CH···π Interaction for Rhenium-Based Rectangles: An Interaction That Is Rarely Designed into a Host−Guest Pair

Alkoxy- and thiolato-bridged ReI molecular rectangles [{(CO)3Re(μ-ER)2Re(CO)3}2(μ-bpy)2] (ER = SC4H9, 1a;
SC8H17, 1b; OC4H9, 2a; OC12H25, 2b; bpy = 4,4‘-bipyridine) exhibit strong interactions with several planar aromatic
molecules. The nature of their binding was studied by spectral techniques and verified by X-ray diffraction analysis.
Standard absorption and fluorescence titrations showed that a relatively strong 1:1 interaction occurs between
aromatic guests such as pyrene and these rectangles. The results of a single-crystal X-ray diffraction analysis
show that the recognition of 1 with a pyrene molecule is mainly due to CH···π interactions and the face of the
guest pyrene is located over the edges of the bpy linkers of 1. This is a fairly novel example of an interaction that
is rarely designed into a host−guest pair. Furthermore, the interaction of 1 with Ag+ results in the self-organization
of supramolecular arrays, as revealed by solid-state data.