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In the context of the investigation of drug-induced oxidative stress in parasitic cells, electrochemical properties of a focused library of polysubstituted menadione derivatives were studied by cyclic voltammetry. These values were used, together with compatible measurements from literature (quinones and related compounds), to build and evaluate a predictive structure-redox potential model (quantitative structure-property relationship, QSPR). Able to provide an online evaluation (through Web interface) of the oxidant character of quinones, the model is aimed to help chemists targeting their synthetic efforts towards analogues of desired redox properties [ABSTRACT FROM AUTHOR]

An Eglinton-Galbraith diethyne cyclization preferentially yielded a structurally unusual macrocycle, comprising a strained conjugated oligo[2]cruciform wire, forced into a 2.2 nm bow-shape by a terpyridine rein or tether, and stabilized towards light and heat by four insulating triisopropylsilylacetylene (TIPSA) substituents. Spectroscopic ion-binding studies revealed the macrocycle to exhibit a particularly high UV/Vis selectivity for PdII in dilute solution, and one of its precursors to afford a variety of luminescence quenching and color responses to particular metals, suggestive of promising ion-sensor applications. Under more concentrated conditions, the new macrocycle is able to bind specific metals (e.g., AuI) within its cavity despite the steric constraints. Intriguingly, variable-temperature (VT) UV/Vis/1H NMR investigations showed the TIPSA substituents to undergo restricted intramolecular motions along with reversible changes in the spectroscopic bandgap of the compound with temperature. In line with the theoretical calculations, the VT UV/Vis observations are consistent with a thermal modulation of the electronic conjugation through the strained oligo[2]cruciform bridge, which is coupled with redistributions within a mixture of conformational isomers of the macrocycle with differing relative twisting between the TIPSA-substituted phenyl rings. Overall, the generation of a para-oligo[2]cruciform, bent and flexed over nanoscopic dimensions through conformational tethering within the macrocyclic ring is noteworthy, and suggests a general approach to nanosized, curved, and strained, yet heat- and light-stable, para-phenyleneethynylene oligomers with unique physicochemical properties and challenging theoretical possibilities. [ABSTRACT FROM AUTHOR]

Maytansinoids are a successful class of natural and semisynthetic tubulin binders, known for their potent cytotoxic activity. Their wider application as cytotoxins and chemical probes to study tubulin dynamics has been held back by the complexity of natural product chemistry. Here we report the synthesis of long‐chain derivatives and maytansinoid conjugates. We confirmed that bulky substituents do not impact their high activity or the scaffold's binding mode. These encouraging results open new avenues for the design of new maytansine‐based probes. [ABSTRACT FROM AUTHOR]

Accelerated ageing reactions that take place between two solid materials on contact in the absence of added solvent have been used to synthesize two spin‐crossover‐active 1D coordination polymers and one of their Cu(II) analogues. The hygroscopy of the ligands and the relative humidity of the reaction chamber have been shown to be particularly important factors in the rate of reaction. Small‐scale reactions between a few individual crystals have allowed observation of deliquescence of the 4‐aminotriazole ligand at high humidity. The metal salt does not dissolve, and the ligand diffuses into the crystal of the metal salt during the reaction. In the case of the Cu analogue, the formation of the product causes the crystal of the metal salt to deform with the formation of pseudocrystals, which have a fibrous structure. [ABSTRACT FROM AUTHOR]

