Search for: All records

The first example of a cyclophane bearing a nitrogen‐containing buckybowl was synthesized via sequential 1,3‐dipolar cycloaddition and palladium‐catalyzed intramolecular cyclization. The key to the successful synthesis is the strain‐induced 1,3‐dipolar cycloaddition of a polycyclic aromatic azomethine ylide to theK‐region of [7](2,7)pyrenophane. The resulting π‐extended azacorannulenophane exhibits intriguing structural and physical properties, including unique variation of bowl depth, extraordinarily high‐field chemical shifts in its¹H NMR spectrum, a decreased HOMO–LUMO gap, and a red shift in the absorption/emission spectrum, when compared to those of the parent azacorannulene. These characteristics are derived from both the π‐extension to the polycyclic aromatic system in the cyclophane structure and the increased curvature enforced by the seven‐carbon aliphatic chain.

The first example of a cyclophane bearing a nitrogen‐containing buckybowl was synthesized via sequential 1,3‐dipolar cycloaddition and palladium‐catalyzed intramolecular cyclization. The key to the successful synthesis is the strain‐induced 1,3‐dipolar cycloaddition of a polycyclic aromatic azomethine ylide to theK‐region of [7](2,7)pyrenophane. The resulting π‐extended azacorannulenophane exhibits intriguing structural and physical properties, including unique variation of bowl depth, extraordinarily high‐field chemical shifts in its¹H NMR spectrum, a decreased HOMO–LUMO gap, and a red shift in the absorption/emission spectrum, when compared to those of the parent azacorannulene. These characteristics are derived from both the π‐extension to the polycyclic aromatic system in the cyclophane structure and the increased curvature enforced by the seven‐carbon aliphatic chain.

Mono‐ and dianions of 2‐tert‐butyl‐3a²‐azapentabenzo[bc,ef,hi,kl,no]corannulene (1 a) were synthesized by chemical reduction with sodium and cesium metals, and crystallized as the corresponding salts in the presence of 18‐crown‐6 ether. X‐ray diffraction analysis of the sodium salt, [{Na⁺(18‐crown‐6)(THF)₂}₃{Na⁺(18‐crown‐6)(THF)}(1 a²⁻)₂], revealed the presence of a naked dianion. In contrast, controlled reaction of1 awith Cs allowed the isolation of singly and doubly reduced forms of1 a, both forming π‐complexes with cesium ions in the solid state. In [{Cs⁺(18‐crown‐6)}(1 a⁻)]⋅THF, asymmetric binding of the Cs⁺ion to the concave surface of1 a⁻is observed, whereas in [{Cs⁺(18‐crown‐6)}₂(1 a²⁻)], two Cs⁺ions bind to both the concave and convex surfaces of the dianion. The present study provides the first successful isolation and characterization of the reduced products of heteroatom‐containing buckybowl molecules.

Mono‐ and dianions of 2‐tert‐butyl‐3a²‐azapentabenzo[bc,ef,hi,kl,no]corannulene (1 a) were synthesized by chemical reduction with sodium and cesium metals, and crystallized as the corresponding salts in the presence of 18‐crown‐6 ether. X‐ray diffraction analysis of the sodium salt, [{Na⁺(18‐crown‐6)(THF)₂}₃{Na⁺(18‐crown‐6)(THF)}(1 a²⁻)₂], revealed the presence of a naked dianion. In contrast, controlled reaction of1 awith Cs allowed the isolation of singly and doubly reduced forms of1 a, both forming π‐complexes with cesium ions in the solid state. In [{Cs⁺(18‐crown‐6)}(1 a⁻)]⋅THF, asymmetric binding of the Cs⁺ion to the concave surface of1 a⁻is observed, whereas in [{Cs⁺(18‐crown‐6)}₂(1 a²⁻)], two Cs⁺ions bind to both the concave and convex surfaces of the dianion. The present study provides the first successful isolation and characterization of the reduced products of heteroatom‐containing buckybowl molecules.