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Building on the MOF approach to prepare porous materials, herein we report the engineering of porous BN‐doped materials using tricarboxylic hexaarylborazine ligands, which are laterally decorated with functional groups at the full‐carbon ‘inner shell’. Whilst an open porous 3D entangled structure could be obtained from the double interpenetration of two identical metal frameworks derived from the methyl substituted borazine, the chlorine‐functionalised linker undergoes formation of a porous layered 2D honeycomb structure, as shown by single‐crystal X‐ray diffraction analysis. In this architecture, the borazine cores are rotated by 60° in alternating layers, thus generating large rhombohedral channels running perpendicular to the planes of the networks. An analogous unsubstituted full‐carbon metal framework was synthesised for comparison. The resulting MOF revealed a crystalline 3D entangled porous structure, composed by three mutually interpenetrating networks, hence denser than those obtained from the borazine linkers. Their microporosity and CO2 uptake were investigated, with the porous 3D BN‐MOF entangled structure exhibiting a large apparent BET specific surface area (1091 m2 g−1) and significant CO2 reversible adsorption (3.31 mmol g−1) at 1 bar and 273 K., The borazine unit was used to prepare crystalline porous MOFs from specifically designed borazine carboxylate linkers. To evaluate the influence of the borazine rings on the gas adsorption properties, the analogous full‐carbon carboxylate linker and the corresponding MOF were also prepared. The structure of the three MOFs was unambiguously determined by single crystal X‐ray analysis.

In this work, we present a new synthetic strategy for fourfold‐substituted perylene monoimides via tetrabrominated perylene monoanhydrides. X‐ray diffraction analysis unveiled the intramolecular stacking orientation between the substituents and semicircular packing behavior. We observed the remarkable influence of the substituent on the longevity and nature of the excited state upon visible light excitation. In the presence of poly(dehydroalanine)‐graft‐poly(ethylene glycol) graft copolymers as solubilizing template, the chromophores are capable of sensitizing [Mo3S13]2− clusters in aqueous solution for stable visible light driven hydrogen evolution over three days., Design and use of perylene monoimide dyes: Novel perylene monoimide dyes have been synthesized, and their properties characterized by XRD, spectroscopic and electrochemical methods. A custom‐made photoreactor was used to exhibit light‐driven hydrogen‐evolution catalysis in the presence of (NH4)2[Mo3S13] catalyst and poly(dehydroalanine)‐graft‐poly(ethylene glycol) solubilizing template for the organic photosensitizers.

Zinc oxide thin films are fabricated by controlled oxidation of sputtered zinc metal films on a hotplate in air at temperatures between 250 and 450 °C. The nanocrystalline films possess high relative densities and show preferential growth in (100) orientation. Integration in thin‐film transistors reveals moderate charge carrier mobilities as high as 0.2 cm2 V−1s−1. The semiconducting properties depend on the calcination temperature, whereby the best performance is achieved at 450 °C. The defect structure of the thin ZnO film can be tracked by Doppler‐broadening positron annihilation spectroscopy as well as positron lifetime studies. Comparably long positron lifetimes suggest interaction of zinc vacancies (VZn) with one or more oxygen vacancies (VO) in larger structural entities. Such VO‐VZn defect clusters act as shallow acceptors, and thus, reduce the overall electron conductivity of the film. The concentration of these defect clusters decreases at higher calcination temperatures as indicated by changes in the S and W parameters. Such zinc oxide films obtained by conversion of metallic zinc can also be used as seed layers for solution deposition of zinc oxide nanowires employing a mild microwave‐assisted process. The functionality of the obtained nanowire arrays is tested in a UV sensor device. The best results with respect to sensor sensitivity are achieved with thinner seed layers for device construction., Thin‐film transistors: Zinc oxide layers can be obtained conveniently through the oxidation of sputter‐deposited thin films of zinc metal at temperatures between 250 and 450 °C. Positron annihilation studies hint at vacancy clusters rather than isolated point defects as the dominating feature in the defect chemistry of these films. This allows the description of the influence of annealing temperature on the resulting electronic performance of the semiconducting layers in thin‐film transistors.

The stabilizing neighboring effect of halo substituents on silyl cations was tested for a series of peri‐halo substituted acenaphthyl‐based silyl cations 3. The chloro‐ (3 b), bromo‐ (3 c), and iodo‐ (3 d) stabilized cations were synthesized by the Corey protocol. Structural and NMR spectroscopic investigations for cations 3 b–d supported by the results of density functional calculations, which indicate their halonium ion nature. According to the fluorobenzonitrile (FBN) method, the silyl Lewis acidity decreases along the series of halonium ions 3, the fluoronium ion 3 a being a very strong and the iodonium ion 3 d a moderate Lewis acid. Halonium ions 3 b and 3 c react with starting silanes in a substituent redistribution reaction and form siliconium ions 4 b and 4 c. The structure of siliconium borate 4 c 2[B12Br12] reveals the trigonal bipyramidal coordination environment of the silicon atom with the two bromo substituents in the apical positions., Silyl cation or halonium ion? That′s the question: The Corey reaction of acenaphthyl‐ and naphthyl‐based silanes allows the synthesis of silyl halonium ions, the nature of which was confirmed by NMR spectroscopy, X‐ray diffraction analysis, and DFT calculations. Moreover, the chloro‐ and bromonium ion can react with the starting silane to form penta‐coordinated siliconium ions, which are intramolecularly stabilized by electron donation from both halogen atoms.

Gramibactin (GBT) is an archetype for the new class of diazeniumdiolate siderophores, produced by Paraburkholderia graminis, a cereal‐associated rhizosphere bacterium, for which a detailed solution thermodynamic study exploring the iron coordination properties is reported. The acid‐base behavior of gramibactin as well as its complexing ability toward Fe3+ was studied over a wide range of pH values (2≤pH≤11). For the latter the ligand‐competition method employing EDTA was used. Only two species are formed: [Fe(GBT)]− (pH 2 to 9) and [Fe(GBT)(OH)2]3− (pH≥9). The formation of [Fe(GBT)]− and its occurrence in real systems was confirmed by LC‐HRESIMS analysis of the bacteria culture broth extract. The sequestering ability of gramibactin was also evaluated in terms of the parameters pFe and pL0.5. Gramibactin exhibits a higher sequestering ability toward Fe3+ than EDTA and of the same order of magnitude as hydroxamate‐type microbial siderophores, but smaller than most of the catecholate‐type siderophores and much higher than the most known phytosiderophores., The sequestration properties of gramibactin as a prototype for the new class of diazeniumdiolate siderophores is presented and compared with siderophores derived from catecholates and hydroxamates. According to pFe and pL0.5 values, gramibactin is a considerably more potent sequestering agent than the known class of phytosiderophores and approximately reaches the ability of typical hydroxamates like desferrioxamines.

Reaction of [Pt(DMSO)2Cl2] or [Pd(MeCN)2Cl2] with the electron‐rich LH=N,N’‐bis(4‐dimethylaminophenyl)ethanimidamide yielded mononuclear [PtL2] (1) but dinuclear [Pd2L4] (2), a paddle‐wheel complex. The neutral compounds were characterized through experiments (crystal structures, electrochemistry, UV‐vis‐NIR spectroscopy, magnetic resonance) and TD‐DFT calculations as metal(II) species with noninnocent ligands L−. The reversibly accessible cations [PtL2]+ and [Pd2L4]+ were also studied, the latter as [Pd2L4][B{3,5‐(CF3)2C6H3}4] single crystals. Experimental and computational investigations were directed at the elucidation of the electronic structures, establishing the correct oxidation states within the alternatives [PtII(L−)2] or [Pt.(L )2], [PtII(L0.5−)2]+ or [PtIII(L−)2]+, [(PdII)2(μ‐L−)4] or [(Pd1.5)2(μ‐L0.75−)4], and [(Pd2.5)2(μ‐L−)4]+ or [(PdII)2(μ‐L0.75−)4]+. In each case, the first alternative was shown to be most appropriate. Remarkable results include the preference of platinum for mononuclear planar [PtL2] with an N‐Pt‐N bite angle of 62.8(2)° in contrast to [Pd2L4], and the dimetal (Pd2 4+→Pd2 5+) instead of ligand (L−→L ) oxidation of the dinuclear palladium compound., Qualitatively different structures and electron transfer behavior have been established for platinum and palladium complexes [PtL2]0/+ and [Pd2L4]0/+ with a redox‐active amidinato ligand L− /L..

