Elucidating regulation of polyhydroxyalkanoate metabolism in R. eutropha: Identification of transcriptional regulators from phasin and depolymerase genes.

Despite the ever-growing research interest in polyhydroxyalkanoates (PHAs) as green plastic alternatives, our understanding of the regulatory mechanisms governing PHA synthesis, storage, and degradation in the model organism Ralstonia eutropha remains limited. Given its importance for central carbon metabolism, PHA homeostasis is probably controlled by a complex network of transcriptional regulators. Understanding this fine-tuning is key for developing improved PHA production strains thereby boosting the application of PHAs. We conducted promoter pull-down assays with crude protein extracts from R. eutropha Re2058/pCB113, followed by LC-MS/MS, to identify putative transcriptional regulators involved in the expression control of PHA metabolism, specifically targeting phasin phaP1 and depolymerase phaZ3 and phaZ5 genes. The impact on promoter activity was studied in vivo using ß-galactosidase assays and the most promising candidates were heterologously produced in Escherichia coli and their interaction with the promoters investigated in vitro by Electrophoretic Mobility Shift Assays. We could show that R. eutropha DNA-binding XRE-family-like protein H16_B1672, specifically binds the phaP1 promoter in vitro with a KD of 175 nM and represses gene expression from this promoter in vivo. Protein H16_B1672 also showed interaction with both depolymerase promoters in vivo and in vitro suggesting a broader role in the regulation of PHA metabolism. Furthermore, in vivo assays revealed that the H-NS-like DNA-binding protein H16_B0227 and the peptidyl-prolyl cis-trans isomerase PpiB, strongly repress gene expression from PphaP1 and PphaZ3, respectively. In summary, this study provides new insights into the regulation of PHA metabolism in R. eutropha, uncovering specific interactions of novel transcriptional regulators.

Fluorinated Dialkyl Chloronium Salts: Synthesis and Reactivity for Fluoroalkylation and Hydride Abstraction.

A new concept for the synthesis of dialkyl chloronium cations [R‒Cl‒R]+ is described (R = CH3, CH2CF3), that allows the formation of fluorinated derivatives. By utilizing the xenonium salt [XeOTeF5][M(OTeF5)n] (M = Sb, n = 6; M = Al, n = 4) chlorine atoms of chloroalkanes or the deactivated chlorofluoroalkane CH2ClCF3 are oxidized and removed as ClOTeF5 leading to the isolation of the corresponding chloronium salt. Since the resulting highly electrophilic cation [Cl(CH2CF3)2]+ is able to alkylate weak nucleophiles, this compound can be utilized for the introduction of a fluorinated alkyl group to those. In addition, the fluorinated alkyl chloronium cation displays a high hydride ion affinity, enabling the activation of linear hydrocarbons by hydride abstraction even at low temperatures ultimately leading to the formation of branched carbocations.

High-cell-density fed-batch strategy to manufacture tailor-made P(HB-co-HHx) by engineered Ralstonia eutropha at laboratory scale and pilot scale.

The transition towards a sustainable bioeconomy requires the development of highly efficient bioprocesses that enable the production of bulk materials at a competitive price. This is particularly crucial for driving the commercialization of polyhydroxyalkanoates (PHAs) as biobased and biodegradable plastic substitutes. Among these, the copolymer poly(hydroxybutyrate-co-hydroxyhexanoate) (P(HB-co-HHx)) shows excellent material properties that can be tuned by regulating its monomer composition. In this study, we developed a high-cell-density fed-batch strategy using mixtures of fructose and canola oil to modulate the molar composition of P(HB-co-HHx) produced by Ralstonia eutropha Re2058/pCB113 at 1-L laboratory scale up to 150-L pilot scale. With cell densities >100 g L-1 containing 70-80 wt% of PHA with tunable HHx contents in the range of 9.0-14.6 mol% and productivities of up to 1.5 g L-1 h-1, we demonstrate the tailor-made production of P(HB-co-HHx) at an industrially relevant scale. Ultimately, this strategy enables the production of PHA bioplastics with defined material properties on the kilogram scale, which is often required for testing and adapting manufacturing processes to target diverse applications.

