Third-harmonic generation in organometallic ruthenium(II) derivatives containing coordinated p-substituted benzonitriles

Abstract

A family of η⁵-monocyclopentadienylruthenium(II) derivatives possessing coordinated p-substituted benzonitriles has been studied by optical third-harmonic generation (THG) at the fundamental wavelength of λ= 1064 nm. Thin films of the compounds in a polymer matrix of poly(methyl methacrylate)(PMMA) were studied using the Maker fringe technique. For the compound possessing the p-NCC₆H₄C₆H₄NO₂ coordinated nitrite the second hyperpolarizability, γ(–3ω;ω,ω,ω), was determined to be 2.3 × 10^–33 esu. Spectroscopic results show evidence of π back-donation resulting in an extension of the electronic π-system. We propose that this π back-donation is the origin of this significant value of γ.