The dynamic equilibria of organomagnesium reagents are known to be very complex, and the relative reactivity of their components is poorly understood. Herein, a combination of DFT calculations and kinetic experiments is employed to investigate the detailed reaction mechanism of the Pummerer coupling between sulfoxides and turbo‐organomagnesium amides. Among the various aggregates studied, unprecedented heterometallic open cubane structures are demonstrated to yield favorable barriers through a concerted anion‐anion coupling/ S−O cleavage step. Beyond a structural curiosity, these results introduce open cubane organometallics as key reactive intermediates in turbo‐organomagnesium amide mixtures., The dynamic equilibria of organomagnesium reagents are known to be very complex, and the relative reactivity of their components is poorly understood. Herein, a combination of DFT calculations and kinetic experiments is employed to investigate the detailed reaction mechanism of the Pummerer coupling between sulfoxides and turbo‐organomagnesium amides.

The cobalt species PPh4[CoIII(TAMLred)] is a competent and stable catalyst for the sulfimidation of (aryl)(alkyl)‐substituted sulfides with iminoiodinanes, reaching turnover numbers up to 900 and turnover frequencies of 640 min−1 under mild and aerobic conditions. The sulfimidation proceeds in a highly chemoselective manner, even in the presence of alkenes or weak C−H bonds, as supported by inter‐ and intramolecular competition experiments. Functionalization of the sulfide substituent with various electron‐donating and electron‐withdrawing arenes and several alkyl, benzyl and vinyl fragments is tolerated, with up to quantitative product yields. Sulfimidation of phenyl allyl sulfide led to [2,3]‐sigmatropic rearrangement of the initially formed sulfimide species to afford the corresponding N‐allyl‐S‐phenyl‐thiohydroxylamines as attractive products. Mechanistic studies suggest that the actual nitrene transfer to the sulfide proceeds via (previously characterized) electrophilic nitrene radical intermediates that afford the sulfimide products via electronically asynchronous transition states, in which SET from the sulfide to the nitrene radical complex precedes N−S bond formation in a single concerted process., Cobalt‐catalyzed sulfimidation of (aryl)(alkyl)‐substituted sulfides with iminoiodinanes proceeds under mild conditions and with high chemoselectivity in presence of alkenes and weak C−H bonds. PPh4[CoIII(TAMLred)] mediates the nitrene transfer reactions with a high turnover number and frequency, while the electrophilicity of the nitrene radical intermediate determines the chemoselectivity.

The use of photoactivatable dyes in STED microscopy has so far been limited by two‐photon activation through the STED beam and by the fact that photoactivatable dyes are poorly solvable in water. Herein, we report ONB‐2SiR, a fluorophore that can be both photoactivated in the UV and specifically de‐excited by STED at 775 nm. Likewise, we introduce a conjugation and purification protocol to effectively label primary and secondary antibodies with moderately water‐soluble dyes. Greatly reducing dye aggregation, our technique provides a defined and tunable degree of labeling, and improves the imaging performance of dye conjugates in general., ONB‐2SIR, a photoactivatable dye resistant against two‐photon uncaging by 775 nm STED light is synthesized and used to perform STED microscopy before and after photoactivation without undesired activation by the STED light. The effects of the low water‐solubility of ONB‐2SIR on antibody conjugation was overcome by glycan labelling with defined degree of labelling (DOL) and a phase separation purification method.

The carriers of the diffuse interstellar bands (DIBs) are still largely unknown although polycyclic aromatic hydrocarbons, carbon chains, and fullerenes are likely candidates. A recent analysis of the properties of n‐acenes of general formula C4n+2H2n+4 suggested that these could be potential carriers of some DIBs. Dehydrogenation reactions of n‐acenes after absorption of an interstellar UV photon may result in dehydroacenes. Here the reaction energies and barriers for formation of n‐cyclacenes from 2,3‐didehydroacenes (n‐DDA) by intramolecular Diels–Alder reaction to dihydro‐etheno‐cyclacenes (n‐DEC) followed by ejection of ethyne by retro‐Diels–Alder reactions are analyzed using thermally assisted occupation density functional theory (TAO‐DFT) for n=10–20. It is found that the barriers for each of the steps depend on the ring strain of the underlying n‐cyclacene, and that the ring strain of n‐DEC is about 75 % of that of the corresponding n‐cyclacene. In each case, ethyne extrusion is the step with the highest energy barrier, but these barriers are smaller than CH bond dissociation energies, suggesting that formation of cyclacenes is an energetically conceivable fate of n‐acenes after multiple absorption of UV photons., n ‐Acenes (C4n+2H2n+4) are potential carrier candidates for diffuse interstellar bands. Their conversion into n‐cyclacenes (C4nH2n) through UV photon‐initiated dehydrogenation followed by Diels–Alder cycloaddition and acetylene expulsion appears energetically plausible. Analysis of the conversion through TAO‐DFT reveals dependency of the energy barriers on ring strains of the primary n‐cyclacene.

The protein myelin oligodendrocyte glycoprotein (MOG) is a key component of myelin and an autoantigen in the disease multiple sclerosis (MS). Post‐translational N‐glycosylation of Asn31 of MOG seems to play a key role in modulating the immune response towards myelin. This is mediated by the interaction of Lewis‐type glycan structures in the N‐glycan of MOG with the DC‐SIGN receptor on dendritic cells (DCs). Here, we report the synthesis of an unnatural Lewis X (LeX)‐containing Fmoc‐SPPS‐compatible asparagine building block (SPPS=solid‐phase peptide synthesis), as well as asparagine building blocks containing two LeX‐derived oligosaccharides: LacNAc and Fucα1‐3GlcNAc. These building blocks were used for the glycosylation of the immunodominant portion of MOG (MOG31‐55) and analyzed with respect to their ability to bind to DC‐SIGN in different biological setups, as well as their ability to inhibit the citrullination‐induced aggregation of MOG31‐55. Finally, a cytokine secretion assay was carried out on human monocyte‐derived DCs, which showed the ability of the neoglycopeptide decorated with a single LeX to alter the balance of pro‐ and anti‐inflammatory cytokines, inducing a tolerogenic response., Immunomodulation. A novel asparagine solid‐phase peptide synthesis building block harboring a Lewis X type DC‐SIGN ligand has been synthesized (see scheme) and incorporated into the immunodominant portion of myelin oligodendrocyte glycoprotein (MOG31‐55). This glycopeptide was evaluated for its ability to inhibit citrullination‐induced aggregation of MOG35‐55, to bind to DC‐SIGN in vitro and for its immunomodulatory effects on human dendritic cells, with the Lewis X yielding a tolerogenic response.

Tridentate Lewis acids with aligned functions were synthesized based on the rigid framework hexadehydrotribenzo[12]annulene. The backbone and its fluorinated analogue were synthesised in one‐pot syntheses, with alkyne deprotection and Sonogashira cross coupling reaction being carried out in one step. Hydrosilylation of the annulene with chlorohydrosilanes proceeded highly selectively and afforded rigid poly‐Lewis acids with three SiCl3 or SiCl2Me substituents perfectly oriented to one side of the molecule in a single step. The progress of hydrosilylation was investigated by time‐correlated NMR spectroscopic studies. The crystal structures show that the framework is symmetrically functionalised and the silyl substituents are aligned in one direction. To increase the acidity of the Lewis acids the chlorosilyl substituents were fluorinated with SbF3. Further investigation of hydrometallation reactions (M=B, Al, Ga, Sn) did not lead to corresponding structures., A single‐step one‐pot synthesis, the hydrosilylation of the planar hydrocarbon hexadehydrotribenzo[12]annulene, provides access to chalice‐like trifunctional Lewis acids of C 3 symmetry with all functions oriented to the same side of the molecule. The synthesis of such poly‐functionalized donor‐free hydrocarbon derivatives is important for the development of new poly‐Lewis acids.