N2 cleavage by silylene and formation of H2Si(µ-N)2SiH2.

Fixation and functionalisation of N2 by main-group elements has remained scarce. Herein, we report a fixation and cleavage of the N ≡ N triple bond achieved in a dinitrogen (N2) matrix by the reaction of hydrogen and laser-ablated silicon atoms. The four-membered heterocycle H2Si(µ-N)2SiH2, the H2SiNN(H2) and HNSiNH complexes are characterized by infrared spectroscopy in conjunction with quantum-chemical calculations. The synergistic interaction of the two SiH2 moieties with N2 results in the formation of final product H2Si(µ-N)2SiH2, and theoretical calculations reveal the donation of electron density of Si to π* antibonding orbitals and the removal of electron density from the π bonding orbitals of N2, leading to cleave the non-polar and strong NN triple bond.

B[double bond, length as m-dash]P double bonds relieved from steric encumbrance: matrix-isolation infrared spectroscopy of the phosphaborene F2B-P[double bond, length as m-dash]BF and the triradical B[double bond, length as m-dash]PF3.

Free phosphaborenes have a labile boron-phosphorus double bond and therefore require extensive steric shielding by bulky substituents to prevent isomerisation and oligomerisation. In the present work, the small free phosphaborene F2B-P[double bond, length as m-dash]BF was isolated by matrix-isolation techniques and was characterised by infrared spectroscopy in conjunction with quantum-chemical methods. In contrast to its sterically hindered relatives, this small phosphaborene exhibits an acute BPB angle of 83° at the CCSD(T) level. An alternative orbital structure for the B[double bond, length as m-dash]P double bond is found in the triradical B[double bond, length as m-dash]PF3, the direct adduct of laser-ablated atomic B and PF3. The single-bonded isomer F2B-PF and the dimer F3P-B[triple bond, length as m-dash]B-PF3 are also tentatively assigned.

Introducing AFS ([Al(SO3F)3]x) - a thermally stable, readily available, and catalytically active solid Lewis superacid.

Common Lewis superacids often suffer from low thermal stability or complicated synthetic protocols, requiring multi-step procedures and expensive starting materials. This prevents their large-scale application. Herein, the easy and comparably cheap synthesis of high-purity aluminium tris(fluorosulfate) ([Al(SO3F)3]x, AFS) is presented. All starting materials are commercially available and no work-up is required. The superacidity of this thermally stable, polymeric Lewis acid is demonstrated using both theoretical and experimental methods. Furthermore, its synthetic and catalytic applicability, e.g. in bond heterolysis reactions and C-F bond activations, is shown.

Silver(i) Perfluoroalcoholates: Synthesis, Structure, and their Use as Transfer Reagents.

Herein we report a general access to silver(i) perfluoroalcoholates, their structure in the solid state and in solution, and their use as transfer reagents. The silver(i) perfluoroalcoholates are prepared by the reaction of AgF with the corresponding perfluorinated carbonyl compounds in acetonitrile and are stable for a prolonged time at -18 °C. X-ray analysis of single crystals of perfluoroalcoholate species showed that two Ag(i) centers are bridged by the alcoholate ligands. In acetonitrile solution, Ag[OCF3] forms different structures as indicated by IR spectroscopy. Furthermore, the silver(i) perfluoroalcoholates can be used as easy-to-handle transfer reagents for the synthesis of Cu[OCF3], Cu[OC2F5], [PPh4][Au(CF3)3(OCF3)], and fluorinated alkyl ethers.

A Highly Sterically Encumbered Boron Lewis Acid Enabled by an Organotellurium-Based Ligand.

