Syntheses and Structures of Thiophene-Containing Cycloparaphenylenes and Related Carbon Nanohoops

Abstract

Thiophene-containing cycloparaphenylenes (CPPs) bearing 8, 10, and 16 aromatic and heteroaromatic units in the macrocyclic ring structures were synthesized. Specifically, two and four thiophene-2,5-diyl units were incorporated into functionalized [6]- and [12]CPP macrocyclic carbon frameworks, respectively. In addition, two 2,2'-bithiophene-5,5'-diyl units were inserted into a functionalized [6]CPP carbon framework. The cyclic and differential pulse voltammetry and the UV-vis and fluorescence spectra of the fully aromatized macrocycles and their precursors exhibited interesting electrochemical and optical properties.

Synthesis of Cycloparaphenylenes Bearing Furan‐2,5‐diyl or 2,2’‐Bifuran‐5,5’‐diyl Units in the Macrocyclic Structures

“…[13] The electrochemistry of the macrocyclicf uran-containing CPP precursors and the corresponding furan-containing CPPs were investigated by cyclic and differential pulse voltammetry in dichloromethane (Table 1a nd the Supporting Information). In comparison with 2,5-diphenylfuran, which exhibitst he first oxidation potential( DE 1/2 )a t0 .78 Vr elative to Fc/Fc + ,t he initial oxidation behavior of 1 is significantly lower at 0.37 V. The first oxidation potentials of 2b and 3b at 0.28 and 0.37 V, respectively,are lower than that of ab ithiophene-containing CPP analogue at 0.49 V. [1] In summary,s ynthetic pathways to the furan-containing CPPs have been developed. The initial Diels-Alder reactionb etween diene 4 and 1,4-benzoquinone (5)p laces the two 4-bromophenyl groups cis to each other in 6,w hich is essential for the macrocyclic ring-forming step.…”

“…We recently developed synthetic pathways for thiophene-containing cycloparaphenylenes (CPPs) using the Diels-Alderr eaction as ak ey synthetic step. [1] Itami and co-workersa lso reported the construction of macrocyclic structures with alternating thiophene-2,5-diyl and benzene-1,4-diyl units. [2] These macrocyclic molecules with radially p-conjugateds ystemsw ere found to exhibit interesting optoelectronica nd redox properties.…”

“…The synthetic pathway to at hiophene-containingC PP possessingt wo thiophene-2,5-diyl units was adopted fort he attempted synthesis of the furan analogue 14 (Scheme1). [1] The Diels-Alder reaction betweend iene 4 and 1,4-benzoquinone (5) [6] produced 6,w hich on treatment with tert-butyldimethylsilyl chloride (TBSCl) in the presence of imidazole produced 7a. Similarly, 7b was obtained by treatment of 6 with triisopropylsilyl chloride (TIPSCl).…”

“…[5a] Ab ithiophene-containing CPP analogueo f2a and 2b exhibits the l abs at 376 nm and the l em at 511nm. [1] For comparison, the parent[ 10]-, [12]-, and [15]CPPse xhibit the l abs at 340,3 38, and 339 nm, respectively, and the l em at 470, 450,and 440 nm, respectively. [13] The electrochemistry of the macrocyclicf uran-containing CPP precursors and the corresponding furan-containing CPPs were investigated by cyclic and differential pulse voltammetry in dichloromethane (Table 1a nd the Supporting Information).…”

Concise Synthesis and Facile Nanotube Assembly of a Symmetrically Multifunctionalized Cycloparaphenylene

“…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. [12] These syntheses skillfully avoid sterically demanding aryl-aryl bond formation, while availablef unctional groups were limited to less polar alkyl anda lkoxy groups, thereby the columnar packing was not observedi nt he crystalline state.…”