Chelating phosphines have long been a mainstay as efficient directing ligands in transition‐metal catalysis. Low‐valent derivatives, namely chelating phosphinidenes, are to date unknown, and could lead to chelating complexes containing more than one metal centre due to the intrisic capacity of phosphinidenes to bind two metal fragments at one P‐centre. Here we describe the synthesis of the first such chelating bis‐phosphinidene ligand, XantP2 (2), generated by the reduction of a diphosphino xanthene derivative, Xant(PH2)2 (1) with iPrNHC (iPrNHC=[:C{N(iPr)C(H)}2]). Initial studies have shown that this novel chelating ligand can act as a bidentate ligand towards element dihalides (i.e. FeCl2, ZnI2, GeCl2, SnBr2), forming cationic complexes with the tetryl elements. In contrast, XantP2 demonstrates an ability to bind multiple metal centres in the reaction with CuCl, leading to a cationic Cu3P3 ring complex, with Cu centres bridged by phosphinidene arms. Density Functional Theory calculations show that 2 indeed holds 4 lone pairs of electrons, shedding further light on the coordination capacity for this novel ligand class through observation of directionality and hybridisation of these electron pairs., It's a P‐P‐Party! A facile synthetic route to a new form of chelating phosphorous ligand, namely the chelating bis‐phosphinidene XantP2, has been developed, allowing for the gram‐scale synthesis of this novel ligand scaffold. Computational investigations corroborate that each P‐centre holds two lone pairs of electrons, allowing for the binding of multiple metal centres. Initial efforts towards the coordination chemistry of XantP2 are reported.

N‐Heteropolycycles are among the most promising candidates for applications in organic devices. For this purpose, a profound understanding of the low‐energy electronic absorbance and emission characteristics is of crucial importance. Herein, we report high‐resolution absorbance and fluorescence spectra of pentacene (PEN) and 6,13‐diazapentacene (DAP) in solid neon obtained using the matrix‐isolation technique. Accompanying DFT calculations allow the assignment of specific vibrationally resolved signals to corresponding modes. Furthermore, we present for the first time evidence for the formation of van der Waals dimers of both substances. These dimers exhibit significantly different optical characteristics resulting from the change of electronic properties evoked by the incorporation of sp2 nitrogen into the molecular backbone., High‐resolution and fluorescence spectra of pentacene and 6,13‐diazapentacene isolated in solid neon are presented. In alliance with quantum‐chemical calculations, the spectra give valuable information about the monomeric compounds. In addition, the matrix‐isolation technique was used to generate weakly bound dimers which were spectroscopically studied for the first time, providing information about the electronic coupling therein.

A six‐step synthesis towards a tribenzotriquinacene (TBTQ) bearing three quinoxalinophenanthrophenazine (QPP) units is presented. The optoelectronic properties are investigated and the effect of the three‐dimensional arrangement of the individual QPP planes is examined using optical spectroscopy, electrochemical analysis and quantum‐chemical calculations.

Artificial nucleic acids are widely used in various technologies, such as nucleic acid therapeutics and DNA nanotechnologies requiring excellent duplex‐forming abilities and enhanced nuclease resistance. 2′‐O,4′‐C‐Methylene‐bridged nucleic acid/locked nucleic acid (2′,4′‐BNA/LNA) with 1,3‐diaza‐2‐oxophenoxazine (BNAP (BH)) was previously reported. Herein, a novel BH analogue, 2′,4′‐BNA/LNA with 9‐(2‐aminoethoxy)‐1,3‐diaza‐2‐oxophenoxazine (G‐clamp), named BNAP‐AEO (BAEO), was designed. The BAEO nucleoside was successfully synthesized and incorporated into oligodeoxynucleotides (ODNs). ODNs containing BAEO possessed up to 104‐, 152‐, and 11‐fold higher binding affinities for complementary (c) RNA than those of ODNs containing 2′‐deoxycytidine (C), 2′,4′‐BNA/LNA with 5‐methylcytosine (L), or 2′‐deoxyribonucleoside with G‐clamp (PAEO), respectively. Moreover, duplexes formed by ODN bearing BAEO with cDNA and cRNA were thermally stable, even under molecular crowding conditions induced by the addition of polyethylene glycol. Furthermore, ODN bearing BAEO was more resistant to 3′‐exonuclease than ODNs with phosphorothioate linkages., Stability by design: Artificial nucleic acids are widely used and in some applications require excellent duplex‐forming abilities and enhanced nuclease resistance. 2′‐O,4′‐C‐Methylene‐bridged nucleic acid/locked nucleic acid (2′,4′‐BNA/LNA) with G‐clamp (BNAP‐AEO) is synthesized and incorporated into oligodeoxynucleotides (ODNs). These modified ODNs show high thermal stabilities toward complementary DNA and RNA.

The boron atoms react with carbon monoxide and dinitrogen forming the end‐on bonded NNBCO complex in solid neon or in nitrogen matrices. The NNBCO complex rearranges to the (η 2‐N2)BCO isomer with a more activated side‐on bonded dinitrogen ligand upon visible light excitation. (η 2‐N2)BCO and its weakly CO‐coordinated complexes further isomerize to the NBNCO and B(NCO)2 molecules with N−N bond being completely cleaved under UV light irradiation. The geometries, energies and vibrational spectra of the molecules are calculated with quantum chemical methods and the electronic structures are analyzed with charge‐ and energy‐partitioning methods., CO‐induced dinitrogen fixation and cleavage mediated by boron atoms is reported. The experimental and theoretical results show that the N≡N activation processes proceed with the initial formation of an end‐on bonded NNBCO complex, which rearranges to the NBNCO and B(NCO)2 isocyanate complexes via a side‐on bonded (η2‐N2)BCO intermediate. The geometries, energies and vibrational spectra of the molecules are calculated with quantum chemical methods and the electronic structures are analyzed with charge‐ and energy‐partitioning methods.

Stabilization of DNA is beneficial for many applications in the fields of DNA therapeutics, diagnostics, and materials science. Now, this phenomenon is studied on heterochiral DNA, an autonomous DNA recognition system with complementary strands in α‐D and β‐D configuration showing parallel strand orientation. The 12‐mer heterochiral duplexes were constructed from anomeric (α/β‐D) oligonucleotide single‐strands. Purine‐2,6‐diamine and 8‐aza‐7‐deaza‐7‐bromopurine‐2,6‐diamine 2′‐deoxyribonucleosides having the capability to form tridentate base pairs with dT were used to strengthen the stability of the dA–dT base pair. T m data and thermodynamic values obtained from UV melting profiles indicated that the 8‐aza‐7‐deaza 2′‐deoxyribonucleoside decorated with a bromo substituent is so far the most efficient stabilizer for heterochiral DNA. Compared with that, the stabilizing effect of the purine‐2,6‐diamine 2′‐deoxyribonucleoside is low. Global changes of helix structures were identified by circular dichroism (CD) spectra during melting., Base pair stabilization: Heterochiral parallel duplexes represent an autonomous recognition system constructed from anomeric (α/β‐D) oligonucleotides. The naturally occurring purine‐2,6‐diamine and the artificial 8‐aza‐7‐deaza‐7‐bromopurine nucleosides 1 and 2 strengthen the dA–dT base pair. The 8‐aza‐7‐deazapurine nucleoside decorated with a bromo substituent is so far the most efficient stabilizer for this pairing system.

