Even though the amphoteric redox behavior of azulenic compounds and materials (i.e., those featuring a combination of fused 5- and 7-membered sp2-carbon rings) is well-documented, the vast majority of such systems operate under the “neutral – cation” redox regime established via oxidation or protonation of the azulenic core (e.g., 1,3-polyazulenes). Azulene-based architectures that can reversibly support the topologically complementary “neutral – anion” redox regime beyond the typical electrochemical time scale at ambient temperatures are rare. This presentation will address the design of 6,6’-biazulenic molecular linkers linearly functionalized at their 2,2’-termini in either symmetrical or non-symmetrical fashion. Such bridging π-conjugated ligand scaffolds are chemically accessible with three different molecular charges (0, -1, and -2). Their radical anion forms are very strong dual visible/near-IR absorbers and have EPR signatures consistent with unpaired electron spin delocalization over the entire biazulenic core. The redox profile of a heptanuclear “nanocomplex”, which has the diameter of ca. 6 nm and features seven Cr(0) centers interlinked with six 6,6’-biazulenic bridges, will be highlighted as well. It shows a 21-e- reversible molecular redox capacity.

Electrochromic ligand platforms involving the 6,6’-biazulenic core

2019 Spring National Meeting

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