Formation of a Macrocycles‐in‐a‐Macrocycle Superstructure with All‐gauche Conformation by Reversible Radical Association

Abstract

The formation of an unprecedented macrocycles-in-a-macrocycle (MIM) superstructure by reversible radical-radical association of a triphenylamine based monomer terminated with three dicyanomethyl radicals is presented. The reaction yield is nearly quantitative and the obtained macrocycle contains three small dimeric macrocycles according to X-ray crystallographic analysis. The six monomer molecules are linked by nine long dynamic covalent C(sp )-C(sp ) bonds that all adopt a gauche conformation. Such a conformation favors the formation of a MIM structure rather than a 2D network with an all-anti conformation. Two enantiomers with left-/ right-handed chirality exist in the single crystals of the superstructure.

Formation and trapping of the thermodynamically unfavoured inverted-hemicucurbit[6]uril

“…Efforts to develop such reactions can, however, be rewarded by leading to complex target compounds in a single step. Many examples of single-step synthesis of oligomeric macrocycles have been described, yet achieving product selectivity often remains an obstacle [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] . Templates can offer control over product formation through preorganization of a corresponding linear precursor, or through altered thermodynamic equilibrium of the reaction.…”

Unveiling the Hidden σ‐Dimerization of a Kinetically Protected Olympicenyl Radical

“…[1] The former mode involves the formation of C(sp 3 )À C(sp 3 ) σ-bond usually with low dissociation energy [2] and anomalous bond length, [3] which quite often renders the bonding process reversible. [4][5][6][7] The latter, on the other hand, is the stacking of the two monoradicals to form a multi-center-two-electron "pancake bond", [8] which is an attractive interaction that outweighs electron repulsion, and therefore leads to closer intermolecular distance and enhancement of aromaticity. [9] The study of the dimerization process is not only of fundamental importance for the understanding of the nature of the chemical bond, [10] but also paves the way for the applications of organic π-radicals as responsive materials to light, [11] temperature [12,13] and solvent, [14,15] particularly with the emergence of the stable πradicals in recent years.…”

Platforms for Stable Carbon‐Centered Radicals

“…[42] Among these "dynamically stable" radicals 15R-18, a,a-dicyanobenzyl [43] derivatives have met with remarkable progress (Figure 3). Sakamaki, Seki, and co-workers explored the stable dicyanomethyls 19 a-c and 20 [44] with nitrogen-based electron donors at the para-positions,a nd they displayed diminished spin densities at the benzyl positions,w eakening the intermolecular C À Cc oupling reactivity.R eflecting the electronic nature,t heir dissociation enthalpy decreased on the order of carbazole-(19 a) > phenothiazine- ( 46] In contrast, Osuka and co-workers prepared the stable subporphyrin-based dicyanomethyls 21X without additional electron-donating moieties. [47] Unlike other dicyanomethyls, 21X were monomeric in solution, though they formed p-stacked dimers in the crystals.…”