Search

The coherent coupling between electronic excitations and vibrational modes of molecules largely affects the optical and charge transport properties of organic semiconductors and molecular solids. To analyze these couplings by means of ultrafast spectroscopy, highly ordered crystalline films with large domains are particularly suitable because the domains can be addressed individually, hence allowing azimuthal polarization-resolved measurements. Impressive examples of this are highly ordered crystalline thin films of perfluoropentacene (PFP) molecules, which adopt different molecular orientations on different alkali halide substrates. Here, we report polarization-resolved time-domain vibrational spectroscopy with 10 fs time resolution and Raman spectroscopy of crystalline PFP thin films grown on NaF(100) and KCl(100) substrates. Coherent oscillations in the time-resolved spectra reveal vibronic coupling to a high-frequency, 25 fs, in-plane deformation mode that is insensitive to the optical polarization, while the coupling to a lower-frequency, 85 fs, out-of-plane ring bending mode depends significantly on the crystalline and molecular orientation. Comparison with calculated Raman spectra of isolated PFP molecules in vacuo supports this interpretation and indicates a dominant role of solid-state effects in the vibronic properties of these materials. Our results represent a first step toward uncovering the role of anisotropic vibronic couplings for singlet fission processes in crystalline molecular thin films.

Aqueous metal corrosion is a major economic concern in modern society. A phenomenon that has puzzled generations of scientists in this field is the so-called anomalous hydrogen evolution: the violent dissolution of magnesium under electron-deficient (anodic) conditions, accompanied by strong hydrogen evolution and a key mechanism hampering Mg technology. Experimental studies have indicated the presence of univalent Mg + in solution, but these findings have been largely ignored because they defy our common chemical understanding and evaded direct experimental observation. Using recent advances in the ab initio description of solid-liquid electrochemical interfaces under controlled potential conditions, we describe the full reaction path of Mg atom dissolution from a kinked Mg surface under anodic conditions. Our study reveals the formation of a solvated [Mg 2+ (OH) - ] + ion complex, challenging the conventional assumption of Mg 2+ ion formation. This insight provides an intuitive explanation for the postulated presence of (Coulombically) univalent Mg + ions, and the absence of protective oxide/hydroxide layers normally formed under anodic/oxidizing conditions. The discovery of this unexpected and unconventional reaction mechanism is crucial for identifying new strategies for corrosion prevention and can be transferred to other metals.

Reaction of the cesium antimonide complex [Cs(18C6) 2 ][SbH 2 ] ( 1 , 18C6 = 18-crown-6 ether) with the triamidoamine actinide separated ion pairs [An(Tren TIPS )(L)][BPh 4 ] (Tren TIPS = {N(CH 2 CH 2 NSi i Pr 3 ) 3 } 3- ; An/L = Th/DME ( 2Th ); U/THF ( 2U )) affords the triactinide undeca-antimontriide Zintl clusters [{An(Tren TIPS )} 3 (μ 3 -Sb 11 )] (An = Th ( 3Th ), U ( 3U )) by dehydrocoupling. Clusters 3Th and 3U provide two new examples of the Sb 11 3- Zintl trianion and are unprecedented examples of molecular Sb 11 3- being coordinated to anything since all previous reports featured isolated Sb 11 3- Zintl trianions in separated ion quadruple formulations with noncoordinating cations. Quantum chemical calculations describe dominant ionic An-Sb interactions in 3Th and 3U , though the data suggest that the latter exhibits slightly more covalent An-Sb linkages than the former. Complexes 3Th and 3U have been characterized by single crystal X-ray diffraction, NMR, IR, and UV/vis/NIR spectroscopies, elemental analysis, and quantum chemical calculations.

A straightforward and general strategy for the catalytic asymmetric synthesis of β 3 -tryptophans by carboxylic-acid-directed intermolecular C-H amination has been developed. The iron-catalyzed C-H amination of 3-indolepropionic acids with BocNHOMs (Boc, tert -butyloxycarbonyl; OMs, methylsulfonate) in the presence of the base piperidine provides N-Boc-protected β 3 -tryptophans in a single step with high enantiomeric excess (ee) of up to >99%. Mechanistic experiments and density functional theory calculations support a mechanism through carboxylate-directed iron-mediated C(sp 3 )-H nitrene insertion. The method incorporates two key sustainability criteria: the use of iron as an abundant, non-toxic, and environmentally benign metal, along with the achievement of streamlined enantioselective C-H functionalization.

Quantum chemical calculations of the six valence isoelectronic complexes [FeL 2 ] 2- , [CoL 2 ] - , and NiL 2 with L = η 4 -P 4 , η 4 -C 4 H 4 using density functional theory have been carried out. The molecular structures were investigated with a variety of methods. The analysis of the electronic structure in [Fe(η 4 -P 4 ) 2 ] 2- shows that the bonding situation is very similar to valence isoelectronic Ni(η 4 -C 4 H 4 ) 2 . The orbital interactions in the 18 electron complexes [TML 2 ] q (TM q = Fe 2- , Co - , Ni) come mainly from TM(d π )→L 2 backdonation, enhanced by smaller contributions from TM(d δ )→L 2 backdonation and TM(s)←L 2 donation. Calculations of the six TML 2 species indicate that all of them are viable candidates for synthetic work. The bonding situation is very similar and can straightforwardly be explained with the Dewar-Chatt-Duncanson bonding model in terms of dative bonding between d 10 metal atoms and the ligands in the electronic singlet state. EDA-NOCV calculations using the ligands and the metal atoms with different charges and electronic states indicate that the metal-ligand bonds in the charged complexes [FeL 2 ] 2- and [CoL 2 ] - are best described with fragments in the electronic triplet state between the metal atoms with d 8 configuration and triplet ligands. The singlet fragments give the degenerate TM(d π )→L 2 π backdonation as the strongest component, whereas the triplet fragments have the related electron-sharing TM q (d π )-(L 2 ) 2- π bonding as the major component, differing only by the assignment of the bonded two electrons to one or both fragments. The calculations of the charge distribution using the Hirshfeld and Voronoi partitioning methods suggest that the metal atoms are nearly neutral or carry small negative charges in all complexes. The NBO method gives erratic charges, because of the neglect of the 4p AOs of the transition metals as genuine valence orbitals.

Reaction of 1 equiv of BeCl 2 with mesityl (Mes) or o -tolyl ( o -Tol) carboxylic acid in benzene gives hexanuclear heterocyles [BeCl(MesCO 2 )] 6 and [BeCl( o -TolCO 2 )] 6 , respectively. Small amounts of the oxocarboxylates [Be 4 O(MesCO 2 ) 6 ] and [Be 4 O( o -TolCO 2 ) 6 ] are also formed. If chloroform is used as the solvent, a mixture of these complexes together with the unprecedented tertranuclear cage compounds [Be 4 Cl 2 (MesCO 2 ) 6 ] and [Be 4 Cl 2 ( o -TolCO 2 ) 6 ] is obtained.

