Topologically Controlled Syntheses of Unimolecular Oligo[n]catenanes

Abstract

Catenanes are a well-known class of mechanically interlocked molecules that possess chain-like architectures and have been investigated for decades as molecular machines and switches. However, the synthesis of higher-order catenanes with multiple, linearly interlocked molecular rings has been greatly impeded by the generation of unwanted oligomeric byproducts and figure-of-eight topologies that compete with productive ring closings. Here, we report two general strategies for the synthesis of oligo[n]catenanes that rely on a molecular “zip-tie” strategy, where the “zip-tie” is a central core macrocycle precursor bearing two phenanthroline (phen) ligands to make odd-numbered oligo[n]catenanes, or a preformed asymmetric iron(II) complex consisting of two macrocycle precursors bearing phen and terpyridine ligands to make even-numbered oligo[n]catenanes. In either case, preformed macrocycles or [2]catenanes are threaded onto the central “zip-tie” core using metal templation prior to ring-closing metathesis (RCM) reactions that generate several mechanical bonds in one pot. Using these synthetic strategies, a family of well-defined linear oligo[n]catenanes were synthesized, where n = 2, 3, 4, 5, or 6 interlocked molecular rings, and n = 6 represents the highest number of linearly interlocked rings reported to date for any isolated unimolecular oligo[n]catenane.

Kinetic trapping of 2,4,6-tris(4-pyridyl)benzene and ZnI2 into M12L8 poly-[n]-catenanes using solution and solid-state processes

“…Poly-[n]-catenanes [1][2][3][4] self-assembled interlocked metal organic cages (MOCs) 5 are classified as mechanically interlocked materials (MIMs) and are receiving considerable interest not only due to their potential applications but also due to their aesthetic synthetic aspects. Despite 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 effect of thread-like monomer structure on the synthesis of poly[n]catenanes from metallosupramolecular polymers

“…1): the cyclic (c-), the linear (l-), the branched (b-), or the network poly[n]catenane. There have been several examples of oligomeric [n] catenanes, [37][38][39][40][41][42][43] most notably the l- [5]catenane (or Olympiadane) 37 and a branched b- [7] catenane 35 synthesized by Stoddart and co-workers. More recently a linear [6]catenane was prepared by Barnes and coworkers.…”

“…More recently a linear [6]catenane was prepared by Barnes and coworkers. 43 While they are all major synthetic achievements, these compounds were synthesized in a stepwise manner, which is less conducive to accessing high molar mass MIPs. In a different approach, Meijer and Di Stefano used ring-opening metathesis of a [2]catenane to yield oligomeric [n] catenated molecules.…”

Supramolecular chemistry of two new bis(1,2,3-triazolyl)pyridine macrocycles: metal complexation, self-assembly and anion binding

“…2). It was also thought that this approach may allow relatively easy access to catenane oligomers [43][44][45][46] such as [3], [5] or [7]catenanes, which are notoriously difficult to prepare. 45 Our planned approach was to use the well-established complexation of two btp motifs around a transition metal ion to form a complex with pendant azide groups and then use copper catalysed azide alkyne cycloaddition (CuAAC) reactions with 2,6-diethynylpyridine as the catenane forming reaction (Fig.…”