11H5Cl6]−, [CHB11Cl11]−) with Me3Si‐E‐SiMe3. In the reaction of Me3Si‐O‐SiMe3 with [Me3Si‐H‐SiMe3][B(C6F5)4], a ligand exchange was observed in the [Me3Si‐H‐SiMe3]+ cation leading to the surprising formation of the persilylated [(Me3Si)2(Me2(H)Si)O]+ oxonium ion in a formal [Me2(H)Si]+ instead of the desired [Me3Si]+ transfer reaction. In contrast, the expected homoleptic persilylated [(Me3Si)3S]+ ion was formed and isolated as [B(C6F5)4]− and [CB]− salt, when Me3Si‐S‐SiMe3 was treated with either [Me3Si‐H‐SiMe3][B(C6F5)4] or Me3Si[CB]. However, the addition of Me3Si[CB] to Me3Si‐O‐SiMe3 unexpectedly led to the release of Me4Si with simultaneous formation of a cyclic dioxonium dication of the type [Me3Si‐μO‐SiMe2]2[CB]2 in an anion‐mediated reaction. DFT studies on structure, bonding and thermodynamics of the [(Me3Si)3E]+ and [(Me3Si)2(Me2(H)Si)E]+ ion formation are presented as well as mechanistic investigations on the template‐driven transformation of the [(Me3Si)3E]+ ion into a cyclic dichalconium dication [Me3Si‐μE‐SiMe2]2 2+., Labile chalconium ions of the type [(Me3Si)3E]+ (E=O, S) were generated by reacting [Me3Si‐H‐SiMe3][B(C6F5)4] and Me3Si[CB] (CB−=carborate=[CHB11H5Cl6]−, [CHB11Cl11]−) with Me3Si‐E‐SiMe3. A ligand exchange in case of the oxonium species, leading to the surprising formation of the persilylated [(Me3Si)2(Me2(H)Si)O]+ oxonium ion, was observed. With Me3Si[CB] as silylating reagent, a cyclic dioxonium dication of the type [Me3Si‐μO‐SiMe2]2[CB]2 was isolated in an anion‐mediated reaction.

Phosphorus (P) is a crucial element for living organisms at both land and sea, but simultaneously, it can cause environmental problems especially in marine ecosystems. The pathway of P from soils through riverine and coastal systems to sea sediments has not been clarified to date. Thus, the main aim of this study was to characterize P species in sediments along a gradient from the coast of Northern Germany to the Baltic Proper. Six sediment samples along a transect from river outlets into the Baltic Sea in northeastern Germany to the deep basins at the Baltic Proper were analyzed. Four complementary methods were applied to explore the different sedimentary P compounds: (i) the sequential P fractionation to extract P from sediment pools of different solubility; (ii) P K-edge X-ray absorption near edge structure (XANES) spectroscopy as an element-specific method for speciation analyses of complex environmental samples; (iii) 31P nuclear magnetic resonance (31P NMR) spectroscopy as a capable technique distinguishing especially different organic P compounds based on their characteristic resonance frequencies and (iv) scanning electron microscopy (SEM) combined with energy-dispersive X-ray microanalyses (EDX) to identify certain solid particles and their elemental composition. Sequential P fractionation revealed a decrease in labile P pools (resin-P; NaHCO3-P) along with an increase in more stable P fractions (H2SO4-P; residual-P) from near-coastal sediments towards the Baltic Proper with increasing water depths of sediment deposits. In comparison, XANES analysis indicated a decline of Fe-associated P compounds in favor of Ca-bound P with increasing distance of sediments from the coastline into the Baltic Sea. Results of 31P NMR spectroscopy showed that the variety of different mono- and diester P compounds decreased with increasing distance from the coast and that high proportions of orthophosphate (ortho-P) were present especially in greater water depths. The SEM-EDX analysis supported most of these results by retriving Fe phosphate particles especially in the sediments near the coast. The integration of several P-specific methods enabled improved insights into P speciation. A trend towards more stable Ca-P compounds towards the Gotland basin was found with sequential fractionation and P-XANES. In the future, different types of sediments will be analyzed with respect to their interactions with adjacent soils to find out a common principle of P-transformations and derive approaches for capturing P before entering susceptible marine systems.