Quantum chemical results at the CCSD(T)/def2-QZVPP and BP86/def2-QZVPP levels are reported for the neutral and charged diatomic molecules EF, EO - (E = B-Tl), EF + , EO, EN - (E = C-Pb), EO + , and EN (E = N-Bi). The theoretically predicted bond lengths and dipole moments are in good agreement with each other and with the available experimental values. It is shown that the total dipole moment of the molecules can be nicely separated into the contributions of the individual occupied molecular orbitals. The σ lone-pair orbital has a dominating influence on the total dipole moment in the lighter EX systems, where E is an atom of the first or second octal row of the periodic table, but it becomes less influential for the heavier species. The HOMO of the heavy cations PbF + , SbO + , and BiO + is the degenerate π-bonding orbital, and the σ lone-pair orbital is the HOMO-2. The orbital energies of the ( n -1)d AOs of the heavier atoms are in the same range as those of the lowest lying genuine valence orbitals, so the division into nuclear and valence orbitals is not so clear.

Although several porous carbon/graphene nanoribbons (GNRs) have been prepared, a direct comparison of the electronic properties between a nonporous GNR and its periodically perforated counterpart is still missing. Here, we report the synthesis of porous 12-atom-wide armchair-edged GNRs from a bromoarene precursor on a Au(111) surface via hierarchical Ullmann and dehydrogenative coupling. The selective formation of porous 12-GNRs was achieved through thermodynamic and kinetic reaction control combined with tailored precursor design. The structure and electronic properties of the porous 12-GNR were elucidated by scanning tunneling microscopy/spectroscopy and density functional theory calculations, revealing that the pores induce a 2.17 eV band gap increase compared to the nonporous 12-AGNR on the same surface.

The electron-nucleus hyperfine coupling constant is a challenging property for density functional methods. For accurate results, hybrid functionals with a large amount of exact exchange are often needed and there is no clear "one-for-all" functional which describes the hyperfine coupling interaction for a large set of nuclei. To alleviate this unfavorable situation, we apply the adiabatic connection random phase approximation (RPA) in its post-Kohn-Sham fashion to this property as a first test. For simplicity, only the Fermi-contact and spin-dipole terms are calculated within the nonrelativistic and the scalar-relativistic exact two-component framework. This requires to solve a single coupled-perturbed Kohn-Sham equation to evaluate the relaxed density matrix, which comes with a modest increase in computational demands. RPA performs remarkably well and substantially improves upon its Kohn-Sham (KS) starting point while also reducing the dependence on the KS reference. For main-group systems, RPA outperforms global, range-separated, and local hybrid functionals─at similar computational costs. For transition-metal compounds and lanthanide complexes, a similar performance as for hybrid functionals is observed. In contrast, related post-Hartree-Fock methods such as Møller-Plesset perturbation theory or CC2 perform worse than semilocal density functionals.

Anisotropic cellulose nanofiber (CNF) foams represent the state-of-the-art in renewable insulation. These foams consist of large (diameter >10 μm) uniaxially aligned macropores with mesoporous pore-walls and aligned CNF. The foams show anisotropic thermal conduction, where heat transports more efficiently in the axial direction (along the aligned CNF and macropores) than in the radial direction (perpendicular to the aligned CNF and macropores). Here we explore the impact on axial and radial thermal conductivity upon depositing a thin film of reduced graphene oxide (rGO) on the macropore walls in anisotropic CNF foams. To obtain rGO films on the foam walls we developed liquid-phase self-assembly to deposit rGO in a layer-by-layer fashion. Using electron and ion microscopy, we thoroughly characterized the resulting rGO-CNF foams and confirmed the successful deposition of rGO. These hierarchical rGO-CNF foams show lower radial thermal conductivity (λ r ) across a wide range of relative humidity compared to CNF control foams. Our work therefore demonstrates a potential method for improved thermal insulation in anisotropic CNF foams and introduces versatile self-assembly for postmodification of such foams.

Climate change poses a significant threat to global agriculture, necessitating innovative solutions. Plant synthetic biology, particularly chloroplast engineering, holds promise as a viable approach to this challenge. Chloroplasts present a variety of advantageous traits for genetic engineering, but the development of genetic tools and genetic part characterization in these organelles is hindered by the lengthy time scales required to generate transplastomic organisms. To address these challenges, we have established a versatile protocol for generating highly active chloroplast-based cell-free gene expression (CFE) systems derived from a diverse range of plant species, including wheat (monocot), spinach, and poplar trees (dicots). We show that these systems work with conventionally used T7 RNA polymerase as well as the endogenous chloroplast polymerases, allowing for detailed characterization and prototyping of regulatory sequences at both transcription and translation levels. To demonstrate the platform for characterization of promoters and 5' and 3' untranslated regions (UTRs) in higher plant chloroplast gene expression, we analyze a collection of 23 5'UTRs, 10 3'UTRs, and 6 chloroplast promoters, assessed their expression in spinach and wheat extracts, and found consistency in expression patterns, suggesting cross-species compatibility. Looking forward, our chloroplast CFE systems open new avenues for plant synthetic biology, offering prototyping tools for both understanding gene expression and developing engineered plants, which could help meet the demands of a changing global climate.

Multipartite bacterial genomes pose challenges for genome engineering and the establishment of additional replicons. We simplified the tripartite genome structure (3.65 Mbp chromosome, 1.35 Mbp megaplasmid pSymA, 1.68 Mbp chromid pSymB) of the nitrogen-fixing plant symbiont Sinorhizobium meliloti . Strains with bi- and monopartite genome configurations were generated by targeted replicon fusions. Our design preserved key genomic features such as replichore ratios, GC skew, KOPS, and coding sequence distribution. Under standard culture conditions, the growth rates of these strains and the wild type were nearly comparable, and the ability for symbiotic nitrogen fixation was maintained. Spatiotemporal replicon organization and segregation were maintained in the triple replicon fusion strain. Deletion of the replication initiator-encoding genes, including the oriV s of pSymA and pSymB from this strain, resulted in a monopartite genome with oriC as the sole origin of replication, a strongly unbalanced replichore ratio, slow growth, aberrant cellular localization of oriC , and deficiency in symbiosis. Suppressor mutation R436H in the cell cycle histidine kinase CckA and a 3.2 Mbp inversion, both individually, largely restored growth, but only the genomic rearrangement recovered the symbiotic capacity. These strains will facilitate the integration of secondary replicons in S. meliloti and thus be useful for genome engineering applications, such as generating hybrid genomes.

The great variety and fascinating complexity of terpenoid skeletons are achieved through different cyclizations catalyzed by terpene cyclases. Here, we report a sesquiterpene cyclase (MfdS) from Aspergillus ustus for the formation of malfilanol D, a member of the group of biochemically less investigated sesquiterpenes with a bicyclo[5.4.0]undecane skeleton. Feeding 13 C-labeled acetates in Aspergillus nidulans with the mfdS sequence provides evidence for a C-1 to C-10 cyclization with subsequent 1,2-alkyl and 1,2-hydride shifts in the formation of the 6/7-fused rings.

