Giant hollow MnL2n spherical complexes: structure, functionalisation and applications

Abstract

Drawing inspiration from the self-assembly of hollow spherical virus capsids and protein cages found in nature, a family of roughly spherical coordination polyhedra with general formula MnL2n was designed and several members of the series have been synthesised. These spherical complexes are self-assembled upon reaction of bent bis(pyridine) ligands with Pd(2+) ions. The introduction of functional side chains into the ligands is straightforward, making the synthesis of both exo- and endohedrally functionalised spherical complexes possible. Accumulation of a high density of functional groups at the periphery of the spherical framework results in an enhancement of the weak interactions used in biomolecular recognition processes and the strong and selective interaction of the complex with a variety of substrates. Discrete and well-defined environments are generated within the spherical framework by functionalisation of the interior of the complex. These environments can be used for the selective encapsulation of guest molecules, including species as diverse as simple metal ions, fluoroalkanes and fullerenes. The well-defined cavity of the spherical complexes can also be exploited for the synthesis of precisely size-controlled nanoparticles and polymers. Most recently, a protein was successfully enclosed within a hollow self-assembled spherical complex, with a long-term view towards the control of protein functions for the development of new applications.

Self-assembled metal–organic polyhedra: An overview of various applications

“…(b) The family of M n L 2n polyhedral cages, where metals (M) and bridging bis(pyridine) ligands (L) are mapped onto the vertices and edges respectively. Reproduced with permission from [12].…”

“…The metal-ligand bond coordination is a cornerstone of various designing strategies such as directional bonding, symmetry interactions, molecular paneling, weak linking, and dimetallic building blocks. These strategies are predominantly used by Atwood [7], Cotton [8,9], Fujita [10][11][12], Lindoy [13][14][15][16], Mirkin [17][18][19], Nitschke [20][21][22], Raymond [23][24][25][26], Stang [27][28][29][30][31], Saalfrank [32,33], Ward [34,35], Yaghi [36][37][38], Zhou [39][40][41], and others [42][43][44][45] in designing 2D and 3D supramolecular architectures. The directional bonding approach relies on the angular orientation (0 to 180°) of binding sites and appropriate stoichiometric ratio of the precursor units.…”

An Introduction to the Mechanical Bond

“…Moreover, despite a lack of formal aesthetic training among most chemistsand the longstanding stigma associated with discussing beauty in the scientific literature-at least 2% of chemistry papers mention 52 aesthetic values as a justification for studying a molecule. Classic examples include a variety of synthetic Platonic and Archimedean objects 53 such as cubane, 54 dodecahedrane, 55,56 buckminsterfullerene, 57 and many metal-ligand coordination complexes and cages 58,59 that have been lauded 42 for their symmetry, simplicity, uniformity, and harmony-"simply beautiful and beautifully simple." On the other hand, natural products and their corresponding organic transformations have been admired [60][61][62] for the beauty in their elegance, complexity, and sophistication.…”

Star PolyMOCs with Diverse Structures, Dynamics, and Functions by Three‐Component Assembly

“…Initially, G′ increases rapidly: from 400 ± 100 Pa for Gel 0 to 3800 ± 200 Pa for Gel 3 ; i.e., Gel 3 was nearly 10 times stiffer than Gel 0 , which is remarkable given that the ~18 SMLs in each MOC in Gel 3 are not elastically effective. As n increases beyond 3, the polyMOCs become softer: G′ dropped to 500 ± 50 Pa for Gel 13 . In these examples, a stoichiometric amount of Pd 2+ was used to fully coordinate all PLs and SMLs.…”

“…[9][10][11][12][13][14][15][16][17][18][19][20][21][22] By rational design of the ligands and proper choice of the metal ions, MOCs of different M x L y stoichiometries, sizes, and geometries can be synthesized. [23][24][25][26][27][28][29] Inspired by this structural versatility and potential applications such as mechanical enhancement, catalysis, encapsulation, sensing, etc., much effort has been recently devoted to installing MOCs into polymer networks to provide 'polyMOC' hybrid materials with tunable viscoelasticity and functionality.…”