Nano-rings with a handle – Synthesis of substituted cycloparaphenylenes

Abstract

SummaryThe research of cycloparaphenylenes (CPPs), the smallest armchair carbon nanotube, has been a quest for the past decades which experienced a revival in 2008 when the first synthesis was achieved. Since then CPPs with various ring sizes have been realized. The incorporation of substituents and the synthesis of CPPs with building blocks different from phenyl rings bear challenges of their own. Such structures, however, are highly interesting, as they allow for an incorporation of CPPs as defined nano-objects for other applications. Therefore, this review provides a status report about the current efforts in synthesizing CPPs beyond the parent unsubstituted oligo-phenylene structure.

Electronic Communication between two [10]cycloparaphenylenes and Bis(azafullerene) (C59N)2 Induced by Cooperative Complexation

“…[1] While nature brilliantly employs the various concepts in supramolecular chemistry to achieve function, the creation of artificial systems is still hampered by al ack of knowledge to control molecular assemblies. [9] Notably, cyclic p-conjugated species composed of multiple aromatic rings,c ycloparaphenylenes (CPPs), [10][11][12] with diameter in the nm range have emerged as model systems to study such p-pinteractions under defined conditions.C PPs represent the smallest armchair carbon nanotube (CNT) segment, [13] hence, offering unique opportunity to gain fundamental insights for the design and preparation of devices with controlled structure,chirality,and electronic properties. [9] Notably, cyclic p-conjugated species composed of multiple aromatic rings,c ycloparaphenylenes (CPPs), [10][11][12] with diameter in the nm range have emerged as model systems to study such p-pinteractions under defined conditions.C PPs represent the smallest armchair carbon nanotube (CNT) segment, [13] hence, offering unique opportunity to gain fundamental insights for the design and preparation of devices with controlled structure,chirality,and electronic properties.…”

“…[14][15][16][17][18][19] Forexample,in [10]CPP'C 60 ,the best fit of [10]CPP,w ith 1.4 nm diameter,w as for C 60 [14,15] as well as Li@C 60 [16] and [11]CPP,with 1.5 nm diameter, for C 70 [17] as well as La@C 82 . In those complexes,t here is ah igh size-specificity between the CPP,b ased on the number of conjugated aromatic rings,a nd the size of the carbon cage.…”

“…[2] Although tremendous progress has been achieved in recent years, [3] fore xample,i nt he preparation of rotaxanes, [4] knots, [5,6] switches [7] or machines, [8] there are still many unexplored ways to tie together and let interact two or more individual molecules.B esides hydrogen bonding,i on pairing,o rm etal complexes, p-p interactions have recently gained much attention owing to their potential in building molecular architectures for electronic applications. [9] Notably, cyclic p-conjugated species composed of multiple aromatic rings,c ycloparaphenylenes (CPPs), [10][11][12] with diameter in the nm range have emerged as model systems to study such p-pinteractions under defined conditions.C PPs represent the smallest armchair carbon nanotube (CNT) segment, [13] hence, offering unique opportunity to gain fundamental insights for the design and preparation of devices with controlled structure,chirality,and electronic properties.…”

“…In those complexes,t here is ah igh size-specificity between the CPP,b ased on the number of conjugated aromatic rings,a nd the size of the carbon cage. [14][15][16][17][18][19] Forexample,in [10]CPP'C 60 ,the best fit of [10]CPP,w ith 1.4 nm diameter,w as for C 60 [14,15] as well as Li@C 60 [16] and [11]CPP,with 1.5 nm diameter, for C 70 [17] as well as La@C 82 . [18,19] Although the association between the CPP species and empty fullerenes is mainly developed via multiple van der Waals forces,i nt he case of endohedral fullerenes Li@C 60 and La@C 82 charge-transfer interactions are also prevalent.…”

Concise Synthesis and Facile Nanotube Assembly of a Symmetrically Multifunctionalized Cycloparaphenylene

“…Although the formation of the columnar structure in the crystalline state was observed in two isolated examples of at hiophene-containing [11] and/or very small CPP [4b] ([4]cyclo-1,4-phenylene-2',5'-thienylene [11] and [6]CPP [4b] ,r espectively), the majority of CPPs does not form ac olumnar structure in the crystalline state [4d,e, 5c,d,f, 6c, 12, 13] and the nanotube assembly on the solid surface hasn ot been reported to date. To this end, it was envisioned that the symmetrical introduction of multiple highly polar functional groups in the ring of CPP [14] would induce the facile nanotube assembly through multiple non-covalent interactions. However,r eadily accessible CPPs are nonsubstituted (unfunctionalized) or mono-substituted ones, [15] because the existing methods employ the aryl-aryl bond forming reactions, which are sensitive to steric hindrance, for the macrocycle formation.R ecently,I sobe, [16] Wang, [17] and Wegner [12] synthesized independently variouss ymmetrically multifunctionalized CPPs and related compoundsb ye mploying 2,8-diboryl-6,12-dihexylchrysene for the platinum-mediated macrocyclization, [16] 5,8-dimethoxy-1,4-dihydronaphthlene as am asked aromatic ring, [17] and the [RhCl(PPh 3 ) 3 ]-catalyzed partially intramolecular alkyne cyclotrimerization for macrocyclization.…”