A Main Group Metal Sandwich: Five Lithium Cations Jammed Between Two Corannulene Tetraanion Decks

Abstract

Lithium-coordinated polyaromatic anions such as tetrareduced corannulene, C(20)H(10)(4-) (1(4-)), are useful substrates to model and ultimately improve the graphitic electrodes in lithium-ion (Li(+)) batteries. Previous studies suggested that 1(4-) forms dimers encasing four Li(+) ions in solution. Here, we report a single-crystal x-ray diffraction analysis confirming the formation of a sandwich-type supramolecular aggregate with a high degree of alkali metal intercalation. In contrast to the prior model, our data reveal that five Li(+) ions are sandwiched between the two tetrareduced corannulene decks, and (7)Li nuclear magnetic resonance spectroscopy delineates a conserved structure in tetrahydrofuran solution. Remarkably, the sandwich is robust in both solution and solid states even in the presence of crown ethers that compete for Li(+) coordination. These results should help elucidate Li(+) intercalation motifs between curved carbon surfaces more broadly.

Self-assembly of tetrareduced corannulene with mixed Li–Rb clusters: dynamic transformations, unique structures and record7Li NMR shifts

“…12 We have also demonstrated that the triple-decker supramolecular aggregate, [Li 5 (C 20 H 10 4– ) 2 ] 3– , can be crystallized in different external coordination environments, showing no significant effect on the geometry of the sandwich core. 11,13 In addition, the formation of the [Li 5 (C 20 H 10 4– ) 2 ] 3– product (abbreviated as Li 5 below) is confirmed in solution based on the observed shifts for sandwiched Li + ions (–11.70 ppm) and a proper 3 : 5 integration of external vs. internal ions in the 7 Li NMR spectra. Importantly, these results illustrated the ability of tetrareduced corannulene to engage all of its adjacent six-membered rings in alkali metal binding and thus to encapsulate a large amount of Li + ions, which can be related to the high charge capacity of the corannulene-based electrodes in Li-ion batteries.…”

“…10 However, structural investigations of the charged π-bowls were lagging behind their solution spectroscopic studies until we have accomplished the first X-ray diffraction characterization of the product formed by the tetrareduced corannulene with lithium counterions. 11 The formation of a remarkable aggregate with a Li 5 -core sandwiched between two C 20 H 10 4– decks has been established (Scheme 2a). This supramolecular aggregation with lithium ions allows to achieving a tetrareduced state of corannulene, as the electrochemical generation of C 20 H 10 4– cannot be accomplished due to a very large negative standard potential located outside of the current experimental window.…”

Electronic transport properties of selected carbon π-bowls with different size, curvature and solid state packing

“…These curved polyarenes (often called p-bowls) are excellent electron acceptors, comparable to planar PAHs [1,2] and fullerenes [3,4], and could serve as key anode components in rechargeable Li-ion batteries. Corannulene, the smallest non-planar fragment of C 60 fullerene [5,6], was shown to exhibit high degree of lithium intercalation upon step-wise reduction [7][8][9][10] and corannulene-based anode materials have demonstrated a high reversible lithium capacity, almost twice as high as that of fully lithiated graphite [11,12]. The family of p-bowls also provides a natural platform for designing new organic materials with applications in light emitting-diodes [13][14][15][16], field-effect transistors [17][18][19], or photovoltaic cells [20].…”

Clamshell Opening in the Mixed‐Metal Supramolecular Aggregates Formed by Fourfold Reduced Corannulene for Maximizing Intercalated Metal Content

“…[9,11,18] On the contrary, while the formation of four-fold reduced corannulene was clearly observed in the reaction mixture with Li and K metals, the assignment of the specific products in solution was problematic. Notably, a shorter reaction time was observed for the mixed Li/K system compared to the Li-only reduction, pointing to a synergism of two metals.…”

“…[9] While the supramolecular aggregation of corannulene anions has been extensively investigated by the groups of Scott and Rabinovitz using solution NMR spectroscopy, [6a, 7-9, 10] structural identification of the resulting products in the solid state was lagging behind until 2011, when we have accomplished the first crystallographic characterization of the aggregate formed by the highly reduced corannulene with lithium counterions (Scheme 1). [11] A remarkable supramolecular structure with five lithium ions sandwiched between two four-fold reduced corannulene decks has been revealed.…”