Anionic Stacks of Alkali-Interlinked Yttrium and Dysprosium Bicyclooctatetraenes in Isolation.

Electrospray ionization of THF solutions of preformed [K(18-c-6)][M(COT) 2 ] (M = Dy(III), Y(III); COT = C 8 H 8 2- ,18-c-6 = C 12 H 24 O 6 ) yields the isolated species [(M(COT) 2 ) n +1 + n K] - with n = 0-3. High-resolution ion mobility spectrometry combined with density functional theory calculations performed for the n = 0-2 aggregates indicate that anionic multidecker stacks interlinked by potassium cations are formed. The alternating metal ions are aligned linearly: COT 2- -M 3+ -COT 2- -K + -COT 2- -M 3+ -COT 2- . The different M 3+ ionic radii lead to slight but resolvable changes in mobility and thus collision cross sections indicative of different overall heights of the multidecker stacks. CID measurements show that the aggregates fragment by cleavage at the K + interconnections.