Toward Thiophene‐Annulated Graphene Nanoribbons

Abstract

Narrow thiophene-edged graphene nanoribbons (GNRs) were prepared from polychlorinated thiophene-containing poly(p-phenylene)s using the photochemical, metalfree cyclodehydrochlorination (CDHC) reaction. 1 HNMR and Raman spectroscopyc onfirmed the structures of the GNRs.T he regioselectivity of the CDHC reaction allows the preparation of both laterally symmetrical and unsymmetrical GNRs and, consequently,t he modulation of their optical and electronic properties. AngewandteChemie Communications 3591

Step-Growth Annulative π-Extension Polymerization for Synthesis of Cove-Type Graphene Nanoribbons

“…Although some top-down approaches such as lithographic cutting from graphene and unzipping of carbon nanotubes can produce subnanometer-sized GNRs, there are some critical problems. For example, these methods result in GNRs with a mixture of widths and edge structures or even with non-negligible defects. , In contrast, bottom-up synthetic approaches such as solution-phase synthesis − and on-surface synthesis , can produce structurally well-defined GNRs with control over the width, length, and edge structure. − In particular, solution-phase synthetic methods have been effectively employed from the viewpoints of scalability and tunability of the width and edge structures. Most such approaches have employed palladium-catalyzed Suzuki–Miyaura cross-coupling polymerization between aryl halides and arylboron compounds (Scheme a), , Ullmann-type homocoupling polymerization ,, of aryl halides, Diels–Alder polymerization between aryl alkynes and tetraryl cyclopentadienones, , or topochemical polymerization for the synthesis of polyarylenes as GNR precursors, which are further treated with FeCl 3 or 2,3-dichloro-4,5-dicyano­benzo­quinone for cyclodehydrogenation (Scholl reaction).…”

“…For example, these methods result in GNRs with a mixture of widths and edge structures or even with non-negligible defects. , In contrast, bottom-up synthetic approaches such as solution-phase synthesis − and on-surface synthesis , can produce structurally well-defined GNRs with control over the width, length, and edge structure. − In particular, solution-phase synthetic methods have been effectively employed from the viewpoints of scalability and tunability of the width and edge structures. Most such approaches have employed palladium-catalyzed Suzuki–Miyaura cross-coupling polymerization between aryl halides and arylboron compounds (Scheme a), , Ullmann-type homocoupling polymerization ,, of aryl halides, Diels–Alder polymerization between aryl alkynes and tetraryl cyclopentadienones, , or topochemical polymerization for the synthesis of polyarylenes as GNR precursors, which are further treated with FeCl 3 or 2,3-dichloro-4,5-dicyano­benzo­quinone for cyclodehydrogenation (Scholl reaction). Although these methods allow for the synthesis of various GNR structures depending on the design of the small arene monomers, they are generally based on multistep protocols consisting of component assembly and graphitization, which prevent the efficient and rapid production of structurally uniform GNRs.…”

Recent Progress in Synthesis of Conjugated Ladder Polymers

“…The optimized conditions afforded about 70% yields on the ladderization of multichlorinated small molecules without any further purification, other than filtration. [10,33] This moderate efficiency, in principle, is insufficient for the synthesis of well-defined cLPs. As a result, it is important to investigate what accounts for the remainder other than the desired products in order to determine whether the synthetic approach is appropriate to prepare cLPs since the high yield for the synthesis of cLPs does not necessarily imply that the method is suitable for the synthesis of cLPs due to the low solubility of cLP intermediates.…”

On-surface activation of benzylic C-H bonds for the synthesis of pentagon-fused graphene nanoribbons

“…To this end, on-surface synthesis based on the polymerization and planarization of tailor-made molecular precursors on metal surfaces under ultrahigh vacuum (UHV) conditions appears particularly powerful and offers the additional advantage of in-situ monitoring by atomic-resolution scanning probe microscopy [5][6][7][8][9][10]. Since the initial demonstration of 7-atomwide armchair-type GNRs (7-AGNRs) on a Au(111) surface using 10,10'-dibromo-9,9'-bianthryl (DBBA) as a precursor [11], a range of GNRs with different structures have been prepared via on-surface synthesis, such as armchair GNRs (N-AGNRs) with different widths N (N = 5, 6, 8, 9, 10, 13, 15 and 17) [12][13][14][15][16][17][18][19], zigzag GNRs (ZGNRs) [20], chevron-type GNRs [11,21], chiral (3,1)-GNRs containing zigzag and armchair edges [22], and heteroatom-doped GNRs with boron, nitrogen, oxygen, or sulfur [23][24][25][26][27][28][29][30]. π-Extension of 7-AGNRs through aryl-substitution of DBBA turned out to be of special value.…”