Synthesis of Defective Nanographenes Containing Joined Pentagons and Heptagons

Abstract

Dedicated to Professor Klaus Müllen on the occasion of his 75 birthdayDefective nanographenes containing joined pentagons and heptagons exhibit striking physicochemical properties from both experimental and theoretical perspectives compared with their pure hexagonal counterparts. Thus, the synthesis and characterization of these unique polyarenes with well-defined defective topologies have attracted increasing attention. Despite extensive research on nonalternant molecules since the last century, most studies focused on the corresponding mutagenic and carcinogenic activities. Recently, researchers have realized that the defective domain induces geometric bending and causes electronic perturbation, thus leading to significant alteration of the photophysical properties. This review discusses the synthesis and characterization of small nonalternant polycyclic hydrocarbons in the early stage and recent developments in embedding pentagon-heptagon (5-7) pairs into large carbon skeletons through in-solution chemistry.

Synthesis, Crystal Analysis, and Physical Properties of Double [6]helicene-Containing Heteroarenes with Circularly Polarized Luminescence

“…The twisted to meso isomer interconversion procedure undergoes the transition state through the face-to-face benzene ring at the terminal of hetero [6]helicenes (Figure S5). The calculated isomerization barriers are 29.02 kcal/mol for 3a and 34.07 kcal/mol for 5a, respectively, which are larger than carbo [5]helicene 31 and comparable to the data for the carbo [6]helicene bearing pentagon ring. 28 Note that the (P,M)-isomer (meso) of 3a is thermodynamically more stable than the (P,P)-or (M,M)-isomers, as evidenced by its X-ray crystal analysis.…”

“…Construction of novel curved polycyclic aromatic hydrocarbons (PAHs) is of great academic significance because building them is an important challenge for synthetic researchers and such materials can be chosen as active layers in organic electronics for realizing the structure–property relationship. In particular, if the five-membered and/or seven-membered rings are doped into the building blocks of the all-carbon PAHs, the resulting arenes bearing saddle- or bowled-shaped architectures present unique optical, electronic, and magnetic properties. − Among them, the highly strained architectures of helical arenes offer more fascinating properties, such as chirality, functional self-assembly, and conductivity, making them widely useful in nonlinear optics, supramolecular chemistry, molecular recognition, and biology. − Campbell and co-workers first developed a circularly polarized light-detecting organic field-effect transistor on the basis of 1-aza[6]­helicene, and a rapid and fully reversible change of the off current was observed exposure to chiral light . Recently, Hatakeyama et al synthesized an expanded BN-embedded heterohelicene via one-shot triple borylation.…”

The road to bis‐periazulene (cyclohepta[def]fluorene): Realizing one of the long‐standing dreams in nonalternant hydrocarbons

“…It should be noted that advances in synthetic methodologies and computational techniques are powerful driving forces in rapidly expanding the related field. [56][57][58][59][60] 3 | PROJECT MOTIVATIONS:…”

Heteroatom-Doped [4]Triangulene: Facile Synthesis and Two-Dimensional On-Surface Self-Assemblies

“…Boron atoms were then incorporated into the skeleton by the tandem demethylation-electrophilic borylation reaction, 46,47 giving air-stable 1a and 1b as white solids in 82% and 95% yields, respectively. Compound 1b was well soluble in common organic solvents and characterized by 1 H and 13 C NMR spectroscopies as well as high-resolution mass spectrometry (HRMS), whereas compound 1a was only characterized by 1 H NMR spectroscopy and HRMS due to its poor solubility. Single crystal of 1b was successfully obtained, allowing or X-ray structural analysis.…”

“…During the past years, a large number of structurally well-defined NGs with various sizes and topological features have been synthesized in solution and on metal surfaces. [6][7][8][9][10][11][12][13][14][15][16][17] Furthermore, incorporation of heteroatoms has further expanded the possibilities of generating novel structures with desirable properties. [18][19][20][21][22][23] On the other hand, steering molecular assembly to form ordered two-dimensional (2D) networks has attracted much attention due to the superiority of 2D materials for optoelectronic applications.…”