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Efficient and reliable methods for the generation of bioactive papers are of growing interest in relation to point‐of‐care testing devices that do not require extensive analytical equipment. Herein, we report the immobilization of functional proteins on paper fibers using a modular chemoenzymatic approach. The synthetic strategy relies on a combination of highly efficient spatially controllable photo‐triggered cycloaddition followed by site‐specific sortase A‐catalyzed transamidation. This site‐directed and regiospecific method has allowed unidirectional and covalent immobilization of several proteins displaying different functional properties, with ramifications for application in paper‐based diagnostics. Protein‐functionalized paper: A modular approach to covalent protein immobilization on paper fibers is reported, which relies on a set of highly efficient pericyclic reactions in combination with site‐specific enzymatic coupling. Following initial derivatization of a cellulosic surface (see figure), light‐triggered covalent anchoring of an enzyme recognition site ensures enzyme‐promoted ligation of desired proteins with preservation of their function. [ABSTRACT FROM AUTHOR]

Invited for the cover of this issue is the group of Ying-Jie Zhu at the Chinese Academy of Sciences. The image depicts a highly flexible and free-standing paper with high antibacterial activity made from silver nanoparticle-decorated ultralong hydroxyapatite nanowires. Read the full text of the article at . [ABSTRACT FROM AUTHOR]

1,2‐benzisothiazol‐3(2H)‐one derivatives are highly active against a broad spectrum of fungi as well as Gram positive and Gram negative bacteria. For this reason they are extensively used, for example, as additives in detergents, leather products, paper coatings, and antifouling paintings. In this paper experimental findings are reported proving that the sulfur atom of benzisothiazolinones have a remarkable tendency to form short and directional chalcogen bondings on the extension of the covalent N−S bond and, to a lesser extent, of the C−S bond. Analyses of the Cambridge Structural Database confirm the interaction as a primary recognition motif of these systems. The electrophilicity of sulfur is crucial in the chemical reactions initiating the cascade of events resulting in the biopharmacological activities of benzisothiazolinones. The reported results suggest that the electrophility of sulfur may play a role also at earlier stages than the reactive ones, namely it may pin the compounds at the active site of target enzymes via chalcogen bondings that preorganize the system in the conformation required for the bonds formation/cleavage determining the biopharmacological activity [ABSTRACT FROM AUTHOR]

Free radicals are increasingly recognized as active intermediate reactive species that can participate in various redox processes, significantly influencing the mechanistic pathways of reactions. Numerous researchers have investigated the generation of one or more distinct photogenerated radicals, proposing various hypotheses to explain the reaction mechanisms. Notably, recent research has demonstrated the emergence of photogenerated radicals in innovative processes, including organic chemical reactions and the photocatalytic dissolution of precious metals. To harness the potential of these free radicals more effectively, it is imperative to consolidate and analyze the processes and action modes of these photogenerated radicals. This conceptual paper delves into the latest advancements in understanding the mechanics of photogenerated radicals. [ABSTRACT FROM AUTHOR]

A new fluorescent 1,3-diaminonaphthalimide conjugate of calix[4]arene receptor ( R) was synthesized and characterized. The receptor displays good selectivity towards trinitrophenol (TNP) over other explosive aromatic- and aliphatic-nitro compounds by exhibiting changes in its fluorescence emission. Receptor-coated cellulose paper strips are equally effective in terms of their selective detection of TNP over other aromatic- and aliphatic-nitro compounds. When used in solution or on cellulose paper strips, R can detect up to submicromolar concentration of TNP by exhibiting changes in its fluorescence emission and in its supramolecular structure upon interaction. Interestingly, the microscopy features of R, TNP, and { R+TNP} are quite distinct, indicating the interactions present between R and TNP, as studied by using AFM and TEM. Computationally modeled complexes of receptor with TNP and TNT show enormous difference in their interaction energies in the favor of TNP by showing the host-guest interaction of cation ⋅⋅⋅anion type in the presence of TNP but not TNT. This is because the receptor adopts an 'arms-open'-type structure in the case of the TNP complex, whereas it adopts an 'arms-closed'-type structure in the presence of TNT. Both the experimental and the computational studies reveal that the receptor selectively binds to TNP over TNT. Thus, R-coated Whatman No.1 filter paper strips provide easy, rapid, and economical detection of trace amounts of TNP both by visual and spectral measurement. [ABSTRACT FROM AUTHOR]

As Liu et al. reported previously ( Appl. Mater. Today 2017, 7, 239-245), the charge transfer to partially oxidized polyaniline (PANI) nanotubes in electrochemical reactions is heavily limited due to the non-conductivity of the reduction/oxidation products. In this paper, the doping level of individual PANI nanotubes was substantially enhanced using nitrite as an electron acceptor in sulfuric acid aqueous solution as recorded by the nano-impact method. The charge transferred to one single tube during reduction process is close to the theoretical value of 170±112 pC per tube (assuming 2-electron reduction for the PANI tubes studied), while the charge during PANI oxidation is dramatically decreased. Reaction processes are proposed based on the oxidative properties of nitrite in acid solution. UV-visible spectroscopy analysis further confirms an oxidation-reduction reaction between PANI and nitrite. In contrast the electrochemical reaction of ensembles (21 μg cm−1) of PANI tubes on glassy carbon electrodes simply show limited electrocatalytic activity. [ABSTRACT FROM AUTHOR]

Liquid-crystalline ionic liquids (LCILs) are ordered materials that have untapped potential to be used as reaction media for synthetic chemistry. This paper investigates the potential for the ordered structures of LCILs to influence the stereochemical outcome of the Diels-Alder reaction between cyclopentadiene and methyl acrylate. The ratio of endo- to exo-product from this reaction was monitored for a range of ionic liquids (ILs) and LCILs. Comparison of the endo: exo ratios in these reactions as a function of cation, anion and liquid crystallinity of the reaction media, allowed for the effects of liquid crystallinity to be distinguished from anion effects or cation alkyl chain length effects. These data strongly suggest that the proportion of exo-product increases as the reaction media is changed from an isotropic IL to a LCIL. A detailed molecular dynamics (MD) study suggests that this effect is related to different hydrogen bonding interactions between the reaction media and the exo- and endo-transition states in solvents with layered, smectic ordering compared to those that are isotropic. [ABSTRACT FROM AUTHOR]

