4‐Acetamido‐3,3,5,5‐[2H4]‐2,2,6,6‐tetra­([2H3]methyl)piperidin‐1‐yloxyl 0.33‐hydrate

The asymmetric unit of the title compound, C₁₁H₅D₁₆N₂O₂·0.33H₂O, is formed by three crystallographically independent piperidin‐1‐yloxyl mol­ecules and a mol­ecule of water. The mol­ecules are crosslinked by nine hydrogen bonds into layers parallel with the ac plane. The water mol­ecule contributes to the stability of the low‐symmetry arrangement by four hydrogen bonds.     

Polymer Nanocontainers for Intracellular Delivery

Carriers for intracellular delivery are required to overcome limitations of therapeutic agents such as low specificity, systemic toxicity, high clearance rate, and low therapeutic index. Nanocontainers comprised of an aqueous core and a polymer shell have received increasing attention because they readily combine stimuli response to improve intracellular payload release and surface modification to enhance selectivity towards the desired region of action. This Minireview summarizes the design and properties of polymer nanocontainers for intracellular delivery, classified according to the polymer architecture.     

A Light‐up Logic Platform for Selective Recognition of Parallel G‐Quadruplex Structures via Disaggregation‐Induced Emission

The design of turn‐on dyes with optical signals sensitive to the formation of supramolecular structures provides fascinating and underexplored opportunities for G‐quadruplex (G4) DNA detection and characterization. Here, we show a new switching mechanism that relies on the recognition‐driven disaggregation (on‐signal) of an ultrabright coumarin‐quinazoline conjugate. The synthesized probe selectively lights‐up parallel G4 DNA structures via the disassembly of its supramolecular state, demonstrating outputs that are easily integrable into a label‐free molecular logic system. Finally, our molecule preferentially stains the G4‐rich nucleoli of cancer cells.     

Charge‐Tagged DNA Radicals in the Gas Phase Characterized by UV/Vis Photodissociation Action Spectroscopy

Adenosine radicals tagged with a fixed‐charge group were generated in the gas phase and structurally characterized by tandem mass spectrometry, deuterium labeling, and UV/Vis action spectroscopy. Experimental results in combination with Born–Oppenheimer molecular dynamics, ab initio, and excited‐state calculations led to unambiguous assignment of adenosine radicals as N‐7 hydrogen atom adducts. The charge‐tagged radicals were found to be electronically equivalent to natural DNA nucleoside radicals.     

Identification of an additional low-lying excited state of carotenoid radical cations

Carotenoids are the crucial pigments involved in photoprotection and in scavenging harmful free radicals in all living organisms. The underlying chemical processes are charge transfer and free radical reactions, both of them leading to carotenoid radical cation (Car*+) formation. Accurate knowledge of the molecular properties of Car*+ is thus a prerequisite for understanding of their function as photoprotective and antioxidant agents. Despite their fundamental importance in nonphotochemical quenching in green plants, only little is known about the Car*+ excited states and their dynamics. Our combined experimental and theoretical investigation employing femtosecond time-resolved pump-probe spectroscopy and quantum chemical calculations proves the existence of a second low-lying pipi* excited-state energetically below the well-known strongly allowed excited-state responsible for the intense absorption of Car*+ in the near-IR region. Hence, we suggest denoting the latter state as D3 state in the future. Our findings have also implications for nonphotochemical quenching in green plants, since direct quenching of chlorophyll excited states by Forster energy transfer to Car*+ is possible and efficient.     

Self-assembled layers based on isomerizable stilbene and diketoarylhydrazone moieties