The unprecedented silylene-supported dibenzodiboraoxepin 2 and 9,10-diboraphenanthrene complexes 6 and 8 were synthesized. The (NHSi) 2 B 2 (xanthene) [NHSi = PhC(NtBu) 2 (Me 2 N)Si:] 2 results from debromination of the bis(NHSi)-stabilized bis(dibromoboryl)xanthene 1 with potassium graphite (KC 8 ); 2 is capable of activating white phosphorus and ammonia to form the B 2 P 4 cage compound 3 and H 2 N-B-B-H diborane species 4 , respectively. The thermal rearrangement of 2 affords the 9,10-dihydro-9,10-diboraphenanthrene 5 through a bis(NHSi)-assisted intramolecular reductive C-O-C deoxygenation process. Notably, the 9,10-diboraphenanthrene derivatives 6 and 8 could be generated by deoxygenation of 2 with KC 8 and 1,3,4,5-tetramethylimidazol-2-ylidene, respectively. The aromaticity of 6 and 8 was confirmed by computational studies. Strikingly, the NHSi ligand in 8 engenders the monodeoxygenation of carbon dioxide in toluene at room temperature to form the CO-stabilized 9,10-diboraphenanthrene derivative 9 via the silaoxadiborinanone intermediate 10 .

In recent years, the fast-growing bacterium Vibrio natriegens has gained increasing attention as it has the potential to become a next-generation chassis for synthetic biology. A wide range of genetic parts and genome engineering methods have already been developed. However, there is still a need for a well-characterized tool to effectively and gradually reduce the expression levels of native genes. To bridge this gap, we created graded-CRISPRi, a system utilizing gRNA variants that lead to varying levels of repression strength. By incorporating multiple gRNA sequences into our design, we successfully extended this concept to simultaneously repress four distinct reporter genes. Furthermore, we demonstrated the capability of using graded-CRISPRi to target native genes, thereby examining the effect of various knockdown levels on growth.

Selective adsorption of multifunctional molecules is rarely observed when the different functional groups react via nonactivated reaction channels. Although the latter is also the case for ether cleavage and the adsorption of C=C double bonds on the highly reactive Si(001) surface, we find that allyl ethers, which combine both functional groups, react on Si(001) selectively via the cleavage of the molecules' ether group. In addition, our XPS measurements at 90, 150, and 300 K indicate an increased reactivity of the ether group when compared to monofunctional ethers. STM investigations furthermore reveal different final adsorption configurations after ether cleavage of allyl methyl ether when compared to diethyl ether as the monofunctional reference molecule. The interaction of the two functional groups in one molecule thus leads to new reaction channels with higher reactivity for ether cleavage on Si(001). As a further consequence, the reactivity of the C=C double bond is suppressed up to room temperature, leading to the observed selective adsorption.

In lithium-ion batteries, the solid electrolyte interphase (SEI) passivates the anode against reductive decomposition of the electrolyte but allows for electron transfer reactions between anode and redox shuttle molecules, which are added to the electrolyte as an internal overcharge protection. In order to elucidate the origin of these poorly understood passivation properties of the SEI with regard to different molecules, we used a four-electrode-based generator-collector setup to distinguish between electrolyte reduction current and the redox molecule (ferrocenium ion Fc + ) reduction current at an SEI-covered glassy carbon electrode. The experiments were carried out in situ during potentiostatic SEI formation close to battery operation potentials. The measured generator and collector currents were used to calculate passivation factors of the SEI with regard to electrolyte reduction and with regard to Fc + reduction. These passivation factors show huge differences in their absolute values and in their temporal evolution. By making simple assumptions about molecule transport, electron transport, and charge transfer reaction rates in the SEI, distinct passivation mechanisms are identified, strong indication is found for a transition during SEI growth from redox molecule reduction at the electrode | SEI interface to reduction at the SEI | electrolyte interface, and good estimates for the transport coefficients of both electrons and redox molecules are derived. The approach presented here is applicable to any type of electrochemical interphase and should thus also be of interest for interphase characterization in the fields of electrocatalysis and corrosion.

Two literature-known sulfido vanadates, Na 3 [VS 4 ] and K 3 [VS 4 ], were obtained through a straightforward and scalable synthetic method. Highly crystalline powders of both compounds were obtained from the homogeneous molten phases of starting materials via a─comparably rapid─solid-state technique. Low-temperature structure determination, ambient temperature powder diffraction, and solid-state NMR spectroscopy verify previous structural reports and indicate purity of the obtained samples. Both compounds show semiconductivity with the optical band gap values in the range of 2.1 to 2.3 eV. Experimental values of the ionic conductivity and dielectric constants are σ = 2.41·10 -5 mS·cm -1 , k = 76.52 and σ = 1.36·10 -4 mS·cm -1 , k = 103.67 at ambient temperature for Na 3 [VS 4 ] and K 3 [VS 4 ], respectively. It is demonstrated that Na 3 [VS 4 ] depicts second-order nonlinear optical properties, i.e., second harmonic generation over a broad wavelength spectrum. The results introduce new aspects of sulfido vanadates as multifunctional candidates for potential optical and electrical applications.

Virus inactivation is a prerequisite for safe handling of high-risk infectious samples. β-Propiolactone (BPL) is an established reagent with proven virucidal efficacy. BPL primarily reacts with DNA, RNA, and amino acids. The latter may modify antigenic protein epitopes interfering with binding properties of affinity reagents such as antibodies and aptamers used in affinity proteomic screens. We investigated (i) the impact of BPL treatment on the analysis of protein levels in plasma samples using the aptamer-based affinity proteomic platform SomaScan and (ii) effects on protein detection in conditioned medium samples using the proximity extension assay-based Olink Target platform. In the former setup, BPL-treated and native plasma samples from patients with ovarian cancer ( n = 12) and benign diseases ( n = 12) were analyzed using the SomaScan platform. In the latter, conditioned media samples collected from cultured T cells with ( n = 3) or without ( n = 3) anti-CD3 antibody stimulation were analyzed using the Olink Target platform. BPL-related changes in protein detection were evaluated comparing native and BPL-treated states, simulating virus inactivation, and impact on measurable group differences was assessed. While approximately one-third of SomaScan measurements were significantly changed by the BPL treatment, a majority of antigen/aptamer interactions remained unaffected. Interaction effects of BPL treatment and disease state, potentially altering detectability of group differences, were observable for less than one percent of targets (0.6%). BPL effects on protein detection with Olink Target were also limited, affecting 3.6% of detected proteins with no observable interaction effects. Thus, effects of BPL treatment only moderately interfere with affinity proteomic detectability of differential protein expression between different experimental groups. Overall, the results prove high-throughput affinity proteomics well suited for the analysis of high-risk samples inactivated using BPL.