Formal coordination of phosphorus(III) by a calix[4]pyrrole Schiff base ligand was achieved through the reaction of this ligand with PCl3 under basic conditions. The reaction product adopts a Pacman conformation with two P-Cl moieties, one in exo and one in endo position. It represents the first non-metal compound of calix[4]pyrrole Schiff base ligands and of Pacman ligands in general. The spatial neighborhood of the two phosphorus atoms enables cooperative reactions. As a first example, the chloride abstraction with AgOTf is presented, yielding a macrocyclic dication with two embedded phosphorus(III) monocations, which both undergo a cooperative, internal activation reaction with an adjacent C=N double bond. This intramolecular redox process affords two pentacoordinated phosphorus(V) centers within the Pacman dication. All reaction products were fully characterized and all results are supported by computations.

The tricyclic azepino[1,2

A new method for the preparation of three new curcumin analogues is described by the connection of pentadienones to carbohydrate units. From L-Rhamnose and D-Galactose, several functionalization reactions were performed to obtain the desired sugar units. The sugars 8, 18 and 19, after obtained, were used as starting material for the association with curcumin-derived pentadienones, thus giving rise to three new chalcones 9 by O-glycosylation, 22 and 23 C-glycosylation. The new compounds were characterized by NMR and mass spectroscopy. The compounds obtained have high potential to exhibit antitumor activity.

The isomerism of 1,5-benzodiazepin-2-ones 3 containing a perfluorinated side chain was investigated by 1 H-, 13 C-, 15 N- and 19 F NMR spectroscopy in different solvents. Compounds 3 exist in CDCl 3 , (D 6 )acetone, CD 3 CN and (D 5 )pyridine solution as one species, whereas in (D 6 )DMSO and (D 7 )DMF partial ( E / Z ) isomerisation about the exocyclic C 2 =C 3 bond occurs resulting in two isomers. Gibbs free energies (ΔG) and Free activation energies (ΔG ≠ ) were calculated based on BP86 and BP86-SCRF DFT computations.

An electrolyte solution of tetrabutylphosphonium hydroxide (TBPH) in water can dissolve over 20 wt % of cellulose in minutes and therefore constitutes a promising alternative green solvent system compared to known imidazolium- or dimethylacetamide-based systems. Overcoming the disadvantage of the extremely high viscosity of TBPH/cellulose solutions can facilitate their use for various applications. In this study, the application of cosolvents for the reduction, and thus adjustability, of the viscosity is addressed. Even well-known antisolvents can be easily deployed, resulting in a dramatic drop in viscosity. High concentrations of cosolvents (excluding ethanol) are tolerated without precipitation of the dissolved cellulose. Furthermore, the effect of the cosolvents on the additional dissolution of cellulose is discussed. The amount of dissolved cellulose is quantified by 13 C NMR spectroscopy.

The reaction of HN3 with the strong Lewis acid B(C6 F5 )3 led to the formation of a very labile HN3 ⋅B(C6 F5 )3 adduct, which decomposed to an aminoborane, H(C6 F5 )NB(C6 F5 )2 , above -20 °C with release of molecular nitrogen and simultaneous migration of a C6 F5 group from boron to the nitrogen atom. The intermediary formation of azide-borane adducts with B(C6 F5 )3 was also demonstrated for a series of organic azides, RN3 (R=Me3 Si, Ph, 3,5-(CF3 )2 C6 H3 ), which also underwent Staudinger-like decomposition along with C6 F5 group migration. In accord with experiment, computations revealed rather small barriers towards nitrogen release for these highly labile azide adducts for all organic substituents except R=Me3 Si (m.p. 120 °C, Tdec =189 °C). Hydrolysis of the aminoboranes provided C6 F5 -substituted amines, HN(R)(C6 F5 ), in good yields.

