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Effect of Edge Functionalization on the Bottom‐Up Synthesis of Nano‐Graphenes
Author(s) -
Ohtomo Manabu,
Hayashi Hironobu,
Hayashi Kenjiro,
Jippo Hideyuki,
Zhu Juanjuan,
Hayashi Ryunosuke,
Yamaguchi Junichi,
Ohfuchi Mari,
Yamada Hiroko,
Sato Shintaro
Publication year - 2019
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201900510
Subject(s) - intramolecular force , anthracene , surface modification , density functional theory , thiophene , polymerization , moiety , materials science , graphene , polymer , polymer chemistry , coupling reaction , photochemistry , chemistry , computational chemistry , nanotechnology , organic chemistry , catalysis
We demonstrate the effect of edge functionalization on the on‐surface Ullmann coupling of nano‐carbon materials. Unlike 10,10′‐Dibromo‐9,9′‐bianthryl (DBBA), which is widely known to form anthracene polymers and armchair‐edge graphene nanoribbons on Au(111), newly‐developed precursor named 5‐bromo‐11(10‐bromoanthracene‐9‐yl)anthra[2,3‐b : 7,6‐b′]dithiophene (BABAT) with isomers, which has similar structure as DBBA with one anthracene substituted with anthradithiophene, was found to make intramolecular C−C bonding instead of long anthracene polymers after annealing at 200 °C on Au(111). The mechanism was investigated using first‐principle density functional theory, which revealed that on‐surface polymerization is not kinetically preferred in case of BABAT. The reaction rate of intramolecular C−C bonding of BABAT is ∼206 times faster than that of DBBA. The intramolecular C−C bonding in DBBA biradicals, on the other hand, do not take place because of faster reverse reaction. By referring to electron density of BABAT biradicals, it was concluded that thiophene functionalization modifies distribution of electron density in BABAT radicals and facilitates electrophilic addition, leading to intramolecular C−C bonding after 200 °C annealing. These results indicate that the design of radical moiety is particularly important in the on‐surface Ullmann‐type coupling.