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The syntheses and characterizations of heptagon-embedded polycyclic aromatic compounds are essential for understanding the effect of negative curvature on carbon allotropes such as fullerene and graphene that have applications in functional organic materials. However, owing to the synthetic difficulties in functionalizing and embedding 7-membered rings, these strain-challenged structures are relatively unexplored. We report here the synthesis and photophysical characterization of a triarylamine core bridged with ethane chains at the 2,2’-positions. In doing so, we provide access to the first heterocycle containing three fused heptagon rings with a nitrogen at its core (BATA-NHAc). DFT calculations and X-ray crystallography reveal a remarkably strained structure wherein two of the bridged aryl units approach coplanarity, whilst the third ring is twisted out of plane. The unique conformation of BATA-NHAc results in distinctive photophysical and electrochemical properties that open new avenues in understanding the structure-property relationships of curved π-aromatics and the construction of π-frameworks of increasing complexion.

Three polynuclear organotin(IV) derivatives of composition [n-Bu3Sn(HL)]n 1, [Ph3Sn(HL)]n 2 and [n-Bu2Sn(HL)2]2 3 were synthesized by reacting 2-((E)-(4-hydroxy-3-((E)-((4-(methoxycarbonyl)phenyl)imino)methyl)phenyl)diazenyl)benzoic acid (H′HL) with (n-Bu3Sn)2O, Ph3SnOH and n-Bu2SnO, respectively. The structures 1–3 were fully characterized by elemental analysis, IR and NMR (1H, 13C, and 119Sn), 119Sn Mössbauer spectroscopy, and additionally, the molecular and crystal structures of 1–3 and its pro-ligand (H′HL) were established by single-crystal X-ray diffraction analysis. The tributyltin(IV) complex 1 is a one-dimensional coordination polymer, in which the azo ligand bridges adjacent Sn(IV) centres solely via the two carboxylate O-atoms. The hydroxy H atom forms an intramolecular O–H···N hydrogen bond with the imine N-atom, as observed in the crystal structure of H′ΗL. The triphenyltin(IV) complex 2 is also a one-dimensional coordination polymer, but in this case the azo ligand bridges adjacent Sn(IV) centres via its carboxylate group and the deprotonated phenol O-atom. Unlike in 1, the phenol H-atom has migrated to the imine N-atom, to give a zwitterionic form of the azo ligand. The tin centers in 1 and 2 are pentacoordinated and reveal a distorted trans-R3SnO2 trigonal-bipyramidal environment. The dibutyltin(IV) complex 3 crystallizes as discrete centrosymmetric dinuclear entities where the unique Sn(IV) center is heptacoordinated in a distorted pentagonal bipyramid coordination geometry. In vitro cytotoxicity studies of compound 1 was performed and compared with 2 across a panel of human tumor cell lines, viz., A498, EVSA-T, H226, IGROV, M19 MEL, MCF-7 and WIDR and the results were compared with the data of six clinically used anticancer drugs. Compounds 1 and 2 are potent cytotoxic agents and warrant further investigation as potential anticancer agents.

Pyridazines are important scaffolds for medicinal chemistry or crop protection agents, yet the selective preparation of 3-bromo-pyridazines with high regiocontrol remains difficult. We achieved the Lewis acid-mediated inverse electron demand Diels-Alder reaction between 3-monosubstituted s-tetrazine and silyl enol ethers and obtained functionalized pyridazines. In the case of 1-monosubstituted silyl enol ethers, exclusive regioselectivity was observed. Downstream functionalization of the resulting 3-bromo-pyridazines was demonstrated utilizing several cross-coupling protocols to synthesize 3,4-disubstituted pyridazines with excellent control over the substitution pattern.