Members of the alphaproteobacterial order Rhodobacterales are metabolically diverse and highly abundant in the ocean. They are becoming increasingly interesting for marine biotechnology, due to their ecological adaptability, wealth of versatile low-copy-number plasmids, and their ability to produce secondary metabolites. However, molecular tools for engineering strains of this bacterial lineage are limited. Here, we expand the genetic toolbox by establishing standardized, modular repABC -based plasmid vectors of four well-characterized compatibility groups from the Roseobacter group applicable in the Rhodobacterales, and likely in further alphaproteobacterial orders (Hyphomicrobiales, Rhodospirillales, Caulobacterales). We confirmed replication of these newly constructed pABC vectors in two members of Rhodobacterales, namely, Dinoroseobacter shibae DFL 12 and Rhodobacter capsulatus B10S, as well as in two members of the alphaproteobacterial order Hyphomicrobiales (synonym: Rhizobiales; Ensifer meliloti 2011 and " Agrobacterium fabrum " C58). Maintenance of the pABC vectors in the biotechnologically valuable orders Rhodobacterales and Hyphomicrobiales facilitates the shuttling of genetic constructs between alphaproteobacterial genera and orders. Additionally, plasmid replication was verified in one member of Rhodospirillales ( Rhodospirillum rubrum S1) as well as in one member of Caulobacterales ( Caulobacter vibrioides CB15N). The modular construction of pABC vectors and the usage of four compatible replication systems, which allows their coexistence in a host cell, are advantageous features for future implementations of newly designed synthetic pathways. The vector applicability was demonstrated by functional complementation of a nitrogenase mutant phenotype by two complementary pABC-based plasmids in R. capsulatus .

It is well established that solid K 2 MnF 6 reacts with excess SbF 5 forming elemental F 2 . However, if the reaction is carried out in anhydrous HF (aHF) as a solvent, this is surprisingly not the case. Instead, the green Mn(IV) compound K 3 [(Mn IV F)(SbF 6 ) 5 ]F is obtained. The reductive elimination of F 2 was not observed under the applied conditions. The compound was characterized by its crystal structure, by Raman spectroscopy, and by quantum-chemical solid-state calculations. It crystallizes in the monoclinic space group P 2 1 / c , mP 164, with the lattice parameters a = 12.2393(13), b = 12.167(2), c = 20.115(5) Å, β = 110.805(8)°, V = 2800.1(9) Å 3 , Z = 4 at T = 200 K. As the use of strictly anhydrous HF is crucial in this and other similar reactions, methods for drying moist HF are discussed.

Phloretin is widely found in fruit and shows various biological activities. Here, we demonstrate the dimethylallylation, geranylation, and farnesylation, particularly the first dimethylallylation at the nonaromatic carbon of phloretin ( 1 ) by the fungal prenyltransferase AnaPT and its mutants. F265 was identified as a key amino acid residue related to dimethylallylation at the nonaromatic carbon of phloretin. Mutants AnaPT_F265D, AnaPT_F265G, AnaPT_F265P, AnaPT_F265C, and AnaPT_F265Y were discovered to generally increase prenylation activity toward 1 . AnaPT_F265G catalyzes the O -geranylation selectively at the C-2' hydroxyl group, which involves an intramolecular hydrogen bond with the carbonyl group of 1 . Seven products, 1D5 , 1D7-1D9 , 1G2 , 1G4 , and 1F2 , have not been reported prior to this study. Twelve compounds, 1D3-1D9 , 1G1-1G3 , and 1F1-1F2 , exhibited potential inhibitory effects on α-glucosidase with IC 50 values ranging from 11.45 ± 0.87 to 193.80 ± 6.52 μg/mL. Among them, 1G1 with an IC 50 value of 11.45 ± 0.87 μg/mL was the most potential α-glucosidase inhibitor, which is about 30 times stronger than the positive control acarbose with an IC 50 value of 346.63 ± 15.65 μg/mL.

Various pathways for the synthesis of beryllium triflate were investigated. The reaction of triflic acid or trimethylsilyl triflate with beryllium metal in liquid ammonia led to the formation of mono-, di-, and tetra-nuclear beryllium ammine complexes. Utilization of SMe 2 as a solvent gave homoleptic Be(OTf) 2 . Various beryllium triflate complexes with N- and O-donor ligands as well as the complex anions [Be(OTf) 4 ] 2- and [Be 2 (OTf) 6 ] 2- were synthesized to evaluate the reactivity and solution properties of beryllium triflate. This showed that OTf - is not a weakly coordinating anion for Be 2+ cations and that it exhibits good bridging properties.

The formation of isolable monatomic Bi I complexes and Bi II radical species is challenging due to the pronounced reducing nature of metallic bismuth. Here, we report a convenient strategy to tame Bi I and Bi II atoms by taking advantage of the redox noninnocent character of a new chelating bis(germylene) ligand. The remarkably stable novel Bi I cation complex 4 , supported by the new bis(iminophosphonamido-germylene)xanthene ligand [(P)Ge II (Xant)Ge II (P)] 1 , [(P)Ge II (Xant)Ge II (P) = Ph 2 P(N t Bu) 2 Ge II (Xant)Ge II (N t Bu) 2 PPh 2 , Xant = 9,9-dimethyl-xanthene-4,5-diyl], was synthesized by a two-electron reduction of the cationic Bi III I 2 precursor complex 3 with cobaltocene (Cp 2 Co) in a molar ratio of 1:2. Notably, owing to the redox noninnocent character of the germylene moieties, the positive charge of Bi I cation 4 migrates to one of the Ge atoms in the bis(germylene) ligand, giving rise to a germylium(germylene) Bi I complex as suggested by DFT calculations and X-ray photoelectron spectroscopy (XPS). Likewise, migration of the positive charge of the Bi III I 2 cation of 3 results in a bis(germylium)Bi III I 2 complex. The delocalization of the positive charge in the ligand engenders a much higher stability of the Bi I cation 4 in comparison to an isoelectronic two-coordinate Pb 0 analogue (plumbylone; decomposition below -30 °C). Interestingly, 4 [BAr F ] undergoes a reversible single-electron transfer (SET) reaction (oxidation) to afford the isolable Bi II radical complex 5 in 5 [BAr F ] 2 . According to electron paramagnetic resonance (EPR) spectroscopy, the unpaired electron predominantly resides at the Bi II atom. Extending the redox reactivity of 4 [OTf] employing AgOTf and MeOTf affords Bi III (OTf) 2 complex 7 and Bi III Me complex 8 , respectively, demonstrating the high nucleophilic character of Bi I cation 4 .

Epipyrone A is a unique C -galactosylated 4-hydroxy-2-pyrone derivative with an antifungal potential from the fungus Epicoccum nigrum . We elucidated its biosynthesis via heterologous expression and characterized an unprecedented membrane-bound pyrone C -glycosyltransferase biochemically. Molecular docking and mutagenesis experiments suggested a possible mechanism for the heterocyclic C -glycosylation and the importance of a transmembrane helix for its catalysis. These results expand the repertoire of C -glycosyltransferases and provide new insights into the formation of C -glycosides in fungi.

