Jiaobing Wang

We report the synthesis and characterization of thio‐tetracosulene 3 , a highly twisted chiral macrocycle constructed via sulfur fluorine annulative substitution from a cyclometaphenylene derivative. It is the first macrocyclic aromatic compound with a plectonemic configuration, and the structure is unambiguously confirmed by single crystal X‐ray diffraction study. The two enantiomers of 3 can be resolved to investigate their chiroptical properties. In contrast to the known topological knot‐, or Möbius‐type macrocycles which induce chirality by specific connection patterns, the asymmetric structure of 3 is formed and maintained by the tendency of a ring in distress to reduce unfavorable strains.

We report the synthesis and characterization of thio‐tetracosulene 3 , a highly twisted chiral macrocycle constructed via sulfur fluorine annulative substitution from a cyclometaphenylene derivative. It is the first macrocyclic aromatic compound with a plectonemic configuration, and the structure is unambiguously confirmed by single crystal X‐ray diffraction study. The two enantiomers of 3 can be resolved to investigate their chiroptical properties. In contrast to the known topological knot‐, or Möbius‐type macrocycles which induce chirality by specific connection patterns, the asymmetric structure of 3 is formed and maintained by the tendency of a ring in distress to reduce unfavorable strains.

We report that fluorinated polyphenylene P50 undergoes folding‐like sulfur fluorine annulative substitution (SFAS) to form a well‐defined tubular helix H50. This is achieved with atomic precision in an exceptionally efficient manner, involving the simultaneous transformation of 98 C−F bonds with the yield per reaction site approaching 99.9 %. The desired product H50 features a fully fused dibenzothiophene skeleton of 5.8 helical turns in total. It is truly monodisperse (Đ=1.0) in nature, allowing for thorough spectroscopic characterizations. Unambiguous single crystal X‐ray structure, distinct chiroptical properties, and intriguing through‐cavity threading complexation are described. These results, in addition to those of H50’s lower congeners, H34 and H18, illustrate the great potential of folding‐like SFAS in shaping random‐coiled polymer chains into higher‐order functional structures.

We report that fluorinated polyphenylene P50 undergoes folding‐like sulfur fluorine annulative substitution (SFAS) to form a well‐defined tubular helix H50. This is achieved with atomic precision in an exceptionally efficient manner, involving the simultaneous transformation of 98 C−F bonds with the yield per reaction site approaching 99.9 %. The desired product H50 features a fully fused dibenzothiophene skeleton of 5.8 helical turns in total. It is truly monodisperse (Đ=1.0) in nature, allowing for thorough spectroscopic characterizations. Unambiguous single crystal X‐ray structure, distinct chiroptical properties, and intriguing through‐cavity threading complexation are described. These results, in addition to those of H50’s lower congeners, H34 and H18, illustrate the great potential of folding‐like SFAS in shaping random‐coiled polymer chains into higher‐order functional structures.

Conjugated π-surfaces are ubiquitous in molecules and materials. However, large π-surfaces up to a few nanometers in size are difficult to construct in an atomically precise manner. They tend to aggregate because of strong π-π interactions, resulting in notorious problems for both purification and spectroscopic investigations. Here, by contrast, we report the design, synthesis, and full characterizations of a nonplanar nanographene 1, which has a large, precise, and nonstacked π-surface. It is soluble in common organic solvents and allows for thorough investigations. The structure of 1, comprising 85 fused rings with an extended π-surface of 3 nm in size, is unambiguously confirmed by single-crystal X-ray diffraction. Unusual electronic structures, record-high near-infrared absorption, pronounced magnetic shielding, and ultrastrong heteromolecular van der Waals complexations are demonstrated, enabling us to establish a clear structure-property relationship, which has been elusive for decades. These results have broad implications for studying and understanding various phenomena and processes relevant to both discrete and interacting π-surfaces.