Nine xanthone derivatives (1-9) were isolated from the roots of Polygala azizsancarii, which is a narrow endemic species for the flora of Türkiye. Based on all of the evidence, the structures of 1-9 were established as two previously undescribed xanthone O-glucosides, 3-O-β-D-glucopyranosyloxy-1,6-dihydroxy-2,5,7-trimethoxyxanthone (1), 3-O-β-D-glucopyranosyloxy-1,6-dihydroxy-2,7-dimethoxyxanthone (2), and seven previously described xanthones, 1,3,6-trihydroxy-2,5,7-trimethoxyxanthone (3), 1,3,6-trihydroxy-2,7-dimethoxyxanthone (4), 1,2,3,4,7-pentamethoxyxanthone (5), 1,3-dihydroxy-2,5,6,7-tetramethoxyxanthone (6), 1,3-dihydroxy-4,7-dimethoxyxanthone (7), 1,7-dihydroxy-3-methoxyxanthone (8), and 1,7-dihydroxy-2,3-methylenedioxyxanthone (9). The structures of the compounds were determined by spectroscopic methods, including 1D-NMR (

A fast and mild method for the Pd-catalyzed cross-coupling reaction of monosubstituted 3-bromo-1,2,4,5-tetrazine is presented. Investigation of silver-based additives revealed that Ag2CO3 is the optimal mediator, enabling the process without the need for strong bases or high temperatures. Electronic modification of the classical 1,1′- bis(diphenylphosphine)ferrocene (dppf) ligand proved to be a powerful strategy in tailoring the catalytic system to the requirements set by the process. Under the optimized conditions a scope comprising a variety of alkyl-, heteroatom-, and halide substituted aryl- and heteroaryl-tetrazines were prepared in good to excellent yields (29 examples, up to 87% yield). This method constitutes the first example of a direct cross-coupling reaction of monosubstituted tetrazines.

The electronic properties of transition-metal oxides with highly correlated electrons are of central importance in modern condensed matter physics and chemistry, both for their fundamental scientific interest, and for their potential for advanced electronic applications. The design of materials with tailored properties has been, however, restricted by the limited understanding of their structure-property relationships, which are particularly complex in the proximity of the regime where localized electrons become gradually mobile. RENiO3 perovskites, characterized by the presence of spontaneous metal to insulator transitions, are one of the most widely used model materials for the investigation of this region in theoretical studies. However, crucial experimental information needed to validate theoretical predictions is still lacking due to their challenging high-pressure synthesis, which has prevented to date the growth of sizable bulk single crystals with RE different than La, Pr and Nd. Here we report the first successful growth of single crystals with RE = Nd, Sm, Gd, Dy, Y, Ho, Er and Lu and sizes up to ~75 {\mu}m, grown from molten salts in temperature gradient under 2000 bar oxygen gas pressure. The crystals display regular prismatic shapes with flat facets, and their crystal structures, metal-insulator and antiferromagnetic order transition temperatures are in excellent agreement with previously reported values obtained from polycrystalline samples. The availability of such crystals opens access to measurements that have hitherto been impossible to conduct. This should contribute to a better understanding of the fascinating properties of materials with highly correlated electrons, and guide future efforts to engineer transition metal oxides with tailored functional properties., Comment: 12 pages, 8 figures, accepted by Crystal Growth & Design. The SI is available at https://pubs.acs.org/doi/10.1021/acs.cgd.1c00474

A concise route toward two advanced fragments in the context of the total synthesis of the unique natural product azamerone is reported. Key synthetic features include the enantioselective synthesis of an epoxysilane and its Lewis-acid-induced cyclization and the installation of the pyridazine ring via a formylation/condensation sequence. This route provides strategic insights into the chemistry of phthalazinediols, facilitating synthetic approaches toward this class of natural products.

Peraryl-X-onium ions of nitrogen and oxygen constitute an underexploited class of organoionic species. Comparison of the syntheses of these onium salts by silyl-cation-promoted C–F activation and diazonium decomposition supports the idea that both methods share a common type of reactive intermediate. Onium ions with carboranyl counterions allowed X-ray crystallographic characterization of these salts. B97-D/Def2-TZVPP(chloroform) computational studies predicted the atropisomerism in oxonium salts analogous to that of substituted biaryls. Ion pairing of racemic atropisomeric oxonium and spirotetraarylammonium ions with enantiopure BINPHAT and BINOL allowed NMR spectral assignment of each diastereomer.

