Hierarchical Assembly of Antiparallel Homochiral Sheets Formed by Hydrogen-Bonded Helixes of a Trapped-Valence Co^II/Co^III Complex

Abstract

On the basis of selected reagents and reaction conditions, a chiral dinuclear trapped-valence CoII/CoIII complex was conveniently obtained {[Co2(L)­(O2CCH2CO2)­(H2O)]­·EtOH­·1.25H2O, being H3L = 2-(5-bromo-2-hydroxyphenyl)-1,3-bis­[4-(5-bromo-2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine)}. This complex behaves as a compact amphiphile, whose hydrophilic pole attracts ethanol and water solvates. Its crystal packing shows a hierarchical structure controlled by an amphiphatic nature. Molecules of each enantiomer are head-to-tail connected through intermolecular hydrogen bonds to give rise to infinite helixes. These helical chains are stacked in homochiral two-dimensional sheets with hydrophilic pockets, where water and ethanol solvates are trapped. Each layer displays its homoenantiomeric helixes with a parallel orientation, while their mirror helixes, which are alternate, are antiparallelly oriented.

2D Supramolecular Structure for a Chiral Heterotrinuclear ZnII2HoIII Complex through Varied HBonds Connecting Solvates and Counterions

“…Consequently, these layers are not connected via classic bonds, but through C-H···A bonds (A = O or Br). This behaviour has been previously observed for other related ligands [24].…”

Filling Tricompartmental Ligands with GdIII and ZnII Ions: Some Structural and MRI Studies

“…In fact, this rear side, which shoes a more clearly hydrophobic nature, with the C-H bonds of imidazolidine, ethylene chains, and aromatic rings pointing towards the outside. This predominance of C-H bonds to form the surface of these layers (Figure 4 and Figure S4 of the Supplementary Materials) could influence on its solubility, as it can lead to forming extended hydrophobic surfaces that have been previously observed [17,54]. In this particular case only a few water molecules are occluded in the middle of these layers by means of an H-bond involving a solvated water molecule (O2w) and a nitrate counterion (Figure 4).…”

“…This value demonstrates that, in spite of the nonacoordination displayed by the Gd 3+ ion in this complex, and the presence of a water molecule in its inner sphere, even fixed by classic hydrogen bonds [55] Gd′ shows a low r1 relaxation and, accordingly, it is not appropriate as contrast agent. The frontal part of the L 3− ligands with the N and O donor atoms shows not only a coordinating character that encloses metal ions, but also a more hydrophilic character than its rear side [54]. In fact, this rear side, which shoes a more clearly hydrophobic nature, with the C-H bonds of imidazolidine, ethylene chains, and aromatic rings pointing towards the outside.…”