Overcrowded Ethylene-Bridged Nanohoop Dimers: Regioselective Synthesis, Multiconfigurational Electronic States, and Global Hückel/Möbius Aromaticity

Abstract

The design and preparation of molecular systems with multiple geometric and electronic configurations are the cornerstones for multifunctional materials with stimuli-responsive behaviors. We describe here the regioselective and facile synthesis of two types of overcrowded ethylene-bridged nanohoop dimers, with folded and twisted geometric structures as well as closed-shell, diradical and dication electronic structures. The strained nanohoop structures have a profound effect on the overall molecular and electronic configurations, which resulted in the destabilized diradical state. X-ray crystallographic analysis revealed the folded molecular geometry for the neutral species and twisted geometry for the dication species. The unique molecular dynamics, optical properties, and dynamic redox properties were disclosed in the solution phase by spectroscopic and electrochemical methods. Furthermore, the global Hückel and Möbius aromaticity were revealed by a combination of experimental and theoretical approaches. Our studies shed light on the design of nanohoop-incorporated multiconfigurational materials with unique topologies and functions.

Redox‐Active Hydrocarbons: Isolation and Structural Determination of Cationic States toward Advanced Response Systems

“…Therefore, the findings on the precise control of the intrinsic properties of organic molecules based on the manipulation of multiple redox states may lead to breakthroughs in the field of organic bulk electronic materials. Very recently, other attractive systems have also been reported in which both neutral and cationic states were successfully isolated by applying the strategies described here [128–131] . The redox chemistry of pure hydrocarbons is expanding rapidly, and these examples will be covered in another review.…”

“…Very recently, other attractive systems have also been reported in which both neutral and cationic states were successfully isolated by applying the strategies described here. [128][129][130][131] The redox chemistry of pure hydrocarbons is expanding rapidly, and these examples will be covered in another review. Furthermore, although excluded from this review, the development of pure hydrocarbon-based response systems based on different approaches from electrochemical stimulation is also being actively pursued.…”

Expanding new chemistry of aza-boracyclophanes with unique dipolar structures, AIE and redox-active open-shell characteristics

“…4 Macrocycles of π-electron systems exhibit particularly intriguing optical, electronic and magnetic behaviors owing to an equivalent of these cycles to well-defined open-chain polymers but with an infinite conjugation length. 2 b ,5 The incorporation of main group heteroatoms (such as B, N, and S) has proved an efficient strategy to build π-conjugated materials with unique optoelectronic properties. 6 Such a group of heteroatom-doped macrocycles are expected to show distinct electronic structures compared with all-carbon based analogues, and their frontier molecular orbitals can be tuned.…”

Synthesis, structures and fluorescence properties ofgem-linked cyclic tetraphenylethylenes and cyclic hexaphenylethylenes

“…6 Oxidation of [ n ]CPPs ( n = 5, 6, 8, 10, and 12) yielded the corresponding stable radical cations, [ n ]CPPs˙ + , and dications, [ n ]CPPs 2+ with global aromaticity. 7 Along with the development of CPP chemistry, many other novel macrocycles, such as [ n ]cyclic 2,12-porphyrinylene nanorings ([ n ]CPs), 8 cyclic diketones, 9 [ n ]cyclo-dibenzopentalenes ([ n ]CDBPs), 10 ethylene-bridged nanohoop dimers, 11 and [4]cyclo-3,11-fulminenylene ([4]CF), 12 which can be regarded as [ n ]CPP analogues by replacing the phenyl units of [ n ]CPPs with other chromophores or inserting other functional groups into the [ n ]CPP rings, have been synthesized to display many interesting properties.…”