Reversible structural rearrangement of π-expanded cyclooctatetraene upon two-fold reduction with alkali metals

Abstract

The reductive core rearrangement upon two-fold electron addition to a π-expanded COT derivative is revealed crystallographically and supported by DFT calculations.

Tridecacyclene Tetraimide: An Easily Reduced Cyclooctatetraene Derivative

“…In fact, the tridecacyclene dianion [ TC ] 2− was reported to have a saddle shape similar to that of [ 3 c ] 2− [35] . This structural preference contrasts with the planarity of the [ COT ] 2− dianion [59] and isomerization observed recently for a tetrabenzo derivative [57] . Because of the nonplanarity, the COT ring in [ 3 c ] 2− is not diatropic, however, it displays geometrical changes (bond equalization and flattening) that are specific to this particular oxidation level of TCTI and are consistent with residual 10‐electron aromaticity.…”

“…[35] This structural preference contrasts with the planarity of the [COT] 2À dianion [59] and isomerization observed recently for a tetrabenzo derivative. [57] Because of the nonplanarity, the COT ring in [3 c] 2À is not diatropic, however, it displays geometrical changes (bond equalization and flattening) that are specific to this particular oxidation level of TCTI and are consistent with residual 10-electron aromaticity. The slight changes of magnetism associated with this local aromatic character are likely obscured by the more pronounced diatropic contributions of the surrounding rings.…”

“…[39,40] The COT motif has been elaborated into a variety of planarized derivatives, [41] saddle-shaped heteroaromatics, [42][43][44][45][46][47][48][49] and negatively curved nanocarbons, [50][51][52] providing access to hole transporters, [46] AIE materials, [47] and as-cast solar cells. [49] COT [53] and its π-extended analogues [35,[54][55][56][57] can be reduced to a variety of anionic states, in particular the aromatically stabilized dianion. [58,59] In the present work, the combination of the COT ring with electron-withdrawing peripheries is shown to result in a relatively small π system that is susceptible to eight-fold reduction and yields anionic species with remarkable absorptions in the near-infrared range.…”

Interplay of Charge and Aromaticity Upon Chemical Reduction of p-Quinquephenyl with Alkali Metals

“…The coordination of each Li + cation is completed by four THF molecules, with the Li−O THF distances ranging from 1.862(10) Å to 1.929(9) Å, which are close to those previously reported. 10,22,67 The crystal structure of 3 contains two crystallographically independent Na + ions (Figure S23). The Na1 ion is bound to the central phenyl ring of 1 2− in an asymmetric η 2 -fashion, with Scheme 2.…”

“…The reduction of polycyclic aromatic hydrocarbons (PAHs) has attracted significant attention over recent years, inspired by fundamental chemistry and material science applications. − Chemical reduction of PAHs with alkali metals enables the formation of charged π-conjugated carbanions with positive and negative curvatures, which undergo structural deformation, − core transformation, − and reductive dimerization processes. − Moreover, the alkali metal intercalated products of PAHs have shown interesting quantum phenomena, thus stimulating the developments of new molecular materials with intriguing electronic, − conducting, − and magnetic properties. , …”