Polymorphism of Macrocyclic Oligothiophehe 8-Mers

Three new macrocyclic π‐extended thiophene hexamers composed of four thienylene‐ethynylene and two thienylene‐vinylene units with or without four alkyl substituents have been synthesized. Despite similar shape‐persistent structures in solution, the alkyl substituents control the solid‐state structures and morphologies. The unsubstituted hexamer exhibited a planar conformation with a theoretically predicted structure in the solid state; however, the planar hexamer with four ethyl substituents formed a closely stacked columnar crystal structure to exhibit π‐π interactions. Interestingly, the hexamer with four butyl substituents adopted both planar and twisted conformations in the solid state, exhibiting polymorphism based on induced‐fit stacking of molecules. Thus, the butyl‐substituted hexamer produces a mixture of yellow, orange, and red single crystals from toluene/acetone, and X‐ray analysis revealed six different conformations. Consequently, the small structural difference in the macrocycles causes a key effect on their functional properties in the solid state, and their morphology governs electrical conductivity and organic field‐effect‐transistor activity. The polymorphism of the hexamers was applied to the switching of film morphology.

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Small Structural Changes in the Alkyl Substituents of Macrocyclic π‐Extended Thiophene Oligomers Causes a Key Effect on Their Stacking and Functional Properties

Fujiwara

Takashika

Hasegawa

et al. 2019

ChemPlusChem

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Reduction of Ethynylenes to Vinylenes in a Macrocyclic π-Extended Thiophene Skeleton Under McMurry Coupling Conditions

et al. 2020

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McMurry coupling is one of the most useful and convenient tools for the preparation of π-conjugated molecules. However, for the synthesis of strained macrocycles containing ethynylene linkages, reduction of ethynylene to vinylene linkage sometimes took place. Especially, for the synthesis of macrocyclic π-extended thiophene hexamers using McMurry coupling of dialdehyde 1 composed of three thienylene, two ethynylene, and two formyl groups, reduction of ethynylenes to vinylenes often takes place to produce unique products in a one-pot procedure, depending on very small steric and electronic effects such as reaction temperature, amounts of titanium reagent, and substituents of thiophene hexamers. The attractive structures and functional properties of reduced thiophene hexamers have been determined using X-ray analysis and OFET measurements.

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π-Extended Macrocyclic Oligothiophene Heptamer and Tetradecamer: Ringsize Effects on the Physical Properties and Morphological Features

Shimizu

Huang

Isomura

et al. 2021

Bulletin of the Chemical Society of Japan

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Synthesis, X-ray structural analysis, redox behavior, and morphological features of π-extended macrocyclic oligothiophene heptamer and tetradecamer are reported. Due to nanophase separation between inner and outer domains, butyl-substituted π-extended macrocyclic oligothiophenes exhibit marked ringsize effects in the solid state. Among macrocycles with the same composition formula, heptamer has a round shape-persistent structure to produce crystals, whereas the corresponding tetradecamer shows morphological diversity to form single crystals, rods, ovals, and balls. The surface structures of small rods, ovals, and balls were investigated by absorption spectra and PXRD analysis. By cyclic voltametric analysis, heptamer and tetradecamer exhibit reversible two-step redox behavior reflecting moderate donor ability, and the first oxidation potentials of heptamer and tetradecamer are roughly consistent with their HOMO levels.

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Polymorphism of Macrocyclic Oligothiophehe 8-Mers

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Small Structural Changes in the Alkyl Substituents of Macrocyclic π‐Extended Thiophene Oligomers Causes a Key Effect on Their Stacking and Functional Properties

Small Structural Changes in the Alkyl Substituents of Macrocyclic π‐Extended Thiophene Oligomers Causes a Key Effect on Their Stacking and Functional Properties

Reduction of Ethynylenes to Vinylenes in a Macrocyclic π-Extended Thiophene Skeleton Under McMurry Coupling Conditions

π-Extended Macrocyclic Oligothiophene Heptamer and Tetradecamer: Ringsize Effects on the Physical Properties and Morphological Features

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