Bacterial bioluminescence with continuous glow has been applied to the fields of environmental toxin monitoring, drug screening, and in vivo imaging. Nonetheless, the chemical form of the bacterial bioluminophore is still a bone of contention. Flavin mononucleotide (FMN), one of the light-emitting products, and 4a-hydroxy-5-hydro flavin mononucleotide (HFOH), an intermediate of the chemical reactions, have both been assumed candidates for the light emitter because they have similar molecular structures and fluorescence wavelengths. The latter is preferred in experiments and was assigned in our previous density functional study. HFOH displays weak fluorescence in solutions, but exhibits strong bioluminescence in the bacterial luciferase. FMN shows the opposite behavior; its fluorescence is quenched when it is bound to the luciferase. This is the first example of flavin fluorescence quenching observed in bioluminescent systems and is merely an observation, both the quenching mechanism and quencher are still unclear. Based on theoretical analysis of high-level quantum mechanics (QM), combined QM and molecular mechanics (QM/MM), and molecular dynamics (MD), this paper confirms that HFOH in its first singlet excited state is the bioluminophore of bacterial bioluminescence. More importantly, the computational results indicate that Tyr110 in the luciferase quenches the FMN fluorescence via an electron-transfer mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Ruthenium‐containing organometallic ionic liquids with the B(CN)4 anion were developed that generate microporous amorphous coordination polymers upon UV irradiation. UV light irradiation of [Ru(C5H5)(C6H5R)][B(CN)4] (R=butyl, ethyl, octyl) quantitatively generated a yellow powder of a coordination polymer with the formula [Ru(C5H5){B(CN)4}]n. In this reaction, the arene ligand is eliminated by UV irradiation and coordination polymer is formed by coordination of the cyano groups of the anion to the Ru ion. The photogenerated solids exhibited nitrogen absorption properties due to their microporous structure. This paper proposes a method to fabricate functional coordination polymers by photoirradiation of liquids. [ABSTRACT FROM AUTHOR]

Choosing the optimal catalyst for a new transformation is challenging because the ideal molecular requirements of the catalyst for one reaction do not always simply translate to another. Large groups at the 3,3′ positions of the binaphthol rings are important for efficient stereoinduction but if they are too large this can lead to unusual or poor results. By applying a quantitative steric assessment of the substituents at the 3,3′ positions of the binaphthol ring, we have systematically studied the effect of modulating this group on enantioselectivity for a wide range of reactions involving imines, and verified this analysis using ONIOM calculations. We have shown that in most reactions, the stereochemical outcome depends on both proximal and remote sterics. Summarising detailed calculations into a simple qualitative model identifies and explains the steric features required for high selectivity. This model is consistent with seventy seven papers reporting reactions (over 1000 transformations in total), and provides a straightforward decision tree for selecting the best catalyst. [ABSTRACT FROM AUTHOR]

The reaction chemistry of the bis‐tetrazinyl pyridine ligand (btzp) towards nitrogen oxyanions coordinated to zinc is studied in order to explore the reduction of the NOx− substrates with a redox‐active ligand in the absence of redox activity at the metal. Following syntheses and characterization of (btzp)ZnX2 for X=Cl, NO3 and NO2, featuring O−Zn linkage of both nitrogen oxyanions, it is shown that a silylating agent selectively delivers silyl substituents to tetrazine nitrogens, without reductive deoxygenation of NOx−1. A new synthesis of the highly hydrogenated H4btzp, containing two dihydrotetrazine reductants is described as is the synthesis and characterization of (H4btzp)ZnX2 for X=Cl and NO3, both of which show considerable hydrogen bonding potential of the dihydrotetrazine ring NH groups. The (H4btzp)ZnCl2 complex does not bind zinc in the pincer pocket, but instead H4btzp becomes a bridge between neighboring atoms through tetrazine nitrogen atoms, forming a polymeric chain. The reaction of AgNO2 with (H4btzp)ZnCl2 is shown to proceed with fast nitrite deoxygenation, yielding water and free NO. Half of the H4btzp reducing equivalents form Ag0 and thus the chloride ligand remains coordinated to the zinc metal center to yield (btzp)ZnCl2. To compare with AgNO2, experiments of (H4btzp)ZnCl2 with NaNO2 result in salt metathesis between chloride and nitrite, highlighting the importance of a redox‐active cation in the reduction of nitrite to NO. [ABSTRACT FROM AUTHOR]

The propensity of organic fluorine acting as a weak hydrogen bond acceptor (HBA) in intermolecular and intramolecular interactions has been the subject of many experimental and theoretical studies often reaching different conclusions. Over the last few years, new and stronger evidences have emerged for the direct involvement of fluorine in weak hydrogen bond (HB) formation. However, not all the fluorine atom types can act as weak HBA. In this work, the differential HBA propensity of various types of fluorine atoms was analyzed with a particular emphasis for the different types of alkyl fluorides. This was carried out by evaluating ab initio computed parameters, experimental 19F NMR chemical shifts and small molecule crystallographic structures (extracted from the CSD database). According to this analysis, shielded (with reference to the 19F NMR chemical shift) alkyl mono‐fluorinated motifs display the highest HBA propensity in agreement with solution studies. Although much weaker than other well‐characterized HB complexes, the fragile HBs formed by these fluorinated motifs have important implications for the chemical‐physical and structural properties of the molecules, chemical reactions, and protein–ligand recognition. [ABSTRACT FROM AUTHOR]