Acenes represent a unique class of polycyclic aromatic hydrocarbons that have fascinated chemists and physicists due to their exceptional potential for use in organic electronics. While recent advances in on-surface synthesis have resulted in higher acenes up to dodecacene, a comprehensive understanding of their fundamental properties necessitates their expansion toward even longer homologues. Here, we demonstrate the on-surface synthesis of tridecacene via atom-manipulation-induced conformational preparation and dissociation of a trietheno-bridged precursor on a Au(111) surface. The generated tridecacene has been investigated by scanning tunneling microscopy and spectroscopy (STM/STS), combined with first-principles calculations. We observe that the STS transport gap (1.09 eV) shrinks again following the gap reopening of dodecacene (1.4 eV). Spin-polarized density functional theory calculations confirm an antiferromagnetic open-shell ground-state electronic configuration for tridecacene in the gas phase. Interestingly, tridecacene's open-shell character is significantly reduced upon interaction with the Au(111) surface despite being only physisorbed. The interaction with the surface leads to a lowering of the magnetization of tridecacene, a reduced gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), compared to the gas phase, and a reduced relative energy to the nonmagnetic state, making it nearly isoenergetic. These observations show qualitatively that the influence of the Au(111) substrate on the properties of long acenes is significant, which is important for interpreting the measured STS transport gaps. Our work contributes to a fundamental understanding of the electronic properties of long acenes, confirming a nonmonotonous length-dependent HOMO-LUMO gap, and to the development of multistep tip-assisted synthesis of elusive compounds.

An efficient framework for the calculation of paramagnetic NMR (pNMR) shifts within exact two-component (X2C) theory and (current-dependent) density functional theory (DFT) up to the class of local hybrid functionals (LHFs) is presented. Generally, pNMR shifts for systems with more than one unpaired electron depend on the orbital shielding contribution and a temperature-dependent term. The latter includes zero-field splitting (ZFS), hyperfine coupling (HFC), and the g -tensor. For consistency, we calculate these three tensors at the same level of theory, i.e., using scalar-relativistic X2C augmented with spin-orbit perturbation theory. Results for pNMR chemical shifts of transition-metal complexes reveal that this X2C-DFT framework can yield good results for both the shifts and the individual tensor contributions of metallocenes and related systems, especially if the HFC constant is large. For small HFC constants, the relative error is often large, and sometimes the sign may be off. 4d and 5d complexes with more complicated structures demonstrate the limitations of a fully DFT-based approach. Additionally, a Co-based complex with a very large ZFS and pronounced multireference character is not well described. Here, a hybrid DFT-multireference framework is necessary for accurate results. Our results show that X2C is sufficient to describe relativistic effects and computationally cheaper than a fully relativistic approach. Thus, it allows use of large basis sets for converged HFCs. Overall, current-dependent meta-generalized gradient approximations and LHFs show some potential; however, the currently available functionals leave a lot to be desired, and the predictive power is limited.

Progress in the synthetic biology field is driven by the development of new tools for synthetic circuit engineering. Traditionally, the focus has relied on protein-based designs. In recent years, the use of RNA-based tools has tremendously increased, due to their versatile functionality and applicability. A promising class of molecules is RNA aptamers, small, single-stranded RNA molecules that bind to a target molecule with high affinity and specificity. When targeting bacterial repressors, RNA aptamers allow one to add a new layer to an established protein-based regulation. In the present study, we selected an RNA aptamer binding the bacterial repressor DasR, preventing its binding to its operator sequence and activating DasR-controlled transcription in vivo . This was made possible only by the combination of an in vitro selection and subsequent in vivo screening. Next-generation sequencing of the selection process proved the importance of the in vivo screening for the discovery of aptamers functioning in the cell. Mutational and biochemical studies led to the identification of the minimal necessary binding motif. Taken together, the resulting combination of bacterial repressor and RNA aptamer enlarges the synthetic biology toolbox by adding a new level of regulation.

The intriguing photophysical properties of monolayer stacks of different transition-metal dichalcogenides (TMDs), revealing rich exciton physics including interfacial and moiré excitons, have recently prompted an extension of similar investigations to hybrid systems of TMDs and organic films, as the latter combine large photoabsorption cross sections with the ability to tailor energy levels by targeted synthesis. To go beyond single-molecule photoexcitations and exploit the excitonic signatures of organic solids, crystalline molecular films are required. Moreover, a defined registry on the substrate, ideally an epitaxy, is desirable to also achieve an excitonic coupling in momentum space. This poses a certain challenge as excitonic dipole moments of organic films are closely related to the molecular orientation and film structure, which critically depend on the support roughness. Using X-ray diffraction, optical polarization, and atomic force microscopy, we analyzed the structure of pentacene (PEN) multilayer films grown on WSe 2 (001) and WS 2 (001) and identified an epitaxial alignment. While (022)-oriented PEN films are formed on both substrates, their azimuthal orientations are quite different, showing an alignment of the molecular L -axis along the ⟨ 110 ⟩ WSe 2 and ⟨ 100 ⟩ WS 2 directions. This intrinsic epitaxial PEN growth depends, however, sensitively on the substrates surface quality. While it occurs on exfoliated TMD single crystals and multilayer flakes, it is hardly found on exfoliated monolayers, which often exhibit bubbles and wrinkles. This enhances the surface roughness and results in (001)-oriented PEN films with upright molecular orientation but without any azimuthal alignment. However, monolayer flakes can be smoothed by AFM operated in contact mode or by transferring to ultrasmooth substrates such as h BN, which again yields epitaxial PEN films. As different PEN orientations result in different characteristic film morphologies (elongated mesa islands vs pyramidal dendrites), which can be easily distinguished by AFM or optical microscopy, this provides a simple means to judge the roughness of the used TMD surface.

The photophysics of organic semiconductor (OSC) thin films or crystals has garnered significant attention in recent years since a comprehensive theoretical understanding of the various processes occurring upon photoexcitation is crucial for assessing the efficiency of OSC materials. To date, research in this area has relied on methods using Frenkel-Holstein Hamiltonians, calculations of the GW-Bethe-Salpeter equation with periodic boundaries, or cluster-based approaches using quantum chemical methods, with each of the three approaches having distinct advantages and disadvantages. In this work, we introduce an optimally tuned, range-separated time-dependent density functional theory approach to accurately reproduce the total and polarization-resolved absorption spectra of pentacene, tetracene, and perylene thin films, all representative OSC materials. Our approach achieves excellent agreement with experimental data (mostly ≤0.1 eV) when combined with the utilization of clusters comprising multiple monomers and a standard polarizable continuum model to simulate the thin-film environment. Our protocol therefore addresses a major drawback of cluster-based approaches and makes them attractive tools for OSC investigations. Its key advantages include its independence from external, system-specific fitting parameters and its straightforward application with well-known quantum chemical program codes. It demonstrates how chemical intuition can help to reduce computational cost and still arrive at chemically meaningful and almost quantitative results.

