Towards Protection of Nucleic Acids from Herbicide Attack: Self-Assembly of Betaines Based on Pillar[5]arene with Glyphosate and DNA

Herbicides are one of the main parts of pesticides used today. Due to the high efficiency and widespread use of glyphosate-based herbicides, the search for substances reducing their genotoxicity is an important interdisciplinary task. One possible approach for solving the problem of herbicide toxicity is to use compounds that can protect DNA from damage by glyphosate derivatives. For the first time, a method for developing DNA-protecting measures against glyphosate isopropylamine salt (GIS) damage was presented and realized, based on low-toxicity water-soluble pillar[5]arene derivatives. Two- and three-component systems based on pillar[5]arene derivatives, GIS, and model DNA from salmon sperm, as well as their cytotoxicity, were studied. The synthesized pillar[5]arene derivatives do not interact with GIS, while GIS is able to bind DNA from salmon sperm with lgKa = 4.92. The pillar[5]arene betaine derivative containing fragments of L-phenylalanine and the ester derivative with diglycine fragments bind DNA with lgKa = 5.24 and lgKa = 4.88, respectively. The study of the associates (pillar[5]arene-DNA) with GIS showed that the interaction of GIS with DNA is inhibited only by the betaine pillar[5]arene containing fragments of L-Phe (lgKa = 3.60). This study has shown a possible application of betaine pillar[5]arene derivatives for nucleic acid protection according to its competitive binding with biomacromolecules.

Metal-organic cycle-based multistage assemblies

Different from polymers or peptides (lacking metals), metal–organic cycles (MOCs) have properties which arise from the combination of metals and common nonmetal elements and topologies. The development of MOC supramolecular materials is in its infancy, and how the coordination bonds work to make the corresponding suprastructures is unknown. This has limited the potential application of these MOC-based materials. Considering the applications of individual MOCs, the study and discovery of the unique factors in MOC-involved multilevel self-assembly are critical to further our knowledge of the underlying molecular mechanisms of metal-containing compounds. Here, a systematic study of MOC assembly in various solvent systems has confirmed the critical role of coordination linkers in tuning the shape and size of the MOC-derived suprastructures.

It is well known that chemical compositions and structural arrangements of materials have a great influence on their resultant properties. Diverse functional materials have been constructed by using either biomolecules (peptides, DNA, and RNA) in nature or artificially synthesized molecules (polymers and pillararenes). The relationships between traditional building blocks (such as peptides) have been widely investigated, for example how hydrogen bonds work in the peptide multistage assembly process. However, in contrast to traditional covalent bond-based building blocks-based assembly, suprastructures formed by noncovalent bonds are more influenced by specific bond features, but to date only a few results have been reported based on noncovalent bond-based building block multistage assembly. Here, three metal–organic cycles (MOCs) were used to show how coordination bonds influence the bimetallacycle conformation then lead to the topology differences of MOC multilevel ordered materials. It was found that the coordination linker (isophthalate-Pt-pyridine) is an important factor to tune the shape and size of the MOC-derived suprastructures.

A pillar[5]arene-based covalent organic framework with pre-encoded selective host-guest recognition

It is highly desirable to maintain both permanent accessible pores and selective molecular recognition capability of macrocyclic cavitands in the solid state. Integration of well-defined discrete macrocyclic hosts into ordered porous polymeric frameworks (e.g., covalent organic frameworks, COFs) represents a promising strategy to transform many supramolecular chemistry concepts and principles well established in the solution phase into the solid state, which can enable a broad range of practical applications, such as high-efficiency molecular separation, heterogeneous catalysis, and pollution remediation. However, it is still a challenging task to construct macrocycle-embedded COFs. In this work, a novel pillar[5]arene-derived (P5) hetero-porous COF, denoted as P5-COF, was rationally designed and synthesized. Featuring the unique backbone structure, P5-COF exhibited selective adsorption of C2H2 over C2H4 and C2H6, as well as significantly enhanced host-guest binding interaction with paraquat, in comparison with the pillar[5]arene-free COF analog, Model-COF. The present work established a new strategy for developing COFs with customizable molecular recognition/separation properties through the bottom-up "pre-porous macrocycle to porous framework" design.