This paper is devoted to the understanding of the reaction mechanism of mycobacterium tuberculosis glutamine synthetase (mtGS) with atomic detail, using computational quantum mechanics/molecular mechanics (QM/MM) methods at the ONIOM M06-D3/6-311++G(2d,2p):ff99SB//B3LYP/6-31G(d):ff99SB level of theory. The complete reaction undergoes a three-step mechanism: the spontaneous transfer of phosphate from ATP to glutamate upon ammonium binding (ammonium quickly loses a proton to Asp54), the attack of ammonia on phosphorylated glutamate (yielding protonated glutamine), and the deprotonation of glutamine by the leaving phosphate. This exothermic reaction has an activation free energy of 21.5 kcal mol−1, which is consistent with that described for Escherichia coli glutamine synthetase (15-17 kcal mol−1). The participating active site residues have been identified and their role and energy contributions clarified. This study provides an insightful atomic description of the biosynthetic reaction that takes place in this enzyme, opening doors for more accurate studies for developing new anti-tuberculosis therapies. [ABSTRACT FROM AUTHOR]

The family of polyoxometalate (POM) intercalated layered double hydroxide (LDH) composite materials has shown great promise for the design of functional materials with numerous applications. It is known that intercalation of the classical Keggin polyoxometalate (POM) of [PW12O40]3− (PW12) into layered double hydroxides (LDHs) is very unlikely to take place by conventional ion exchange methods due to spatial and geometrical restrictions. In this paper, such an intercalated compound of Mg0.73Al0.22(OH)2 [PW12O40]0.04⋅0.98 H2O (Mg3Al-PW12) has been successfully obtained by applying a spontaneous flocculation method. The Mg3Al-PW12 has been fully characterized by using a wide range of methods (XRD, SEM, TEM, XPS, EDX, XPS, FT-IR, NMR, BET). XRD patterns of Mg3Al-PW12 exhibit no impurity phase usually observed next to the (003) diffraction peak. Subsequent application of the Mg3Al-PW12 as catalyst in Knoevenagel condensation reactions of various aldehydes and ketones with Z-CH2-Z′ type substrates (ethyl cyanoacetate and malononitrile) at 60 °C in mixed solvents ( V2-propanol: Vwater=2:1) demonstrated highly efficient catalytic activity. The synergistic effect between the acidic and basic sites of the Mg3Al-PW12 composite proved to be crucial for the efficiency of the condensation reactions. Additionally, the Mg3Al-PW12-catalyzed Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate demonstrated the highest turnover number (TON) of 47 980 reported so far for this reaction. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of both polysubstituted oxazolo-pyrrolidinones and -piperidinones by a domino process. The methodology is based on the reaction between hydroxyl halogenoamides and Michael acceptors, which leads efficiently to bicyclic lactams. The process is compatible with unsymmetrical electron-withdrawing groups on the Michael acceptor, which allows the formation of two contiguous and fully controlled tertiary and quaternary stereocenters. In the case of tetrasubstituted Michael acceptors, two adjacent quaternary stereocenters are formed in good yield. Starting from ( R)-phenylglycinol derived amides results in the formation of enantioenriched bicyclic lactams in low to good yields and with high levels of stereoselectivity, thus greatly increasing the scope and interest of this strategy. The origins of chirality transfer and diastereoselectivity were studied by DFT calculations and have been attributed to a kinetic control in one of the last two steps of the reaction sequence. This selectivity is dependent upon both the substituents on the Michael acceptor and the sodium cation chelation. [ABSTRACT FROM AUTHOR]

Thermal adaptation of enzymes is essential for both living organism development in extreme conditions and efficient biocatalytic applications. However, the molecular mechanisms leading to a shift in catalytic activity optimum temperatures remain unclear, and there is increasing experimental evidence that thermal adaptation involves complex changes in both structural and reactive properties. Here, a combination of enhanced protein conformational sampling with an explicit chemical reaction description was applied to mesophilic and thermophilic homologues of the dihydrofolate reductase enzyme, and a quantitative description of the stability and catalytic activity shifts between homologues was obtained. The key role played by temperature‐induced shifts in protein conformational distributions is revealed. In contrast with pictures focusing on protein flexibility and dynamics, it is shown that while the homologues' reaction free energies are similar, the striking discrepancy between their activation energies is caused by their different conformational changes with temperature. An analytic model is proposed that combines catalytic activity and structural stability, and which quantitatively predicts the shift in homologue optimum temperatures. It is shown that this general model provides a molecular explanation of changes in optimum temperatures for several other enzymes. [ABSTRACT FROM AUTHOR]

Octa‐ and tetrafluorinated bisanthene derivatives were synthesized for investigating the effect of electronegative fluorine substitution on the structure and physical property of bisanthene. Notably, a triisopropylsilylethynyl‐substituted octafluorinated derivative exhibited strong fluorescence with high fluorescence quantum yield and excellent photostability. Moreover, the derivative self‐assembled to form bundles of long semicrystalline nanofibers exhibiting hole‐transporting properties, see the Full Paper by H. Yamada et al. on page 7000. [ABSTRACT FROM AUTHOR]

In the “chemical billiard” reaction shown on the front cover, a counter ion directs the attack of the azide anion to one or another electrophilic center of the organic substrate. Covalently bonded metal azides transfer N3− to the β ‐ carbon atom through a Lewis ‐ acid ‐ promoted SN’ process, while ionic azides react through SN2 attack on the silicon. These two pathways lead to entirely different products. More information can be found in the Full Paper by A. Yu. Sukhorukov et al. on page 4570 ff. [ABSTRACT FROM AUTHOR]

Lanthanide Single‐Ion Magnets The adequate choice of the ligands coordinated to LnIII centres plays a key role in raising the effective energy barrier Ueff in SIMs. Thus, in homoleptic LnL3 complexes showing field induced SMM behaviour with low thermal eneygy barriers, when a tridentate N3‐phenanthroline tetrazolate ligand (L) is substituted by a β‐diketonate ligand (L’), Ueff increases significantly allowing to these new LnL2L’ complexes to behave as SMMs at zero field. More information can be found in the Full Paper by J. M. Herrera et al. on page 14548 ff. [ABSTRACT FROM AUTHOR]

