A focused library of newly designed monomeric and dimeric naphthalene diimides (NDIs) was analyzed in its ability to recognize specific G-quadruplex (G4) structures discriminating duplex DNA. The best G4 ligands—according to an affinity chromatography-based screening method named G4-CPG—were tested on human cancer and healthy cells, inducing DNA damage at telomeres, and in parallel, showing selective antiproliferative activity on HeLa cancer cells with IC50 values in the low nanomolar range. CD and fluorescence spectroscopy studies allowed detailed investigation of the interaction in solution with different G4 and duplex DNA models of the most promising NDI of the series, as determined by combining the biophysical and biological assays’ data.
If you like brighter TADF then you should put a ring on it. We report rotaxanes containing a carbazole-containing TADF luminophore in which the mechanical bond improves key photophysical properties, including the photoluminescence quantum yield and the singlet-triplet energy gap (DEST). Computational simulations, supported by X-ray crystallography, suggest this is due to weak interactions between the axle and macrocycle, enforced by the mechanical bond.
In 1960, Wasserman synthesized a molecule in which two rings are held together like links in a chain. This molecule, which is called a catenane, is a topological isomer of the separated rings, which highlighted that molecules could be topologically non-trivial. This insight has found wider implications in biochemistry, where the topology of knotted and catenated proteins and oligonucleotides is thought to play a significant role in their properties, but it also led to the assumption that the stereochemistry of catenanes that are chiral due to the orientation of their rings is inherently topological in nature. Here we show that this assumption is incorrect by synthesizing an example that contains the same fundamental stereogenic unit but whose stereochemistry is Euclidean. Thus, we can unite the stereochemistry of catenanes with that of their topologically trivial cousins, the rotaxanes, paving the way for a more unified approach to their discussion.Topology and topological are often misapplied in chemistry to mean "shape", perhaps through confusion with topography and topographical respectively 1 . Formally, chemical topology finds its roots in mathematical topology 2 , the study of the properties of networks, surfaces, and objects under topologically allowed transformations. To consider the topology of a molecule, its structure is reduced to labelled vertices (the atoms) and edges (bonds between them) to generate a molecular graph 1 . One of the first applications of topology in chemistry was to enumerate the available isomers of higher order alkanes (CnH2n+2) 3 and there is continued interest in how molecular topology can be used to digitize and analyze chemical structures and their properties 4 . Conversely, the ultimately incorrect proposal by Lord Kelvin that atoms were knotted vortices in the aether motivated Tait to develop a systematic categorization of knots 5 .If only covalent bonding interactions are included 6,7 , the key difference between a chemical topologist's graph and a chemist's structural diagram is that the former does not consider molecular rigidity or geometry; when considering its topology, a molecular graph can be distorted arbitrarily provided the bonds are not broken or pass through one anotherall other transformations are valid, including the stretching of bonds and Commented [SG1]: E4. Title (15 words, 150 characters)Reviewers #1 and #3 both comment on the titleboth find it confusing, and I have to say that I agree with them. Although both suggest alternative titles, I'm afraid that neither meet our formatting requirements. I've included further guidance below.Response: we have reworded the title.To avoid unwieldy titles, we ask that you use no punctuation and no more than 15 words and 150 characters. Multi-part titles separated by dashes or colons (or similar), such as the one suggested by Reviewer #1, are not allowed. I've doublechecked with our copy editors and have been very firmly told that inverted commas and quotation marks (such as those in the titles suggested by Reviewers #1...
We report the characterization of rotaxanes based on a carbazole‐benzophenone thermally activated delayed fluorescence luminophore. We find that the mechanical bond leads to an improvement in key photophysical properties of the emitter, notably an increase in photoluminescence quantum yield and a decrease in the energy difference between singlet and triplet states, as well as fine tuning of the emission wavelength, a feat that is difficult to achieve when using covalently bound substituents. Computational simulations, supported by X‐ray crystallography, suggest that this tuning of properties occurs due to weak interactions between the axle and the macrocycle that are enforced by the mechanical bond. This work highlights the benefits of using the mechanical bond to refine existing luminophores, providing a new avenue for emitter optimization that can ultimately increase the performance of these molecules.
Hydrogen-bonded supramolecular systems are usually characterized in solution through analysis of NMR data such as complexation-induced shifts and nuclear Overhauser effects (nOe). Routine direct detection of hydrogen bonding particularly in multicomponent mixtures, even with the aid of 2D NMR experiments for full assignment, is more challenging. We describe an elementary rapid 1H–15N HMQC NMR experiment which addresses these challenges without the need for complex pulse sequences. Under readily accessible conditions (243/263 K, 50 mM solutions) and natural 15N abundance, unambiguous assignment of 15N resonances facilitates direct detection of intra- and intermolecular hydrogen bonds in mechanically interlocked structures and quadruply hydrogen-bonded dimersof dialkylaminoureidopyrimidinones, ureidopyrimidinones, and diamidonaphthyridinesin single or multicomponent mixtures to establish tautomeric configuration, conformation, and, to resolve self-sorted speciation.
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