Molecular recognition by multiple metal coordination inside wavy-stacked macrocycles

Abstract

Most biological and synthetic receptors for small organic molecules employ a combination of relatively weak intermolecular interactions such as hydrogen bonds. A host compound that utilizes stronger yet reversible bonding in a synergistic manner could realize precise recognition, but the regulation and spatial arrangement of such reactive interaction moieties have been a challenge. Here, we show a multinuclear zinc complex synthesized from a macrocyclic ligand hexapap, which inwardly arranges labile metal coordination sites for external molecules. The metallomacrocycle forms a unique wavy-stacked structure upon binding a suitable length of dicarboxylic acids via multipoint coordination bonding. The saddle-shaped deformation and dimerization realize the differentiation of the interaction moieties, and change of guest-binding modes at specific metal coordination sites among the many present have been achieved utilizing acid/base as external stimuli.

A Sandwich‐Shaped Hexanuclear Silver Complex with a Giant Cavity Constructed from a Macrocycle with Inward Chelating Units

“…Furthermore, the coordination linking of multiple macrocycles is a useful strategy to provide a large and well‐defined inner space that cannot be created only by its macrocyclic component [16–22] . We have recently reported hexapap, a macrocyclic hexamer of pap (2‐[(pyridin‐2‐ylmethylene)amino]phenol) [23,24] . Six pap chelating units of the hexapap are inwardly arranged on the giant and rigid macrocyclic scaffold.…”

“…The metals’ coordination sites that are not filled by the pap units have been utilized for the assembly of multiple metal complexes [28–30] and catalytic reactions [31–33] . We previously reported a zinc(II) complex of hexapap, which has 5‐coordinate trigonal‐bipyramidal Zn centers [23] . Two coordination sites per zinc (twelve per macrocycle) are not filled by the chelating unit, and these sites are utilized for the formation of a wavy‐stacked dimer and for the multipoint recognition of dicarboxylates.…”

Polynuclear alkoxy–zinc complexes of bowl-shaped macrocycles and their use in the copolymerisation of cyclohexene oxide and CO2

“…Multidentate macrocycles are attractive as ligands for di-and polynuclear complexes of transition-and f-block metals as they can control both the basic coordination chemistry and the relative spatial positioning of metals within the macrocyclic framework, so providing a pre-organised chemical environment. [1][2][3][4] This ligand design strategy can deliver a diversity of physical and reaction properties in the resulting complexes leading to, for example, clustering and aggregation, [5][6][7][8][9][10][11][12][13][14] catalytic activity, [15][16][17][18][19][20][21][22][23][24][25][26][27][28] molecular magnetism, 29 allosteric constructs, 30,31 and molecular sensing. [32][33][34][35] We have been studying macrocycles in which two donor compartments comprising two dipyrromethane and two Schiff-base nitrogen donors (i.e.…”

A twisted macrocyclic hexanuclear palladium complex with internal bulky coordinating ligands

“…The differentiated units can play distinctive roles in the resulting desymmetrized structures. 3,4 In this context, focusing on the dissymmetry of the macrocycles composed of the same repeating unit is an interesting approach to create elaborate functional molecules.…”

“…We have previously reported a macrocyclic hexapap ligand with a tBu substituent at each pap unit. 4 However, its solubility in common organic solvents is low due to the structure in which many aromatic rings are consecutively arranged. To overcome this problem, we designed a novel hexapap ligand H61 possessing the N, N-bis[2-(2-methoxyethoxy)ethyl]amide group (Scheme 1).…”