Ultramacrocyclization through Reversible Catenation

Highly Efficient Self-Assembly of Heterometallic [2]Catenanes and Cyclic Bis[2]catenanes via Orthogonal Metal-Coordination Interactions

Although catenated cages have been widely constructed due to their unique and elegant topological structures, cyclic catenanes formed by the connection of multiple catenane units have been rarely reported. Herein, based on the orthogonal metal-coordination-driven self-assembly, we prepare a series of heterometallic [2]catenanes and cyclic bis[2]catenanes, whose structures are clearly evidenced by single-crystal X-ray analysis. Owing to the multiple positively charged nature, as well as the potential synergistic effect of the Cu(I) and Pt(II) metal ions, the cyclic bis[2]catenanes display broad-spectrum antibacterial activity. This work not only provides an efficient strategy for the construction of heterometallic [2]catenanes and cyclic bis[2]catenanes but also explores their applications as superior antibacterial agents, which will promote the construction of advanced supramolecular structures for biomedical applications.

Mechanically interlocked molecular handcuffs

The field of mechanically interlocked molecules that employ a handcuff component are reviewed. The variety of rotaxane and catenane structures that use the handcuff motif to interlock different components are discussed and a new nomenclature, distilling diverse terminologies to a single approach, is proposed. By unifying the interpretation of this class of molecules we identify new opportunities for employing this structural unit for new architectures.

Mechanically interlocked molecules that employ a handcuff component provide a pathway to highly unusual structures, a new nomenclature is proposed which helps to identify opportunities for employing this structural unit for new architectures.

A cyclic bis[2]catenane metallacage

Catenated cages represent chemistry’s challenging synthetic targets because a three-dimensional assembly is necessary for their formation. Herein, a cyclic bis[2]catenane is constructed through the coordination-driven self-assembly of the interlocked bis-metallacage, by the 90° Pt(II) heteroligation of the endo-functionalized double-bridged tweezer bearing pyridyl moieties and the tetra-carboxylated linker. NMR spectrometry, X-ray crystallography and mass spectrometry confirm the formation of a cyclic bis[2]catenane with “∞”-shaped topology via a 14-component self-assembly. Particularly, reversibly responsive transformation between the bis[2]catenane and the bis-metallacage can be realized by guest exchange, concentration effect and solvent effect. This work represents a novel example of a cyclic cage-based [2]catenane oligomer.

Catenated cages are challenging synthetic targets in chemistry. Here, the authors employ a multi-component coordination strategy using a Pt(II) heteroligation to construct a cyclic bis[2]catenane metallacage, which could be reversibly transformed between the catenated structure and the bis-metallacage.

Ultramacrocyclization via selective catenation in water

A set of two cyclic [2]catenane dimers were self-assembled in aqueous media via selective hydrazone condensation, by means of either one-pot or post-functionalization procedures.

Chirality in rotaxanes and catenanes

Although chiral mechanically interlocked molecules (MIMs) have been synthesised and studied, enantiopure examples are relatively under-represented in the pantheon of reported catenanes and rotaxanes and the underlying chirality of the system is often even overlooked. This is changing with the advent of new applications of MIMs in catalysis, sensing and materials and the appearance of new methods to access unusual stereogenic units unique to the mechanical bond. Here we discuss the different stereogenic units that have been investigated in catenanes and rotaxanes, examples of their application, methods for assigning absolute stereochemistry and provide a perspective on future developments.

Coordination-Driven Self-Assembly of a Molecular Knot Comprising Sixteen Crossings

Molecular knots have become highly attractive to chemists because of their prospective properties in mimicking biomolecules and machines. Only a few examples of molecular knots from the billions tabulated by mathematicians have been realized and molecular knots with more than eight crossings have not been reported to date. We report here the coordination-driven [8+8] self-assembly of a higher-generation molecular knot comprising as many as sixteen crossings. Its solid-state X-ray crystal structure and multinuclear 2D NMR findings confirmed its architecture and topology. The formation of this molecular knot appears to depend on the functionalities and geometries of donor and acceptor in terms of generating appropriate angles and strong π-π interactions supported by hydrophobic effects. This study shows coordination-driven self-assembly offers a powerful potential means of synthesizing more and more complicated molecular knots and of understanding differences between the properties of knotted and unknotted structures.

Studies towards the synthesis of Pd(ii)-containing [2] and [3]catenanes in aqueous media

Here is reported the investigation of a synthetic route for the preparation of Pd(ii)-containing catenanes in aqueous media.