The lithium complexes [(WCA‐NHC)Li(toluene)] of anionic N‐heterocyclic carbenes with a weakly coordinating anionic borate moiety (WCA‐NHC) reacted with iodine, bromine, or CCl4 to afford the zwitterionic 2‐halogenoimidazolium borates (WCA‐NHC)X (X=I, Br, Cl; WCA=B(C6F5)3, B{3,5‐C6H3(CF3)2}3; NHC=IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene, or NHC=IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene). The iodine derivative (WCA‐IDipp)I (WCA=B(C6F5)3) formed several complexes of the type (WCA‐IDipp)I⋅L (L=C6H5Cl, C6H5Me, CH3CN, THF, ONMe3), revealing its ability to act as an efficient halogen bond donor, which was also exploited for the preparation of hypervalent bis(carbene)iodine(I) complexes of the type [(WCA‐IDipp)I(NHC)] and [PPh4][(WCA‐IDipp)I(WCA‐NHC)] (NHC=IDipp, IMes). The corresponding bromine complex [PPh4][(WCA‐IDipp)2Br] was isolated as a rare example of a hypervalent (10‐Br‐2) system. DFT calculations reveal that London dispersion contributes significantly to the stability of the bis(carbene)halogen(I) complexes, and the bonding was further analyzed by quantum theory of atoms in molecules (QTAIM) analysis., Halogen complexes with N‐heterocyclic carbenes with a weakly coordinating anionic borate moiety, (WCA‐NHC)X (X=I, Br,Cl), were prepared and their ability to serve as halogen bond donors was investigated. Their reaction with carbenes afforded bis(carbene)iodine(I) and ‐bromine(I) complexes with an unusual hypervalent 10‐X‐2 bonding situation.

A set of four luminescent EuIII complexes bearing an extended aryl‐alkynylpyridine chromophore has been studied, showing very different pH‐dependent behaviour in their absorption and emission spectral response. For two complexes with pK a values of 6.45 and 6.20 in protein‐containing solution, the emission lifetime increases very significantly following protonation. By varying the gate time during signal acquisition, the ‘switch‐on’ intensity ratio could be optimised, and enhancement factors of between 250 to 1330 were measured between pH 8 and 4. The best‐behaved probe showed no significant emission dependence on the concentration of endogenous cations, reductants, and serum albumin. It was examined in live‐cell imaging studies to monitor time‐dependent lysosomal acidification, for which the increase in observed image brightness due to acidification was a factor of 50 in NIH‐3T3 cells., Watching lysosomes age with a ‘switch‐on’ optical sensor is shown to be possible by using four europium complexes with extended aryl‐alkylnyl pyridine antennae that show very different pH‐dependent behaviour. A ‘switch‐on’ of europium luminescence occurs at low pH, allowing confocal microscopy to reveal increases in image brightness of ageing lysosomes in live‐cell imaging studies.

Several amines with three bulky alkyl groups at the nitrogen atom, which exceed the steric crowding of triisopropylamine significantly, were synthesized, mainly by treating N‐chlorodialkylamines with Grignard reagents. In six cases, namely tert‐butyldiisopropylamine, 1‐adamantyl‐tert‐butylisopropylamine, di‐1‐adamantylamines with an additional N‐cyclohexyl or N‐exo‐2‐norbonyl substituent, as well as 2,2,6,6‐tetramethylpiperidine derivatives with N‐cyclohexyl or N‐neopentyl groups, appropriate single crystals were generated that enabled X‐ray diffraction studies and analysis of the molecular structures. The four noncyclic amines adopt triskele‐like conformations, and the sum of the three C−N−C angles is always in the range of 351.1° to 352.4°. Consequently, these amines proved to be structurally significantly flatter than trialkylamines without steric congestion, which is also signalized by the smaller heights of the NC3 pyramids (0.241–0.259 Å). There is no clear correlation between the heights of these pyramids and the degree of the steric crowding in the new amines, presumably because steric repulsion is partly compensated by dispersion interaction. In the cases of the two heterocyclic amines, the steric stress is smaller, and the molecular structures include quite different conformations. Quantum chemical calculations led to precise gas‐phase structures of the sterically overcrowded trialkylamines exhibiting heights of the NC3 pyramids and preferred molecular conformers which are similar to those resulting from the X‐ray studies., Chemistry - A European Journal, 27 (11), ISSN:0947-6539, ISSN:1521-3765

This work describes the synthesis and coordination behavior of a new mixed‐donor ligand PhC(NtBu)2SiC6H4PPh2 (1) containing both silylene and phosphine donor sites. Ligand 1 was synthesized from a reaction of ortho‐lithiated diphenylphosphinobenzene (LiC6H4PPh2) with chlorosilylene (PhC(NtBu)2SiCl). Treatment of 1 with Se and GeCl2 resulted in SiIV compounds 2 and 3 by selective oxidation of the silylene donor. This strong σ‐donor ligand induces dissociation of CuCl and PhBCl2 leading to formation of ionic complexes 4 and 5 respectively. The reaction of 1 with ZnCl2 and AlCl3 resulted in the formation of chelate complexes 5 and 7, respectively, while treatment with EtAlCl2 and GaCl3 forms monodentate complexes 8 and 9. X‐ray analysis of 4 showed that the copper is in the spiro center of the two five‐membered rings. Moreover, the copper(I)chloride has not been oxidized but dissociates to Cu+ and [CuCl2]−. All the compounds are well characterized by mass spectrometry, elemental analysis, NMR spectroscopy, and single‐crystal X‐ray diffraction studies., A ligand with different Lewis base donor sites of phosphorus(III) and silicon(II). The ligands are arranged in 1,2‐position at the benzene ring to generate mainly five‐membered ring compounds containing a metal atom. The exceptions of the compounds show clearly that the metal is preferentially coordinated to the silylene atom rather than to the phosphane site of the ligand.

Quinoline photobases exhibit a distinctly higher pK a in their electronically excited state than in the ground state, thereby enabling light‐controlled proton transfer reactions, for example, in molecular catalysis. The absorption of UV light translates to a pK a jump of approximately 10 units, as established for small‐molecule photobases. This contribution presents the first synthesis of quinoline‐based polymeric photobases prepared by reversible addition‐fragmentation chain‐transfer (RAFT) polymerization. The integration of quinolines as photobase chromophores within copolymers offers new possibilities for light‐triggered proton transfer in nanostructured materials, that is, in nanoparticles, at surfaces, membranes and interfaces. To exploit the light‐triggered reactivity of photobases within such materials, we first investigated how the ground‐ and excited‐state properties of the quinoline unit changes upon polymer integration. To address this matter, we combined absorption and emission spectroscopy with time‐resolved transient‐absorption studies to reveal photoinduced proton‐transfer dynamics in various solvents. The results yield important insights into the thermodynamic and kinetic properties of these polymeric quinoline photobases., Back to base: We present the synthesis of the first polymeric photobase prepared by RAFT polymerization carrying quinolines moieties pendant to the polymer backbone. UV‐light‐induced proton capture is investigated within a representative molecular and macromolecular quinoline photobase regarding the influence on ground and excited state and enables insights into thermodynamic and kinetic properties.

The efficient production of many medicinally or synthetically important starting materials suffers from wasteful or toxic precursors for the synthesis. In particular, the aromatic non‐protected primary amine function represents a versatile synthetic precursor, but its synthesis typically requires toxic oxidizing agents and transition metal catalysts. The twofold electrochemical amination of activated benzene derivatives via Zincke intermediates provides an alternative sustainable strategy for the formation of new C−N bonds of high synthetic value. As a proof of concept, we use our approach to generate a benzoxazinone scaffold that gained attention as a starting structure against castrate‐resistant prostate cancer. Further improvement of the structure led to significantly increased cancer cell line toxicity. Thus, exploiting environmentally benign electrooxidation, we present a new versatile and powerful method based on direct C−H activation that is applicable for example the production of medicinally relevant compounds., Efficient and sustainable access to medicinally and synthetically important C−N bonds is in high demand. However, aromatic primary amine functions via direct C−H amination still remain the major challenge in synthetic organic chemistry. Herein, a new environmentally benign twofold electrochemical C−H amination procedure to provide versatile primary amines and valuable heterocycles for biomedical applications is reported.

