Synthesis and structure of (cis)-[1-ferrocenyl-2-(4-nitrophenyl)ethylene], an organotransition metal compound with a large second-order optical nonlinearity

Abstract

There is considerable interest in materials with nonlinear optical properties. Two important manifestations of light interacting with a nonlinear optical material are, the process of second-harmonic generation (SHG) which is relevant to new laser technology, and the electro-optic effect which has applications in telecommunications and in integrated optics¹. Several inorganic and organic materials with unusually large second-order nonlinearities are known¹. However, reports of organometallic compounds with second-order nonlinear optical properties are few^2–4 and they have relatively small values for SHG efficiencies. Here we describe a new compound (cis)-[1-ferrocenyl-2-(4-nitrophenyl)ethylene] (compound 2) exhibits solvatochromic behaviour. A Kurtz-powder measurement, using 1.907 µm light from a Raman shifted Nd-YAG laser operating at 1.064 µm, shows the compound provides highly efficient second harmonic generation, with a signal some 62 times that from a urea reference sample. The single crystal X-ray structure of (cis)-[1-ferrocenyl-2-(4-nitrophenyl)ethylene] has been determined. The large nonlinear optical property of this compound demonstrates that organotransition metal compounds can play an important role in the development of the nonlinear optical properties of materials.