Lewis acidic boron compounds are ubiquitous in chemistry due to their numerous applications, yet tuning and optimizing their properties towards different purposes is still a challenging field of research. In this work, the boron-based Lewis acid B[OTeF3(C6F5)2]3 was synthesized by reaction of the teflate derivative HOTeF3(C6F5)2 with BCl3 or BCl3 ⋅ SMe2. This new compound presents a remarkably high thermal stability up to 300 °C, as well as one of the most sterically encumbered boron centres known in the literature. Theoretical and experimental methods revealed that B[OTeF3(C6F5)2]3 exhibits a comparable Lewis acidity to that of the well-known B(C6F5)3. The affinity of B[OTeF3(C6F5)2]3 towards pyridine was accessed by Isothermal Titration Calorimetry (ITC) and compared to that of B(OTeF5)3 and B(C6F5)3. The ligand-transfer reactivity of this new boron compound towards different fluorides was demonstrated by the formation of an anionic Au(III) complex and a hypervalent iodine(III) species.

Investigation of Isolated IrF5 -, IrF6 - Anions and M[IrF6] (M=Na, K, Rb, Cs) Ion Pairs by Matrix-Isolation Spectroscopy and Relativistic Quantum-Chemical Calculations.

The molecular IrF5 -, IrF6 - anions and M[IrF6] (M=Na, K, Rb, Cs) ion pairs were prepared by co-deposition of laser-ablated alkali metal fluorides MF with IrF6 and isolated in solid neon or argon matrices under cryogenic conditions. The free anions were obtained as well by co-deposition of IrF6 with laser-ablated metals (Ir or Pt) as electron sources. The products were characterized in a combined analysis of matrix IR spectroscopy and electronic structure calculations using two-component quasi-relativistic DFT methods accounting for spin-orbit coupling (SOC) effects as well as multi-reference configuration-interaction (MRCI) approaches with SOC. Inclusion of SOC is crucial in the prediction of spectra and properties of IrF6 - and its alkali-metal ion pairs. The observed IR bands and the computations show that the IrF6 - anion adopts an Oh structure in a nondegenerate ground state stabilized by SOC effects, and not a distorted D4h structure in a triplet ground state as suggested by scalar-relativistic calculations. The corresponding "closed-shell" M[IrF6] ion pairs with C3v symmetry are stabilized by coordination of an alkali metal ion to three F atoms, and their structural change in the series from M=Na to Cs was proven spectroscopically. There is no evidence for the formation of IrF7, IrF7 - or M[IrF7] (M=Na, K, Rb, Cs) ion pairs in our experiments.

Generation and Identification of the Trifluorosilylarsinidene F3SiAs and Isomeric Perfluorinated Arsasilene FAsSiF2.

The trifluorosilylarsinidene F3SiAs in the triplet ground state has been generated through the reaction of laser-ablated silicon atoms with AsF3 in cryogenic Ne- and Ar-matrices. The reactions proceed with the initial formation of perfluorinated arsasilene FAsSiF2 in the singlet ground state by two As-F bonds insertion reaction on annealing. The trifluorosilylarsinidene F3SiAs was formed via F-migration reactions of FAsSiF2 under irradiation at UV light (λ = 275 nm). The characterization of FAsSiF2 and F3SiAs by IR matrix-isolation spectroscopy is supported by computations at CCSD(T)-F12/aug-cc-pVTZ and B3LYP/aug-cc-pVTZ levels of theory.

Bichloride-based ionic liquids for the merged storage, processing, and electrolysis of hydrogen chloride.

Hydrogen chloride is produced as a by-product in industrial processes on a million-ton scale. Since HCl is inherently dangerous, its storage and transport are avoided by, e.g., on-site electrolysis providing H2 and Cl2 which usually requires complex cell designs and PFAS-based membranes. Here we report a complementary approach to safely store 0.61 kilogram HCl per kilogram storage material [NEt3Me]Cl forming the bichloride [NEt3Me][Cl(HCl)n]. Although HCl release is possible from this ionic liquid by heat or vacuum, the bichloride can be used directly to produce base chemicals like vinyl chloride. Alternatively, [NEt3Me][Cl(HCl)n] is electrolyzed under anhydrous conditions using a membrane-free cell to generate H2 and the corresponding chlorination agent [NEt3Me][Cl(Cl2)n], enabling the combination of these ionic liquids for the production of base chemicals.

Spectroscopic Identification of Trifluorosilylphosphinidene and Isomeric Phosphasilene and Silicon Trifluorophosphine Complex.

