Synthesis and X-Ray Structure of a Ditopic Ligand for Constructing Crown Ether-Based Metalloassemblies

ABSTRACT

A novel dialkylammonium salt, 1.PF₆, bearing a pyridyl group has been prepared and characterised by x-ray crystallography: triclinic space group P-1, a = 8.8141(1), b = 9.8902(2), c = 10.2611(1), A˚  and α = 82.008(1)°, β = 85.212(1)°, γ = 71.058(1)°, Z = 2, R = 0.0542 for 3902 independent reflections. The hydrogen-bonded tape generated within the crystal lattice is augmented by water molecules between the divided units in an N-H…O and O-H…N_py manner. The nature of the [2]pseudorotaxane formed upon the addition of DB24C8 to 1.PF₆ (K_a = 2293 M⁻¹) is characterised in the solid state (monoclinic space group P 2₁/c, a = 14.3808(4), b = 15.0194(4), c = 18.2599(6), A˚  and β = 95.723(1)°, Z = 4, R = 0.0766 for 9313 independent reflections) by hydrogen bonds between NH₂ and CH₂ groups of the guest with polyether oxygens of the crown ether. These hydrogen bond distances vary with close contacts between 2.01 and 2.58 A˚.  ¹H NMR spectroscopy and mass spectrometry further support the presence of the [2]pseudorotaxane in solution.

Keywords:

• ¹H NMR spectroscopy
• hydrogen bonding
• pseudorotaxane
• supramolecular chemistry
• X-ray crystal structure