Synthesis, properties, and solid-state assemblies of β-alkyl-substituted dipyrrolyldiketone BF2 complexes

In this paper, the synthesis and solid-state structures of beta-alkyl-substituted dipyrrolyldiketone BF2 complexes are discussed; these complexes can function as pi-conjugated acyclic anion receptors ("molecular flippers") and are potential building subunits of anion-responsive pi-conjugated oligomers or polymers. Modes of the solid-state assemblies in these complexes determined by performing single-crystal X-ray analysis are found to depend on the lengths of the alkyl chains at the beta-positions. A beta-methyl-substituted receptor has a highly planar structure, which efficiently forms stacking assemblies in the core pi-plane in the solid state, while a beta-ethyl-substituted receptor shows no stacking assemblies due to the presence of bulky ethyl moieties, which form only dimeric structures by hydrogen bonding. beta-Alkyl-substituted anion receptors can be used not only as monomer units of stimuli-responsive polymeric macromolecules but also as components of solid-state electronic materials. (C) 2009 Elsevier B.V. All rights reserved.