A dual‐cavity host, with six terminal alkynes at the periphery of its two fused cavitands, is obtained at the gram scale by following straightforward synthetic protocols. This structurally unique and multivalent cavitand can be efficiently clicked to carbohydrates, polymers, or small functional molecules. The stage is thus set for exploring the preparation of novel multivalent drugs and nanostructured soft materials. More information can be found in the Full Paper by J. D. Badjić et al. on page 1242. [ABSTRACT FROM AUTHOR]

Combining biocatalytic oxidation with protective‐group chemistry enables one to modulate the site of oxidation. Lead compounds protected with different solubilizing biomimetic docking/protecting groups yield different hydroxylated derivatives with the same P450BM3‐mutant. Additional hydroxylation products are obtained when the P450BM3‐mutant is also varied. Derivatives of this type are difficult to obtain otherwise. Additionally, molecular‐dynamic simulations help to rationalize the observed oxidation patterns. For more information, see the Full Paper by U. E. W. Lange et al. on page 17936 ff. [ABSTRACT FROM AUTHOR]

Is S2N2 aromatic? According to off‐nucleus shielding calculations reported here, S2N2 is the first example of an inorganic ring showing substantial changes in aromaticity upon transition from the aromatic ground state to either the strongly antiaromatic and unstable first singlet excited, or the antiaromatic lowest triplet electronic states. More information can be found in the Full Paper by P. B. Karadakov et al. on page 16803. [ABSTRACT FROM AUTHOR]

[(BDI)Mg+][B(C6F5)4−] (1; BDI=CH[C(CH3)NDipp]2; Dipp=2,6‐diisopropylphenyl) was prepared by reaction of (BDI)MgnPr with [Ph3C+][B(C6F5)4−]. Addition of 3‐hexyne gave [(BDI)Mg+⋅(EtC≡CEt)][B(C6F5)4−]. Single‐crystal X‐ray analysis, NMR investigations, Raman spectra, and DFT calculations indicate a significant Mg‐alkyne interaction. Addition of the terminal alkynes PhC≡CH or Me3SiC≡CH led to alkyne deprotonation by the BDI ligand to give [(BDI‐H)Mg+(C≡CPh)]2⋅2 [B(C6F5)4−] (2, 70 %) and [(BDI‐H)Mg+(C≡CSiMe3)]2⋅2 [B(C6F5)4−] (3, 63 %). Addition of internal alkynes PhC≡CPh or PhC≡CMe led to [4+2] cycloadditions with the BDI ligand to give {Mg+C(Ph)=C(Ph)C[C(Me)=NDipp]2}2⋅ 2 [B(C6F5)4−] (4, 53 %) and {Mg+C(Ph)=C(Me)C[C(Me)=NDipp]2}2⋅2 [B(C6F5)4−] (5, 73 %), in which the Mg center is N,N,C‐chelated. The (BDI)Mg+ cation can be viewed as an intramolecular frustrated Lewis pair (FLP) with a Lewis acidic site (Mg) and a Lewis (or Brønsted) basic site (BDI). Reaction of [(BDI)Mg+][B(C6F5)4−] (1) with a range of phosphines varying in bulk and donor strength generated [(BDI)Mg+⋅PPh3][B(C6F5)4−] (6), [(BDI)Mg+⋅PCy3][B(C6F5)4−] (7), and [(BDI)Mg+⋅ PtBu3][B(C6F5)4−] (8). The bulkier phosphine PMes3 (Mes=mesityl) did not show any interaction. Combinations of [(BDI)Mg+][B(C6F5)4−] and phosphines did not result in addition to the triple bond in 3‐hexyne, but during the screening process it was discovered that the cationic magnesium complex catalyzes the hydrophosphination of PhC≡CH with HPPh2, for which an FLP‐type mechanism is tentatively proposed. Reactions of a strong Mg Lewis acid: (BDI)Mg+‐alkyne reactivity has been extensively investigated. Depending on the alkyne, it can follow pathways of (i) coordination, (ii) deprotonation, or (iii) cycloaddition. Since (BDI)Mg+ may have potential as a strong Lewis acid in frustrated Lewis pair (FLP) chemistry, its interactions with a variety of phosphines have been studied in detail. The possibility of alkyne activation by (BDI)Mg+/phosphine combinations has also been explored (BDI=CH[C(CH3)NDipp]2; Dipp=2,6‐diisopropylphenyl). [ABSTRACT FROM AUTHOR]

The kinetics of water oxidation by K2FeO4 has been reinvestigated by UV/Vis spectrophotometry from pH 7–9 in 0.2 m phosphate buffer. The rate of reaction was found to be second‐order in both [FeO42−] and [H+]. These results are consistent with a proposed mechanism in which the first step involves the initial equilibrium protonation of FeO42− to give FeO3(OH)−, which then undergoes rate‐limiting O−O bond formation. Analysis of the O2 isotopic composition for the reaction in H218O suggests that the predominant pathway for water oxidation by ferrate is intramolecular O−O coupling. DFT calculations have also been performed, which support the proposed mechanism. Reaction mechanism: Water oxidation by K2FeO4 at pH 7–9 in phosphate buffer is proposed to occur by initial condensation of two FeO3(OH)− anions to generate the diferrate anion Fe2O72−, which then releases O2 by intramolecular O−O coupling (see scheme). [ABSTRACT FROM AUTHOR]

From the reaction of manganese halides with the chiral Schiff bases obtained by condensation of o‐vanillin and (R)‐ or (S)‐phenylglycinol, 11 complexes based on pentanuclear cages with trigonal bipyramidal [MnIIMnIII3M′] (M′=NaI, CaII, MnII) or enneanuclear [MnIIMnIII6NaI2] cores were synthesized. Structural, supramolecular chirality, and optical properties were explored. The magnetic properties of related systems were reviewed, and the magnetic response of the new systems was rationalized to the bond parameters. Mirror, mirror: A family of chiral clusters with [MnIIMnIII3M′] or [MnIIMnIII6NaI2] cores (see figure) was obtained from enantiomerically pure Schiff bases. Structural characteristics, optical properties, and magnetic response were studied for these complexes. [ABSTRACT FROM AUTHOR]

