Controllable Coordination Self‐Assembly Based on Flexible Tripodal Ligands: From Finite Metallocages to Infinite Polycatenanes Step by Step

Abstract

This article describes the developments in coordination self-assembly based on flexible tripodal ligands with different metal species. Various finite metallocages such as M3 L2 , M6 L8 , M6 L4 , M4 L4 and different catenanes based on discrete metallocages constructed from flexible tripodal ligands with suitable metal species are presented here. Many M3 L2 metallocages based on ligands L(1) -L(12) and different two-coordinated metal species have been prepared, in which various Ag(I) salts and other metal species that have been protected by suitable groups, such as Zn(OAc)2 , ZnBr2 , and PdBr2 , have been used as effective acceptors. All of the M6 L8 -type metallocages are constructed from ligands L(2) or L(12) -L(20) and different four-coordinated metal species, such as various palladium(II) salts or NiCl2 , and have similar topological structures. Only a few discrete M6 L4 -type metallocages, based on ligands L(21) -L(24) , have been reported, using different strategies such as protecting groups and steric hindrance. All of the M4 L4 -type cages have similar topological structures and are constructed from ligands L(25) -L(29) with multiple donor sites. More intriguing interlocking ensembles constructed from discrete metallocages are also described here in detail, namely, three [2]catenanes based on ligands L(30) -L(32) and four polycatenanes based on ligands L(33) -L(34) .

Increasing the histidine ‘density’ in tripodal peptides by gradual N -functionalization of tris (2-aminoethyl)amine (tren) with l -histidyl units: The effect on zinc(II) complexes

“…At pH 6 the parent Zn 3 L3 2 is formed; this stoichiometry implies that the zinc(II) ions are coordinated by two arms of the tripod, originated from either the same or two different ligand molecules (Scheme 4). Such M 3 L 2 type cluster formation is well described in the literature regarding tripodal ligand complexes [30], and a similar species was detected in the copper(II)-L3 system, too [12]. correspond to a single (de)protonation state (at this pH ~95% of zinc(II) is bound in Zn 3 H −4 L3 2 ).…”

Metal–organic tube or layered assembly: reversible sheet-to-tube transformation and adaptive recognition

“…1). In order to prepare desired assemblies, M-N (M ¼ Pd(II), Ag(I), Zn(II), N ¼ pyridyl ligand) units with moderate coordination strength have been selected and tested, then a series of exible ligands has been synthesized, 68,69 and various two-coordinated metal acceptors such as orthogonal ethylenediamine "capping" Pd(II), linear Ag(I) salts, and rhombic ZnX 2 (X ¼ Cl À , Br À , I À ) have been screened in the trials. We nally nd that the combination of tri-((pyridin-4-yloxy)methyl)ethane (TPOME) and ZnBr 2 leads to the successful assembly of both 1D metal-organic tubes with nanochannels and 2D layered metal-organic assembly driven by different templates (Fig.…”

Controllable Coordination Self‐Assembly Based on Flexibility of Ligands: Synthesis of Supramolecular Assemblies and Stimuli‐Driven Structural Transformations

“…Furthermore, such metal‐organic assemblies based on flexible ligands usually display excellent flexibility and variability, and can be further assembled driven by suitable external stimuli ,,. Since 2000, our group has been striving to uese flexible ligands to controllably prepare metal‐organic coordination compounds ,,,. Herein, we would like to highlight our research, how to controllably construct supramolecular assemblies based on flexibility of ligands driven by different external stimuli.…”

“…So far, many delicate and elegant coordination assemblies such as helices, metallocycles, metallocages and polyhedrons, have been successfully prepared by the groups of Lehn, Stang, Fujita, Raymond, Mirkin,, Nitschke, and others Furthermore, by taking advantage of the relatively rigid and dynamic nature of coordination bonds, various stimuli such as temperature, concentration, solvents, pH, anions, guests, light, and change in component fractions or chemical compositions have been successfully used to transform assembly process ,…”