This review discusses recent advances in the chemistry of saturated boronic acids, boronates, and trifluoroborates. Applications of the title compounds in the design of boron‐containing drugs are surveyed, with special emphasis on α‐amino boronic derivatives. A general overview of saturated boronic compounds as modern tools to construct C(sp3)−C and C(sp3)‐heteroatom bonds is given, including recent developments in the Suzuki‐Miyaura and Chan‐Lam cross‐couplings, single‐electron‐transfer processes including metallo‐ and organocatalytic photoredox reactions, and transformations of boron "ate" complexes. Finally, an attempt to summarize the current state of the art in the synthesis of saturated boronic acids, boronates, and trifluoroborates is made, with a brief mention of the "classical" methods (transmetallation of organolithium/magnesium reagents with boron species, anti‐Markovnikov hydroboration of alkenes, and the modification of alkenyl boron compounds) and a special focus on recent methodologies (boronation of alkyl (pseudo)halides, derivatives of carboxylic acids, alcohols, and primary amines, boronative C−H activation, novel approaches to alkene hydroboration, and 1,2‐metallate‐type rearrangements). [ABSTRACT FROM AUTHOR]

Heavy‐atom‐free sensitizers forming long‐living triplet excited states via the spin‐orbit charge transfer intersystem crossing (SOCT‐ISC) process have recently attracted attention due to their potential to replace costly transition metal complexes in photonic applications. The efficiency of SOCT‐ISC in BODIPY donor‐acceptor dyads, so far the most thoroughly investigated class of such sensitizers, can be finely tuned by structural modification. However, predicting the triplet state yields and reactive oxygen species (ROS) generation quantum yields for such compounds in a particular solvent is still very challenging due to a lack of established quantitative structure‐property relationship (QSPR) models. In this work, the available data on singlet oxygen generation quantum yields (ΦΔ) for a dataset containing >70 heavy‐atom‐free BODIPY in three different solvents (toluene, acetonitrile, and tetrahydrofuran) were analyzed. In order to build reliable QSPR model, a series of new BODIPYs were synthesized that bear different electron donating aryl groups in the meso position, their optical and structural properties were studied along with the solvent dependence of singlet oxygen generation, which confirmed the formation of triplet states via the SOCT‐ISC mechanism. For the combined dataset of BODIPY structures, a total of more than 5000 quantum‐chemical descriptors was calculated including quantum‐chemical descriptors using density functional theory (DFT), namely M06‐2X functional. QSPR models predicting ΦΔ values were developed using multiple linear regression (MLR), which perform significantly better than other machine learning methods and show sufficient statistical parameters (R=0.88–0.91 and q2=0.62–0.69) for all three solvents. A small root mean squared error of 8.2 % was obtained for ΦΔ values predicted using MLR model in toluene. As a result, we proved that QSPR and machine learning techniques can be useful for predicting ΦΔ values in different media and virtual screening of new heavy‐atom‐free BODIPYs with improved photosensitizing ability. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A rational approach to modulating easy‐axis magnetic anisotropy by varying the axial donor ligand in heptacoordinated FeII complexes has been explored. In this series of complexes with formulae of [Fe(H4L)(NCS)2]⋅3 DMF⋅0.5 H2O (1), [Fe(H4L)(NCSe)2]⋅3 DMF⋅0.5 H2O (2), and [Fe(H4L)(NCNCN)2]⋅DMF⋅H2O (3) [H4L=2,2′‐{pyridine‐2,6‐diylbis(ethan‐1‐yl‐1‐ylidene)}bis(N‐phenylhydrazinecarboxamide)], the axial positions are successively occupied by different nitrogen‐based π‐donor ligands. Detailed dc and ac magnetic susceptibility measurements reveal the existence of easy‐axis magnetic anisotropy for all of the complexes, with 1 [Ueff=21 K, τ0=1.72×10−6 s] and 2 [Ueff=25 K, τ0=2.25×10−6 s] showing field‐induced slow magnetic relaxation behavior. However, both experimental studies and theoretical calculations indicate the magnitude of the D value of complex 3 to be larger than those of complexes 1 and 2 due to the axial bond angle being smaller than that for an ideal geometry. Detailed analysis of the field and temperature dependences of relaxation time for 1 and 2 has revealed that multiple relaxation processes (quantum tunneling of magnetization, direct, and Raman) are involved in slow magnetic relaxation for both of these complexes. Magnetic dilution experiments support the role of intermolecular short contacts. [ABSTRACT FROM AUTHOR]