Construction of pillar[4]arene[1]quinone-1,10-dibromodecane pseudorotaxanes in solution and in the solid state

We report novel pseudorotaxanes based on the complexation between pillar[4]arene[1]quinone and 1,10-dibromodecane. The complexation is found to have a 1:1 host–guest complexation stoichiometry in chloroform but a 2:1 host–guest complexation stoichiometry in the solid state. From single crystal X-ray diffraction, the linear guest molecules thread into cyclic pillar[4]arene[1]quinone host molecules in the solid state, stabilized by CH∙∙∙π interactions and hydrogen bonds. The bromine atoms at the periphery of the guest molecule provide convenience for the further capping of the pseudorotaxanes to construct rotaxanes.

The synthesis of water-soluble phosphate pillar[5]arenes functionalized graphene as a fluorescent probe for sensitive detection of paraquat

We describe a selective and sensitive fluorescence platform for the detection of paraquat (PQ) based on competitive host-guest recognition between phosphate pillar[5]arenes (PWP5) and probe (Safranine T, ST) with using PWP5 functionalized reduced graphene (PWP5-rGO) as the receptor. PQ is a positive charge molecule that is captured by PWP5 via electrostatic interactions. The host-guest interaction between PWP5 and PQ is studied by ¹H NMR. Therefore, a selective and sensitive fluorescence sensing of detection PQ is developed. It has a linear response ranges of 0.01-2.0 and 2.0-50.0 μM and a low detection limit of 0.0035 μM (S/N = 3) for PQ. The sensing platform is also used to test PQ in two water samples with satisfying results. It suggests that this approach has potential applications for the determination of PQ.

Pillararene-based self-assembled amphiphiles

Pillararenes are a unique group of supramolecular macrocycles, presenting important features and potential applications on account of their intrinsic structural properties and functionality. Developing pillararene-based self-assembled amphiphiles (PSAs) is an efficient approach to translate pillararenes into functional systems and materials for facilitating their practical applications. In this review article, we highlight recent significant advancements in PSAs. A new standard according to the number, solubility, and amphiphilicity of building blocks is employed for dividing PSAs into different categories. The fabrication of PSAs based on various building blocks and supramolecular interactions, and the formation of amphiphile-based self-assemblies are then discussed based on this standard. Furthermore, interesting stimulus-responsiveness to various factors, such as pH, redox, temperature, light, ionic effect, and host-guest competition, generated by the functional groups on various building blocks is summarized, and the corresponding supramolecular interactions in PSAs and their self-assemblies are elaborated. In addition, some important applications of PSAs and their assemblies are discussed. This review not only provides fundamental findings on the construction of PSAs, but also foresees future research directions in this rapidly developing area.

Synthesis of diamido-bridged bis-pillar[5]arenes and tris-pillar[5]arenes for construction of unique [1]rotaxanes and bis-[1]rotaxanes

The pillar[5]arene mono- and di(oxyalkoxy)benzoic acids were successfully prepared in high yields by sequential alkylation of ω-bromoalkoxy-substituted pillar[5]arenes with methyl or ethyl p-hydroxybenzoate followed by a hydrolytic reaction under basic conditions. Under catalysis of HOBt/EDCl, the amidation reaction of pillar[5]arene mono(oxybutoxy)benzoic acid with monoamido-functionalized pillar[5]arenes afforded diamido-bridged bis-pillar[5]arenes. 1H NMR and 2D NOESY spectra clearly indicated that [1]rotaxanes were formed by insertion of longer diaminoalkylene unit into the cavity of one pillar[5]arene with another pillar[5]arene acting as a stopper. The similar catalysed amidation reaction of pillar[5]arene di(oxybutoxy)benzoic acid with monoamido-functionalized pillar[5]arenes resulted in the diamido-bridged tris-pillar[5]arenes, which successfully form the unique bis-[1]rotaxanes bearing longer than diaminopropylene diamido bridges.

Self-locked dipillar[5]arene-based pseudo[1]rotaxanes and bispseudo[1]rotaxanes with different lengths of bridging chains

The relationships between lengths of bridging chains and self-locked behaviors of dipillar[5]arene-based pseudo[1]rotaxanes and bispseudo[1]rotaxanes were studied in detail.

Pillar[5]arene-based fluorescent polymer for selective detection and removal of mercury ions

A novel pillar[5]arene-based fluorescent polymer has been synthesized, and it is used for fluorescence detection and removal of the toxic mercury ions.