Preorganizing Linear (Self-Complementary) Quadruple Hydrogen-Bonding Arrays Using Intramolecular Hydrogen Bonding as the Sole Force

In this article we describe a rational approach for prefixing multiple cooperative binding sites in
an ideal spatial arrangement on a structurally rigid backbone, constrained exclusively by
intramolecular hydrogen bonding. The idea is exemplified by the ability of the self-assembling
constructs 1a−e and 2a,b to form hydrogen-bonded dimers, whose structural preorganization has
been solely effected by intramolecular hydrogen bonding. The readily accessible amidinourea
backbone has been used as a common platform for the construction of a variety of such
self-assembling systems. ESI mass spectrometry and single-crystal X-ray diffraction studies have
been particularly effective in investigating the self-assembling propensities of these systems.
Remarkably, most the H-bonded dimers reported herein undergo an unusual mode of self-assembly,
using intermolecular four-membered ring hydrogen-bonded interaction, affording extended supramolecular networks.