The molecular structures of five diorganotin(IV) carboxylates, (I)–(V), can be categorized into two main well-known structural types for such Sn complexes. One is the mononuclear dialkytin(IV) carboxylates with an [R2Sn(LH)2]-type skew-trapezoidal bipyramid, where the alkyl ligands are in pseudo-axial positions and the O atoms from two asymmetrically coordinated bidentate carboxylate ligands are in the equatorial plane. This structure type is adopted by dibutylbis{(E)-2-hydroxy-5-[(3-methylphenyl)diazenyl]benzoato}tin(IV) cyclohexane hemisolvate, [Sn(C4H9)2(C14H11N2O3)2]·0.5C6H12, (I), dibenzylbis{(E)-5-[(4-bromophenyl)diazenyl]-2-hydroxybenzoato}tin(IV), [Sn(C7H7)2(C13H8BrN2O3)2], (II), and aquadibenzylbis(4-{(E)-[(Z)-4-hydroxypent-3-en-2-ylidene]amino}benzoato)tin(IV) benzene disolvate, [Sn(C7H7)2(C12H12NO3)2(H2O)]·2C6H6, (III), although the latter has an additional water ligand to give a distorted pentagonal bipyramidal coordination geometry in which the carboxylate groups are more symmetrically coordinated to the Sn atom than in (I) and (II). The other structure motif is that of the tetranuclear bis(dicarboxylatotetraorganodistannoxanes), {[R2Sn(LH)]2O}2, which contain an Sn4O2 core decorated with four bridging carboxylate ligands, plus two alkyl ligands at each SnIV centre. The complexes octabutyltetrakis{μ-(E)-4-[(4-hydroxy-3,5-dimethylphenyl)diazenyl]benzoato}di-μ3-oxido-tetratin(IV) ethanol disolvate, [Sn4(C4H9)8(C15H13N2O3)4O2]·2C2H6O, (IV), and octabutyltetrakis{(E)-3-[(2-hydroxybenzylidene)amino]propanoato}di-μ3-oxido-tetratin(IV), [Sn4(C4H9)8(C10H10NO3)4O2], (V), display this motif. The structures obtained correlate with the 1:1 and 1:2 stoichiometric ratios of the dialkyltin(IV) and carboxylic acid starting materials in the syntheses. The supramolecular structures arising from consideration of secondary Sn...O interactions and/or classic hydrogen bonds include discrete molecules for (V), centrosymmetric dimers for (I), extended chains for (II) and (III), and sheets for (IV).

The nucleophilic addition to nitrogen in 3-monosubstituted s-tetrazines under mild conditions is reported, by using silyl-enol ethers as the nucleophiles and mediated by BF3. The preference for this azaphilic addition over the usually observed inverse electron demand Diels-Alder reactions was determined experimentally and evaluated theoretically. In this regard, the influence of the effect of BF3-coordination to s-tetrazines was investigated thoroughly. The substrate dependency of this unusual reaction was rationalized by determination of the activation barriers and on the basis of the activation strain model by employing density functional theory. Lastly, the decomposition of the unstable adducts was examined and an interesting rearrangement to a triazine derived structure was observed.