Reversed-phase liquid chromatography (RPLC) operates with water-organic solvent (W-OS) mobile phases where preferential solvation (PS) of solutes is likely. To investigate the relevance of the solute solvation shell in the mobile phase for RPLC retention, we combine data from molecular dynamics simulations of small, neutral solutes (six analytes and two dead time markers) in W-methanol (MeOH) and W-acetonitrile (ACN) mixtures with corresponding retention data obtained on an RPLC column over a wide range of W/OS ratios. Data derived from Kirkwood-Buff integrals show PS by the OS for analytes vs low or negative PS for dead time markers. W-ACN mixtures generate a higher amount of PS than W-MeOH mixtures, which contributes to the higher eluent strength of ACN in RPLC. Difference spatial distribution functions reveal anisotropic solvation shells with OS excess at hydrocarbon elements and W excess at functional groups, predicting that retention by the hydrophobic stationary phase is favored by hydrocarbon elements and limited by functional groups. Analysis of solute-solvent hydrogen bonds pinpoints the hydrogen-bond requirements toward W as the retention-limiting factor. The relation between the solute solvation shell and retention confirms the importance of W-OS and solute-W hydrogen bonding for RPLC retention.

The Shigella pathogenicity factor IpgC belongs to the class II of type III secretion system chaperones, whose members are characterized by a tetratricopeptide repeat (TPR) domain consisting of three and a half TPR motifs. Since IpgC is essential for Shigella virulence, we determined a high-resolution crystal structure of this chaperone to facilitate its use as a target for the structure-based design of anti-shigellosis compounds. The crystal structure revealed two possible homodimer assemblies, which strongly differ from the homodimer architectures so far known for IpgC and orthologues thereof. Through crystallographic fragment screening, we identified 10 small molecules that bind to IpgC and, therefore, are available for expansion to generate larger, more potent binders. A follow-up compound, based on one of our fragment hits, binds to a strictly conserved site, which overlaps with the binding site of the chaperone's substrates, IpaB and IpaC. Therefore, it constitutes a promising starting point for the design of functional IpgC inhibitors., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Lithium-ion batteries (LIBs) are the dominating energy storage technology for electric vehicles and portable electronic devices. Since the resources of raw materials for LIBs are limited and recycling technologies for LIBs are still under development, improvements in the long-term stability of LIBs are of paramount importance and, in addition, would lead to a reduction in the levelized cost of storage (LCOS). A crucial limiting factor is the aging of the solid electrolyte interphase (SEI) on the active material particles in the anode. Here, we demonstrate the potential of atom probe tomography for elucidating the complex mosaic-type structure of the SEI in a graphite composite anode. Our 3D reconstruction shows unseen details and reveals the existence of an apolar organic microphase pervading the SEI over its entire thickness. This finding is in stark contrast to the prevalent two-layer SEI model, in which organic compounds are the dominating species only in the outer SEI layer being in contact with the liquid electrolyte. The observed spatial arrangement of the apolar organic microphase promises a better understanding of the passivation capability of the SEI, which is necessary to expand the battery lifetime.

Quantum chemical studies using density functional theory were carried out for the (L) 4 C 4 complexes with L = cAAC, DAC, NHC, SNHC, MIC1, and MIC2. The results show that the title complexes are highly stable with respect to dissociation, (L) 4 C 4 → C 4 + 4L. However, their stability with respect to (L) 4 C 4 → 2(L) 2 C 2 is crucial for the assessment of their experimental viability. The (L) 4 C 4 complexes with L = cAAC and DAC dissociate exergonically at room temperature into two (L) 2 C 2 units. In contrast, the other (L) 4 C 4 complexes with L = NHC, SNHC, MIC1, and MIC2 are thermochemically stable with respect to dissociation, (L) 4 C 4 → 2(L) 2 C 2 . The computed adiabatic ionization potentials of (L) 4 C 4 complexes with L = NHC, MIC1, and MIC2 are lower than those for the cesium atom. Particularly, (MIC1) 4 C 4 and (MIC2) 4 C 4 will very easily lose electrons to form cationic complexes. The SNHC ligand is the best for the experimental realization of (L) 4 C 4 complexes, followed by NHC. The bonding analysis using charge and energy decomposition methods suggests that the (L) 3 C 4 -C L bond can be best described as a typical electron-sharing double bond with a strong σ-bond and a weaker π-bond. Therefore, the core bonding pictures in the title complexes resemble a [4]radialene. Larger substituents at the carbene ligands enhance the stability of the complexes (L) 4 C 4 against dissociation.

The first series of 9-bisma-10-pnictatriptycenes Bi(C 6 H 4 ) 3 Pn ( 2-Pn , Pn = P-Bi; see graphic) has been synthesized in a two-step procedure via suitable tris(2-bromophenyl)pnictanes 1-Pn and characterized in solution as well as in the solid state. DFT calculations suggest preferential interactions between 2-Pn and soft Lewis acids via the lighter pnictogen donor atom. Experimental studies demonstrate that even the weakest Lewis base in the series of 2-Pn , namely the dibismatriptycene 2-Bi , interacts with Lewis acidic [BiMe 2 (SbF 6 )] in solution. Analytical techniques include (VT-)NMR spectroscopy, DOSY NMR spectroscopy, high-resolution mass spectrometry, single-crystal X-ray diffraction analyses, and DFT calculations.

Lead halide perovskites and related main-group halogenido metalates offer unique semiconductor properties and diverse applications in photovoltaics, solid-state lighting, and photocatalysis. Recent advances in incorporating chiral organic cations have led to the emergence of chiral metal-halide semiconductors with intriguing properties, such as chiroptical activity and chirality-induced spin selectivity, enabling the generation and detection of circularly polarized light and spin-polarized electrons for applications in spintronics and quantum information. However, understanding the structural origin of chiroptical activity remains challenging due to macroscopic factors and experimental limitations. In this work, we present an achiral perovskite derivative [Cu 2 (pyz) 3 (MeCN) 2 ][Bi 3 I 11 ] ( CuBiI ; pyz = pyrazine; MeCN = acetonitrile), which exhibits remarkable circular dichroism (CD) attributed to the material's noncentrosymmetric nature. CuBiI features a unique structure as a poly-threaded iodido bismuthate, with [Bi 3 I 11 ] 2- chains threaded through a cationic two-dimensional coordination polymer. The material possesses a low, direct optical band gap of 1.70 eV. Notably, single crystals display both linear and circular optical activity with a large anisotropy factor of up to 0.16. Surprisingly, despite the absence of chiral building blocks, CuBiI exhibits a significant degree of circularly polarized photoluminescence, reaching 4.9%. This value is comparable to the results achieved by incorporating chiral organic molecules into perovskites, typically ranging from 3-10% at zero magnetic field. Our findings provide insights into the macroscopic origin of CD and offer design guidelines for the development of materials with high chiroptical activity.