Starting from fluoridosilicate precursors in neat cyanotrimethylsilane, Me3 Si-CN, a series of different ammonium salts [R3 NMe]+ (R=Et, n Pr, n Bu) with the novel [SiF(CN)5 ]2- and [Si(CN)6 ]2- dianions was synthesized in facile, temperature controlled F- /CN- exchange reactions. Utilizing decomposable, non-innocent cations, such as [R3 NH]+ , it was possible to generate metal salts of the type M2 [Si(CN)6 ] (M+ =Li+ , K+ ) via neutralization reactions with the corresponding metal hydroxides. The ionic liquid [BMIm]2 [Si(CN)6 ] (m.p.=72 °C, BMIm=1-butyl-3-methylimidazolium) was obtained by a salt metathesis reaction. All the synthesized salts could be isolated in good yields and were fully characterized.

Little is known about phosphorus (P) in biological soil crusts (BSCs) and their role in biogeochemical P cycling. The present study evaluated P in BSCs with an array of methodological approaches including sequential P fractionation, solution 31P nuclear magnetic resonance (NMR) spectroscopy, synchrotron-based P K-edge X-ray absorption near-edge structure (XANES) spectroscopy, elemental mapping (μ-XRF) combined with μ-XANES and P-lipid quantification. BSCs (light algal crusts) were collected at seven sites along a sediment weathering gradient in north-eastern Germany (based on feldspar weathering indices) from non-weathered dune sands at the Baltic Sea coast to more strongly weathered Weichselian glacio-fluvial sands near Berlin. The total P (Pt) concentrations of BSCs ranged from 93 to 389 mg kg−1 and were not significantly correlated with the change in feldspar weathering index. While concentrations of stable P (H2SO4-extractable) strongly decreased, labile P (resin- + NaHCO3-extractable P) in BSCs increased with increasing sediment weathering. Based on 31P NMR spectra, 20 to 62% of NaOH-EDTA extracted P was orthophosphate monoesters and 0 to 9% was diesters. For BSCs, P K-edge XANES showed that Ca-P species decreased with increasing weathering. Heterogeneity of the BSCs was exemplarily shown at the micrometre scale by element mapping μ-XRF and μ-XANES, using four 10 × 10 μm spots of a vertical cross-section within a coastal dune BSC. While only the P-lipid class phosphatidic acid (PA) increased with increasing weathering, analyses of BSC phospholipid fatty acids (PLFAs) revealed decreasing contributions of Gram-positive bacteria with increasing coastal sediment weathering but different taxa were independent of any investigated P parameter. Proportions of lipid-P varied between 0.02 and 0.1% of Pt, indicating a constant share of living biomass in BSCs along the gradient. In conclusion, this multi-method study of P speciation in BSCs showed that these communities play a key role in the biogeochemical P cycle, especially by transforming stable P into labile, easily bioavailable P.

Biradicals were applied as molecular switches to control chemical reactions that involve the activation of small molecules. The mechanism was studied by experimental and computational methods., Molecular switches are molecules that can reversibly be shifted between at least two stable states with different physical and chemical properties, making them interesting for application as chemical sensors or molecular machines. We recently discovered that five-membered, cyclic biradicals based on group 15 elements are efficient and robust photochemical switches that can be activated by red light. The quantum yield of the photo-isomerization is as high as 24.6%, and the thermal equilibration of the photo-activation product proceeds rapidly at ambient temperature. The fully reversible process was studied by experimental and high-level ab initio techniques. We could further demonstrate that the biradical character could be completely turned on and off, so the system could be applied to control chemical equilibria that involve activation products of the cyclic biradicals.