The syntheses of the homoleptic bis(arene) niobium cations [Nb(arene)2]+ (arene = C6H3Me3, C6H5Me) with 16 valence electrons and heteroleptic arene‐carbonyl cations [(CO)Nb(arene)2]+ (arene = C6H3Me3, C6H5Me) and [(arene)M(CO)4]+ (arene = C6H3Me3, C6H6) obeying 18 valence electrons are described. Stabilization of these complexes was achieved by using the weakly coordinating anions [Al(ORF)4]− or [F{Al(ORF)3}2]− (RF = C(CF3)3). The limits of two synthesis routes starting from neutral Nb(arene)2 (arene = C6H3Me3, C6H5Me) or [NEt4][M(CO)6] (M = Nb, Ta) were investigated. All compounds were analyzed by single crystal X‐ray determination, vibrational and NMR spectroscopy. DFT calculations were executed to support the experimental data., A variety of niobium‐sandwich and piano‐stool cations were stabilized by the weakly coordinating anions [Al(OC(CF3)4]− and [F{Al(OC(CF)3)3}2]−. Besides the analysis by single‐crystal X‐ray diffraction, vibrational and NMR spectroscopy, DFT calculations were executed to support the experimental data.

Thirteen N‐butylpyridinium salts, including three monometallic [C4Py]2[MCl4], nine bimetallic [C4Py]2[M1−x aMx bCl4] and one trimetallic compound [C4Py]2[M1−y‐z aMy bMz cCl4] (M=Co, Cu, Mn; x=0.25, 0.50 or 0.75 and y=z=0.33), were synthesized and their structure and thermal and electrochemical properties were studied. All compounds are ionic liquids (ILs) with melting points between 69 and 93 °C. X‐ray diffraction proves that all ILs are isostructural. The conductivity at room temperature is between 10−4 and 10−8 S cm−1. Some Cu‐based ILs reach conductivities of 10−2 S cm−1, which is, however, probably due to IL dec. This correlates with the optical bandgap measurements indicating the formation of large bandgap semiconductors. At elevated temperatures approaching the melting points, the conductivities reach up to 1.47×10−1 S cm−1 at 70 °C. The electrochemical stability windows of the ILs are between 2.5 and 3.0 V., Mixed metal tetrahalidometallate ionic liquids (ILs) were for the first time synthesized and studied for their structural, optical, and electrochemical properties. The ILs exhibit high conductivities and tunable optical absorption and are thus novel and highly versatile candidates for application in electronic and optical devices.

10 p.-6 fig.-3 tb., Functional pairing between cellular glyco-con-ju-gates and tissue lectins like galectins has wide (patho)physio-logical significance. Their study is facilitated by non-hydrolyzable deri-va-tives of the natural O-glycans, such as S- and Se-glycosides. The latter en-able extensive analyses by specific 77 Se NMR spectroscopy, but still remain under-explored. By the example of seleno--digalac-to-side (SeDG) and the human galectins 1 and 3, we evaluate diverse 77 Se NMR detec-tion methods and pro-pose selec-tive 1 H, 77 Se hetero-nuclear Hartmann-Hahn transfer for efficient use in com-peti-tive NMR screening against a seleno-glycoside spy ligand. By fluores-cence aniso-tropy, circular dichroism, and isothermal titra-tion calori-metry (ITC) we show that affinity and thermodynamics of SeDG bind-ing by galectins are similar to thiodi-galac-toside (TDG) and N-acetyl-lactos-amine (LacNAc), con-firm-ing that Se substitution has no major impact. ITC data in D 2 O vs. H 2 O are similar for TDG and LacNAc binding by both galectins, but a solvent effect, indicating solvent rearrangement at the binding site, is hinted for SeDG and clearly observed for LacNAc dimers with extend-ed chain length., We are much indebted to L. Szilágyi (University of Debrecen,Hungary) for kindly providing selenoglycosides for this study. We are grateful for inspiring discussions to Drs. B. Friday, A. Leddoz and A. W. L. Nose as well as for generous funding from the Spanish Ministry of Economy and Competitiveness (grant BFU2016-77835-R; to A.R.), the Department of Industry, Tourism and Trade of the Government of the Autonomous Community of the Basque Country (Elkartek BG2019; to T.D.), the Severo Ochoa Excellence Accreditation from MCIU (SEV-2016-0644; to T.D.), the Science Foundation of Ireland (grants 13/IA/1959 and 16/RC/3889;to S.O.), National Institute of Health (NIH) grant CA242351 to M.Cudic, and the COST Action CA 18103 (InnoGly; to H.-J.G.).

The synthesis of unsubstituted oligo‐para‐phenylenes (OPP) exceeding para‐hexaphenylene—in the literature often referred to as p‐sexiphenyl—has long remained elusive due to their insolubility. We report the first preparation of unsubstituted para‐nonaphenylenes (9PPs) by extending our precursor route to poly‐para‐phenylenes (PPP) to a discrete oligomer. Two geometric isomers of methoxylated syn‐ and anti‐cyclohexadienylenes were synthesized, from which 9PP was obtained via thermal aromatization in thin films. 9PP was characterized via optical, infrared and solid‐state 13C NMR spectroscopy as well as atomic force microscopy and mass spectrometry, and compared to polymeric analogues. Due to the lack of substitution, para‐nonaphenylene, irrespective of the precursor isomer employed, displays pronounced aggregation in the solid state. Intermolecular excitonic coupling leads to formation of H‐type aggregates, red‐shifting emission of the films to greenish. 9PP allows to study the structure–property relationship of para‐phenylene oligomers and polymers, especially since the optical properties of PPP depend on the molecular shape of the precursor., Unsubstituted para ‐nonaphenylenes were prepared via thermal aromatization of cyclohexadienylene precursors in thin films. The greenish fluorescence of the material is caused by pronounced aggregation in the solid state, in which electronic couplings leads to formation of H‐type aggregates. The emission bands of this small‐molecule are similar with respect to its polymer analogue.

The synthesis of an unprecedented, π‐extended hexabenzocorene (HBC)‐based diaza[7]helicene is presented. The target compound was synthesized by an ortho‐fusion of two naphthalene diimide (NDI) units to a HBC‐skeleton. A combination of Diels–Alder and Scholl‐type oxidation reactions involving a symmetric di‐NDI‐tolane precursor were crucial for the very selective formation of the helical superstructure via a hexaphenyl‐benzene (HPB) derivative. The formation of the diaza[7]helicene moiety in the final Scholl oxidation is favoured, affording the symmetric π‐extended helicene as the major product as a pair of enantiomers. The separation of the enantiomers was successfully accomplished by HPLC involving a chiral stationary phase. The absolute configuration of the enantiomers was assigned by comparison of circular dichroism spectra with quantum mechanical calculations., Super naphthalene, super helix: A diaza[7]helicene was formed as the only isomer via the fusion of two naphthalene diimides (NDIs) to a hexabenzocorene (HBC) core, generating a fully conjugated superstructure with a wide lateral π‐extension of the inner heterohelix. The helical twist brings along an attractive spatial arrangement and affects the chemical and photophysical features. Isolation of the corresponding enantiomers was accomplished by HPLC on a chiral stationary phase and the absolute configurations were determined by comparison of their circular dichroism spectra with quantum mechanical calculations.

Phytochrome photoreceptors operate via photoisomerization of a bound bilin chromophore. Their typical architecture consists of GAF, PAS and PHY domains. Knotless phytochromes lack the PAS domain, while retaining photoconversion abilities, with some being able to photoconvert with just the GAF domain. Therefore, we investigated the ultrafast photoisomerization of the Pr state of a knotless phytochrome to reveal the effect of the PHY domain and its “tongue” region on the transduction of the light signal. We show that the PHY domain does not affect the initial conformational dynamics of the chromophore. However, it significantly accelerates the consecutively induced reorganizational dynamics of the protein, necessary for the progression of the photoisomerization. Consequently, the PHY domain keeps the bilin and its binding pocket in a more reactive conformation, which decreases the extent of protein reorganization required for the chromophore isomerization. Thereby, less energy is lost along nonproductive reaction pathways, resulting in increased efficiency., More reactive, more efficient: The influence of the PHY domain on the photoconversion of a knotless phytochrome was investigated. The interaction of its “tongue” region with the GAF domain keeps the bilin chromophore and the binding pocket in a more reactive conformation. This results in accelerated reorganization of the protein environment necessary to accommodate the photoisomerization of the chromophore and, in effect, in an increased overall quantum efficiency.