TURBOMOLE is a highly optimized software suite for large-scale quantum-chemical and materials science simulations of molecules, clusters, extended systems, and periodic solids. TURBOMOLE uses Gaussian basis sets and has been designed with robust and fast quantum-chemical applications in mind, ranging from homogeneous and heterogeneous catalysis to inorganic and organic chemistry and various types of spectroscopy, light-matter interactions, and biochemistry. This Perspective briefly surveys TURBOMOLE's functionality and highlights recent developments that have taken place between 2020 and 2023, comprising new electronic structure methods for molecules and solids, previously unavailable molecular properties, embedding, and molecular dynamics approaches. Select features under development are reviewed to illustrate the continuous growth of the program suite, including nuclear electronic orbital methods, Hartree-Fock-based adiabatic connection models, simplified time-dependent density functional theory, relativistic effects and magnetic properties, and multiscale modeling of optical properties.

Starting from the respective metal M , we have synthesized the hexafluorides M F 6 of M = Ru, Rh, and Pt by the use of a laser-based heating system and a remote fluorine plasma source using a mixture of Ar and NF 3 as the feed gas. The formation of the hexafluorides was confirmed by several different spectroscopic methods, including IR, Raman, UV/vis, and NMR spectroscopy. In addition, we present first experimental hints that RuF 6 is more reactive than PtF 6 , because RuF 6 is able to oxidize lower fluorides of platinum to PtF 6 .

ConspectusThe ligand shells of colloidal nanoparticles (NPs) can serve different purposes. In general, they provide colloidal stability by introducing steric repulsion between NPs. In the context of biological applications, the ligand shell plays a critical role in targeting, enabling NPs to achieve specific biodistributions. However, there is also another important feature of the ligand shell of NPs, namely, the creation of a local environment differing from the bulk of the solvent in which the NPs are dispersed. It is known that charged ligand shells can attract or repel ions and change the effective charge of a NP through Debye-Hückel screening. Positively charged ions, such as H + (or H 3 O + ) are attracted to negatively charged surfaces, whereas negatively charged ions, such as Cl - are repelled. The distribution of the ions around charged NP surfaces is a radial function of distance from the center of the NP, which is governed by a balance of electrostatic forces and entropy of ions and ligands. As a result, the ion concentration at the NP surface is different from its bulk equilibrium concentration, i.e., the charged ligand shell around the NPs has formed a distinct local environment. This not only applies to charged ligand shells but also follows a more general principle of induced condensation and depletion. Polar/apolar ligand shells, for example, result in a locally increased concentration of polar/apolar molecules. Similar effects can be seen for biocatalysts like enzymes immobilized in nanoporous host structures, which provide a special environment due to their surface chemistry and geometrical nanoconfinement. The formation of a local environment close to the ligand shell of NPs has profound implications for NP sensing applications. As a result, analyte concentrations close to the ligand shell, which are the ones that are measured, may be very different from the analyte concentrations in bulk. Based on previous work describing this effect, it will be discussed herein how such local environments, created by the choice of used ligands, may allow for tailoring the NPs' sensing properties. In general, the ligand shell around NPs can be attractive/repulsive for molecules with distinct properties and thus forms an environment that can modulate the specific response. Such local environments can also be optimized to modulate chemical reactions close to the NP surface (for example, by size filtering within pores) or to attract specific low abundance proteins. The importance hereby is that this is based on interaction with low selectivity between the ligands and the target molecules.

p -Terphenyls contain a central benzene ring substituted with two phenyl residues at its para positions. Heterologous expression of a biosynthetic gene cluster from Aspergillus ustus led to the formation of four new p -terphenyl derivatives. Gene deletion experiments proved the formation and reductive dehydration of the terphenylquinone atromentin, followed by O-methylation and prenylation. Spontaneous dibenzofuran formation led to the final products. These results provide new insights into the biosynthesis of p -terphenyls in fungi and dibenzofuran formation in the biosynthesis of numerous natural products.

The selective methylation and butylation of chalcogenido metalate clusters by utilizing imidazolium-based ionic liquids turned out to be not only a comparably mild but at the same time also the only known method for postsynthetic alkylation of such species in order to increase their solubility. For additional impact on the crystal structures, selective alkylation with longer alkyl chains was addressed by utilizing the ionic liquid (C 10 C 1 Im)[BF 4 ] (C 10 = decyl group at position 1 and C 1 = methyl group at position 3 of the cation's Im = imidazolium ring) for ionothermal syntheses of functionalized tellurido mercurate clusters. Herein, we report three novel compounds, two of which comprise cluster anions that exhibit a selective organic functionalization of their terminal telluride ligands upon in situ alkylation with the ionic liquid: [Hg 6 Te 6 (Te 2 ) 2 (TeDec) 2 ] 6- (in 1 ; Dec = decyl) represents the first decylated chalcogenido metalate cluster. A unique heteroleptic functionalization, combining methylation and decylation, was achieved for the second cluster, [Hg 6 Te 6 (Te 2 ) 2 (TeDec)(TeMe)] 6- (in 2 ; Me = methyl). The third cluster is purely inorganic, but based on the same cluster core architecture: [Hg 4 Te 2 (Te 2 ) 2 (Te 3 ) 2 ] 4- (in 3 ) comprises a tritelluride unit instead of two HgTeR groups (R = Me, Dec). As a consequence of the long alkyl chains, both at the cluster and at the charge-compensating cations, all three crystal structures are characterized by lamellar assemblies of cations and anions. For further comparison of the properties of the organometallic versus purely inorganic compounds, vibrational and optical properties of crystalline samples of the compounds comprising clusters 1 and 3 were studied by means of infrared, Raman, and UV-visible spectroscopy. The results clearly show the effect of the presence of an organic decoration (in 1 ) relative to its absence (in 3 ), reflected by a red shift of the band gap energy ( 1 → 3 ) and a replacement of the Te-C bands (in 1 ) with bands for tritelluride units (in 3 ).