A series of highly diversified 3‐aroylmenadiones was prepared by a new Friedel–Crafts acylation variant/oxidative demethylation strategy. A mild and versatile acylation was performed between 1,4‐dimethoxy‐2‐methylnaphthalene and various activated/deactivated benzoic and heteroaromatic carboxylic acids, in the presence of mixed trifluoroacetic anhydride and triflic acid, at room temperature and in air. The 1,4‐dimethoxy‐2‐methylnaphthalene‐derived benzophenones were isolated in high yield, and submitted to oxidative demethylation with cerium ammonium nitrate to produce 3‐benzoylmenadiones. All 1,4‐naphthoquinone derivatives were investigated as redox‐active electrophores by cyclic voltammetry. The electrochemical data recorded for 3‐acylated menadiones are characterized by a second redox process, the potentials of which cover a wide range of values (500 mV). These data emphasize the ability of the generated structural diversity at the 3‐aroyl chain of these electrophores to fine‐tune their corresponding redox potentials. These properties are of significance in the context of antimalarial drug development and understanding of the mechanism of bioactivation/action. [ABSTRACT FROM AUTHOR]

Angle‐strained alkyne‐containing π‐conjugated macrocycles are attractive compounds both in functional materials chemistry and biochemistry. Their interesting reactivity as well as photophysical and supramolecular properties have been revealed in the past three decades. This review highlights the recent advances in angle‐strained alkyne‐containing π‐conjugated macrocycles, especially their synthetic methods, the bond angles of alkynes (∠sp at C≡C−C), and their functions. The theoretical and experimental research on cyclo[n]carbons and para‐cyclophynes consisting of ethynylenes and para‐phenylenes are mainly summarized. Related macrocycles bearing other linkers, such as ortho‐phenylenes, meta‐phenylenes, heteroaromatics, biphenyls, extended aromatics, are also overviewed. Bond angles of strained alkynes in π‐conjugated macrocycles, which are generable, detectable, and isolable, are summarized at the end of this review. [ABSTRACT FROM AUTHOR]

All pharmaceutical products contain organic molecules; the source may be a natural product or a fully synthetic molecule, or a combination of both. Thus, it follows that organic chemistry underpins both existing and upcoming pharmaceutical products. The reverse relationship has also affected organic synthesis, changing its landscape towards increasingly complex targets. This Review article sets out to give a concise appraisal of this symbiotic relationship between organic chemistry and drug discovery, along with a discussion of the design concepts and highlighting key milestones along the journey. In particular, criteria for a high‐quality compound library design enabling efficient virtual navigation of chemical space, as well as rise and fall of concepts for its synthetic exploration (such as combinatorial chemistry; diversity‐, biology‐, lead‐, or fragment‐oriented syntheses; and DNA‐encoded libraries) are critically surveyed. [ABSTRACT FROM AUTHOR]

Abstract: The grafts of fluorophores 9‐anthraldehyde (AD) and 9‐phenanthrenecarboxaldehyde (PD), respectively, on the one‐dimensional spin‐crossover compound [Fe(L)3](ClO4)2 (FeL, L=4‐amino‐1,2,4‐triazole) by post‐synthetic aldimine condensation reactions produced two spin‐crossover (SCO)–fluorescent hybrid materials, that is, FeL‐AD and FeL‐PD. The spin‐crossover critical temperatures of the two materials both centered at Tc↓=254 and Tc↑=256 K, whereas the fluorescence intensities of the two materials featured functions of the temperature that strictly synchronized with the spin‐crossover processes, which showed that the ligand‐centered fluorescence was dominated by the spin states of the ferrous ions. The bifunctional entities (spin‐crossover centers and fluorophores) in FeL‐AD or FeL‐PD showed spectral band overlap that purported the Förster resonance energy transfer mechanism of such spin‐crossover–fluorescence correlation. The post‐synthetic modification of SCO materials and the relationship between the fluorescence and the SCO may be helpful in the development of multifunctional materials that can be sensitive to multiple stimuli. [ABSTRACT FROM AUTHOR]