Late‐stage functionalization of lead compounds is of high interest in drug discovery since it offers an easy access to metabolites and derivatives of a lead compound without the need to redesign an often long multistep synthesis. Owing to their high degree of chemoselectivity, biocatalytic transformations, enzymatic oxidations in particular, are potentially very powerful because they could allow the synthesis of less lipophilic derivatives of a lead compound. In the majority of cases, enzymatic oxidations have been used in an empirical way as their regioselectivity is difficult to predict. In this publication, the concept of using docking/protecting groups in a biomimetic fashion was investigated, which could help steer the regioselectivity of a P450BM3‐mediated oxidation. A novel set of docking/protecting groups was designed that can be cleaved under very mild conditions and address the often problematic aqueous solubility of the substrates. Vabicaserin was used as tool compound containing typical groups such as basic, aliphatic, and aromatic moieties. The results were rationalized with the help of in silico docking and molecular dynamic studies. Novel solubilizing docking‐protecting groups enable the regioselective P450BM3‐mutant mediated late‐stage oxidation of lead compounds by binding the substrate (orange) in a biomimetic fashion (e.g. palmitic acid, green). Enzymatic oxidation, mild deprotection and purification yields hydroxylated derivatives that are difficult to obtain by classical chemical synthesis. [ABSTRACT FROM AUTHOR]

A sulfur ‐ bridged inorganic macrocycle and a room temperature singlet biradicaloid dianion have been isolated in the Wurtz reduction of a mixture of cis ‐ and trans ‐ dichlorophosph(V)azane. It appears that these products from the same reaction are the outcome of two different reduction pathways. This approach may facilitate the discovery of new types of inorganic macrocycles and new polymeric assemblies similar to those observed in this work. More information can be found in the Full Paper by S. Singh, D. S. Wright et al. on page 12027 ff. [ABSTRACT FROM AUTHOR]

The stereochemistry of the addition of NH3 to the stereoisomers of 1,2‐di‐tert‐butyl‐1,2‐bis(2,4,6‐triisopropylphenyl)disilene (Z‐5 or E‐5) is 100 % stereospecific giving two isomeric disilylamines 6 and 7, respectively, derived from syn‐addition to the stereoisomeric disilenes. Variable time normalization analysis studies of the reaction of tetramesityldisilene (3) with isopropylamine (iPrNH2) revealed that the order in both amine and disilene is 1. The kinetic isotope effect for the addition of iPrNH2/iPrND2 to tetramesityldisilene was determined to be 3.04±0.06 at 298 K, a primary KIE, indicating that the proton is transferred in the rate determining step. Competition studies between the addition of PrNH2 and iPrNH2 to tetramesityldisilene resulted in the exclusive formation of the PrNH2 adduct consistent with a nucleophilic addition. Computational studies of the mechanism of the addition of ammonia to E‐5 revealed the lowest energy pathway involves the formation of the donor adduct derived from syn‐addition, followed by intramolecular syn‐transfer of the proton. The formation of the donor adduct is the rate determining step. The results of this study, together with previous studies on the addition of ammonia and amines to disilenes, allow for a refinement of our understanding of the mechanism of this important fundamental reaction in disilene chemistry, and allow us to understand our ability to reliably predict the stereochemical outcomes of future NH σ‐bond activation reactions. [ABSTRACT FROM AUTHOR]

The reversal of selectivity in the addition of N ‐ methylpyrrole versus N ‐ methyl indole to an iminium ion reported in this study is due to directing interactions of the catalyst framework with N ‐ methylindole. The Nautilus half in the background illustrates the notion of chirality. For more details, see the Full Paper by R. Gilmour et al. on page 10031 ff. [ABSTRACT FROM AUTHOR]

Raman spectroscopy and powder X ‐ ray diffraction probe the mechanochemical reaction in tandem and in situ, each providing complementary information on the reaction course and insight into reaction mechanism. Both can quantitatively evaluate reaction profiles, and Raman spectroscopy—even in situations when powder diffraction fails. This cover art was made by Perica Matijević, academy ‐ trained sculptor. It represents a glimpse to the dark side of the reaction vessel enabled by the two techniques used in tandem. More information can be found in the Full Paper by K. Užarević, I. Halasz et al. on page 13941. [ABSTRACT FROM AUTHOR]

Abstract: Silicon complexes of corrole were obtained for the first time by reaction of the free‐base corrole with hexachlorodisilane. The peripheral substituents of corrole strongly influence the nature of the reaction products: β‐octaalkyl corrole was mainly isolated as the μ‐oxo dimer, while a hydroxo complex was obtained in the case of 5,10,15‐tris‐(pentafluorophenyl)corrole. In the case of meso‐tritolyl corrole, a mixture of monomer/μ‐oxo dimer was obtained. The silicon corrole complexes are more stable toward hydrolysis than the corresponding porphyrin derivatives and are endowed with brilliant luminescence properties. The high affinity of silicon for fluoride ion allowed investigation of the ability of an Si corrole to serve as a sensor for F− detection. The strong color variation due to the interaction with the halide ion makes the Si corrole an interesting material for the naked‐eye detection of inorganic fluoride. [ABSTRACT FROM AUTHOR]

