Manipulation of molecular aggregation and supramolecular structure using self-assembled lithium mixed-anion complexes

Abstract

A set of zero-, one-, two-, and three-dimensional materials have been synthesized by systematically varying the stoichiometry of the two components 2,4,6-Me₃-C₆H₂OLi (ArOLi) and Me₂N(CH₂)₂OLi (ROLi) within single aggregates, while using 1,4-dioxane (diox) as a ditopic linker. The homoleptic complex [{(ArOLi)₄·(diox)₂}⊃3(diox)]_∞1 forms a 3D diamondoid extended structure, where Li₄O₄ cubanes act as tetrahedral nodes. Attempts to rationally alter the dimensionality of the network through the sequential replacement of ArOLi vertices by potentially chelating ROLi units have succeeded. The mixed-anion complexes [{(ROLi)(ArOLi)₃·(diox)_1.5}⊃1/2(C₆H₁₄)]_∞2 and [(ROLi)₄(ArOLi)₂·(diox)]_∞4, adopt 2D hexagonal net and 1D chain structures respectively. Furthermore, the two complexes [{(ROLi)₃(ArOLi)₃·(diox)_0.5}(C₆H₁₄)]_∞3 and [(ROLi)₅(ArOLi)·(diox)_0.5]_∞5 both form unusual 0D molecular dumbbell structures in the solid state. Incorporation of multiple ROLi units in the mixed-anion complexes not only results in reducing the number of possible sites for polymer extension through chelation, but also changes the aggregation state of the building block from tetrametallic Li₄O₄ units to hexametallic Li₆O₆ units.