Intertidal rocky shore ecosystems are affected by steep environmental gradients such as fluctuating solar irradiation and salinity along the marine-terrestrial interface. The eulittoral red alga Pyropia plicata (Bangiales) is endemic and abundant to coastal regions of New Zealand and almost unstudied in terms of ecophysiological performance under radiation and salinity stress. Therefore, the acclimation potential of this species against enhanced ultraviolet radiation (UVR) and osmotic stress was evaluated in a combination of field and laboratory experiments with an emphasis on stress metabolite concentrations (UV-sunscreens, organic osmolytes). Samples of P. plicata were collected at the same site in the intertidal zone of Wellington, New Zealand over three seasons (April–November 2016) and used in independent UV and salt stress experiments under controlled conditions. The mycosporine-like amino acids (MAA) shinorine and porphyra-334 were the quantitatively dominant UV-sunscreen compounds, and the total concentrations varied over the year between 5 and 14 mg g −1 dry weight (DW), but neither UVR nor PAR had a significant impact on the total or individual MAA concentrations. A UV radiation stress experiment was conducted, but the total MAA concentrations of 6–8 mg g−1 DW did not change, neither did the contents of shinorine (~ 3 mg g−1 DW) nor that of porphyra-334 (4–5 mg g−1 DW). This suggests, that P. plicata has sufficiently high UV-sunscreen amounts and hence does not respond to changes in UV radiation. Pyropia plicata contained three heterosides (floridoside, D- and L-isofloridoside), which act as organic osmolytes. Seasonally the total concentrations of these compounds varied between 203 and 1226 mmol kg−1 DW, with L-isofloridoside quantitatively dominating all samples. A salt stress experiment showed an increase in the total heteroside concentrations in P. plicata with increasing salinities. However, floridoside was the most up-regulated heteroside under hypersaline conditions indicating its key role in osmotic acclimation. Our data indicate that P. plicata always contains various stress metabolites in consistently high concentrations which mitigate against environmental changes typical of the intertidal zone of New Zealand.

Conversion of 1,2‐bis(dichlorophosphino)benzene with sterically demanding primary amines led to the formation of 1,3‐dichloro‐2‐aza‐1,3‐diphosphaindanes of the type C6H4(μ‐PCl)2N‐R. Reduction yielded the corresponding 2‐aza‐1,3‐diphosphaindane‐1,3‐diyls (1), which can be described as phosphorus‐centered singlet biradical(oid)s. Their stability depends on the size of the substituent R: While derivatives with R=Dmp (2,6‐dimethylphenyl) or Ter (2,6‐dimesitylphenyl) underwent oligomerization, the derivative with very bulky R=tBuBhp (2,6‐bis(benzhydryl)‐4‐tert‐butylphenyl) was stable with respect to oligomerization in its monomeric form. Oligomerization involved activation of the fused benzene ring by a second equivalent of the monomeric biradical and can be regarded as formal [2+2] (poly)addition reaction. Calculations indicate that the biradical character in 1 is comparable with literature‐known P‐centered biradicals. Ring‐current calculations show aromaticity within the entire ring system of 1., Only one very bulky substituent R is required to stabilize the first stable heteroindanediyls (see picture), which represent a group of resonance‐stabilized phosphorus‐centered biradicals. Different types of oligomers formed by self‐activation of the aromatic backbone were observed for smaller substituents.

The thermodynamics of halogen bonding of a series of isostructural Group 10 metal pincer fluoride complexes of the type [(3,5‐R2‐tBuPOCOPtBu)MF] (3,5‐R2‐tBuPOCOPtBu=κ 3‐C6HR2‐2,6‐(OPtBu2)2 with R=H, tBu, COOMe; M=Ni, Pd, Pt) and iodopentafluorobenzene was investigated. Based on NMR experiments at different temperatures, all complexes 1‐tBu (R=tBu, M=Ni), 2‐H (R=H, M=Pd), 2‐tBu (R=tBu, M=Pd), 2‐COOMe (R=COOMe, M=Pd) and 3‐tBu (R=tBu, M=Pt) form strong halogen bonds with Pd complexes showing significantly stronger binding to iodopentafluorobenzene. Structural and computational analysis of a model adduct of complex 2‐tBu with 1,4‐diiodotetrafluorobenzene as well as of structures of iodopentafluorobenzene in toluene solution shows that formation of a type I contact occurs., Pincer complexes studied: Group 10 POCOP (κ 3‐C6HR2‐2,6‐(OPtBu2)2; R=H, tBu) fluoride complexes show pronounced halogen bonding with iodopentafluorobenzene in toluene. Along an isostructural series of complexes, Pd fluorides show the strongest interactions.