Nine known com­pounds have been isolated from Combretum glutinosum leaves, including flavonoids and triterpenes. The crystal structures of umuhengerin and (20S,24R)-ocotillone are reported for the first time; the latter structure confirms the absolute configuration. The crude extracts and the isolated com­pounds were tested for their anthelmintic activity on the larvae and adult worms of Haemonchus contortus. The best activity on both stages of the parasite was obtained with the flavonoids., A chemical study of the hydro-ethanol extract of the leaves of Combretum glutinosum resulted in the isolation of nine com­pounds, including 5-de­methyl­sin­en­se­tin (1), umuhengerin (2), (20S,24R)-ocotillone (3), lupeol (4), β-sitosterol (5), oleanolic acid (6), betulinic acid (7), corymbosin (8) and β-sito­sterol glucoside (9). Four com­pounds have been isolated for the first time from the genus Combretum [viz. (1), (2), (3) and (8)]. The crystal structures of flavonoid (2), C20H20O8, Z′ = 2, and triterpene (3), C30H50O3, Z′ = 1, have been determined for the first time; the latter confirmed the absolute configuration of native (20S,24R)-ocotillone previously derived from the crystal structures of related derivatives. The mol­ecules of (3) are linked into supra­molecular chains by inter­molecular O—H⋯O hydrogen bonds. The crude extracts obtained by aqueous decoction and hydro-ethano­lic maceration, as well as the nine isolated com­pounds, were tested for their anthelmintic activity on the larvae and adult worms of Haemonchus contortus, a hematophage that causes parasitic disorders in small ruminants. The evaluated anthelmintic activity showed that the extracts at different doses, as well as all the com­pounds tested at 150 µg ml−1, inhibited the migration of the larvae and the motility of the adult worms of the parasite com­pared with the phosphate buffer solution negative reference control. The best activity was obtained with flavonoids (1), (2) and (8) on both stages of the parasite. The flavones that showed good activity can be used for the further development of other derivatives, which could increase the anthelmintic efficacy.

A new family of cationic, bidentate (P^N)gold(III) fluoride complexes has been prepared and a detailed characterization of the gold‐fluoride bond has been carried out. Our results correlate with the observed reactivity of the fluoro ligand, which undergoes facile exchange with both cyano and acetylene nucleophiles. The resulting (P^N)arylgold(III)C(sp) complexes have enabled the first study of reductive elimination on (P^N)gold(III) systems, which demonstrated that C(sp2)−C(sp) bond formation occurs at higher rates than those reported for analogous phosphine‐based monodentate systems.

In addition to two known ecdysteroids, 20-hydroxyecdysone and turkesterone, three previously undescribed stigmastane-type ecdysteroids were isolated from the underground parts of Rhaponticum acaule (L.) DC. by chromatographic techniques (CC, VLC, MPLC). The structures of the compounds were established by chemical (acetylation) and spectroscopic methods including UV, IR, HRMS, 1D-NMR: 1H-NMR, 13C-NMR, DEPT-135. and 2D-NMR: COSY, NOESY, HSQC, HMBC. Two compounds were isolated as an isomeric mixture and each of them was purified and converted to the corresponding acetylated derivative. Based on all of the evidence, the structures of three undescribed stigmastane-type ecdysteroids were established as 2β,3β,11α,20β,22α,24,28-heptahydroxy-6-oxo-stigmast-7-en-25,29-lactone and the cyclic 22,29-hemiacetals 22R and 22S stigmast-7-en-29-al,2β,3β,11α,20α,22,28-hexahydroxy-6-oxo, and the trivial names acaulesterone and rhapocasterones A and B are suggested, respectively. The structures and absolute configurations of 20-hydroxyecdysone and cyclic-22,29-hemiacetal-22R-stigmast-7-en-29-al,2β,3β,11α,20α,22,28-hexahydroxy-6-oxo were confirmed by X-ray crystal-structure analyses of their acetyl derivatives.