The perfluorinated silylphosphinidene, F3SiP, in the triplet ground state is generated by the reaction of laser-ablated silicon atoms with PF3 in solid neon and argon matrices. The reactions proceed with the initial formation of a silicon trifluorophosphine complex, F3PSi, in the triplet ground state, and a more stable inserted phosphasilene, FPSiF2, in the singlet ground state upon deposition. The trifluorosilylphosphinidene was formed through F-migration reactions of FPSiF2 and F3PSi following a two-state mechanism under irradiation with visible light (λ = 470 nm) and full arc light (λ > 220 nm), respectively. High-level quantum-chemical methods support the identification of F3PSi, FPSiF2, and F3SiP by matrix-isolation IR spectroscopy.

Questing for homoleptic mononuclear manganese complexes with monodentate O-donor ligands.

Compounds containing Mn-O bonds are of utmost importance in biological systems and catalytic processes. Nevertheless, mononuclear manganese complexes containing all O-donor ligands are still rare. Taking advantage of the low tendency of the pentafluoroorthotellurate ligand (teflate, OTeF5) to bridge metal centers, we have synthesized two homoleptic manganese complexes with monomeric structures and an all O-donor coordination sphere. The tetrahedrally distorted MnII anion, [Mn(OTeF5)4]2-, can be described as a high spin d5 complex (S = 5/2), as found experimentally (magnetic susceptibility measurements and EPR spectroscopy) and using theoretical calculations (DFT and CASSCF/NEVPT2). The high spin d4 electronic configuration (S = 2) of the MnIII anion, [Mn(OTeF5)5]2-, was also determined experimentally and theoretically, and a square pyramidal geometry was found to be the most stable one for this complex. Finally, the bonding situation in both complexes was investigated by means of the Interacting Quantum Atoms (IQA) methodology and compared to that of hypothetical mononuclear fluoromanganates. Within each pair of [MnXn]2- (n = 4, 5) species (X = OTeF5, F), the Mn-X interaction is found to be comparable, therefore proving that the similar electronic properties of the teflate and the fluoride are also responsible for the stabilization of these unique species.

Unravelling highly oxidized nickel centers in the anodic black film formed during the Simons process by in situ X-ray absorption near edge structure spectroscopy.

The Simons process is an electrochemical fluorination method to prepare organofluorine compounds. Despite the wide application, the underlying mechanism is still unclear. We report the investigation of the black film formed on the surface of the anodes in aHF by an in situ Ni K-edge X-ray absorption near edge structure (XANES) investigation. An electrochemical cell for in situ X-ray absorption spectroscopy (XAS) is presented.

Formation of Peroxynitrite, [O-N-O-O]-, via a Cascade of Reactions between Ozonide and Ammonia.

We report on an unexpected reaction between ammonia and potassium ozonide dissolved in liq. NH3 resulting in the formation of peroxynitrite, [ONOO]-, which exclusively happens in the presence of a specific partially fluorinated aniline-based ammonium cation. High-resolution structural data of the peroxynitrite anion in cis-conformation have been obtained. We further studied this molecule anion by single crystal Raman spectroscopy. The cis and trans isomers of peroxynitrite were analysed computationally with respect to their relative energies, the cis-trans transition barrier and their decomposition pathways to the nitrate anion. By experimentally examining cations decorated with fluorine ligands to different degrees, we demonstrate that fluorine specific interactions play a crucial role in the unexpected formation of peroxynitrite and as a conspicuously structure directing factor for the underlying crystalline solid phases, exhibiting distinct micro-separations of fluorine and hydrogen enriched regions.

Microbially synthesized poly(hydroxybutyrate-co-hydroxyhexanoate) with low to moderate hydroxyhexanoate content: Properties and applications.