ConspectusUnderstanding and harnessing the properties of nanoscale molecular entities are considered as new frontiers in basic chemistry. In this regard, synthetic nanographene with atomic precision has attracted much attention recently. For instance, taking advantage of the marvelous bonding capability of carbon, flat, curved, ribbon-type, or cone-shaped nanographenes have been prepared in highly controllable and elegant manner, allowing one to explore fascinating molecular architectures with intriguing optical, electrochemical, and magnetic characteristics. This stands in stark contrast to other carbon-rich nanomaterials, such as graphite oxides or carbon quantum dots, which preclude thorough investigations because of complicate structural defects. Undoubtedly, synthetic nanographene contributes strongly to modern aromatic chemistry and represents a vibrant field that may deliver transforming functional materials crucial for optoelectronics, nanotechnologies, and biomedicine.Nonetheless, in many cases, synthesis and characterization of nanographene compounds are highly demanding. Low solubility, high molecular strain, undesired selectivity, as well as incomplete or excessive C-C bond formation are common impediments, that require formidable efforts to control the molecular geometry, to modulate the edge structure, to achieve accurate doping, or to push the upper size boundary. These endeavors are indispensable for establishing structure-property relationships, and lay down foundation for exploring synthetic nanographenes at a high level of sophistications.In this Account, we summarize our contributions to this field by presenting a series of helical synthetic nanographenes, such as hexapole [7]helicene (H7H), nitrogen-doped H7H, hexapole [9]helicene (H9H), superhelicene, and supertwistacene. This kind of giant synthetic nanographene reaches the size domain of carbon quantum dots, albeit has precise atomic structure. It provides a unique platform to study aromatic chemistry and chirality at the nanoscale. We discuss synthetic methods and point out, in particular, the strengths and pitfalls of Scholl oxidation, which are expected to be valuable for making synthetic nanographenes in general. In addition, we illustrate their exciting electrochemical and photophysical performance, which include, but are not limited to, reversible multielectron redox chemistry, record high panchromatic absorption, impressive photothermal behavior, and extremely strong Cotton effect. These unusual characteristics are convincingly traced back to their three-dimensional conjugated architectures, highlighting the critical roles of π-electron delocalization, heteroatom-doping, substitution, and molecular symmetry in determining nanographenes' properties and functions. Lastly, we put forward our understanding on the challenges and opportunities that lies ahead and hope this Account will inspire ever more ambitious achievements from this attractive area of research.

This work reports the first double π‐extended undecabenzo[7]helicene1, which is a large chiral nanographene, composed of 65 fused rings and 186 conjugated carbon atoms. The molecular identity of1has been confirmed by single crystal X‐ray diffraction. A wine coloured solution of1in dichloromethane absorbs light from ultraviolet to the near infrared, featuring an extremely large molar absorption coefficient of 844 000 M⁻¹ cm⁻¹at 573 nm. Optically pure1shows a record high electronic circular dichroism intensity in the visible spectral range (|Δϵ|=1375 M⁻¹ cm⁻¹at 430 nm) known for any discrete polycyclic aromatic hydrocarbon. These unusual photophysical properties of1contrast sharply with those of a mono‐undecabenzo[7]helicene derivative2.

This work reports the first double π‐extended undecabenzo[7]helicene1, which is a large chiral nanographene, composed of 65 fused rings and 186 conjugated carbon atoms. The molecular identity of1has been confirmed by single crystal X‐ray diffraction. A wine coloured solution of1in dichloromethane absorbs light from ultraviolet to the near infrared, featuring an extremely large molar absorption coefficient of 844 000 M⁻¹ cm⁻¹at 573 nm. Optically pure1shows a record high electronic circular dichroism intensity in the visible spectral range (|Δϵ|=1375 M⁻¹ cm⁻¹at 430 nm) known for any discrete polycyclic aromatic hydrocarbon. These unusual photophysical properties of1contrast sharply with those of a mono‐undecabenzo[7]helicene derivative2.

Two synthetic nanographenes (NGs),N‐H7HandC‐H7H, were prepared.N‐H7His doped with nitrogen, andC‐H7His the all‐carbon analogue. Both are hexapole [7]helicenes (H7Hs), and their structures were identified by single‐crystal X‐ray diffraction. Sharp contrasts in absorption (^absλ_max, 683 vs. 593 nm), emission (^emλ_max, 894 vs. 777 nm), and electrochemical behavior (^oxE₁, 0.28 vs. 0.53 V) were observed betweenN‐H7HandC‐H7H, and the origin of these differences was rationalized by theoretical calculations. Studies onN‐H7HandC‐H7Hset a clear example to elucidate the remarkable effects of N‐doping on the physical properties of NGs.