The crystal structures of six halobismuth(III) salts of variously substituted aminopyridinium cations display discrete mononuclear [BiCl6]3− and dinuclear [Bi2 X 10]4− anions (X = Cl or Br), and polymeric cis-double-halo-bridged [Bi nX 4 n ] n− anionic chains (X = Br or I). Bis(2-amino-3-ammoniopyridinium) hexachloridobismuth(III) chloride monohydrate, (C5H9N3)2[BiCl6]Cl·H2O, (1), contains discrete mononuclear [BiCl6]3− and chloride anions. Tetrakis(2-amino-3-methylpyridinium) di-μ-chlorido-bis[tetrachloridobismuth(III)], (C6H9N2)4[Bi2Cl10], (2), tetrakis(2-amino-3-methylpyridinium) di-μ-bromido-bis[tetrabromidobismuth(III)], (C6H9N2)4[Bi2Br10], (3), and bis(4-amino-3-ammoniopyridinium) di-μ-chlorido-bis[tetrachloridobismuth(III)] dihydrate, (C5H9N3)2[Bi2Cl10]·2H2O, (4), incorporate discrete [Bi2 X 10]4− anions (X = Cl or Br), while catena-poly[2,6-diaminopyridinium [[cis-diiodidobismuth(III)]-di-μ-iodido]], {(C5H8N3)[BiI4]} n , (5), and catena-poly[2,6-diaminopyridinium [[cis-dibromidobismuth(III)]-di-μ-bromido]], {(C5H7N2)[BiBr4]} n , (6), include [Bi nX 4 n ] n− anionic chains (X = Br or I). Structures (2) and (3) are isostructural, while that of (5) is a pseudomerohedral twin. There is no discernible correlation between the type of anionic species obtained and the cation or halide ligand used. The BiIII centres always have a slightly distorted octahedral geometry and there is a correlation between the Bi—X bond lengths and the number of classic N—H...X hydrogen bonds that the X ligand accepts, with a greater number of interactions corresponding with slightly longer Bi—X distances. The supramolecular networks formed by classic N—H...X hydrogen bonds include ladders, bilayers and three-dimensional frameworks.

We report experimental studies on the development of photoactivatable fluorophores for rapid, light-induced synthesis of protein conjugates. Proof-of-concept studies demonstrated that electronic excitation of photoactivatable BODIPY-ArN3 (1) in the presence of different proteins leads to efficient labeling in less than 10 min. After synthesis and isolation of the fluorescently tagged protein, photochemical conversion yields using human serum albumin and onartuzumab were 47 ± 7% and 42 ± 5%, respectively.

A series of tetrapeptide amides containing two aminoisobutyric acids (Aib) and two α-methylphenylalanine ((αMe)Phe) units were prepared through the ‘azirine/oxazolone method’. New 2-benzyl-2-methyl-2H-azirin-3- amines have been used for the selective introduction of (S)- and (R)-(αMe)Phe, respectively. The solid-state conformations of five tetrapeptide amides were determined by X-ray crystallography. In all cases, two β-turns stabilize 310-helical conformations and it was confirmed that, in contrast to proteinogenic amino acids, the configuration of (αMe)Phe does not determine the screw sense of the helix.

We report the synthesis and first characterisation of the novel chemical probe 3-bromotetrazine and establish its reactivity towards nucleophiles. This led to the synthesis of several novel classes of 3-monosubstituted s-tetrazines. A remarkable functional group selectivity is observed and is utilised to site-selectively functionalise different complex molecules. The stability of 3-bromotetrazine under the reaction conditions facilitated the development of a protocol for protein functionalisation, which enabled a “minimal”, bifunctional tetrazine unit as a bio-orthogonal handle for inverse electron demand Diels–Alder reactions. Additionally, a novel tetrazine-based chemical probe was developed and its application in the context of thiol-targeted natural product isolation and labelling of mammalian cells is demonstrated., 3-Bromotetrazine selectively labels small and macromolecules up to proteins and can then be used as a fluorophore or as a bio-orthogonal handle for downstream functionalisation.

A new molecular thermometric sensor based on the terbium(III) complex [C2mim][Tb(fod)4] (C2mim – 1-methyl-3-ethylimidazolium, fod− - tetrakis-6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate), doped with 0.015% of its europium(III) analogue (1, [C2mim][Tb(fod)4]0.99985:[C2mim][Eu(fod)4]0.00015), was prepared and its thermochromic behaviour evaluated from ambient temperature up to 75 °C, including in the physiological range (35–45 °C). It was found that the intensity ratio of the 5D4→7F5 (TbIII) and 5D0→7F2 (EuIII) transitions is correlated with temperature having three different linear regimes. Visual colorimetry allowed the evaluation of the temperature in different ranges from green at ambient temperature, to yellow and finally red at higher temperatures. The TbIII complex emission intensity is extremely sensitive to small temperature variations, particularly between 25 and 35 °C, were it reaches only 40% of the initial intensity. Confinement of the dopped TbIII tetrakis-complex in the organic polymeric matrix poly(methylmethacrylate) (PMMA) induced higher thermal stability in 1, together with a strong temperature dependence of the most intense emissive transition of the TbIII complexes. The photoluminescence quantum yield of polymer-lanthanide hybrid materials increased significantly compared with that of 1. Under 366 nm irradiation, the hybrid material presents a green colour at 25 °C that evolves to yellow at 30 °C and to a white tone at 35 °C.

