An “All-in-One” Synthetic Strategy for Linear Metalla[4]Catenanes

Abstract

One fascinating and challenging synthetic target in the field of mechanically interlocked molecules is the family of linear [4]­catenanes, which are topologically identical to the logo of automobile maker Audi. Herein, we report an “all-in-one” synthetic strategy for the synthesis of linear metalla­[n]­catenanes (n = 2–4) by the coordination-driven self-assembly of Cp*Rh-based (Cp* = η5-pentamethylcyclopentadienyl) organometallic rectangle π-donors and tetracationic organic cyclophane π-acceptors. We selected the pyrenyl group as the π-donor unit, leading to homogeneous metalla[2]­catenanes and cyclic metalla[3]­catenanes via π-stacking interactions. By taking advantage of the strong electrostatic interactions between π-donor units and π-acceptor units, a heterogeneous metalla[2]­catenanes and linear metalla[3]­catenanes, respectively, could be obtained by the simple stirring of homogeneous metalla[2]­catenanes with a suitable tetracationic cyclophane. On this basis, this “all-in-one” synthetic strategy was further used to realize a quantitative one-step synthesis of a linear metalla[4]­catenanes via the self-assembly of cyclic metalla[3]­catenanes and tetracationic cyclophanes. All heterogeneous metalla­[n]­catenanes (n = 2–4) were fully characterized by single-crystal X-ray analysis, NMR spectroscopy and electrospray ionization mass spectrometry.

Distinctive features and challenges in catenane chemistry

“…50,51 A few other linear [4]-and [5] catenanes from either stepwise or one-pot synthesis have also been recently reported. [52][53][54][55] In 2017, Rowan and co-workers have explored the use of a metallopolymer to obtain [n]catenanes. 56 The metallopolymer consists of ditopic macrocycles and linear components coordinated via Zn 2+ ions in an alternate fashion, from which a mixture of branched, linear and cyclic [n]catenanes were obtained upon ring-closing metathesis (Fig.…”

Supramolecular-controlled regioselective photochemical [4 + 4] cycloaddition within Cp*Rh-based metallarectangles

“…In the exploration of synthetic strategies to construct supramolecular assemblies, half-sandwich rhodium-based organometallic fragments have shown distinct advantages in synthesizing a range of metallarectangles with adjustable sizes and diverse functional groups. 15–17 Herein, we designed and synthesized rhodium-based photoactive metallarectangles bearing 2,6- and 2,7- AD s, respectively. In general, dipolar repulsions of substituted anthracenes favor antiparallel isomers.…”

Highly selective synthesis and near-infrared photothermal conversion of metalla-Borromean ring and [2]catenane assemblies

“…34,35 The group of Jin has reported the selective construction of a series of intricate structures, such as molecular Borromean ring assemblies, [44][45][46][47][48][49][50][51] Solomon links, [52][53][54] 3 1 , 55 double trefoil, 56 and 4 1 knots, 57 and [2,3,4]catenanes. 24,58 The topological transformations between these structures were explored in detail through concentration-, solvent-and hostguest chemistry effects or via the chemical reactivity of the metal ions and organic ligands. 47,59 Aer careful analysis of the structural characteristics of these supramolecular topologies, we have found that although a number of different forces, such as hydrogen bonding interactions, 57 hydrophobic effects, and others, 49 play diverse roles in the formation of these complexes, the decisive factor in the generation of these structures is generally p-p stacking interactions.…”