Abstract: Ammonia decomposition is an important technology for extracting hydrogen from ammonia toward the realization of a hydrogen economy. Herein, it is reported that large oblate hemispheroidal Ru particles on Ca(NH2)2 function as efficient catalysts for ammonia decomposition. The turnover frequency of Ru/Ca(NH2)2 increased by two orders of magnitude when the Ru particle size was increased from 1.5 to 8.4 nm. More than 90 % ammonia decomposition was achieved over Ru/Ca(NH2)2 with large oblate hemispheroidal Ru particles at 360 °C, which is comparable to that of alkali‐promoted Ru catalysts with small Ru particle sizes. XAFS analyses revealed that Ru particles are immobilized on Ca(NH2)2 by Ru−N bonds formed at the metal/support interface, which lead to oblate hemispheroidal Ru particles. Such a strong metal–support interaction in Ru/Ca(NH2)2 is also substantiated by DFT calculations. The high activity of Ru/Ca(NH2)2 with large Ru particles primarily originates from the shape and appropriate size of the Ru particles with a high density of active sites rather than the electron‐donating ability of Ca(NH2)2. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of [(Cp′′′Co)2(μ,η2:2‐As2)2] with the decamethylsamarocenes [Cp*2Sm(THF)2] or [Cp*2Sm], or the bis(tetramethyl‐n‐propyl)samarocene [(C5Me4(n‐propyl))2Sm] resulted in the mixed d/f polyarsenides [(Cp′′′Co)2As4Sm(η5‐C5Me4R)2] (R=Me, n‐propyl). They are the first structural representatives of open chain‐like polyarsenides as ligands in the coordination sphere of lanthanides. Their formation can be explained by an intramolecular As–As coupling within the cobalt polyarsenide complex after reduction by the divalent samarium complex. Density functional theory calculations give insight into the structural change of the (As2)2 unit in [{Cp′′′Co(μ,η2:2‐As2)}2] upon reduction. [ABSTRACT FROM AUTHOR]

Abstract: The complex trans‐[Pt(F)(SF3)(PCy3)2] (1) shows a diverse reactivity pattern at the SF3 ligand towards ethanol and Me3SiOEt. This led by deoxyfluorination or alcoholysis to the generation of platinum complexes bearing a metal‐bound S(O)F or S(OEt)2 group. For the latter reaction trans‐[Pt(F){S(F)(OEt)2}(PCy3)2] is suggested as an intermediate. In reactivity studies of trans‐[Pt(F)(SF2)(PCy3)2][BF4] the complex [Pt(F){S(F)(OEt)}(PCy3)2][BF4] was prepared, which does not react with ethanol. [ABSTRACT FROM AUTHOR]

Abstract: Three hetero‐biradical derivatives, with the structure of a back‐to‐back connected benzotriazinyl and tetramethyl or tetraethylisoindoline N‐oxyl sharing a common benzo ring, 3‐tert‐butyl‐1‐phenyl‐1,4,6,8‐tetrahydro‐6,6,8,8‐tetramethyl‐pyrrolo[4,5‐g]‐1,2,4‐benzotriazin‐4‐yl‐7‐oxyl (1‐tBu), 1,3‐diphenyl‐1,4,6,8‐tetrahydro‐6,6,8,8‐tetramethyl‐pyrrolo[4,5‐g]‐1,2,4‐benzotriazin‐4‐yl‐7‐oxyl (1‐Ph), and 3‐tert‐butyl‐1‐phenyl‐1,4,6,8‐tetrahydro‐6,6,8,8‐tetraethyl‐pyrrolo[4,5‐g]‐1,2,4‐benzotriazin‐4‐yl‐7‐oxyl (2‐tBu), were synthesized and characterized by single‐crystal X‐ray analyses, variable‐temperature magnetic susceptibility studies, and DFT calculations. Temperature dependences of the magnetic susceptibilities of 1‐tBu, 1‐Ph, and 2‐tBu exhibit broad maxima at 70, 71, and 43 K, respectively. Although these radical derivatives form a columnar or chained assembly in the solid state, magnetic measurements of diluted samples in the polymer matrices and computational results imply that the magnetic properties of the polycrystalline sample can be explained by a two‐spin system with an intramolecular antiferromagnetic interaction. The magnetic behavior can be reproduced by using the Bleaney–Bowers model, with 2J=−80.0 cm−1 for 1‐tBu, 2J=−77.1 cm−1 for 1‐Ph, and 2J=−48.9 cm−1 for 2‐tBu. The moderately strong intramolecular antiferromagnetic interactions can be interpreted by a through‐bond interaction through the nonconjugated framework and/or through‐space interactions based on molecular orbital theory. The strong distance dependency between the N−O spin site and vinylic carbon atoms indicates that the orbital interaction plays an important role in the intramolecular magnetic interaction. The reduced magnetic interaction in 2‐tBu relative to those of 1‐tBu and 1‐Ph can be attributed to restricted rotation of the tetraethyl group. [ABSTRACT FROM AUTHOR]

Abstract: A catalytic [1,3] O‐to‐C rearrangement from enyne‐ethers was developed for the rapid synthesis of diverse bridged bicyclic systems. In this reaction, a vinyl oxonium intermediate, generated in situ from enyne‐ether, was the precursor for the [1,3] O‐to‐C rearrangement. This versatile protocol represents the first example of catalytic [1,3] O‐to‐C rearrangement based on ring‐expansion strategy, enabling efficient access to bridged bicyclic scaffolds. [ABSTRACT FROM AUTHOR]

The design of Si-(B)-C materials is investigated, with detailed insight into the precursor chemistry and processing, the precursor-to-ceramic transformation, and the ceramic microstructural evolution at high temperatures. In the early stage of the process, the reaction between allylhydridopolycarbosilane (AHPCS) and borane dimethyl sulfide is achieved. This is investigated in detail through solid-state NMR and FTIR spectroscopy and elemental analyses for Si/B ratios ranging from 200 to 30. Boron-based bridges linking AHPCS monomeric fragments act as crosslinking units, extending the processability range of AHPCS and suppressing the distillation of oligomeric fragments during the low-temperature pyrolysis regime. Polymers with low boron contents display appropriate requirements for facile processing in solution, leading to the design of monoliths with hierarchical porosity, significant pore volume, and high specific surface area after pyrolysis. Polymers with high boron contents are more appropriate for the preparation of dense ceramics through direct solid shaping and pyrolysis. We provide a comprehensive study of the thermal decomposition mechanisms, and a subsequent detailed study of the high-temperature behavior of the ceramics produced at 1000 °C. The nanostructure and microstructure of the final SiC-based ceramics are intimately linked to the boron content of the polymers. B4C/C/SiC nanocomposites can be obtained from the polymer with the highest boron content. [ABSTRACT FROM AUTHOR]

