A Hubbard model for the second hyperpolarizability in alternating polymers

[(NH3)5Ru(1,2,4,5-tetrazine)]2+: Synthesis and Experimental and Theoretical Study of Its Solvatochromism in the Visible Spectral Region

The title compound has been first synthesized and fully characterized as both tetraphenylborate and perchlorate salt. Its 300-900 nm absorption spectrum, recorded in nitromethane, water, and dimethyl sulfoxide, reveals the peculiar existence of two distinct bands whose intensities depend on the solvent donor number. This feature can be attributed to two separate metal-to-ligand charge-transfer transitions, in agreement with the theoretical predictions obtained by extensive configuration interaction calculations, which take into account the solvent effects. The calculation of the potential energy curves of the ground and excited states along the Ru-tetrazine coordinate allows the interpretation of the relative intensities of the observed bands, as well as the interpretation of their line-shape profiles.

Trinuclear pyrazine-bridged ruthenium complexes: syntheses, electrochemistry, NIR-Vis spectra, and their interpretation in terms of a 5-orbital-3-parameter model

A study of absorption spectra in the near-infrared (NIR) and visible (vis) regions of trinuclear Ru complexes containing pyrazine (pyz) as bridging ligand, trans-[(Ru(NH(3))(5)pyz)(2)Ru(NH(3))(4)](m+)(m = 6-9), is reported. The spectra were recorded on aqueous solutions containing the described species formed in situ by stoichiometric additions of a standard solution of Ce(SO(4))(2). They were interpreted in terms of a simple 5-orbital-3-parameter model which includes the effects of d-pi interaction and electronic correlation. The model is shown to account for the observed NIR-vis spectra of the complex ions. The 6+ parent species was synthesized by an improved literature method and fully characterized. The novel 8+ complex was also prepared and characterized. The 9+ ion was established to be slowly reduced by water, with dioxygen formation. Electrochemical (CV and DPV) studies were performed on the trinuclear 6+ complex, as well as on its constituent fragments [Ru(NH(3))(5)(pyz)](2+) and trans-[Ru(NH(3))(4)(pyz)(2)](2+).