The reaction of ferrous salts and square-planar tetracyanometallates [MII(CN)4]2− (M=Pd, Pt) with ligand 4-(1H-pyrazol-3-yl)pyridine (Hppy) resulted in the formation of two two-dimensional (2D) Hofmann-like coordination polymers (CPs) with the general formula of {FeII(Hppy)2[MII(CN)4]}⋅H2O (M=Pd for 1Pd, Pt for 1Pt). The two CPs have been studied by variable-temperature single-crystal X-ray crystallography, differential scanning calorimetry, and magnetic measurements. Polymers 1Pd and 1Pt are isostructures, in which the FeII atoms are equatorially coordinated with [MII(CN)4]2− to form 2D undulating layers and axially coordinated with Hppy ligands. Both compounds undergo cooperative, complete spin crossover (SCO), with characteristic abrupt and remarkable two equal steps, featuring hysteresis widths of 14 K and 19 K (1Pd) and 17 and 23 K (1Pt) for the two steps. The SCO cooperativity may result from the hydrogen bonds and π⋅⋅⋅π interactions within and between such 2D layers, and the two-step SCO behavior is accompanied with phase transitions. [ABSTRACT FROM AUTHOR]

Reaction prediction and retrosynthesis are the cornerstones of organic chemistry. Rule-based expert systems have been the most widespread approach to computationally solve these two related challenges to date. However, reaction rules often fail because they ignore the molecular context, which leads to reactivity conflicts. Herein, we report that deep neural networks can learn to resolve reactivity conflicts and to prioritize the most suitable transformation rules. We show that by training our model on 3.5 million reactions taken from the collective published knowledge of the entire discipline of chemistry, our model exhibits a top10-accuracy of 95 % in retrosynthesis and 97 % for reaction prediction on a validation set of almost 1 million reactions. [ABSTRACT FROM AUTHOR]

The ability to reason beyond established knowledge allows organic chemists to solve synthetic problems and invent novel transformations. Herein, we propose a model that mimics chemical reasoning, and formalises reaction prediction as finding missing links in a knowledge graph. We have constructed a knowledge graph containing 14.4 million molecules and 8.2 million binary reactions, which represents the bulk of all chemical reactions ever published in the scientific literature. Our model outperforms a rule-based expert system in the reaction prediction task for 180 000 randomly selected binary reactions. The data-driven model generalises even beyond known reaction types, and is thus capable of effectively (re-)discovering novel transformations (even including transition metal-catalysed reactions). Our model enables computers to infer hypotheses about reactivity and reactions by only considering the intrinsic local structure of the graph and because each single reaction prediction is typically achieved in a sub-second time frame, the model can be used as a high-throughput generator of reaction hypotheses for reaction discovery. [ABSTRACT FROM AUTHOR]

Hexagonal shape-persistent macrocycles (SPMs) consisting of three pyridine and three phenol rings linked with acetylene bonds were developed as a preorganized host for saccharide recognition by push-pull-type hydrogen bonding. Three tert-butyl or 2,4,6-triisopropylphenyl substituents were introduced on the host to suppress self-aggregation by steric hindrance. In spite of the simple architecture, association constants Ka of the host with alkyl glycoside guests reached the order of 106 m−1 on the basis of UV/Vis titration experiments. This glycoside recognition was much stronger than that in the cases of acyclic equivalent hosts because of the entropic advantage brought by preorganization of the hydrogen-bonding sites. Solid-liquid extraction and liquid-liquid transport through a liquid membrane were demonstrated by using native saccharides, and much preference to mannose was observed. [ABSTRACT FROM AUTHOR]

The article presents abstracts of papers published in various chemistry journals, including "Electrochemical Red Blood Cell Counting: One at a Time," by L. Sepunaru et al., "Redox Polypharmacology As an Emerging Strategy to Combat Malarial Parasites," by P. Sidorov et al., and "Cobalt-Catalyzed Derivative Dimerization of 2-Phenylpyridine Derivatives" by Y. Xie et al.

