Synthesis of organometallic Ru(II) and Fe(II) complexes containing fused rings hemi-helical ligands as chromophores : evaluation of non-linear optical properties by HRS

A new family of three-legged piano stool structured organometallic compounds containing the fragment η5-cyclopentadienyl-ruthenium(II)/iron(II) has been synthesized to evaluate the existence of electronic metal to ligand charge transfer upon coordination of the novel benzodithiophene ligands (BDT), benzo[1,2-b;4,3-b′]dithiophen-2-carbonitrile (L1) and benzo[1,2-b;4,3-b′]dithiophen-2′nitro-2-carbonitrile (L2). All the compounds were characterized by 1H, 13C, 31P NMR, IR and UV-Vis. spectroscopies and their electrochemistry studied by cyclic voltammetry. The X-ray structures of [Ru(η5-C5H5)(PPh3)2(NCC10H5S2)][PF6] (1Ru), [Ru(η5-C5H5)(PPh3)2(NCC10H5S2)][CF3SO3] (1′Ru), [Ru(η5-C5H5)(DPPE)(NCC10H5S2)][PF6] 2Ru and [Fe(η5-C5H5)(DPPE)(NCC10H5S2)][PF6] (2Fe) were determined by X-ray diffraction showing centric crystallization on groups P over(1, ̄) and P21/n, respectively. Quadratic hyperpolarizabilities (β) of some of the complexes (2Fe, 2Ru and 3Fe) have been determined by hyper-Rayleigh scattering (HRS) measurements at a fundamental wavelength of 1500 nm, to minimize the probability of fluorescence due to two-photon absorption and to reduce the effect of resonance enhancement, in order to estimate static β values