International audience; Chiral corannulenes abound, but suffer generally from configurational lability associated with bowl-to-bowl inversion, [1] thus obviating questions of stereogenicity and stereoelement construction. [2] In contrast, peri-annulated cor-annulenes show greatly increased barriers for bowl-to-bowl inversion; specifically indenocorannulenes invert on a time scale too slow to observe by normal NMR methods and raise the possibility of creating chiral atropisomeric bowl-shaped aromatics. [3] Two methods for preparing indenocorannulene from simple 2-haloarylcorannulenes-silyl cation C-F activation , [4] and Pd-mediated C-Cl activation [5]-enable the synthesis of an array of such chiral atropisomeric indeno-corannulenes. [6] Resolution of the enantiomers by high-performance liquid chromatography over chiral support phases motivates the study of chiroptical properties, the assignment of absolute "Cartesian" configuration, and the assessment of configurational stability. [7] These studies bring into question any systematic assignment of nontrivial stereoelements (i.e. not the molecule in its entirety) and refute any assertion of congruence between "Cahn-Ingold-Prelog elements" and the physical or "Cartesian" basis of chirality. Theminimum-energystaticbowlformofindenocorannulene manifests bilateral (C s) symmetry. All of the hydrogen atoms are chirotopic (local symmetry C 1) and therefore replacement of any single hydrogen atom by a non-hydrogen atom lowers the symmetry of the molecule to C 1. This study focuses on chiral molecules resulting from substitutions to the indeno six-membered ring. Iodocorannulene couples efficiently with a variety of 2-haloarylboronic acids to provide the immediate synthetic precursors to indenocorannulenes 1 a-1 f (Scheme 1). Fluoro precursors were subjected to silyl cation C-F activation/ coupling, whereas chloro precursors underwent Pd-catalyzed C-Cl activation/coupling. Although both methods cleanly provide product, the yields for Pd-catalyzed C-Cl activation/ coupling are in general higher (80 % vs. 40 %, see the Supporting Information) and the reaction is less sensitive to moisture and oxygen. Indenocorannulenes in general embody useful photo-physical and electrochemical properties. Compared to cor-annulene with a first reduction potential of À2.49 V, the parent monoindenocorannulene has a first reduction potential of À2.06 V and azaindenocorannulene 1 f has a first reduction potential of À2.00 V. [8] Clearly the effect of introducing an indeno annulation (ca. 0.5 V) outweighs the modulating influence of simple substituents (< 0.1 V). Across the series, the optical spectra display absorption peaks around 270 nm and 300-350 nm, and one broad emission peak at about 580 nm (ca. 100 nm width at half-height). Quantum efficiencies are routinely observed to be less than 1 %. Indenocorannulenes are predicted to have high barriers and low rates for bowl inversion. [3] As such, one expects the products of the reactions described above, monosubstituted derivatives 1 a-1 f, to be nonfluxional racemic mixtures. HPLC over a chiral stationary phase effected the resolution of 1 a-1 f, specifically using (S,S)-WHELK-O1, Chirapak ID, (S,S)-WHELK-O1, Chirapak IE, Chirapak IG, and Chirapak IC, respectively (see the Supporting Information). Kinetic studies on the first-order decay of optical activity allowed determination of activation free energies for race-mization by bowl-to-bowl inversion (Table 1). The kinetics of enantiomerization were measured in ethanol at 78 8 8C. Rate constants of enantiomerization were determined assuming first-order decay of the optical activity during the early stages of the reaction. Half-lives of racemization were determined using the first-order rate constants. Scheme 1. Chiral indenocorannulenes prepared by C-F or C-Cl activation. DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene, DMA = dimethylaceta-mide, MW = microwave irradiation. Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.org/10.1002/anie.201801325.

