Loading Linear Arrays of Cu^II Inside Aromatic Amide Helices

Abstract

The very stable helices of 8‐amino‐2‐quinolinecarboxylic acid oligoamides are shown to uptake CuII ions in their cavity through deprotonation of their amide functions with minimal alteration of their shape, unlike most metallo‐organic structures which generally differ from their organic precursors. The outcome is the formation of intramolecular linear arrays of a defined number of CuII centers (up to sixteen in this study) at a 3 Å distance, forming a molecular mimic of a metal wire completely surrounded by an organic sheath. The helices pack in the solid state so that the arrays of CuII extend intermolecularly. Conductive‐AFM and cyclic voltammetry suggest that electrons are transported throughout the metal‐loaded helices in contrast with hole transport observed for analogous foldamers devoid of metal ions.

Directing the Self‐Assembly of Aromatic Foldamer Helices using Acridine Appendages and Metal Coordination

“…For instance, ferromagnetic exchange between paramagnetic Cu(II) centers has been measured on crystals of Cu-containing aromatic helical foldamers, and electron transport properties have been evidenced in monolayers of the same compounds. [34] Furthermore, the ability of acridine units to form complexes with Pd(II) was efficiently used to form stable cyclic supramolecular assemblies of helices in solution. Self-assembly was somewhat complicated by the presence of isomers associated with helix handedness and helix C-to-N orientation.…”

“…[10a,b,33] Unlike Cu(II), which forms stable helicates within Q n helices, Pd(II) does not coordinate to Q n oligomers and does not interfere with helical folding. [34] Complex formation was first validated upon mixing PdCl 2 (CH 3 CN) 2 with a Q a derivative in CDCl 3 (Figure S10). A distinctive downfield shift of the acridine H4/H5 NMR signals above 11 ppm was observed.…”

Molecular torsion springs: alteration of helix curvature in frustrated tertiary folds

“…[50][51][52][53] Oligomers consisting of Q and P units are easily accessible by solid phase synthesis, 52 and show a high propensity to crystallise. They may find applications in diverse areas, including circularly polarised luminescence, 54,55 charge transport and metal coordination, 56 and protein surface recognition. 11,16,[57][58][59] Early steps were made towards abiotic tertiary structures by connecting several Q n helices to various types of linkers.…”