The complexes [MCl2(TzH)4] (M=Mn ( 1), Fe ( 2); TzH=1,2,4-1 H-triazole) and [ZnCl2(TzH)2] ( 3) have been obtained by mechanochemical reactions of the corresponding divalent metal chloride and 1,2,4-1 H-triazole. They were successfully used as precursors for the formation of coordination polymers either by a microwave-assisted reaction or by thermal conversion. For manganese, the conversion directly yielded [MnCl2TzH] ( 4), whereas for the iron-containing precursor, [FeCl2TzH] ( 6), was formed via the intermediate coordination polymer [FeCl(TzH)2]Cl ( 5). For cobalt, the isotypic polymer [CoCl(TzH)2]Cl ( 7) was obtained, but exclusively by a microwave-induced reaction directly from CoCl2. The crystal structures were resolved from single crystals and powders. The dielectric properties were determined and revealed large differences in permittivity between the precursor complexes and the rigid chain-like coordination polymers. Whereas the monomeric complexes exhibit very different dielectric behaviour, depending on the transition metal, from 'low- k' to 'high- k' with the permittivity ranging from 4.3 to >100 for frequencies of up to 1000 Hz, the coordination polymers and complexes with strong intermolecular interactions are all close to 'low- k' materials with very low dielectric constants up to 50 °C. Therefore, the conversion procedures can be used to deliberately influence the dielectric properties from complex to polymer and for different 3d transition-metal ions. [ABSTRACT FROM AUTHOR]

[Fe(tvp)2(NCS)2] ( 1) (tvp= trans-(4,4′-vinylenedipyridine)) consists of two independent perpendicular stacks of mutually interpenetrated two-dimensional grids. This uncommon supramolecular conformation defines square-sectional nanochannels (diagonal≈2.2 nm) in which inclusion molecules are located. The guest-loaded framework 1@guest displays complete thermal spin-crossover (SCO) behavior with the characteristic temperature T1/2 dependent on the guest molecule, whereas the guest-free species 1 is paramagnetic whatever the temperature. For the benzene-guest derivatives, the characteristic SCO temperature T1/2 decreases as the Hammet σp parameter increases. In general, the 1@guest series shows large entropy variations associated with the SCO and conformational changes of the interpenetrated grids that leads to a crystallographic-phase transition when the guest is benzonitrile or acetonitrile/H2O. [ABSTRACT FROM AUTHOR]

The coordination chemistry of cyclic stannylene-based intramolecular Lewis pairs is presented. The P→Sn adducts were treated with [Ni(COD)2] and [Pd(PCy3)2] (COD=1,5-cyclooctadiene, PCy3=tricyclohexylphosphine). In the isolated coordination compounds the stannylene moiety acts either as an acceptor or a donor ligand. Examples of a dynamic switch between these two coordination modes of the PSn ligand are illustrated and the structures in the solid state together with heteronuclear NMR spectroscopic findings are discussed. In the case of a Ni0 complex, 119Sn Mössbauer spectroscopy of the uncoordinated and coordinated phosphastannirane ligand is presented. [ABSTRACT FROM AUTHOR]

The article presents abstracts on chemistry topics including the use of nuclear magnetic resonance (NMR) spectroscopy to map functional interaction site of human prune C-terminal domain in human cell lysates, lanthanide oxide clusters, and coronene molecular rotors in charge-transfer solids.

One-dimensional coordination FeII polymers constructed through triple N1, N2-1,2,4-triazole bridges form a unique class of spin-crossover materials, the synthetic versatility of which allows tuning the spin-crossover properties, the design of gels, films, liquid crystals, and nanoparticles and single-particle addressing. This Minireview provides the first complete overview of these very attractive switchable materials and their most recent developments. [ABSTRACT FROM AUTHOR]