Plastic pollution is the biggest environmental concern of our time. Breakdown products like micro- and nano-plastics inevitably enter the food chain and pose unprecedented health risks. In this scenario, bio-based and biodegradable plastic alternatives have been given a momentum aiming to bridge a transition towards a more sustainable future. Polyhydroxyalkanoates (PHAs) are one of the few thermoplastic polymers synthesized 100 % via biotechnological routes which fully biodegrade in common natural environments. Poly(hydroxybutyrate-co-hydroxyhexanoate) [P(HB-co-HHx)] is a PHA copolymer with great potential for the commodity polymers industry, as its mechanical properties can be tailored through fine-tuning of its molar HHx content. We have recently developed a strategy that enables for reliable tailoring of the monomer content of P(HB-co-HHx). Nevertheless, there is often a lack of comprehensive investigation of the material properties of PHAs to evaluate whether they actually mimic the functionalities of conventional plastics. We present a detailed study of P(HB-co-HHx) copolymers with low to moderate hydroxyhexanoate content to understand how the HHx monomer content influences the thermal and mechanical properties and to link those to their abiotic degradation. By increasing the HHx fractions in the range of 2 - 14 mol%, we impart an extension of the processing window and application range as the melting temperature (Tm) and glass temperature (Tg) of the copolymers decrease from Tm 165 °C to 126 °C, Tg 4 °C to -5.9 °C, accompanied by reduced crystallinity from 54 % to 20 %. Elongation at break was increased from 5.7 % up to 703 % at 14 mol% HHx content, confirming that the range examined was sufficiently large to obtain ductile and brittle copolymers, while tensile strength was maintained throughout the studied range. Finally, accelerated abiotic degradation was shown to be slowed down with an increasing HHx fraction decreasing from 70 % to 55 % in 12 h.

Trifluoromethyl Fluorosulfonate (CF3OSO2F) and Trifluoromethoxy Sulfur Pentafluoride (CF3OSF5) - Two Gaseous Sulfur(VI) Compounds with Insulating Properties.

In this work, we analyzed trifluoromethyl fluorosulfonate (CF3OSO2F) and trifluoromethoxy sulfur pentafluoride (CF3OSF5) regarding their potential use as dielectrics by investigating some of their intrinsic and extrinsic properties. Both compounds show a higher breakdown voltage than SF6 with averaged relative breakdown voltages of 1.3±0.2 for CF3OSO2F and 1.4±0.2 for CF3OSF5 compared to SF6 with 1.0. Like the dielectric (CF3)2CFCN, both compounds decompose during the breakdown process. The decomposition products were analyzed by IR spectroscopy and GCIR methods. Furthermore, the molecular structures of both gaseous compounds CF3OSO2F and CF3OSF5 have been determined by in situ crystallization, and their physical properties were determined as well.

Photoinduced Dual C-F Bond Activation of Hexafluorobenzene Mediated by Boron Atom.

The reaction of laser-ablated boron atoms with hexafluorobenzene (C6 F6 ) was investigated in neon and argon matrices, and the products are identified by matrix isolation infrared spectroscopy and quantum-chemical calculations. The reaction is triggered by a boron atom insertion into one C-F bond of hexafluorobenzene on annealing, forming a fluoropentafluorophenyl boryl radical (A). UV-Vis light irradiation of fluoropentafluorophenyl boryl radical causes generation of a 2-difluoroboryl-tetrafluorophenyl radical (B) via a second C-F bond activation. A perfluoroborepinyl radical (C) is also observed upon deposition and under UV-Vis light irradiation. This finding reveals the new example of a dual C-F bond activation of hexafluorobenzene mediated by a nonmetal and provides a possible route for synthesis of new perfluorinated organo-boron compounds.

[Xe(OTeF5)(pyF)]+: a strong oxidizing xenonium(II) teflate cation with N-donor bases.

Herein we report on the formation of the adduct salts [Xe(OTeF5)(pyF)][Al(OTeF5)4] (pyF = C5F5N, C5H3F2N) by abstraction of an -OTeF5 group from Xe(OTeF5)2 with the Lewis superacid Al(OTeF5)3 and subsequent adduct formation of the generated [XeOTeF5]+ cation with fluorinated pyridines. These salts represent the first xenonium cations with the weakly coordinating [Al(OTeF5)4]- anion. The strong oxidizing property of these compounds is further assessed.