PdII and PtII Metal-Directed Self-Assembly of Supramolecular Structures Based on N-Monoalkyl-4,4¢-Bipyridinium Derivatives - Molecular Self-Assembly: Advances and Applications - page 369

-1 -1 -1

M , K = 915

±

35 M , and K = 1292

±

47 M , respectively). The

a a

slightly higher K value for BPP34C10 pseudorotaxane compared

a

to those of presumably reflects the greater

flexibility of this cyclophane to maximize the [C-H … O] hydrogen
bonds.

DB24C8 and DN38C10

The crystal structure of the 1:1 complex between L5 ·2PF and

6

1

DB24C8 H NMR data, that the complex

is stabilized by [C-H … O] hydrogen bonds between methylene
protons and the oxygen atoms of the polyether chain in addition with
[C-H … O] interactions between the

revealed, in agreement with

α

-CH bipyridinium hydrogens

and these oxygen atoms. has adopted a rare C-shaped

conformation in contrast to a the S-shaped one observed in 1,2-bis-
(pyridinium)ethane systems [32]. A π

DB24C8

stacking interaction is also
observed between one of the aromatic rings of

- π

and one
of the bipyridine systems. The angle between the planes is 5

DB24C8

°

, and

the distance between the centroid of the DB24C8 ring involved in

the π stacking interaction and the centroid of the bypyridinium

system is 3.55 Å (Fig. 11.10a).

- π

(a)

(b)

Figure 11.10 (a) Crystal structure of pseudorotaxane complex between

L5 showing [C-H … O] hydrogen bonds ·2PF and DB24C8 6

stacking interaction. (b) Crystal structure of the [3]
catenane (

and

π−π

). Solvent molecules, counter
ions, and hydrogen atoms have been omitted for clarity.
Color labeling scheme as in Fig. 11.5.

BPP3410 ) -( M5a

2

Therefore, our strategy involves the threading of the crown
ethers BPP34C10 , DB24C8 , and DN38C10 with the ligand L5 ·2PF 6

followed by closing of the resulting pseudorotaxanes with metal
centers owning two cis labile ligands affording in that manner the