How Charging Corannulene with One and Two Electrons Affects Its Geometry and Aggregation with Sodium and Potassium Cations

Abstract

Bowl-shaped mono- and dianions are prepared by reduction of corannulene (C(20)H(10), 1) with sodium and potassium metals in the presence of [18]crown-6 ether. Single-crystal X-ray diffraction studies of two sodium salts, [Na(THF)(2)([18]crown-6)](+)[1(-)] (2a) and [Na([18]crown-6)](+)[1(-)] (2b), reveal the presence of naked corannulene monoanions 1(-) in both cases. In contrast, the potassium adduct, [K([18]crown-6)](+)[1(-)] (3), shows an η(2)-binding of the K(+) ion to the convex face of 1(-). For the first time, corannulene dianions have been isolated as salts with sodium, [Na(2)([18]crown-6)](2+)[1(2-)] (4a) and [Na(THF)(2)([18]crown-6)](+)[Na([18]crown-6)](+)[1(2-)] (4b), and potassium counterions, [K([18]crown-6)](2)(+)[1(2-)] (5). Their structural characterization reveals geometry perturbations upon addition of two electrons to a bowl-shaped polyarene. It also demonstrates η(5)- or η(6)-binding of metals to the curved carbon surface of 1(2-), depending on the crystallization conditions. Both mono- and doubly-charged corannulene bowls show the preferential exo binding of Na(+) and K(+) ions in all investigated compounds. Various types of C-H···π interactions are found in the crystals of 2-5. The UV/Vis, ESR, and (1)H NMR spectroscopic studies of 2-5 indicate different coordination environment of corannulene anions in solution, depending on the metal ion.

Fusing a Planar Group to a π‐Bowl: Electronic and Molecular Structure, Aromaticity and Solid‐State Packing of Naphthocorannulene and its Anions

“…Dark brown blocks of ( 3 ⋅THF) were isolated in moderate yield after 4 days. In 3 (Figure a), the sodium ion is coordinated by one axial 18‐crown‐6 ether (Na⋅⋅⋅O crown , 2.681(5)–2.874(6) Å) and two capping THF molecules (Na⋅⋅⋅O THF , 2.282(6) and 2.357(6) Å), with all Na⋅⋅⋅O distances being close to those previously reported . The observed full encapsulation of sodium cation precludes its binding to the monoanion of 1 .…”

“…Based on these observations, we targeted the isolation of crystalline products of both mono‐ and doubly‐reduced states of 1 . We primarily chose sodium metal for the first chemical reduction study because it is well known to result in the formation of “naked” carbanions . This should allow us to analyze the geometric perturbations of carbon framework of 1 upon acquisition of one and two electrons without the influence of direct metal binding.…”

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

“…11,13 While mono- and dianions of corannulene do not form such supramolecular species, they exhibit a variety of coordination modes that depend on the size of alkali metal ions and other experimental variables. 16,17 The corannulene bowl is not flattened upon acquisition of the first electron but more pronounced changes can be seen upon addition of the second electron. In contrast, a significant bowl depth decrease and C–C bond length alteration pattern are observed for tetrareduced corannulene.…”

Functional Corannulene: Diverse Structures, Enhanced Charge Transport, and Tunable Optoelectronic Properties

“…Even corannulene-derived ferrocene donor-acceptor systems are reportedly synthesized to show H···p interactions and slipped p-stacking interactions. [14] Corannulene can be charged with one or two electrons to affect its geometry [15] and its deca-heterosubstituted counterpart (general structure 1,3,5,7,9-penta-X,2,4,6,8,10-penta-Y-corannulene; X = alkoxy, aryl, aryloxy, etc. [12] The corannulene fragment has also been used for the synthesis of novel blue emitters, namely 1,2-bis(corannulenylethynyl)benzene and 1,4-bis(corannulenylethynyl)benzene [13] and as a buckycatcher by acting as molecular clips and tweezers for guest fullerene cages.…”