Self-Assembly, Structure, and Dynamic Interconversion of Metallosupramolecular Architectures Generated by Pb(II) Binding-Induced Unfolding of a Helical Ligand

Abstract

The binding of lead(II) cations to the terpyridine-type subunits of the helical ligand 1 leads to the self-assembly of different polynuclear metallosupramolecular architectures of nanometric size. Three different entities are generated and may be interconverted as a function of metal/ligand stoichiometry: a [4 x 4]Pb(16)(II) grid-type array 2, a [4 # 4]Pb(12)(II) double-cross species 4, and an intermediate complex 3. The structures of 2 and 4 have been confirmed by X-ray crystallography; that of 3 is based on NMR spectral data. The interconversion of the three species generates dynamic diversity and represents an expression of constitutional dynamic chemistry. In the course of ion binding, the helical molecules of ligand 1 unwrap to yield fully extended strands arranged in perpendicular fashion in the architectures 2-4 generated. This process amounts to molecular motions in two directions which confer to the present systems characteristics of two-dimensional nanomechanical devices, capable of performing 2D-contraction/extension motions. The triple features of self-organization, dynamic interconversion, and potential addressability displayed by the processes described trace a self-fabrication approach to nanoscience and nanotechnology.

Enzymnachbildungen auf der Basis supramolekularer Koordinationschemie

“…B. Halogenid oder Cyanid) und wegen der nun fehlenden Chelatisierung zu einer insgesamt flexibleren Struktur. [27] Die katalytische Aktivität von Strukturen, die über diese Ansätze der supramolekularen Koordinationschemie hergestellt wurden, kann hinsichtlich der katalytischen Erhöhung der Reaktionsgeschwindigkeit über Naheffekte in Käfi-gen, [10l, 28] [2, 3,5,[7][8][9]30] Ein wichtiger Gesichtspunkt ist dabei die Aufklärung der Rolle von Mangan-und Eisenporphyrinen bei katalytischen Oxidationen. [31] Viele dieser Systeme entstehen aber nicht durch supramolekulare Koordinationschemie, sondern als Produkte mehrstufiger organischer Synthesen, sodass sie nicht in den Themenbereich dieses Aufsatzes fallen.…”

Mesomeric metallosupramolecular grid architectures

“…Metallosupramolecular grid-type architectures consisting of a regular array of metal -ions coordinated between perpendicular sets of parallel ligands have been shown an intriguing interest as information storage devices for nanotechnology (2,3). A given ligand may generate various supramolecular architectures depending on internal parameters (i.e.…”

“…(2 -5). Within this context, the grid-type architectures may present a number of novel behaviours such as cooperativity, diversity, selection and adaptation (2,3). The simple building block N,N 0 -bis-pyridin-2-ylmethylene-benzene-1,4-diamine (1) carrying two 2-iminopyridine functionalities, gives easy access to bipyridine-type binding sites, with a exobidentate coordination mode via both the pyridine and the imine nitrogen atoms.…”

“…metal ions (7,8). Among the non-exclusive examples of metal complexes with the ligand 1 reported so far are (1) mononuclear [Re(CO) 3 Cl] 2 (m 2 1) (7a) and polynuclear [Zn1(DMF) 2 ] n ·(DMF) n ·(ClO 4 ) 2n (6a) complexes; (2) heteroleptic complexes [Cu 2 (L 1 ) 2 (1)](PF 6 ) 2 , L 1 -2,9-diarylphenanthroline (7b); (3) one-dimensional coordination polymers FeCl 2 1·2CH 3 OH (7c), [{(h 6 -C 6 H 6 )RuCl} 2 (m-1)] (BF 4 ) 2 , [{(h 6 -C 10 H 14 )RuCl} 2 (m-1)](BF 4 ) 2 and [{(h 6 -C 6 Me 6 )RuCl} 2 (m-1)](BF 4 ) 2 (7d); (4) the grid-type compounds 1 4 Cu 4þ 4 and 1 4 Ag 41 4 (7e) and (5) the zig -zag polymeric coordination arrays [{Ag 2 1 2 }(ClO 4 ) 2 (CH 3 CN)] n reorganising in solution to form the [{Ag 4 1 4 }(ClO 4 ) 4 ] grid species (7f). Previous studies also suggested that a partial hydrolysis of the ligand occurs, due to the hydration water/ moisture of the metal salts, resulting in the presence of ligand 1 0 in the complexes of Zn 2þ , Cd 2þ , Hg 2þ (8a) and Ru 2þ (6b) instead of corresponding complexes with 1.…”

2-(1H-pyrazol-3-yl)pyrazine: a polytopic N-donor ligand used to construct Cu-[2+2] molecular grid: synthesis, structure, and magnetic properties

“…The choice of ligand lies in two main factors, namely, rigidity (to minimize variability) and the use of polytopic coordination sites (to ensure multiple metal centers are coordinated) (e.g. pyridazine, pyrimidine, phenoxide) [7][8][9][10][11][12][13][14]. N 3 -(2-pyridoyl)-2-pyridinecarboxamidrazone and analogs are often employed to construct homometallic or heterometallic [2þ2] molecular grids [1][2][3].…”