Confinement of reactive chemical species uniquely affects chemical reactivity by restricting the physical space available and by restricting access to interactions with the solvent. In Nature, for example, confined protein binding pockets govern processes following photoisomerization reactions and the isomerizations themselves. Here we describe the first example of a dihydroazulene/vinylheptafulvene (DHA/VHF) photo-switch functioning in water, and we show how its switching behavior is strongly influenced by supramolecular interactions with a series of cucurbit[ n]uril (CB) host molecules. In CB7 inclusion complexes, the kinetics of the thermal VHF-to-DHA back-reaction is accelerated, while in CB8 inclusion complexes, the kinetics is slowed down as compared to the free photo-switch. The effect of the CB encapsulation of the photo-switch can be effectively canceled by introducing a guest that binds the CB more strongly. According to DFT calculations, a stabilization of the reactive s- cis VHF conformer relative to the s- trans VHF appears to be a contributing factor responsible for the accelerated back-reaction when encapsulated in CB7. [ABSTRACT FROM AUTHOR]

We report on the synthesis and structure, as well as on the mechanism of formation of the [Ge9−CH=CH−CH=CH−Ge9]6− unit. As shown by in situ NMR spectroscopy (1H, COSY, HSQC, HMBC), both (1 Z,3 Z)- and (1 E,3 Z)-[Ge9−CH=CH−CH=CH−Ge9]6− are formed during the reaction of a mixture of 1,4-bis(trimethylsilyl)butadiyne and A4Ge9 (A=K, Rb) with ethylenediamine. However, upon layering of the obtained solution with 222-crypt/toluene (222-crypt=4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo-[8.8.8]hexacosan) only the (1 Z,3 Z)-isomer crystallizes as {[A(222-crypt)]6[(1 Z,3 Z)-(Ge9−CH=CH−CH=CH−Ge9)]}(tol)2(en)2 (A=K, Rb) salts. Single crystals of these salts were characterized by X-ray structure analysis and Raman spectroscopy, indicating the presence of three superimposed conformers of (1 Z,3 Z)-[Ge9−CH=CH−CH=CH−Ge9]6−, which show different orientations of the cluster units with respect to the planar (1 Z,3 Z)-buta-1,3-dien-1,4-diyl linker unit. [ABSTRACT FROM AUTHOR]

Direct catalytic C−C bond-forming addition to N-unprotected ketimines is an efficient and straightforward method of synthesizing N-unprotected tetrasubstituted amines that eliminates prior protection/deprotection steps and allows facile transformation of the products. Despite its advantages, however, N-unprotected ketimines have difficulties in C−C bond-forming reactions, and only a limited number of reactions and substrates are reported compared with their N-protected counterparts. Herein we report that N-unprotected trifluoromethyl ketimines are effective for C−C bond-forming reactions using Mannich-type reactions as a model case. We demonstrate that Lewis acid catalysis was effective for promoting reactions with various N-unprotected trifluoromethyl ketimines, and thiourea organocatalysis was effective for promoting highly enantioselective reactions with various carbonyl nucleophiles, providing direct access to various N-unprotected α- and/or β-tetrasubstituted amino acid esters. Furthermore, direct construction of vicinal tetrasubstituted chiral carbon stereocenters was achieved for the first time in a highly enantio- and diastereoselective manner. These results demonstrate the potential of N-unprotected ketimines as substrates applicable to many other addition reactions. [ABSTRACT FROM AUTHOR]

Multicomponent porous colloidal spheres are of interest because they not only show a combination of the properties associated with all different components, but also usually present synergy effects. However, a combination of different components in a single porous sphere is still greatly challenged due to the different precipitation behaviors of each component. In this work, we have developed a general synthetic route to prepare several categories of porous monodisperse rare-earth (RE)-based colloidal spheres with customizable elemental compositions and a uniform element distribution. The two-step synthetic strategy is based on the integration of coordination chemistry precipitation of RE ions and a subsequent ion-exchange process, which steers clear of obstacles, such as differences in solubility product constant, that are to be found in traditional co-precipitation methods. Our approach provides a new mixing mechanism to realize homogeneous distribution of each element within the porous spheres. An array of binary, ternary, and even senary RE colloidal porous spheres with diameters of 500 nm to 700 nm has been successfully synthesized. Taking advantage of their good dispersibility, porosity, and customizable components, these porous RE oxide spheres show excellent catalytic activity for the reduction of 4-nitrophenol, and promising application in single-phase multifunctional bioprobes. [ABSTRACT FROM AUTHOR]

A detailed analysis of the C(sp3)−H activation process by vinylidene AuI complexes is described based on an intrinsic bond orbital analysis. Based on our analysis this event can be divided into three phases: (i) hydride transfer, (ii) C−C bond formation, and (iii) σ to π rearrangement of the lone pair coordinated to Au. Small perturbations of the system lead to either a concerted asynchronous reaction, or a stepwise reaction featuring an intermediate with a C-H-C three-centre two-electron (3c-2e) bond. The role of π-donating substituents is highlighted and provides a way of controlling reactions of this type in future experimental studies. [ABSTRACT FROM AUTHOR]

The structure solution, prediction, and targeted synthesis of a family of embedded isoreticular zeolites (EIZs) with expanding structural complexity, denoted the RHO family, were reported recently. Here, the naming and building rules of body-centered cubic EIZs with the lta cage as the lattice point are presented. The rearrangement of a pair of pau and d8r cages between two lta cages and its repetitive insertion, combined with the strong reflections and fragment methods, allows the creation of three other new zeolite families, designated the HPO, RHO(b), and KFI families. Among them, the KFI family is found to be the only EIZ family, on the basis of the similarity of structure factor amplitudes and phases of strong reflections, that is, structural coding, within its family members. The structural credibility of this family is confirmed by both local interatomic distances and T−T−T angle analyses. The existence of tetragonal EIZ families is also demonstrated. The overall results provide useful insights into the prediction of unprecedented EIZ families. [ABSTRACT FROM AUTHOR]