Ion pairing is one of the most fundamental atomic interactions in chemistry and biology. In contrast, pairing between like-charged ions remains an elusive concept. So far, this phenomenon was observed only for large-scaled structures, assemblies, stabilizing frameworks, or in aqueous solution wherein like-charge attraction is supported by mediating water molecules. Recently, we reported the formation of cationic clusters in pure ionic liquids (ILs) which all include hydroxyl groups (OH) for possible hydrogen bonding. In such structures like-charge repulsion is overcome by cooperative hydrogen bonds. The vibrational bands in the OH-stretch region of the infrared spectra can be clearly assigned to H-bonded ion pairs (c–a) or to H-bonded cationic clusters (c–c). The equilibrium between both types of ionic clusters can be controlled by using the same cation but differently strong interacting anions. In the present work, we study the influence of the cationic cluster formation on structural and dynamical NMR properties of ionic liquids, where we know that they form cationic clusters to different extent. First, we measure proton chemical shifts, δ1H, and determine deuteron quadrupole coupling constants, χD, from a calculated relation between both NMR properties. Reliable χD values for the liquid phase are a prerequisite for calculating reorientational correlation times, τOH, from measured deuteron relaxation times, T1. It is shown that the correlation times are significantly influenced by the amount of cationic clusters present in the IL. The Stokes–Einstein–Debye (SED) relation is valid for the ILs wherein H-bonded ion pairs (c–a) are the dominant species. With increasing cationic cluster (c–c) formation of e.g. cyclic tetramers, SED breaks down because of the structural heterogeneities.

To elucidate the ecological role of biological soil crusts (BSCs) in the P-cycle and to disclose vegetation (pine vs. beech), soil horizon (A horizon vs. C horizon) and land use intensity effects, we examined BSCs collected from a temperate forest in Schorfheide-Chorin (Germany). Total C, N and P of the three sample compartments crust, crust-adhering soil underneath and crust-free soil were quantified and inorganic and organic P (P i , P o ) contents in five sequentially extracted P fractions of the different compartments were determined. In addition, P species were characterized using P K -edge XANES (X-ray absorption near edge structure) and 31 P NMR (nuclear magnetic resonance) spectroscopy. BSC biodiversity of algae was morphologically determined using enrichment cultivation. Results showed an accumulation of total P in the BSC with high shares of P o . Proportions of labile and moderately labile P o pools were higher in BSC than crust-free soil in expense of residual P indicating weathering of Fe/Al-P species by BSC organisms. Vegetation affected the C/N ratio and proportion of labile P i in total P of BSC; they were significantly higher under beech compared with pine. XANES results revealed BSC weathering of mainly Fe-P under beech and Al-P under pine. Soil horizon affected the composition of BSC organisms; there were more filamentous algae in BSCs on C horizon than A horizon. Moderately labile P i concentrations were higher in BSC on C horizon compared with A horizon while the share of the labile P o pool in total P was lower on C horizon than A horizon. Increasing forest management intensity decreased the share of moderately labile P and P o in total P as well as the monoester-P/diester-P ratio in pine BSC. While in BSC under pine changes occurred in microbial diversity, under beech changes occurred in algal richness and life form. We conclude that BSCs in Central European forests are particularly involved in the transformation of P i to P o fractions and respond differently to management intensity depending on the predominating tree species.

