Sequence Matters: Precise Synthesis of Hetero[3]rotaxane Isomers with Sequence-dependent Chemical Reactivity and Circularly Polarized Luminescence

Abstract

Sequence isomerism plays fundamental roles in the encoding of biological information and in tuning material performance, but engineering sequences and elucidating their effects remain a major and largely unmet challenge in synthetic chemistry. Herein, We develop a novel wheel assembling approach aiming at the precise sequence control of hetero[3]rotaxanes, a typical family of mechanically interlocked molecules. Based on a key [2]rotaxane precursor with exchangeable pentafluorophenyl ester stoppers, We successfully synthesized both sequence isomers of diverse hetero[3]rotaxanes. Moreover, taking advantage of the chirality retention along with the wheel assembling process, corresponding sequence isomers of chiral functionalized hetero[3]rotaxanes were further precisely synthesized. Impressively, these hetero[3]rotaxanes revealed remarkable sequence-dependent chemical reactivity and circularly polarized luminescence, highlighting fantastic sequence effects. This proof-of-concept study lays the foundation for the investigations on the structure-property relationships of heterorotaxanes, which would further direct the rational design and precise synthesis of sequence-defined heterorotaxanes with desired properties for practical use.

Crown Ether Active Template Synthesis of Rotaxanes**

“…Unlike passive template syntheses, there is no need to integrate strong binding interactions into the rotaxane structure. In this regard, CEATS is already [39] proving to be a 'supramolecular late-stage functionalisation methodology' [40] where a primary amine or electrophilic group on a complex molecule (or assembly) can be used as a handle for rotaxane formation. For Systems Chemists, the ability to integrate chemical reaction networks (including transient Fmoc protection and transamidation) with rotaxane (dis)assembly provides an exciting opportunity to develop responsive nanotechnology and transient materials, as exemplified by the realisation of autonomous and sequence specific molecular pumps.…”

Triphasic circularly polarized luminescence switch quantum simulation of a topologically chiral catenane

“…[20][21][22] In this context, the emergence of a chiral topology in these entangled molecules offers the possibility to study the intricate interplay between the topological features and the circularly polarized luminescence (CPL). Notwithstanding the burgeoning of MIMs in many research articles, [23][24][25][26] their use as chiral emitters is still extremely limited: in fact, very few examples of CPL-active mechanically interlocked molecules are reported in the literature [27][28][29][30] and just one in this chemical elite is a catenane. 31 This unicum exploits the excimer nature of pyrene units to create a CPL multistate switch based on a mechanically interlaced platform as excellently described in a recent article by Yang et al 31 In this unexplored landscape, a theoretical treatment of a CPL-switch is still missing, and to the best of our knowledge, quantum simulation of chiral emission spectra generated by MIMs has never been reported.…”

Catalytic Enantioselective Synthesis of Planar Chiral Pillar[5]arenes via Asymmetric Sonogashira Coupling

“…Herein, based on our on-going research interests in pillar [5]arene-based mechanically interlocked molecules (MIMs), especially rotaxane dendrimers [33][34][35][36][37] and CPL-active chiral rotaxanes, [38][39][40] we assumed that the asymmetric Sonogashira coupling reaction [41][42] would be a suitable choice for the synthesis of novel planar chiral pillar [5]arenes. On the one hand, the further extension of the conjugated skeletons of the resultant products would endow them with attractive tunable chiroptical properties, making them promising platforms as novel chiral luminescent materials for practical applications.…”