The herein-reported oxyfluoridometallate salts were synthesized and structurally characterized during the studies of the Lewis acidity of M OF 4 ( M = Mo, W) with various fluoride ion donors (RbF, CsF, TlF, AgF, SrF 2 , BaF 2 , PbF 2 ) in different solvents (aqHF 48%, aHF, BrF 3 , ClF 3 ). Phase-pure MoOF 4 was either synthesized by hydrolysis of MoF 6 with SiO 2 in anhydrous HF (aHF) or by reactions of BrF 3 with MoO 2 or MoO 3 , respectively. The compound was characterized by infrared and Raman spectroscopy, solid-state quantum-chemical calculations, as well as powder and single-crystal X-ray diffraction. MoOF 4 reacted with PbF 2 in aHF forming Pb[MoOF 5 ] 2 , while under comparable conditions, WOF 4 formed Pb 3 [WOF 5 ] 4 F 2 , containing the [WOF 5 ] - anion. Salts containing such [MoOF 5 ] - anions were also directly obtained from reactions of BrF 3 , MoO 3 , and A F 2 ( A = Sr, Ba), while with AgF, the compound Ag[Mo 2 O 2 F 9 ] was observed. ClF 3 reacted with MoO 3 to form [ClOF 2 ][Mo 3 O 3 F 13 ]. Carrying out similar reactions in aqueous HF (aqHF) in autoclaves under hydrofluorothermal conditions leads to O-richer compounds with the composition A [MoO 2 F 4 ] ( A = Sr, Ba). With RbF or Tl 2 (CO 3 ), the compounds A [MoO 2 F 3 ] ( A = Rb, Tl) were obtained. With CsF reduction to Mo(V) occurred as Cs 2 [Mo V OF 5 ] was formed. We report on similarities and differences within the respective anions and within the crystal structures of these compounds.

[NH 4 ][SeCN] and Ag[SeCN] were synthesized by salt metathesis starting from the respective chlorides and K[SeCN]. Both products were fully characterized by single-crystal and powder X-ray diffraction, differential scanning calorimetry-thermogravimetric analysis (DSC-TGA), and solid-state IR and Raman spectroscopy. Quantum-mechanical calculations allowed for detailed assignment and interpretation of vibrational spectra. For dissolved [NH 4 ][SeCN], nuclear magnetic resonance spectra were collected. High-temperature powder X-ray diffraction (HT-PXRD) allowed for the analysis of the thermal behavior of solid [NH 4 ][SeCN]. Furthermore, the reaction of [NH 4 ][SeCN] with Ag[SeCN] leads to the formation of the ternary salts [NH 4 ][Ag(SeCN) 2 ] and [NH 4 ] 3 [Ag(SeCN) 4 ]. The structures of the latter were determined from single-crystal X-ray diffraction (SC-XRD) data, and bulk analysis was performed by Rietveld refinement, Raman spectroscopy, and elemental analysis.

Four undescribed plant growth inhibitory indole derivatives, colletotriauxins A-D ( 1-4 ), along with two known analogues indole-3-acetic acid (IAA) ( 5 ) and its amide indole-3-acetamide ( 6 ), were isolated from the phytopathogenic fungus Colletotrichum gloeosporioides NRRL 45420. Their structures were elucidated by NMR and MS analyses. 1 and 2 are rhamnosides of indole-3-ethanol (tryptophol) and its methylated derivative, respectively. In the structures of 3 and 4 , the two terminal hydroxyl groups of hexitol and pentane-1,2,3,4,5-pentol are connected with indole-3-(2-methyl)-acetyl and acetyl moieties. Compounds 1-6 inhibit Lepidium sativum seedling growth. The inhibition activities of colletotriauxins for stem growth were even stronger than IAA, with compounds 3 and 4 as the most active ones. These results suggested that colletotriauxins could serve as potential candidates as herbicides.

The non-classical carbonyl complex [Hg{Fe(CO) 5 } 2 ] 2+ [SbF 6 ] - 2 is prepared by reaction of Hg(SbF 6 ) 2 and excess Fe(CO) 5 in anhydrous HF. The single-crystal X-ray structure reveals a linear Fe-Hg-Fe moiety as well as an eclipsed conformation of the eight basal CO ligands. Interestingly, the Hg-Fe bond length of 2.5745(7) Å is relatively similar to the corresponding Hg-Fe bonds in literature-known [Hg{Fe(CO) 4 } 2 ] 2- dianions (2.52-2.55 Å), which intrigued us to analyze the bonding situation in both the dications and dianions with the energy decomposition analysis with natural orbitals for chemical valence (EDA-NOCV) method. Both species are best described as Hg(0) compounds, which are also confirmed by the shape of the HOMO-4 and HOMO-5 of the dication and dianion, respectively, in which the electron pair is located mainly at the Hg. Furthermore, for the dication and the dianion, the σ back-donation from Hg into the [Fe(CO) 5 ] 2 2+ or the [Fe(CO) 4 ] 2 2- fragment is the most dominant orbital interaction and surprisingly these interaction energies are also very similar even in absolute values. The fact that both iron-based fragments are missing two electrons explains their prominent σ-acceptor properties.

Cyclodipeptides from fungi and bacteria are often modified by different tailoring enzymes. They display various biological and pharmacological activities, and some derivatives are used as drugs. In a previous study, we elucidated the function of the silent guatrypmethine gene cluster from Streptomyces cinnamoneus containing a cyclodipeptide synthase (CDPS) core gene gtmA and four genes gtmB-gtmE for tailoring enzymes. The latter are used in this study for the design of modified cyclodipeptides by genetic engineering. Addition of six different cyclodipeptides to the Streptomyces albus transformant harboring gtmB-gtmE led to the detection of different pathway products. Coexpression of five CDPS genes from four Streptomyces strains with gtmB-gtmE resulted in the formation of diketopiperazine derivatives, differing in their modification stages. Our results demonstrate the potential of rational gene combination to increase structural diversity.

Most naturally occurring indole diterpenes share a 6/5/5/6/6/6 hexacyclic ring system, while a 6/8/6/6/6 pentacyclic skeleton is occasionally observed. In this study, we demonstrate the formation of an eight-membered C-N heteroring via nonenzymatic flavin-catalyzed oxidative indole ring opening. More interestingly, 18 O-labeled experiments proved that the two incorporated oxygen atoms are predominantly originated from water instead of molecular oxygen. In this process, the oxidized form of flavin catalyzes two successive oxidations of amines to imines with involvement of hydrolysis for the ring expansion. The reduced flavin is then regenerated by oxidation with molecular oxygen to form H 2 O 2 .

We present a new approach combining diffusive equilibrium in thin-film gels and spectrophotometric methods to determine the spatial distribution of arsenite, arsenate, and phosphate at submillimeter resolution. The method relies on the simultaneous deployment of three gel probes. Each retrieved gel is exposed to malachite green reagent gels differing in acidity and oxidant addition, leading to green coloration dependent on analyte speciation and concentration. Hyperspectral images of the gels enable mapping the three analytes in the 2.5-20 μM range. This method was applied in a contaminated brook in the Harz mountains, Germany, together with established mapping of dissolved iron. The use of two-dimensional (2D) gel probes was compared to traditional porewater extraction. The gels revealed banded porewater patterns on a mm-scale, which were undetectable using traditional methods. Small-scale correlation analyses of arsenic and iron microstructures in the gels suggested active iron-driven local redox cycling of arsenic. Overall, the results indicate continuous net release of arsenic from contaminant particles and deepen our understanding of arsenate transformation under anaerobic conditions. This study is the first fine-scale 2D characterization of arsenic speciation in porewater and represents a crucial step toward understanding the transfer and redox cycling of arsenic in contaminated sediment/soil ecosystems.