Strategies and tactics for the metal-directed synthesis of rotaxanes, knots, catenanes, and higher order links

More than a quarter of a century after the first metal template synthesis of a [2]catenane in Strasbourg, there now exists a plethora of strategies available for the construction of mechanically bonded and entwined molecular level structures. Catenanes, rotaxanes, knots and Borromean rings have all been successfully accessed by methods in which metal ions play a pivotal role. Originally metal ions were used solely for their coordination chemistry; acting either to gather and position the building blocks such that subsequent reactions generated the interlocked products or by being an integral part of the rings or "stoppers" of the interlocked assembly. Recently the role of the metal has evolved to encompass catalysis: the metal ions not only organize the building blocks in an entwined or threaded arrangement but also actively promote the reaction that covalently captures the interlocked structure. This Review outlines the diverse strategies that currently exist for forming mechanically bonded molecular structures with metal ions and details the tactics that the chemist can utilize for creating cross-over points, maximizing the yield of interlocked over non-interlocked products, and the reactions-of-choice for the covalent capture of threaded and entwined intermediates.

Construction of [(η5-C5Me5)MoS3Cu3]-Based Supramolecular Assemblies from the [(η5-C5Me5)MoS3(CuNCS)3]- Cluster Anion and Multitopic Ligands with Different Symmetries

The assembly of a new family of [(eta5-C5Me5)MoS3Cu3]-supported supramolecular compounds from a preformed cluster [PPh4][(eta5-C5Me5)MoS3(CuNCS)3].DMF (1.DMF) with four multitopic ligands with different symmetries is described. Reactions of 1 with 1,2-bis(4-pyridyl)ethane (bpe) (Cs symmetry) or 1,4-pyrazine (1,4-pyz) (D2h symmetry) in aniline gave rise to two polymeric clusters {[{(eta5-C5Me5)MoS3Cu3}2(NCS)3(mu-NCS)(bpe)3].3aniline}n (2) and [(eta5-C5Me5)MoS3Cu3(1,4-pyz)(mu-NCS)2]n (3). On the other hand, solid-state reactions of 1 with 2,4,6-tri(4-pyridyl)-1,3,5-triazine (tpt) (D3h symmetry) or 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphyrin (H2tpyp) (D4h symmetry if 21H and 23H of the H2tpyp are omitted) at 100 degrees C for 12 h followed by extraction with aniline yielded another two polymeric clusters {[(eta5-C5Me5)MoS3Cu3(tpt)(aniline)(NCS)2].0.75aniline. 0.5H2O}n (4) and {[(eta5-C5Me5)MoS3Cu3(NCS)(mu-NCS)(H2tpyp)0.4(Cu-tpyp)0.1].2aniline.2.5benzene}n (5). These compounds were characterized by elemental analysis, IR spectra, UV-vis spectra, 1H NMR, and X-ray analysis. Compound 2 consists of a 2D (6,3) network in which [(eta5-C5Me5)MoS3Cu3] cores serve both a T-shaped three-connecting node and an angular two-connecting node to interconnect other equivalent units through single bpe bridges, double bpe bridges, and mu-NCS bridges. Compound 3 has a 3D diamondlike framework in which each [(eta5-C5Me5)MoS3Cu3] core, acting as a tetrahedral connecting node, links four other neighboring units by 1,4-pyz bridges and mu-NCS bridges. Compound 4 contains a honeycomb 2D (6,3)core(6,3)tpt network in which each cluster core, serving a trigonal-planar three-connecting node, links three pairs of equivalent cluster cores via three tpt lignads. Compound 5 has a rare scalelike 2D (4,62)core(42,62)ligand network in which each cluster core acts as a T-shaped three-connecting node to link with other equivalent ones through mu-NCS bridges and H2tpyp (or Cu-tpyp) ligands. The results showed that the formation of the four different multidimensional topological structures was evidently affected by the symmetry of the ligands used. In addition, the third-order nonlinear optical properties of 1-5 in aniline were also investigated by using Z-scan techniques at 532 nm.

Synthesis of [3]Catenanes Based on Metal-Directed Self-Assembly and π-Donor/π-Acceptor Interactions

A metal-directed self-assembly of [3]catenanes in combination with pi-pi interactions was investigated. Ligands based on 4,4'-bipyridinium or 2,7-diazapyrenium were used in conjunction with dioxoaryl cyclophanes (4-6) and trans-PdCl2(CH3CN)2. The [3]catenanes show a dinuclear palladium 46-membered metallomacrocycle interlocked by two pi-complementary dioxoaryl macrocycles. [structure: see text].