Three enantiomerically pure chiral analogues of 4-[(E)-2-ferrocenyl-ethenyl
]pyridinium iodide have been synthesized. Their bulk efficiencies in second
harmonic generation (SHG) have been measured (from 0 to 0.25 times that of
urea). Furthermore, the crystal structures for two of them and for the par
ent 4-[(E)-2-ferrocenyl-ethenyl]pyridinium iodide have been determined by X
-ray diffraction studies. Crystal packing could explain the very different
SHG bulk efficiencies in this family of materials. (C) 2001 Elsevier Scienc
e B.V. All rights reserved.