The properties of ionic liquids are described by a subtle balance between Coulomb interaction, hydrogen bonding, and dispersion forces. We show that lowering the attractive Coulomb interaction by choosing weakly coordinating anions leads to the formation of cationic clusters. These clusters of like-charged ions are stabilized by cooperative hydrogen bonding and controlled by the interaction potential of the anion. IR and NMR spectroscopy combined with computational methods are used to detect and characterize these unusual, counter-intuitively formed clusters. They can be only observed for weakly coordinating anions. When cationic clusters are formed, cyclic tetramers are particularly stable. Therein, cooperative hydrogen-bond attraction can compete with like-charge repulsion. We present a simple but effective spectroscopic scale for the possibility of like-charge attraction in ionic liquids, based on IR and NMR signatures.

We show that deuteron quadrupole coupling constants (DQCCs), and reorientational correlation times of molecular bonds N-D that are involved in hydrogen bonding, can be determined from NMR T1 relaxation time experiments simultaneously. For this purpose, we used trialkylammonium-based protic ionic liquids (PILs) as model compounds. They exhibit high viscosities and wide liquid ranges that allow measurements far beyond the extreme narrowing region (ω0τc ≪ 1). The T1 minima already occur at temperatures significantly above room temperature. We obtain reasonable DQCCs for the liquid phase if anisotropic motion is considered. The DQCCs are very small due to attractive Coulomb interaction between the cation and anion, which is further enhanced by hydrogen bonding. The DQCCs strongly depend on the interaction strength of the anion but are independent of the alkyl chain length of the trialkyl ammonium cations pointing to the exclusive cation-anion interaction along the hydrogen bond.

The hydrogenation of gossypol using supported noble metal catalysts led to a new derivative named gossoxol in 5 to 69% yield. The most active and selective catalyst was 5 wt% Rh/C. The mechanism of the hydrogenation was discussed and plausible intermediates of the catalytic cycle were determined by tracking the behavior of gossypol in different solvents and at elevated temperature using 1H NMR spectroscopy. The hydrogenation of anhydrogossypol also led to gossoxol, therefore it was regarded as an intermediate.

A possible application of glycerol, which is produced in large amounts as by-product from the biodiesel industry, is its fermentation to serinol (2-amino-1,3-propanediol), a glycerol derivative. The downstream processing of this glycerol-based fermentation broth was investigated. The challenge of the isolation of serinol was the complex media and the solubility of the desired substance in aqueous media. In this study, the isolation of serinol was investigated by an appropriate reversible derivatization method. Serinol was isolated by protecting the amino group with diethyl ethoxymethylenemalonate directly in the aqueous phase, followed by extraction of the 2,2-bis(ethoxycarbonyl)vinyl-serinol (BECV-serinol) with ethyl acetate resulting in an isolated yield of 63%. We demonstrate the possibility of isolation of a hydroscopic amino alcohol from the fermentation broth and the comparison of the products in water as well as the cleavage of the 2,2-bis(ethoxycarbonyl)vinyl group (BECV group). The procedure can also be used for other amino group containing molecules such as serine, glucosamine, hexylamine and amino methyl laureate. This article is protected by copyright. All rights reserved

The stability of ligands and catalysts is an almost neglected issue in homogeneous catalysis, but it is crucial for successful application of this methodology in technical scale. We have studied the effect of water on phosphites, which are the most applied cocatalysts in the n-regioselective homogeneous Rh-catalyzed hydroformylation of olefins. The stability of the bidentate nonsymmetrical diphosphite L1, as well as its two monophosphite constituents L2 and L3, toward hydrolysis was investigated by means of in situ NMR spectroscopy under similar conditions as applied in industry. Hydrolysis pathways, intermediates, and kinetics were clarified. DFT calculations were used to support the experimentally found data. The acylphosphite unit L2, which reacts with water in an unselective manner, was proven to be much less stable than the phenolphosphite L3. The stability of the bidentate ligand L1 can be therefore mainly attributed to its phenolphosphite moiety. With an excess of water, the hydrolysis of L1 and L2...