Atropisomerism is a fundamental feature of substituted biaryls resulting from rotation around the biaryl axis. Different stereoisomers are formed due to restricted rotation about the single bond, a situation often found in substituted porphyrins. Previously NMR determination of porphyrin atropisomers proved difficult, if not almost impossible to accomplish, due to low resolution or unresolvable resonance signals that predominantly overlapped. Here, we shed some light on this fundamental issue found in porphyrinoid stereochemistry. Using benzenesulfonic acid (BSA) for host‐guest interactions and performing 1D, 2D NMR spectroscopic analyses, we were able to characterize all four rotamers of the nonplanar 5,10,15,20‐tetrakis(2‐aminophenyl)‐2,3,7,8,12,13,17,18‐octaethylporphyirin as restricted H‐bonding complexes. Additionally, X‐ray structural analysis was used to investigate aspects of the weak host–guest interactions. A detailed assignment of the chemical signals suggests charge‐assisted complexation as a key to unravel the atropisomeric enigma. From a method development perspective, symmetry operations unique to porphyrin atropisomers offer an essential handle to accurately identify the rotamers using NMR techniques only., Porphyrin atropisomers: Upon full assignment of all NMR signals symmetry elements were found to play a crucial part in the atropisomeric characteristics. A detailed study on nonplanar porphyrin atropisomers highlights new means to detect and identify individual rotamers in solution while X‐ray crystallographic analyses identified new supramolecular binding modes and specified aspects of weak interactions.

H‐bond donor catalysts able to modulate the reactivity of ionic substrates for asymmetric reactions have gained great attention in the past years, leading to the development of cooperative multidentate H‐bonding supramolecular structures. However, there is still a lack of understanding of the forces driving the ion recognition and catalytic performance of these systems. Herein, insight into the cooperativity nature, anion binding strength, and folding mechanism of a model chiral triazole catalyst is presented. Our combined experimental and computational study revealed that multi‐interaction catalysts exhibiting weak binding energies (≈3–4 kcal mol−1) can effectively recognize ionic substrates and induce chirality, while strong dependencies on the temperature and solvent were quantified. These results are key for the future design of catalysts with optimal anion binding strength and catalytic activity in target reactions., Brought into the fold! Fundamental insight into the folding mechanism, cooperativity nature and anion binding strength requirements in supramolecular anion‐binding catalysis is presented. This is afforded by a combined experimental and computational study with a prototypical foldameric triazole‐based chiral anion‐binding catalytic system, implying multi‐recognition sites to the ionic substrate units and weak binding energies as success factors.

The nature of cyclopropyl gold(I) carbene‐type intermediates has been reexamined as part of a mechanistic study on the formation of cis‐ or trans‐fused bicyclo[5.1.0]octanes in a gold(I)‐catalyzed cascade reaction. Benchmark of DFT methods together with QTAIM theory and NBO analysis confirms the formation of distinct intermediates with carbenic or carbocationic structures in the cycloisomerizations of enynes., Going for gold: The nature of cyclopropyl gold(I) carbene‐type intermediates has been explored as part of a mechanistic study on the gold(I)‐catalyzed formation of trans‐fused bicyclo[5.1.0]octanes. Complete computational analysis, that includes QTAIM theory and NBO analysis, confirms the formation of different species with carbenic or cationic nature as intermediates in the cycloisomerizations of enynes.

C−C cross coupling products of bowl‐shaped as‐indaceno[3,2,1,8,7,6‐pqrstuv]picene (Idpc) and different planar arenes and ethynyl‐arenes were synthesized. Photoluminescence as well as electrochemical properties of all products were investigated and complemented by time‐dependent quantum chemical calculations. UV/Vis spectroelectrochemistry investigations of the directly linked (Idpc)2 indicated the absence of any intramolecular charge‐transfer transition of intermittently formed (Idpc)2 .−. All coupling products showed fluorescence. Ferrocene‐1‐yl‐Idpc was structurally characterized by X‐ray diffraction and is a rare example of a ferrocene‐containing buckybowl exhibiting luminescence., Buckybowl‐planar conjugates of as‐indaceno[3,2,1,8,7,6‐pqrstuv]picene (Idpc) and different arenes and ethynyl‐arenes were synthesized. Photoluminescence as well as electrochemical properties of all products were investigated and complemented by time‐dependent quantum chemical calculations. Ferrocene‐1‐yl‐Idpc was structurally characterized by X‐ray diffraction and is a rare example of a ferrocene‐containing buckybowl exhibiting luminescence.

Reaction of a 2,5‐dilithiated silole with excess dichlorodimethylsilane gives the respective 2,5‐bis(chlorodimethylsilyl) substituted silole. This compound can be converted to 2,5‐bis(oligosilanyl) substituted siloles by addition of a suitable oligosilanide. In the UV spectra of the thus obtained compounds the lowest energy absorptions are bathochromically shifted compared to the absorptions of the two constituents, namely the 2,5‐disilyl substituted silole and a trisilane. The bathochromic shift is interpreted as being caused by a mixed σ‐conjugation/cross‐hyperconjugation. This assumption is supported by TD‐DFT calculations, which show a significant contribution from Si−Si bonds to the HOMO of the molecule., Attaching oligosilanyl units to the 2‐ and 5‐positions of a silole was found to cause a ca. 30 nm bathochromic shift of the low energy absorption band. Computational analysis shows hyperconjugational interaction of σ (Si−Si) bonds in the oligosilanyl units with the occupied π‐orbitals of the butadiene part of the silole ring, which leads to higher energy of the HOMO and consequently to a smaller HOMO/LUMO energy difference.

We report the preparation of enantiomerically pure constrained geometry complexes (cgc) of the rare‐earth metals bearing a pentadienyl moiety (pdl) derived from the natural product (1R)‐(−)‐myrtenal. The potassium salt 1, [Kpdl*], was treated with ClSiMe2NHtBu, and the resulting pentadiene 2 was deprotonated with the Schlosser‐type base KOtPen/nBuLi (tPen=CMe2(CH2Me)) to yield the dipotassium salt [K2(pdl*SiMe2NtBu)] (3). However, 3 rearranges in THF solution to its isomer 3’ by a 1,3‐H shift, which elongates the bridge between the pdl and SiMe2NtBu moieties by one CH2 unit. This is crucial for the successful formation of various monomeric C 1‐ or dimeric C 2‐symmetric rare‐earth cgc complexes with additional halide, tetraborohydride, amido and alkyl functionalities. All compounds have been extensively characterised by solid‐state X‐ray diffraction analysis, solution NMR spectroscopy and elemental analyses., Proton migration as key to success. A 1,3‐H shift enables the synthesis of the first enantiomerically pure pentadienyl‐based constrained geometry complexes, which can be further functionalised to silyamido and alkyl compounds.

A parallel quadruplex derived from the Myc promoter sequence was extended by a stem‐loop duplex at either its 5′‐ or 3′‐terminus to mimic a quadruplex–duplex (Q–D) junction as a potential genomic target. High‐resolution structures of the hybrids demonstrate continuous stacking of the duplex on the quadruplex core without significant perturbations. An indoloquinoline ligand carrying an aminoalkyl side chain was shown to bind the Q–D hybrids with a very high affinity in the order K a≈107 m −1 irrespective of the duplex location at the quadruplex 3′‐ or 5′‐end. NMR chemical shift perturbations identified the tetrad face of the Q–D junction as specific binding site for the ligand. However, calorimetric analyses revealed significant differences in the thermodynamic profiles upon binding to hybrids with either a duplex extension at the quadruplex 3′‐ or 5′‐terminus. A large enthalpic gain and considerable hydrophobic effects are accompanied by the binding of one ligand to the 3′‐Q–D junction, whereas non‐hydrophobic entropic contributions favor binding with formation of a 2:1 ligand‐quadruplex complex in case of the 5′‐Q–D hybrid., An indoloquinoline‐based G4 ligand binds with very high affinity at the quadruplex–duplex junction of a parallel G‐quadruplex featuring a stem‐loop duplex extension. Thermodynamic profiles and modes of binding differ for hybrids with duplex extensions at either the 5′‐ or 3′‐face of the G‐quadruplex.

