Alkenylruthenium ferrocenyl and triarylamine conjugates for the quantitative analysis of electronic coupling in unsymmetrical mixed-valent compounds at the Class II/III borderline

点击翻译按钮获取中文摘要

This project aims at utilizing the radical cations of alkenyl- or styryl-modified ferrocenes and triarylamines to explore the borderline region between partial and full electron and spin delocalisation in unsymmetrical mixed-valent compounds. Both kinds of compounds feature two strongly coupled, yet chemically different redox sites, whose intrinsic redox potentials can be independently varied by the introduction of suitable substituents at the ferrocene or triarylamine subunit or the coligands at the ruthenium site. This will allow us to directly influence the vertical offset of the local minima on the potential hypersurface and hence the degree of valence delocalisation in the ground state of the corresponding mixed-valent radical cations. Furthermore, both redox-active subunits will offer indicative IR or EPR addressable spectroscopic tags which provide quantitative measures of the charge and spin densities at the respective sites at inherently different timescales. With these compounds in hand we will address the following issues:- How are the redox-splitting between the two redox waves and the degree of charge and spin delocalisation in the electronic ground state of the mixed-valent forms of these compounds affected by the difference in the intrinsic redox potentials of the individual sites?- Can we obtain a congruent picture of charge and spin density distributions over the individual redox sites by analyzing the spectroscopic shifts of different charge-sensitive IR markers and the analysis of the hyperfine splitting patterns to different spin density markers within these molecules?- How are the position, the intensity and the half-width of the low energy electronic absorption bands of the mixed-valent radical cations affected by the redox asymmetry?- Can we obtain a method for determining the effective charge-transfer distance in such mixed-valent systems by comparing the characteristic parameters of that electronic band with the quantitative information on charge and spin delocalisation derived from IR and EPR spectroscopy?- Can we identify environmental effects that control valence (de)localization and can we utilize them for switching from one to the other?