Selective synthesis and physical properties of a bismacrocycle:Cycloparaphenylene-pillar[5]arene

Macrocyclic materials have attracted much attention due to their particular chemical and physical properties.Herein we report the precise synthesis and characterization of a new bismacrocycle structure base on cycloparaphenylene(CPP)and pillar[5]arene,named cycloparaphenylene-pillar[5]arenes(CPPn[5]).The bismacrocycle was fully characterized by NMR and HR-MS.The photophysical properties of CPPn[5]were investigated by UV–vis,and the maximum absorption peak was located at 331 nm,which was consistent with density functional theory(DFT)calculations.The fluorescence spectrum was further studied and the emission peak was maximized at 458 nm.The computational results indicate the strain energy of CPPn[5]is 27.80 kcal/mol and the HOMO-LUMO gap is 3.39 eV Notably,CPPn[5]showed interesting supramolecular properties.

Carbon Nanobelts:Brief History and Perspective

Carbon nanotubes(CNTs)are an emerging nanomaterial because of their outstanding performance in various applications.In recent years,the segment molecules of CNTs,referred to as carbon nanorings(CNRs)or carbon nanobelts(CNBs),have gained attention for their unique structures and properties,as well as their potential as seed molecules for the precise synthesis of CNTs.CNBs are rigid and thick segments of CNTs whose synthesis has been addressed by scientists fascinated by the uniqueness of CNBs long before the discovery of CNTs.After 60 years of efforts by synthetic chemists all over the world,the synthesis of the first CNB,(6,6)CNB,was achieved by our group in 2017.Since this milestone,diverse types of nanobelts have been synthesized through various synthetic routes,thereby demonstrating their photophysical,magnetic,and redox properties derived from rigid belt structures.The applications of CNBs have also been introduced recently.The formation of the host−guest complex,transformation to three-dimensional molecules,and measurement of conductivity have been reported for CNBs.This paper summarizes the brief history and perspective of CNBs.Further synthetic campaigns and aggressive application of CNBs would create novel and groundbreaking scenes in materials science.

Merging a Negatively Curved Nanographene and a Carbon Nanoring

Two molecular nanocarbons result from merging a negatively curved nanographene and a carbon nanoring in two constitutional isomers of D2 and C2v symmetry,respectively.They were synthesized by attachment o f C-shaped paraphenylene precurso rsto 2,11,18,27-tetrabromooctabenzo[8]circulene and the subsequent intramolecular Yamamoto coupling and reductive aromatization reactions.The flexible nature of octabenzo[8]circulene enabled two different ways of connection in the Yamamoto coupling reactions,leading to the two constitutional isomers.The D2 isomer is shaped like a figure eight,as revealed by X-ray crystallography,and is resolved into two enantiomers by chiral HPLC.The synthesis of the C2v isomer is regarded as a further step toward precision synthesis of carbon schwarzites through a bottom-up approach.

All-hydrocarbon,all-conjugated cycloparaphenylene-polycyclic aromatic hydrocarbon host–guest complexes stabilized by CH–πinteractions

Polycyclic aromatic hydrocarbons(PAHs)are promising nanocarbon materials with diverse optoelectronic properties,yet they also pose concerning environmental and health risks.Despite the ubiquity of PAHs in the environment(crude oil,emissions,and biomass),most supermolecules rely on heteroatoms for stability.We discovered and characterized a family of all-hydrocarbon,all-π-conjugated[n]cycloparaphenylene-PAH host–guest complexes.We built a theoretical framework to rapidly select these complexes and predict their stabilities,driven exclusively by CH–πinteractions.More than a dozen complexes were confirmed experimentally and assembled directly from commercially available compounds.This motif offers a versatile way to combine the advantageous properties of organic semiconductors with the rich dynamic,stereochemical,stimulus-responsive,and stressdissipative behavior of host–guest complexes,while creating new opportunities for bespoke PAH separation or remediation materials.

Self-Assembly of Crystalline Vesicles from Nonplanarπ-Conjugated Nanocycles

There is a great demand for self-assembled carbon nanomaterials because of their importance in optoelectronics,biomaterials,and so forth.Herein,we report a novel type of self-assembled,nanoscale,crystalline vesicle from nonplanarπ-conjugated nanocycles.We designed four different structural[8]cycloparaphenylenes([8]CPPs)molecules and demonstrated that these nonplanarπ-conjugated CPP nanocycles could self-assemble into multilamellar,crystalline vesicles in tetrahydrofuran(THF)/H2O mixed solvent.