Syntheses of three-dimensional catenanes under kinetic control

Abstract

Significance During the past decades, the development of efficient methodologies for the creation of mechanically interlocked molecules (MIMs), such as catenanes and rotaxanes, has not only laid the foundation for the design and syntheses of artificial molecular machines (AMMs) but also opened up new research opportunities in multiple disciplines, ranging from contemporary chemistry to materials science. In this study, we describe a suitane-based strategy for the construction of three-dimensional (3D) catenanes, a subset of MIMs that are far from easy to make. Together with synthetic methodologies based on the metal coordination and dynamic covalent chemistry, this approach brings us one step closer to realizing routine syntheses of 3D catenanes.

Experimental X-ray and DFT Structural Analyses of M12L8 Poly-[n]-catenanes Using exo-Tridentate Ligands

“…Like in other catenanes, efficient aromatic−aromatic interactions are crucial for a good π−π stacking interaction stabilizing the catenane's structure. [19][20][21]31 In the present case, the TPB benzene−benzene distance is 3.839 Å (Figure 1c). In 1•p-CT, the M 12 L 8 "f ramework" is slightly more disordered than in the chloride isostructural version.…”

“…These large openings in the M 12 L 8 nanocages are important for allowing the material to explore the best ligand–ligand interactions during the self-assembling process and the mechanical bond formation. − , Two adjacent triangular empty faces allow the interlacing of other M 12 L 8 nanocages. Like in other catenanes, efficient aromatic–aromatic interactions are crucial for a good π–π stacking interaction stabilizing the catenane’s structure. − , In the present case, the TPB benzene–benzene distance is 3.839 Å (Figure c).…”

“…The self-assembly of discrete metal organic cages ( MOCs ) with well-defined voids is attracting much attention . Besides the exceptional symmetric structures, this finds functional applications in areas such as molecular separation, − catalysis, − and emergent behavior because of their internal nanoconfined space. ,− One strategy to combine the structural properties of MOCs and metal–organic frameworks ( MOFs ) − is by the preparation of poly-[ n ]-catenanes by mechanically interlocking metal organic cages − through mechanical bonds . − However, the synthesis of polycatenanes made of MOCs is not trivial because the cages need to have large windows where catenation can take place. − The self-assembly of Platonic icosahedral MOCs is elusive with very few examples reported so far. , Even more rare are the so-called one-dimensional (1D) M 12 L 8 poly-[ n ]-catenanes which are formed by the interlocking of M 12 L 8 nanocages in one crystallographic direction. This is because enthalpic and entropic aspects play a crucial role in the self-assembly of such large host guest systems. ,− Using exo-tridentate 2,4,6-tris-(4-pyridyl)­pyridine ( TPP ) , or 2,4,6-tris-(4-pyridyl)­benzene ( TPB ) ligands and ZnX 2 (where X = Cl and I), a new class of poly-[ n ]-catenanes self-assembled with large M 12 L 8 icosahedral nanocages have been synthesized in solution.…”

Kinetic Trapping of 2,4,6-Tris(4-pyridyl)benzene and ZnI 2 into M 12 L 8 poly-[n]-catenanes using unconventional self-assembling processes

“…Despite the advances in the synthesis of catenanes 6 , the formation of catenanes made of interlocked MOCs is still very challenging. 7 Interestingly, the combination of properties of MOFs and MOCs 8,9,10,11 can be achieved with poly-[n]catenanes formed by the interlocking of large icosahedral M 12 L 8 nanocages via the mechanical bond. 12 The long extension along one direction of the mechanical bond confers poly-[n]-catenanes the strength, stability but also dynamic behavior of a metal-organic material similar to those observed in MOFs.…”

Stereoselective Construction of Chiral Linear [3]Catenanes and [2]Catenanes

“…The aesthetic appeal and functionality of interlocking structures in nature and in everyday life have led to great research interest in artificial mechanically interlocked molecules (MIMs) . Numerous intricate MIMs, including rotaxanes, molecular knots, catenanes, interlocked molecular cages, and other types of mechanically interlocked architectures, have been obtained by design or by chance. Although chirality has become a central topic in chemistry, the exploration of its manifestation in MIMs remains very limited .…”