Helical Sexithiophenes:  An Experimental and Theoretical Study Implicating the Alternating 2,2‘:3,3‘ Regioisomer as a Reliable Helical Motif

Marsella, Michael J.; Yoon, Kunsang; Almutairi, Adah; Butt, Sheraz K.; Tham, Fook S.

doi:10.1021/ja038260e

Cited by 22 publications

(16 citation statements)

References 7 publications

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“…Based on this model, the simulated P5HT with 16 units was optimized and found to adopt a helical structure with end units twisted, which is different from the 3 1 helical geometry of oligo(othiophene)s revealed by single X-ray analysis ( Figure S9). 6 We then estimated the helical pitch of P5HT as 0.56 nm and diameter of the helix as 1.81 nm, which are consistent with the observed parameters of P5BT by STM. 68 Our simulation result further revealed that the protons on the alkyl chain carbons are oriented closer (<5 Å) to the H4 on the (same) thiophene ring.…”

Section: ■ Results and Discussionsupporting

confidence: 80%

Helical Poly(5-alkyl-2,3-thiophene)s: Controlled Synthesis and Structure Characterization

Zhang

Bonnesen

et al. 2016

Macromolecules

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Whereas poly(3-alkyl-2,5-thiophene)s (P3AT), with many potential applications, have been extensively investigated, their ortho-connected isomers, poly(5-alkyl-2,3-thiophene)s (P5AT), have never been reported because of the difficulty in their syntheses. We herein present the first synthesis of regioregular P5AT via controlled Suzuki cross-coupling polymerization with PEPPSI-IPr as catalyst, affording the polymers with tunable molecular weight, narrow polydispersity (PDI), and well-defined functional end groups at the gram scale. The helical geometry of P5AT was studied by a combination of NMR, small-angle X-ray scattering (SAXS), and scanning tunneling microscopy (STM). Particularly, the single polymer chain of poly(5-butyl-2,3-thiophene) (P5BT) on highly oriented pyrolytic graphite (HOPG) substrates with either M or P helical conformation was directly observed by STM. The comparison of UV−vis absorption between poly(5-hexyl-2,3-thiophene) (P5HT) (λ = 345 nm) and poly(3-hexyl-2,5-thiophene) (P3HT) (λ = 450 nm) indicated that the degree of conjugation of the backbone in P5HT is less than in P3HT, which may be a consequence of the helical geometry of the former compared to the more planar geometry of the latter. Moreover, we found that P5HT can emit green fluorescence under UV (λ = 360 nm) irradiation. ■ INTRODUCTIONConjugated polyarylenes have found a wide range of applications including optical sensors, electrochromic devices, field effect transistors, and organic solar cells. 1−3 Their physical properties are controlled by the manner in which their rings are connected. As a result, ortho-, meta-, and para-linked polyarylenes each show distinctive optoelectronic properties and accordingly constitute different classes of functional polymers. 4,5 Although meta-and para-linked polyarylenes have been extensively investigated over the past decades, the study of poly(o-arylene)s is still at an early stage because of the synthesis challenges.It has been reported recently that oligo(o-arylene)s intrinsically possess a compressed helical structure with a helical pitch of 0.3−0.5 nm in the solid state as revealed by single crystal X-ray analysis, including oligo(o-phenylene)s, oligo(o-thiophene)s, oligo(o-thiazole)s, and oligo(o-furan)s. 6−10 Moreover, Hartley and co-workers disclosed that this compressed helical structure of oligo(o-arylene)s is stabilized by aromatic stacking interactions, 11,12 which is different from traditional helical polymers commonly stabilized by steric effects or hydrogen bonding. 13−15 Thus, due to their helical structures, oligo(o-arylene)s are reported to possess certain unique properties with potential applications different from their meta-or para-counterparts. 16 For example, Fukushima and Aida et al. reported that oligo(ophenylene)s possessed a main chain redox active property that responded to electrical inputs by a conformation change and acted as surface modifiers for homeotropic columnar ordering of discotic liquid crystals. 8,17 Ito and co-workers reported poly-(quinoxaline-2,3-diyl)s...

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Section: ■ Results and Discussionsupporting

confidence: 80%

Helical Poly(5-alkyl-2,3-thiophene)s: Controlled Synthesis and Structure Characterization

Zhang

Bonnesen

et al. 2016

Macromolecules

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“…Note that we have had excellent success in predicting solid-state conformers of orthooligothiophenes using this level of theory. 4 In further support, the three lowest energy MMFF conformers of tetramer 3 are in complete agreement with that established from reported X-ray analysis. 6 Guided by MMFF conformational searches, our screening of candidates revealed that simply replacing the two terminal a-thienyl groups of compound 3 with phenyl rings (compound 2) fulfils three of our desired goals.…”

Section: Design and Synthesissupporting

confidence: 87%

ortho-Tetraaryls as helical building blocks: a study of structure, theory, electrochemistry, and optical properties

2004

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“…Because the number of π‐stacked units affecting the methyl groups is unchanged from (N,S) 6 (double‐stacked C⋅⋅⋅F and A⋅⋅⋅D) to (N,S) 8 (double‐stacked C⋅⋅⋅F, see Figure S16 in the Supporting Information), the biased formation of a helical conformation with pinned ends should be responsible for the upfield shift. The upfield shift in the 4‐Me group of (N,S) 8 is not as prominent as that of 5‐Me, which suggests the contribution of the second most stable conformer with a frayed end8a in a similar manner to (N,S) 6 . The signal pattern in the phenyl region becomes complicated in (N,S) 8 .…”

Section: Resultsmentioning

confidence: 92%

Synthesis, Structure, and Properties of α,β‐Linked Oligothiazoles with Controlled Sequence

Nakashima

Imamura

Yamamoto

et al. 2014

Chemistry A European J

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α,β-Linked oligothiazoles with head-to-tail connectivity are presented as a new family of helical scaffolds. Combinations of palladium-catalyzed cross-coupling reactions at the 5- and 4-positions of 2-phenylthiazole led to the synthesis of oligo(2-phenylthiazoles) with ortho linkages with a variety of defined sequences. The secondary structures of the α,β-linked oligo(2-phenylthiazoles) showed a clear dependence on their sequences. X-ray crystallography of the trimer, tetramer, and hexamer with head-to-tail connection revealed the formation of a helical structure, which was stabilized by a combination of intramolecular forces, including interheteroatom (S⋅⋅⋅N), CH-π, and π-π interactions. The introduction of a chiral end-group successfully led to the induction of chirality into the helical conformations. Programmable sequences for controlled geometries and photofunctions have been demonstrated through the manifold connection pathways in α,β-linked oligothiazoles.

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Helical Sexithiophenes: An Experimental and Theoretical Study Implicating the Alternating 2,2‘:3,3‘ Regioisomer as a Reliable Helical Motif

Cited by 22 publications

References 7 publications

Helical Poly(5-alkyl-2,3-thiophene)s: Controlled Synthesis and Structure Characterization

Helical Poly(5-alkyl-2,3-thiophene)s: Controlled Synthesis and Structure Characterization

ortho-Tetraaryls as helical building blocks: a study of structure, theory, electrochemistry, and optical properties

Synthesis, Structure, and Properties of α,β‐Linked Oligothiazoles with Controlled Sequence

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