The oxidative dissolution of citrate-capped silver nanoparticles (AgNPs, ∼50 nm diameter) is investigated herein by two electrochemical techniques: nano-impacts and anodic stripping voltammetry. Nano-impacts or single nanoparticle-electrode collisions allow the detection of individual nanoparticles. The technique offers an advantage over surface-immobilized methods such as anodic stripping voltammetry as it eliminates the effects of particle agglomeration/aggregation. The electrochemical studies are performed in different electrolytes (KNO3, KCl, KBr and KI) at varied concentrations (≤20 m m). In nano-impact measurements, the AgNP undergoes complete oxidation upon impact at a suitably potentiostated electrode. The frequency of the nanoparticle-electrode collisions observed as current-transient spikes depends on the electrolyte identity, its concentration and the potential applied at the working electrode. The frequencies of the spikes are significantly higher in the presence of halide ions and increase with increasing potentials. From the frequency, the rate of AgNP oxidation as compared with the timescale the AgNP is in electrical contact with the electrode can be inferred, and hence is indicative of the relative kinetics of the oxidation process. Primarily based on these results, we propose the initial formation of the silver (I) nucleus (Ag+, AgCl, AgBr or AgI) as the rate-determining process of silver oxidation on the nanoparticle. [ABSTRACT FROM AUTHOR]

A totally unanticipated regio- and stereoisomerically pure C2h-symmetric trans-1-(bis-pyrrolidine)-tetra-malonate hexa -adduct of C60 was obtained via a topologically controlled method, followed by a 1,3-dipolar cycloaddition reaction. The structures of the products were elucidated by 1H and 13C NMR and by X-ray crystallography. The unexpected regio- and stereoselectivity observed, supported by theoretical calculations, was found to be a consequence of malonate-pyrrolidine interactions. [ABSTRACT FROM AUTHOR]

A discrete tetragonal tube-shaped complex ( MT-1) has been synthesised by coordination-driven self-assembly of a carbazole-based tetraimidazole donor L and a Pd(II) 90° acceptor, that is, [ cis-(dppf)Pd(OTf)2] (dppf=diphenylphosphinoferrocene, OTf=CF3SO3−). Complex MT-1 was characterised by multinuclear NMR, ESI-MS and single-crystal X-ray diffraction analysis (SCXRD), which showed its symmetrical tetrafacial tube-shaped architecture possessing a large cavity described by four aromatic walls. This coordination cage was successfully utilised as a molecular vessel to perform intramolecular cycloaddition reactions of O-allylated benzylidinebarbituric acid derivatives inside its confined nanospace. The presence of a catalytic amount of MT-1 promoted [4+2] cycloaddition reactions in a regio- and stereoselective manner, yielding the corresponding penta/tetracyclouracil derivatives in good yields under mild reaction conditions. This protocol is interesting compared with the literature reports for the synthesis of similar chromenopyran pyrimidinedione derivatives under high-temperature reflux conditions or solid-state melt reactions (SSMRs). [ABSTRACT FROM AUTHOR]

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Organophosphate-degrading enzyme from Agrobacterium radiobacter P230 exhibits promiscuity, not only in the reactions it catalyzes, but also in the metals it uses to catalyze those reactions. Here, three different binuclear metal centers were studied: di-CdII, di-MnII and ZnII-FeII. This enzyme uses these metal centers for hydrolyzing trimethyl- and dimethyl-phosphates. Both mechanisms were studied at DFT level of theory using a cluster model approach. The ground spin state was determined for each enzyme. The outcomes confirmed that the hydrolysis of phosphotriester is faster than that of phosphodiester and in some case the phosphodiesterase reaction does not occur. The computed activation energies are in agreement with previous experimental results for phosphotriesterase enzymes. [ABSTRACT FROM AUTHOR]

2-Pyrrolines and 6-oxo-hexa-2,4-dienals have been prepared through the divergent reactions of 1-benzenesulfonyl-4-aryl-1,2,3-triazoles with functionalized allenes. The rhodium-catalyzed reactions between allenols and 1-benzenesulfonyl-4-aryl-1,2,3-triazoles yielded 2-pyrrolines. This transformation is compatible with the presence of aliphatic, aromatic, heterocyclic, amide, and halogen functional groups. Interestingly, a reactivity switch took place when the allene-tethered alcohol substrate was replaced by its ketone counterpart. When the rhodium-catalyzed reaction of 1-benzenesulfonyl-4-phenyl-1,2,3-triazole was performed with allenones, acyclic 6-oxo-hexa-2,4-dienals were stereoselectively formed as (2 Z,4 E) isomers. [ABSTRACT FROM AUTHOR]

A combined experimental and theoretical study of the high-temperature reaction of SiCl4 and elemental silicon is presented. The nature and reactivity of the product formed upon rapid cooling of the gaseous reaction mixture is investigated by comparison with the defined model compounds cyclo-Si5Cl10, n-Si5Cl12 and n-Si4Cl10. A DFT assessment provides mechanistic insight into the oligosilane formation. Experimental 29Si NMR investigations, supported by quantum-chemical 29Si NMR calculations, consistently show that the reaction product is composed of discrete molecular perchlorinated oligosilanes. Low-temperature chlorination is an unexpectedly selective means for the transformation of cyclosilanes to acyclic species by endocyclic Si−Si bond cleavage, and we provide a mechanistic rationalization for this observation. In contrast to the raw material, the product obtained after low-temperature chlorination represents an efficient source of neo-Si5Cl12 or the amine-stabilized disilene EtMe2N ⋅SiCl2Si(SiCl3)2 through reaction with aliphatic amines. [ABSTRACT FROM AUTHOR]