Highly Crowded Twisted Thienylene‐Phenylene Structures: Evidence for Through‐Space Orbital Coupling in a [4]Catenated Topology

Abstract

Dedicated to Prof. Dr. Dr. h.c. Klaus Müllen on the occasion of his 75 th birthday Sterically highly crowded and twisted thienylene-phenylenes are synthesized and structurally characterized. Single-crystal X-ray structure analyses and theoretical studies give evidence of through-space delocalization of 𝝅-electrons of peripheral (hetero)aromatic rings in toroidal and catenated topology.

Spacial structures induced by sterical hindrance of large substituents: A dendritic macromolecular “snowflake” molecule

“…The isolated reaction mixture was investigated by mass spectra and consisted of fivefold reacted derivative 14 with one ethyne group resting and the fully reacted 15 . Unfortunately, higher reaction temperatures than 200 °C were not constructive, because cyclopentadienone 13 is thermally labile in contrast to tetracyclone, which could be more efficiently reacted at 280 °C 13–15 . Separation of the two products by chromatographic methods was not feasible due to their low solubility.…”

“…Mp > 220 C decomp. ; 1 H-NMR (400 MHz, DCM-d 2 ): δ 7.33 (dd, 3 J (H,H) = 5.2 Hz, 4 J = 1.1 Hz, 6H, α-H 5" -Th), 7.26 (dd, 3 J (H,H) = 3.6 Hz, 4 J (H,H) = 1.2 Hz, 6H, β-H 3" -Th), 7.10 (d, 3 J (H,H) = 3.9 Hz, 6H, β-H 3 -Th), 7.01 (dd, 3 J (H, H) = 5.2, 3.7 Hz, 6H, β-H 4" -Th), 6.93 (d, 3 J (H,H) = 3.8 Hz, 6H, β-H 4 -Th), 6.90 (d, 3 J (H,H) = 3.8 Hz, 6H, β-H 3 0 -Th), 6.66 (d, 3 J (H,H) = 3.7 Hz, 6H, β-H 4 0 -Th) ppm; 13 Then, benzene 12 (100 mg, 0.06 mmol), which was dissolved in abs. DCB (18 ml), was slowly added dropwise and the reaction mixture stirred for 3 days at the same temperature.…”

“…HPLC was performed on a Shimadzu CBM-20A equipped with an SPD-20A UV/VIS detector and a LC-8A solvent system with a Macherey-Nagel column (Nucleosil 100-5 NO 2 ). NMR spectra were recorded on a Bruker Avance 400 ( 1 H-NMR: 400 MHz, 13 Büchi Melting Point M-565. High-resolution mass spectra (HRMS, MALDI-FT-ICR) were recorded on a Bruker Solarix (Bruker Daltonik GmbH), MALDI-TOF mass spectra on a Maldi-TOF REFLEX III (Bruker Daltonik GmbH) using trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) as a matrix.…”

“…The combined organic phases were dried over sodium sulfate, the solvent was removed, and the residue purified by column chromatography (flash silica gel, petroleum ether [PE]/DCM 3:1) to yield ethyne 8 as a yellow solid (442 mg, 1.25 mmol, 87%). Mp 144-146 C; 1 H-NMR (400 MHz, DCM-d 2 ): δ 7.29 (dd, 3 J (H,H) = 5.1 Hz, 4 J (H,H) = 1.2 Hz, 2H, α-H 5 0 -Th), 7.24 (dd, 3 J (H,H) = 3.6 Hz, 4 J (H,H) = 1.2 Hz, 2H, β-3 0 -Th), 7.20 (d, 3 J (H,H) = 3.8 Hz, 2H, β-H 3 -Th), 7.11 (d, 3 J (H,H) = 3.9 Hz, 2H, β-H 4 -Th), 7.05 (dd, 3 J (H,H) = 5.1, 3.6 Hz, 2H, β-H 4 0 -Th) ppm; 13 C NMR (101 MHz, CD 2 Cl 2 ): δ 140.0, 137.0, 133.7, 128.6, 125.9, 125.0, 124. 1,2-Di([2,2 0 -bithien]-5-yl)ethyne 8 (300 mg, 0.85 mmol) was dissolved in abs.…”

“…The isolated reaction mixture was investigated by mass spectra and consisted of fivefold reacted derivative 14 with one ethyne group resting and the fully reacted 15. Unfortunately, higher reaction temperatures than 200 C were not constructive, because cyclopentadienone 13 is thermally labile in contrast to tetracyclone, which could be more efficiently reacted at 280 C. [13][14][15] Separation of the two products by chromatographic methods was not feasible due to their low solubility. In order to shift the product ratio into the direction of the six-fold Diels-Alder cycloaddition product 15, the mixture was multiply additionally heated with excessive cyclopentadienone 13 and the product ratio monitored by mass spectra.…”