Hybrid perovskite crystals with organic and inorganic structural components are able to combine desirable properties from both classes of materials. Electronic interactions between the anionic inorganic framework and functional organic cations (such as chromophores or semiconductors) can give rise to unusual photophysical properties. Cyanine dyes are a well known class of cationic organic dyes with high extinction coefficients and tunable absorption maxima all over the visible and near-infrared spectrum. Here we present the synthesis and characterization of an original 1D hybrid perovskite composed of NIR-absorbing cyanine cations and polyanionic lead halide chains. This first demonstration of a cyanine-perovskite hybrid material is paving the way to a new class of compounds with great potential for applications in photonic devices.

The title compound is the product of a new synthetic route towards tetra­aryl/hetaryl-substituted ethenes that reduces the occurrence of side-products. In the crystal, the mol­ecule is centrosymmetric and the cyclo­penta­dienyl rings are nearly coplanar and aligned slightly closer to a staggered conformation than to an eclipsed one., The title compound, [Fe2(C5H5)2(C20H14O2)], is the product of a new synthetic route towards tetra­aryl/hetaryl-substituted ethenes that reduces the occurrence of side-products. In the crystal, the mol­ecule is centrosymmetric and the cyclo­penta­dienyl (Cp) rings are nearly coplanar and aligned slightly closer to a staggered conformation than to an eclipsed one. The ethene plane is tilted by 32.40 (18)° with respect to that of the substituted Cp ring and by 63.19 (19)° with respect to that of the furan ring. C—H⋯π inter­actions link the mol­ecules into a three-dimensional supramolecular framework.

The first stable gold(III) formate and experimental evidence for its β-hydride elimination are described. A catalytic dehydrogenation of formic acid together with mechanistic studies shed light on potential pathways operating in fundamental gold-catalyzed transformations.

The in situ generated nitrilimines are trapped efficiently with heteroaryl thioketones bearing thiophen-2-yl or selenophen-2-yl substituents. The exclusive products observed in these reactions are 2,3-dihydro-1,3,4-thiadiazoles formed via regioselective [3+2]-cycloaddition. Competitive head-to-tail dimerization of the intermediate 1,3-dipoles was not observed in any of the studied reactions.

A series of hetaryl-substituted methanols were used for direct conversion into the corresponding thiols by treatment with Lawesson’s reagent in boiling toluene. Unexpectedly, the respective sulfides were formed exclusively. In the case of chiral alcohols, the sulfides were obtained as 1:1-mixtures of meso- and dl-diastereoisomers. In contrast to hetaryl-substituted alcohols, the analogous protocol applied for benzhydryl alcohol led to a mixture of the expected secondary thiol and a bis(diphenylmethyl) trithiophosphonate. Finally, the analogous reactions with ferrocenyl(phenyl)methanol and diferrocenylmethanol, respectively, led to the corresponding thiols in good yield.

The reaction of the lacunary polyoxometalate precursor Na9[B-α-BiW9O33]·19.5H2O with Cu(II) ions was explored in search of new economic ways to copper tungstobismuthates as interesting prototypes for water oxidation and reduction catalysts. The emerging series of new 0D–3D polyoxometalate architectures with distinct copper cores was structurally characterized. Na6Rb6[Cu3(H2O)3(BiW9O33)2] (Cu-4) and 3D-K6.56Cu0.43H2.20[(Cu3Cl)(K2.62Cu0.38(H2O)3)(B-α-BiW9O33)2]·13H2O (Cu-5) display a Cu3(H2O)3 core. The 2D representatives Na12[Cu2(H2O)4Cl2(BiW10O35)2] (Cu-1a), Na10[Cu2(H2O)6(BiW10O35)2] (Cu-1b), 2D-Na7K3Cu0.5Cl[Cu2(H2O)4(BiW10O35)2] (Cu-2), and 2D-Na5.5K2.5Cu[Cu2(H2O)4(BiW10O35)2] (Cu-3) contain Cu2(H2O)nW2O4 cores. Interestingly, the bismuth-free 1D paratungstate B Na4K4Cu[H2W12O42] (Cu-6) is formed through reassembly of the precursor. Cu-5 displays a disordered transition metal core, implying the presence of the polyanions [Cu4(H2O)4(BiW9O33)2]10– and [Cu5(H2O)5(BiW9O33)2]8–. The magnetic properties of Cu...