The ability to form self-assembled layers on gold (Au) using five organosulfur compounds that contain isomerizable groups has been investigated. The isomerizable groups are either stilbene or diketoarylhydrazone derivatives. To anchor them on a gold surface, the isomerizable groups have been combined with sulfur-containing groups (disulfide, 1,2-dithiolane, and thiophene). The resulting thin films assembled on gold were characterized by X-ray photoelectron spectroscopy (XPS), infrared (FTIR) reflectance spectroscopy, ellipsometry, and water contact angle measurements. Though all substances have the potential to form self-assembled monolayers (SAMs), only two of them, disulfanediyl-bis(ethane-2,1-diyl) bis(4-styrylbenzoate) (1) and 4-[(2,4-dioxo-3-pentylidene)diazane-2,2,1-triyl]phenyl thioctate (4), yield the expected structure, the latter one showing the possibility to incorporate diarylketohydrazone moieties into SAMs. The compound 4-[(2,4-dioxo-3-pentylidene)diazane-2,2,1-triyl]phenyl thiophene-2-carboxylate (5) does not self-assemble on gold, but 4-styrylphenyl thioctate (3) presumably forms multilayers. In the case of disulfanediyl-bis(ethane-2,1-diyl) bis[4-(p-nitrostyryl)benzoate] (2), we propose a structure with a fraction of the molecules bound to gold via the nitro group. The results show that the propensity of organosulfur compounds to self-assemble on gold not only is determined by the sulfur-containing group but also is affected by the complete molecule.     

Current trends in isolation, separation, determination and identification of isoflavones: a review

Isoflavones are natural substances which elicit a number of physiological effects in living organisms. The substances are synthesized in plant tissues as protective agents against biotic stress (i. e. bacterial infection). Isoflavones are also an important dietary constituent in human nutrition. Modern trends in studies of isoflavones in plant materials and foodstuffs and procedures for chemical analyses of isoflavones in human body fluids and plant tissues are discussed in this review. Highly effective extraction and purification techniques, i. e. solid-phase extraction, accelerated-solvent extraction, and Soxhlet extraction, are presented. Latest procedures in chromatographic separation of isoflavones that apply different types of sorbents are described. Immunochemical analysis, electrochemical sensing of isoflavones, and spectrometric and other analytical techniques and their applications are also mentioned. Special attention is paid to the highly selective and sensitive technique of mass spectrometry and its application for identification of isoflavones and their glucosides in plants. Studies of interactions of isoflavones with cell receptors and a number of biologically active substances such as DNA and proteins are described. The review does not intend to give a complete overview of the topics considered but rather to present modern and most recent methods used in studies of isoflavones.     

New ferromagnetic dinuclear triply-bridged copper(II) compounds containing carboxylato bridges: Synthesis,X-ray structure and magnetic properties

The new triply-bridged dinuclear copper(II) complexes, [Cu₂(μ-O₂CH)(μ-OH)₂(dpyam)₂](ClO₄) · H₂O (1), [Cu₂(μ-O₂CCH₃)(μ-OH)(μ-OH₂)(dpyam)₂](S₂O₈) (2), [Cu₂(μ-O₂CCH₃)(μ-OH)(μ-OH₂)(bpy)₂](NO₃)₂ (3), [Cu₂(μ-O₂CCH₃)(μ-OH)(μ-OH₂)(phen)₂](BF₄)₂ · 0.5H₂O (4), [Cu₂(μ-O₂CCH₂CH₃)(μ-OH)(μ-OH₂)(phen)₂](NO₃)₂ (5) and [Cu₂(μ-O₂CCH₃)(μ-OH)(μ-Cl)(bpy)₂]Cl · 8.5H₂O (6) (dpyam = di-2-pyridylamine, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline), have been synthesized and characterized crystallographically and also their spectroscopic and magnetic properties have been studied. A structural classification of this type of dimers, based on the data obtained from X-ray diffraction analysis in the present work and those reported in the literature has been performed. In these complexes, the local geometry around the copper centre is generally a distorted square pyramid and distorted trigonal bipyramid with different degrees of distortion. The global geometry of the dinuclear complexes can be described in terms of the relative arrangement of the two five-coordinate environments, giving rise to different classes (A–F) of complexes. The most logical explanations have been provided for each class describing different magnetic interactions. Practically, there is a clear correlation between structural data and J values of the class B complexes. Extended Hückel calculations were performed for the present complexes 1–6, as well as for some other class B complexes, showing the different molecular orbitals involved in their corresponding frontier orbitals, together with their energy. The results are found to be useful for the proper interpretation and correlation of the magnetic data and the dinuclear structure of the present complexes.