Subcomponent Assembly and Transmetalation of Dinuclear Helicates

Abstract

Metallosupramolecular self-assembly strategies and principles have been thoroughly investigated in the past 20 years with the aim of mimicking natures ability to assemble impressive supramolecular structures.[1] Despite the remarkable metal selectivity and recognition in self-assembly reactions, directed metal exchange (i.e. transmetalation) in such supramolecular structures is still underdeveloped, [2] which is surprising as transmetalation is the missing link between the currently known self-assembly strategies "classical selfassembly" and "subcomponent self-assembly". Classical self-assembly of pre-designed ligands with suitable metal ions is a powerful tool, and is most impressively demonstrated by the synthesis of molecular clusters and their application as hosts, [3] catalysts, [4] and molecular traps. [5] However, this strategy is limited by the often time-consuming synthesis of pre-designed ligands and their intrinsic stability.[6] Developing an alternative approach, Nitschke et al. recently described the "subcomponent self-assembly" strategy, which is based on the reversible condensation of suitable amines at metal-coordinated aldehydes under formation of the thermodynamically most stable product. [7] Although this strategy has led to impressive results, such as the assembly of an unlockablerelockable molecular cage, [8] it is still limited by the need for stable (subcomponent) precursor complexes that allow reversible imine formation within their metal coordination sphere. [8,9] Transmetalation of supramolecular structures obtained by classical or subcomponent assembly constitutes a promising strategy to overcome these shortcomings. Following this strategy, supramolecular structures containing ligands not accessible by conventional organic synthesis could be obtained by subcomponent assembly, and transmetalation will subsequently allow the use such ligands in classical supramolecular chemistry. Herein, we present the subcomponent self-assembly of dinuclear complexes and the subsequent transmetalation reaction.Building on our previous work involving sulfur-containing ligands, [10] we investigated the incorporation of the sulfur donor function into Schiff base ligands. In contrast to most Schiff bases, the thiosalicylaldimine (o-mercaptobenzaldimine) subunit is not accessible by direct condensation of an amine with the corresponding o-mercaptobenzaldehyde, which instead leads to 1,5-dithiocines.[11] However, treatment of a preformed complex bearing 2-thiolatobenzaldehyde ligands with appropriate primary amines leads in a template-controlled reaction to the desired complexes with N,S donor functions. [12] We found that nickel(II) and zinc(II) are excellent templates for this chemistry, as indicated by the facile synthesis and stability of the 2-thiolatobenzaldehyde complexes 1 and 2 (Scheme 1). While the molecular structure of the square-planar nickel complex 1·CHCl 3 (see the Supporting Information) shows the cis configuration of the oxygen donors, zinc complex 2 probably has a tetrahedral coordinati...

Self‐Assembly of Conjugated Metallopolymers with Tunable Length and Controlled Regiochemistry

“…[5] These materials have exhibited high luminescence efficiencies, [6] stimuliresponsive behavior, [7] and self-healing properties, [8] and have been used to construct molecular electronics devices. [13] Polymer growth is favored by the strong mutual reinforcement between these two linkages,w hich allows the self-assembly of functional and persistent structures. [13] Polymer growth is favored by the strong mutual reinforcement between these two linkages,w hich allows the self-assembly of functional and persistent structures.…”

“…[1e, 9] Recently,others [7a,10] and our group [11] have demonstrated that metallopolymers can be generated through subcomponent self-assembly,w herein amine and aldehyde subcomponents condense around metal ions to form dynamic covalent [12] C=Na nd coordinative N!Metal bonds simultaneously. [13] Polymer growth is favored by the strong mutual reinforcement between these two linkages,w hich allows the self-assembly of functional and persistent structures. [7a] The resulting metallopolymers can exhibit reversible stimuliresponsive behavior and they have been incorporated into various devices; [7a,11b,c,14] however,control over the length and polymerization process of these materials is yet to be demonstrated.…”

Blockable Zn10L15 Ion Channels through Subcomponent Self‐Assembly

“…Subcomponent self-assembly,i nw hich aldehyde and amine subcomponents come together around metal-ion templates,h as been used to generate complex structures in am odular and hence tunable fashion by other research groups [19] and ourselves. [20] Examples of such structures have been shown to be water-a nd buffer-stable.…”

Symmetry breaking in self-assembled M 4 L 6 cage complexes

“…5), halting the anti ligands' rapid rotation. Although transmetallation has been demonstrated in macrocyclic complexes (47) and helicates (48), to our knowledge this is a unique example of the conversion of one metal-organic polyhedron into another via metal exchange.…”