We provide herein a mechanistic analysis of aryl sulfoxide excited state processes, inspired by our recent report of aryl sulfoxide based fluorescent chemosensors. The use of aryl sulfoxides as reporting elements in chemosensor development is a significant deviation from previous approaches, and thus warrants closer examination. We demonstrate that metal ion binding suppresses nonradiative excited state decay by blocking formation of a previously unrecognized charge transfer excited state, leading to fluorescence enhancement. This charge transfer state derives from the initially formed locally excited state followed by intramolecular charge transfer to form a sulfoxide radical cation/aryl radical anion pair. With the aid of computational studies, we map out ground and excited state potential energy surface details for aryl sulfoxides, and conclude that fluorescence enhancement is almost entirely the result of excited state effects. This work expands previous proposals that excited state pyramidal inversion is the major nonradiative decay pathway for aryl sulfoxides. We show that pyramidal inversion is indeed relevant, but that an additional and dominant nonradiative pathway must also exist. These conclusions have implications for the design of next generation sulfoxide based fluorescent chemosensors.

Depsipeptides and cyclodepsipeptides are analogues of the corresponding peptides in which one or more amide groups are replaced by ester functions. Reports of crystal structures of linear depsipeptides are rare. The crystal structures and conformational analyses of four depsipeptides with an alternating sequence of an α,α-disubstituted α-amino acid and an α-hydroxy acid are reported. The molecules in the linear hexadepsipeptide amide in (S)-Pms-Acp-(S)-Pms-Acp-(S)-Pms-Acp-NMe2 acetonitrile solvate, C47H58N4O9·C2H3N, (3b), as well as in the related linear tetradepsipeptide amide (S)-Pms-Aib-(S)-Pms-Aib-NMe2, C28H37N3O6, (5a), the diastereoisomeric mixture (S,R)-Pms-Acp-(R,S)-Pms-Acp-NMe2/(R,S)-Pms-Acp-(R,S)-Pms-Acp-NMe2 (1:1), C32H41N3O6, (5b), and (R,S)-Mns-Acp-(S,R)-Mns-Acp-NMe2, C30H37N3O6, (5c) (Pms is phenyllactic acid, Acp is 1-aminocyclopentanecarboxylic acid and Mns is mandelic acid), generally adopt a β-turn conformation in the solid state, which is stabilized by intramolecular N—H...O hydrogen bonds. Whereas β-turns of type I (or I′) are formed in the cases of (3b), (5a) and (5b), which contain phenyllactic acid, the torsion angles for (5c), which incorporates mandelic acid, indicate a β-turn in between type I and type III. Intermolecular N—H...O and O—H...O hydrogen bonds link the molecules of (3a) and (5b) into extended chains, and those of (5a) and (5c) into two-dimensional networks.

Ferrocene- and ruthenocenecarboxaldehydes have been employed in Betti-type condensation reactions with 2-naphthol and (S)-phenylethylamine to give metallocenyl-substituted aminomethylnaphthols in a diastereoisomerically pure form. The absolute configurations of the new chiral compounds have been determined by means of NMR experiments and confirmed by X-ray crystallography. The chiral metallocenyl-aminomethylnaphthols have been tested as pre-catalysts for the addition of diethyl zinc to aldehydes, with enantioselectivities of up to 88% ee.