To overcome bacterial resistances, the need for novel antimicrobial agents is urgent. The class of so‐called nucleoside antibiotics furnishes promising candidates for the development of new antibiotics, as these compounds block a clinically unexploited bacterial target: the integral membrane protein MraY, a key enzyme in cell wall (peptidoglycan) biosynthesis. Nucleoside antibiotics exhibit remarkable structural diversity besides their uridine‐derived core motifs. Some sub‐classes also show specific selectivities towards different Gram‐positive and Gram‐negative bacteria, which are poorly understood so far. Herein, the synthesis of a novel hybrid structure is reported, derived from the 5′‐defunctionalized uridine core moiety of muraymycins and the peptide chain of sansanmycin B, as a new scaffold for the development of antimicrobial agents. The reported muraymycin–sansanmycin hybrid scaffold showed nanomolar activity against the bacterial target enzyme MraY, but displayed no significant antibacterial activity against S. aureus, E. coli, and P. aeruginosa., Two become one: Nucleoside antibiotics are natural products that show remarkable structural diversity. Herein, the synthesis of a novel non‐natural hybrid structure is reported, derived from the simplified uridine core moiety of muraymycins and the peptide chain of sansanmycin B. This muraymycin–sansanmycin hybrid scaffold showed nanomolar activity against the bacterial target enzyme MraY, thus suggesting it may be used for the development of antibacterial agents.

The Periodic Table, and the unique chemical behavior of the first element in a column (group), were discovered simultaneously one and a half centuries ago. Half a century ago, this unique chemistry of the light homologs was correlated to the then available atomic orbital (AO) radii. The radially nodeless 1s, 2p, 3d, 4f valence AOs are particularly compact. The similarity of r (2s)≈r(2p) leads to pronounced sp‐hybrid bonding of the light p‐block elements, whereas the heavier p elements with n≥3 exhibit r (ns) ≪ r (np) of approximately −20 to −30 %. Herein, a comprehensive physical explanation is presented in terms of kinetic radial and angular, as well as potential nuclear‐attraction and electron‐screening effects. For hydrogen‐like atoms and all inner shells of the heavy atoms, r (2s) ≫ r (2p) by +20 to +30 %, whereas r (3s)≳r(3p)≳r(3d), since in Coulomb potentials radial motion is more radial orbital expanding than angular motion. However, the screening of nuclear attraction by inner core shells is more efficient for s than for p valence shells. The uniqueness of the 2p AO is explained by this differential shielding. Thereby, the present work paves the way for future physical explanations of the 3d, 4f, and 5g cases., 2p or not 2p? Similarity of radii (and energies) of the atomic valence orbitals is the precondition for hybridization and hybrid bonding. In the Coulomb potential of H‐like atoms, the 2p orbital without a radial node is much smaller than 2s (2s≫2p), whereas higher p orbitals are comparably less contracted (ns≳np). The screening of nuclear attraction by the core shells is more effective for the core penetrating s orbitals, so that for the valence orbital radii of ordinary many‐electron atoms of the 2nd row, 2s≈2p, whereas in rows n>2, hybridization is less pronounced owing, i.a., to ns≪ np.

A pair of diastereomeric dinuclear complexes, [Tp′(CO)BrW{μ‐η2‐C,C′‐κ2‐S,P‐C2(PPh2)S}Ru(η5‐C5H5)(PPh3)], in which W and Ru are bridged by a phosphinyl(thiolato)alkyne in a side‐on carbon P,S‐chelate coordination mode, were synthesized, separated and fully characterized. Even though the isomers are similar in their spectroscopic properties and redox potentials, the like‐isomer is oxidized at W while the unlike‐isomer is oxidized at Ru, which is proven by IR, NIR and EPR‐spectroscopy supported by spectro‐electrochemistry and computational methods. The second oxidation of the complexes was shown to take place at the metal left unaffected in the first redox step. Finally, the tipping point could be realized in the unlike isomer of the electronically tuned thiophenolate congener [Tp′(CO)(PhS)W{μ‐η2‐C,C′‐κ2‐S,P‐C2(PPh2)S}Ru(η5‐C5H5)‐(PPh3)], in which valence trapped WIII/RuII and WII/RuIII cationic species are at equilibrium., Diastereomers differ in physical properties: A case of real metal/metal redox isomerism is observed in a dinuclear complex with a particularly short bridging ligand. The two stereogenic complex moieties at W and Ru, respectively, are linked by an alkyne based phosphine thiolate chelate ligand. Oxidation of the like isomer pertains to tungsten, whereas the unlike isomer is oxidised at ruthenium. The diastereomers show opposite redox behaviour!

The synthesis of three complex series of the form [AnCl2(salen)(Pyx)2] (H2salen=N,N′‐bis(salicylidene)ethylenediamine; Pyx=pyridine, 4‐methylpyridine, 3,5‐dimethylpyridine) with tetravalent early actinides (An=Th, U, Np, Pu) is reported with the goal to elucidate the affinity of these heavy elements for small neutral N‐donor molecules. Structure determination by single‐crystal XRD and characterization of bulk powders with infrared spectroscopy reveals isostructurality within each respective series and the same complex conformation in all reported structures. Although the trend of interatomic distances for An−Cl and An−N (imine nitrogen of salen or pyridyl nitrogen of Pyx) was found to reflect an ionic behavior, the trend of the An−O distances can only be described with additional covalent interactions for all elements heavier than thorium. All experimental results are supported by quantum chemical calculations, which confirm the mostly ionic character in the An−N and An−Cl bonds, as well as the highest degree of covalency of the An−O bonds. Structurally, the calculations indicate just minor electronic or steric effects of the additional Pyx substituents on the complex properties., Th–PuIV salen complexes: A series of monosalen complex with Th–PuIV has been synthesized and characterized in the solid state and with quantum chemical (QC) calculations. They reveal the salen's potential to provide a fixed binding pocket to AnIV, allowing a facile exchange of pyridine‐based solvents in the labile positions. Differences in binding strength explain the findings: all AnIV−N are of mostly ionic nature but AnIV−O have a significant covalent contribution.

We report herein a mild procedure for the copper‐catalyzed oxidative cross‐coupling of electron‐deficient polyfluorophenylboronate esters with terminal alkynes. This method displays good functional group tolerance and broad substrate scope, generating cross‐coupled alkynyl(fluoro)arene products in moderate to excellent yields. Thus, it represents a simple alternative to the conventional Sonogashira reaction., BFF: A mild procedure is reported for the synthesis of alkynyl(fluoro)arenes via copper‐catalyzed oxidative cross‐coupling of polyfluorophenylboronate esters with terminal alkynes.

Squaraine dyes are well known for their strong absorption in the visible regime. Reports on chiral squaraine dyes are, however, scarce. To address this gap, we here report two novel chiral squaraine dyes and their achiral counterparts. The presented dyes are aggregated in solution and in thin films. A detailed chiroptical study shows that thin films formed by co‐assembling the chiral dye with its achiral counterpart exhibit exceptional photophysical properties. The circular dichroism (CD) of the co‐assembled structures reaches a maximum when just 25 % of the chiral dye are present in the mixture. The solid structures with the highest relative CD effect are achieved when the chiral dye is used solely as a director, rather than the structural component. The chiroptical data are further supported by selected spin‐filtering measurements using mc‐AFM. These findings provide a promising platform for investigating the relationship between the dissymmetry of a supramolecular structure and emerging material properties rather than a comparison between a chiral molecular structure and an achiral counterpart., Helicity control: An unexpected outcome of the co‐assembly of achiral squaraine dye a‐SQ‐1 with its chiral counterpart S ‐SQ‐1 is reported. A maximum in optical activity is observed in the supramolecular aggregates of a 3:1 mixture with a‐SQ‐1 as the major component. Intriguingly, the highest spin‐selective electron transport is observed for this mixing ratio as well, illustrating the direct relationship between optical activity and spin‐selective electron transport.

