Chromium-containing organometallic nanomaterials for non-linear optics

Novel nonlinear optical polymeric film-producing nanocomposites based on bis(arene)chromium complexes incorporated into a CN-containing matrix have been developed. Polymer-precursors were prepared by the reaction of Cr(EtnC6H6 n)2 (n = 1,2,3) with CN-containing vinyl monomers (acrylonitrile, crotononitrile or ethyl 2-cyanopropenoate). Extraordinarily high third-order nonlinear optical susceptibilities of the ultra-fast electronic type have been demonstrated at various wavelengths for polymer films prepared from these composites by using the Z-scan technique and the spectrally-resolved two-beam coupling method. A notable electro-optical response of the composite with an essential contribution of orientational effects was established. The electron-diffraction pattern in films and the presence of a non-zero electro-optical coefficient in the absence of an external poling field indicates the formation of self-organized structures. In CrPAN and [CrPAN]+TCNE–, a single Cr-C distance was found in the EXAFS data refinement, showing that the arene rings are parallel and symmetric as in bis(benzene)chromium. The Cr-C distances in these two materials are very similar to the 2.13 Angstroms in bis(benzene)chromium. In [CrPAN]+OH–, more than one metal-carbon distance was resolved, showing either that the two arene rings are at different distances from the metal, or that they are tilted rather than parallel.