title: Induced-fit binding of pi-electron-donor substrates to macrocyclic aromatic ether imide sulfones: a versatile approach to molecular assembly.
abstract: Novel macrocyclic receptors that bind electron-donor aromatic substrates through pi-stacking donor-acceptor interactions are obtained by cycloimidisation of an amine-functionalised aryl ether sulfone with pyromellitic and 1,4,5,8-naphthalenetetracarboxylic dianhydrides. These macrocycles can form complexes with a wide variety of pi-donor substrates, including tetrathiafulvalene, naphthalene, anthracene, pyrene, perylene and functional derivatives of these polycyclic hydrocarbons. The resulting supramolecular assemblies range from simple 1:1 complexes to [2]- and [3]pseudorotaxanes and even (as a result of crystallographic disorder) an apparent polyrotaxane. Direct five-component self-assembly of a metal-centred [3]pseudorotaxane is also observed on complexation of a macrocyclic ether imide with 8-hydroxyquinoline in the presence of palladium(II) ions. Binding studies in solution were carried out by using (1)H NMR and UV/Vis spectroscopy, and the stoichiometries of binding were confirmed by Job plots based on the charge-transfer absorption bands. The highest association constants were found for strong pi-donor guests with large surface areas, notably perylene and 1-hydroxypyrene, for which K(a) values of 1.4x10(3) and 2.3x10(3) M(-1), respectively, were found. Single-crystal X-ray analyses of the receptors and their derived complexes reveal large induced-fit distortions of the macrocyclic frameworks as a result of complexation. These structures provide compelling evidence for the existence of strong attractive forces between the electronically complementary aromatic pi systems of host and guest.
authors: Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD, UK. h.m.colquhoun@rdg.ac.uk
authors: Howard M
authors: HM
authors: Colquhoun
authors: Zhixue
authors: Z
authors: Zhu
authors: David J
authors: DJ
authors: Williams
authors: Michael G B
authors: MG
authors: Drew
authors: Christine J
authors: CJ
authors: Cardin
authors: Yu
authors: Y
authors: Gan
authors: Andrew G
authors: AG
authors: Crawford
authors: Todd B
authors: TB
authors: Marder