The synthesis of chiral metal–organic frameworks (MOFs) is highly relevant for asymmetric heterogenous catalysis, yet very challenging. Chiral MOFs with MOF‐74 topology were synthesised by using post‐synthetic modification with proline. Vibrational circular dichroism studies demonstrate that proline is the source of chirality. The solvents used in the synthesis play a key role in tuning the loading of proline and its interaction with the MOF‐74 framework. In N,N′‐dimethylformamide, proline coordinates monodentate to the Zn2+ ions within the MOF‐74 framework, whereas it is only weakly bound to the framework when using methanol as solvent. Introducing chirality within the MOF‐74 framework also leads to the formation of defects, with both the organic linker and metal ions missing from the framework. The formation of defects combined with the coordination of DMF and proline within the framework leads to a pore blocking effect. This is confirmed by adsorption studies and testing of the chiral MOFs in the asymmetric aldol reaction between acetone and para‐nitrobenzaldehyde., Chemistry - A European Journal, 26 (61), ISSN:0947-6539, ISSN:1521-3765

Mild reaction conditions are highly desirable for bio‐orthogonal side chain derivatizations of amino acids, peptides or proteins due to the sensitivity of these substrates. Transition metal catalysed cross‐couplings such as Suzuki–Miyaura reactions are highly versatile, but usually require unfavourable reaction conditions, in particular, when applied with aryl bromides. Ligand‐free solvent‐stabilised Pd‐nanoparticles represent an efficient and sustainable alternative to conventional phosphine‐based catalysts, because the cross‐coupling can be performed at considerably lower temperature. We report on the application of such a highly reactive heterogeneous catalyst for the Suzuki–Miyaura cross‐coupling of brominated tryptophan derivatives. The solvent‐stabilised Pd‐nanoparticles are even more efficient than the literature‐known ADHP‐Pd precatalyst. Interestingly, the latter also leads to the formation of quasi‐homogeneous Pd‐nanoparticles as the catalytic species. One advantage of our approach is the compatibility with aqueous and aerobic conditions at near‐ambient temperatures and short reaction times of only 2 h. The influence of different N α‐protecting groups, boronic acids as well as the impact of different amino acid side chains in bromotryptophan‐containing peptides has been studied. Notably, a surprising acceleration of the catalysis was observed when palladium‐coordinating side chains were present in proximal positions., Gentle conditions: Ligand‐free solvent‐stabilised Pd‐nanoparticles serve as a highly efficient catalyst at ambient temperature for a sustainable and biocompatible Suzuki–Miyaura cross‐coupling between aryl bromides and boronic acids under mild, aerobic and aqueous conditions.

We have investigated the cannibalistic self‐trapping reaction of an ortho‐benzyne derivative generated from 1,11‐bis(p‐tolyl)undeca‐1,3,8,10‐tetrayne in an HDDA reaction. Without adding any specific trapping agent, the highly reactive benzyne is trapped by another bisdiyne molecule in at least three different modes. We have isolated and characterized the resulting products and performed high‐level calculations concerning the reaction mechanism. During the cannibalistic self‐trapping process, either a C≡C triple bond or an sp–sp3 C−C single bond is cleaved. Up to seven rings and nine C−C bonds are formed starting from two 1,11‐bis(p‐tolyl)undeca‐1,3,8,10‐tetrayne molecules. Our experiments and calculations provide considerable insight into the variety of reaction pathways which the ortho‐benzyne derivative, generated from a bisdiyne, can take when reacting with another bisdiyne molecule., Go for the throat: The benzyne derivative generated from a linked bisdiyne in a hexadehydro‐Diels–Alder reaction undergoes cannibalistic self‐trapping by at least three different pathways. Three highly conjugated products resulting from self‐trapping were isolated, fully characterized and their photophysical properties examined. The mechanisms leading to their formation were investigated by high‐level calculations.

C−H hydroxylation of aryl acetamides and alkyl phenylacetyl esters was accomplished via challenging distal weak O‐coordination by versatile ruthenium(II/IV) catalysis. The ruthenium(II)‐catalyzed C−H oxygenation of aryl acetamides proceeded through C−H activation, ruthenium(II/IV) oxidation and reductive elimination, thus providing step‐economical access to valuable phenols. The p‐cymene‐ruthenium(II/IV) manifold was established by detailed experimental and DFT‐computational studies., C−H hydroxylation of aryl acetamides and alkyl phenylacetyl esters is achieved via a challenging distal weak O‐coordination by a ruthenium(II/IV) catalyst. The process includes C−H activation, ruthenium(II/IV) oxidation and reductive elimination which provides step‐economical access to valuable phenols.

Spontaneous development of chirality in systems composed of achiral molecules is important for new routes to asymmetric synthesis, chiral superstructures and materials, as well as for the understanding of the mechanisms of emergence of prebiotic chirality. Herein, it is shown that the 4,4′‐diphenylbenzil unit is a universal transiently chiral bent building block for the design of multi‐chained (polycatenar) rod‐like molecules capable of forming a wide variety of helically twisted network structures in the liquid, the liquid crystalline (LC) and the crystalline state. Single polar substituents at the apex of tricatenar molecules support the formation of the achiral (racemic) cubic double network phase with Ia 3‾ d symmetry and relatively small twist along the networks. The combination of an alkyl chain with fluorine substitution leads to the homogeneously chiral triple network phase with I23 space group, and in addition, provides a mirror symmetry broken liquid. Replacing F by Cl or Br further increases the twist, leading to a short pitch double gyroid Ia 3‾ d phase, which is achiral again. The effects of the structural variations on the network structures, either leading to achiral phases or chiral conglomerates are analyzed., Soft helical networks: Achiral benzil‐based multi‐chained molecules form a series of spontaneously mirror‐symmetry‐broken soft matter structures; the steric and electronic effects of polar substituents on helical self‐assembly, local and long range network formation as well as through‐space interhelical interactions are discussed.

We describe multimodal imaging probes for gastrin‐releasing peptide receptor (GRPR)‐specific targeting suited for positron emission tomography and optical imaging (PET/OI), consisting of PESIN (PEG3‐BBN7‐14) dimers connected to multimodal imaging subunits. These multimodal agents comprise a fluorescent dye for OI and the chelator ((1,4,7‐triazacyclononane‐4,7‐diyl)diacetic acid‐1‐glutaric acid) (NODA‐GA) for PET radiometal isotope labelling. Special focus was put on the influence of the used dyes on the properties of the whole bioconjugates. For this, several compounds with different fluorescent dyes and non‐dye carrying subunits were synthesized and investigated. As fluorescent dyes, dansyl, NBD, derivatives of fluorescein, coumarin and rhodamine as well as three pyrilium‐based dyes were employed. Considerable influence of the charge of the colored unit on hydrophilicity as well as in vitro target receptor binding was observed and classified. High radiochemical yields and purities were found during radiolabeling of the multimodal imaging subunits as well as their GRPR‐specific bioconjugates with 68Ga. Examinations of the photophysical properties of both molecule species displayed no loss or alteration of fluorescence characteristics., Multimodal imaging: Different PESIN‐homodimers, suited for positron emission tomography and optical imaging, were synthesized. Special focus was set on the influence of different dyes on biomedical‐related properties.

Cyclic silylated chalconium borates 13[B(C6F5)4] and 14[B(C6F5)4] with peri‐acenaphthyl and peri‐naphthyl skeletons were synthesized from unsymmetrically substituted silanes 3, 4, 6, 7, 9 and 10 using the standard Corey protocol (Chalcogen Ch=O, S, Se, Te). The configuration at the chalcogen atom is trigonal pyramidal for Ch=S, Se, Te, leading to the formation of cis‐ and trans‐isomers in the case of phenylmethylsilyl cations. With the bulkier tert‐butyl group at silicon, the configuration at the chalcogen atoms is predetermined to give almost exclusively the trans‐configurated cyclic silylchalconium ions. The barriers for the inversion of the configuration at the sulfur atoms of sulfonium ions 13 c and 14 a are substantial (72–74 kJ mol−1) as shown by variable temperature NMR spectroscopy. The neighboring group effect of the thiophenyl substituent is sufficiently strong to preserve chiral information at the silicon atom at low temperatures., The Corey reaction of acenaphthyl‐ and naphthyl‐based chiral silanes allows the synthesis of silylchalconium ions with control of the stereochemistry at the chalcogen atom (shown here for the sulfonium ion). The chalcogen neighboring group effect on the silyl cation is sufficiently strong to conserve the stereochemistry in a consecutive nucleophilic attack.