Hydrogen bonding of two 1-(phi-ammonioalkyl)-2-acyl-cyclopentadienides in the solid state

The solid-state structures of a 1-(phi-ammoniopropyl)-2-(2-thienylcarbonyl) -cyclopentadienide (2) and a 1-(phi-ammoniopentyl)-2-(4-methoxybenzoyl)-cyc lopentadienide (3) have been determined. Both betaines self-assemble by NH ... O hydrogen bonds, but the motifs are different. In the ammoniopropyl ca se, both intramolecular and intermolecular hydrogen bonds of this type exis t, the latter bond being responsible for the formation of infinite chains. In the ammoniopentyl case, intermolecular hydrogen bonds build up a two-dim ensional network which contains centrosymmetric dimers held together by NH ... O=C-aryl hydrogen bonds.