MOLECULAR MATERIALS FOR NONLINEAR OPTICS - 2ND-HARMONIC GENERATION AND THE CRYSTAL AND MOLECULAR-STRUCTURE OF THE 4-NITROPHENYLIMINE OF FERROCENECARBOXALDEHYDE

Ferrocenyl derivatives of the form [(eta-C5H5)Fe(eta-C5H4)CHN-(p-C6H4X)], where X=NO2, F, Br, were tested for second harmonic generation (s.h.g.). Only when X = NO2 was such activity observed. This was not large, however, at 1/3 times that of the urea standard. X-ray analysis confirms that the material is non-centrosymmetric, crystallizing in the space group P2(1)2(1)2(1). This dictates that despite being acentric the crystal arrangement essentially ensures a cancelling of the dipolar nature of the molecule. The residual s.h.g. must arise from intermolecular effects. This is only the second structural report of such a metallocene derivative to display s.h.g. The possible influence of the molecular shape of 1 and of related compounds is also discussed.