The reaction of perfluorinated 3,5-dioxoesters with 1,2-diaminobenzenes or 2,3-diaminonaphthalenes afforded two types of 1H-benzo-1,5-diazepine derivatives containing a perfluorinated side chain. 2,5-Dihydro-1H-benzo-1,5-diazepin-2-ones were formed by cyclocondensation via the central keto and the ester group, whereas 1H-benzo-1,5-diazepines resulted from cyclocondensation via the two keto groups. The tautomerism and isomerization of these compounds have been investigated by 1H-, 13C-, and 19F-NMR spectroscopy. The 1,5-diazepines appear in CDCl3 solution as mixtures of two tautomeric forms, the enaminoimine I and diaminodiene II. In DMSO solution, besides I and II, two further species, III and IV, are formed by (E/Z) isomerization on the exocyclic C=C bond.

A new synthetic approach enabled the generation of highly labile thionylimide, H-NSO, which was trapped by adduct formation with the bulky Lewis acid B(C6 F5 )3 and fully characterized. For comparison, a series of different Me3 Si-NSO Lewis acid adducts were studied. Treatment of Me3 Si-NSO with the silylium ion [Me3 Si](+) led to the formation of the hitherto unknown iminosulfonium ion [Me3 Si-N=S-O-SiMe3 ](+) , which could be isolated and fully characterized as a salt in the presence of weakly coordinating carborate anions.

We describe a method for the accurate determination of deuteron quadrupole coupling constants χD for N-D bonds in triethylammonium-based protic ionic liquids (PILs). This approach was first introduced by Wendt and Farrar for O-D bonds in molecular liquids, and is based on the linear relationship between the deuteron quadrupole coupling constants χD, and the proton chemical shifts δ(1)H, as obtained from DFT calculated properties in differently sized clusters of the compounds. Thus the measurement of δ(1)H provides an accurate estimate for χD, which can then be used for deriving reorientational correlation-times τND, by means of NMR deuteron quadrupole relaxation time measurements. The method is applied to pure PILs including differently strong interacting anions. The obtained χD values vary between 152 and 204 kHz, depending on the cation-anion interaction strength, intensified by H-bonding. We find that considering dispersion corrections in the DFT-calculations leads to only slightly decreasing χD values. The determined reorientational correlation times indicate that the extreme narrowing condition is fulfilled for these PILs. The τc values along with the measured viscosities provide an estimate for the volume/size of the clusters present in solution. In addition, the correlation times τc, and the H-bonded aggregates were also characterized by molecular dynamics (MD) simulations.

Efficient reduction of the tertiary amide bond in amino acid derivatives and peptides is described. Functional group selectivity has been achieved by applying a commercially available rhodium precursor and bis(diphenylphosphino)propane (dppp) ligand together with phenyl silane as a reductant. This methodology allows for specific reductive derivatization of biologically interesting peptides and offers straightforward access to a variety of novel peptide derivatives for chemical biology studies and potential pharmaceutical applications. The catalytic system tolerates a variety of functional groups including secondary amides, ester, nitrile, thiomethyl, and hydroxy groups. This convenient hydrosilylation reaction proceeds at ambient conditions and is operationally safe because no air-sensitive reagents or highly reactive metal hydrides are needed.

The cyclization of 1,5-bis[(trimethylsilyl)oxy]penta-1,4-dienes with quinoxalines and chloroformates afforded 2,3,3a,9a-tetrahydro-1H-cyclopenta[b]quinoxaline-1,3,4,9-tetracarboxylate.

The properties of the hydrogen bonds in ethylammonium nitrate are analyzed by using molecular dynamics simulations and infrared as well as nuclear magnetic resonance experiments. Ethylammonium nitrate features a flexible three-dimensional network of hydrogen bonds with moderate strengths, which makes it distinct from related triethylammonium-based ionic liquids. First, the network's flexibility is manifested in a not very pronounced correlation of the hydrogen bond geometries, which is caused by rapid interchanges of bonding partners. The large flexibility of the network leads to a substantial broadening of the mid-IR absorption band, with the contributions due to N-H stretching motions ranging from 2800 to 3250~\cm. Finally, the different dynamics are also seen in the rotational correlation of the N-H bond vector, where a correlation time as short as 16.1~ps is observed., Comment: revised version