Heterochiral Diastereomer-Discriminative Diphanes That Form Hierarchical Superstructures with Nonlinear Optical Properties

Abstract

In order to study the emergence of homochirality during complex molecular systems, most works mainly concentrated on the resolution of a pair of enantiomers. However, the preference of homochiral over heterochiral isomers has been overlooked, with very limited examples focusing only on noncovalent interactions. We herein report on diastereomeric discrimination of twin-cavity cages (denoted as diphanes ) against heterochiral tris-(2-aminopropyl)amine (TRPN) bearing triple stereocenters. This diastereomeric selectivity results from distinct spatial orientation of reactive secondary amines on TRPN. Homochiral TRPNs with all reactive moieties rotating in the same way facilitate the formation of homochiral and achiral meso diphanes with low strain energy, while heterochiral TRPNs with uneven orientation of secondary amines preclude the formation of cage-like entity, since the virtual diphanes exhibit considerably high strain. Moreover, homochiral diphanes self-assemble into an acentric superstructure composed of single-handed helices, which exhibits interesting nonlinear optical behavior. Such a property is a unique occurrence for organic cages, which thus showcases their potential to spawn novel materials with interesting properties and functions.

Unraveling the Dynamic Molecular Motions of a Twin‐Cavity Cage with Slow Configurational but Rapid Conformational Interconversions

“…As part of our ongoing endeavor for the study on cage-like compounds with exotic shapes, we recently became interested in exploring the structural properties and functions of twin-cavity cages denoted as diphanes. [32,33] In the current study, we synthesized Diphane-5 by cycloimination reaction between hexaamino-containing precursor 5 and 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (TP), subsequently followed by keto-enol tautomerization (Scheme 1). The comprehensive synthetic procedure and structural characterizations are provided in Supporting Information.…”

“…To address the challenges associated with the kinetic study of complex systems exhibiting multiple correlated transitions between molecular changes, the development of an effective methodology capable of decoupling these interconnected processes could be highly helpful. [28,31] To this end, we designed and synthesized a twin-cavity cage (denoted as diphane [32,33] ) that is featured by its intricate dynamic structural transformations. The diphane molecule exhibits two interconvertible configurations, namely a highsymmetry C 3 -configuration and a low-symmetry C 1 -configuration.…”