Gas-phase conformations and exciton couplings in 5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene

Hamza, Abdulhamid

doi:10.1007/s11224-010-9612-z

Cited by 6 publications

(5 citation statements)

References 19 publications

(42 reference statements)

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“…Specifically, TM-DBCOD was synthesized from (4,5-dimethyl-1,2-phenylene)dimethanol (di-OH) on a large scale, sequentially through bromination 49 using phosphorous tribromide and dimerization [50][51] in the presence of lithium sands. 1,10-di-CHO was formed via Rieche formylation.…”

Section: Resultsmentioning

confidence: 99%

“…Specifically, TM-DBCOD was synthesized from (4,5-dimethyl-1,2-phenylene)dimethanol (di-OH) on a large scale, sequentially through bromination using phosphorus tribromide and dimerization , in the presence of lithium sands. 1,10-di-CHO was formed via Rieche formylation. , One-step column purification of 1,10-di-CHO was adequate instead of the multistep column purification required for the preparation of 2,9-di-CHO (Scheme S1 and Figures S1 and S2).…”

Section: Results and Discussionmentioning

confidence: 99%

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Arene Substitution Design for Controlled Conformational Changes of Dibenzocycloocta-1,5-dienes

Alam

et al. 2020

J. Am. Chem. Soc.

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We report that the agile eight-membered cycloalkane can be stabilized by fusing two rigid benzene rings, substituted with proper functional groups. The conformational change of dibenzocycloocta-1,5-diene (DBCOD), a rigid-flexible-rigid organic moiety, from Boat to Chair conformation requires an activation energy of 42 kJ/mol that is substantially lower than that of existing submolecular shape-changing unit. Experimental data corroborated by theory calculations demonstrate that intramolecular hydrogen bonding can stabilize Boat whereas electron repulsive interaction from opposing ester substituents favors Chair. Intramolecular hydrogen bonding, formed by 1,10-diamide substitution stabilizes Boat, spiking the temperature at which Boat and Chair can readily interchange from -60 °C to 60 °C. Concomitantly this intramolecular attraction raises the energy barrier from 42 kJ/mol of unsubstituted DBCOD to 68 kJ/mol of diamide-substituted DBCOD. Remarkably, this value falls within the range of the activation energy of highly efficient enzyme catalyzed biological reactions. With shape changes once considered only possible with high-energy, our work reveals a potential pathway exemplified by a specific submolecular structure to achieve low-energy driven shape changes for the first time. Together with intrinsic cycle stability and high energy output systems that would have incurred damage under high-energy stimuli, could particularly benefit from this new kind of low-energy driven shape-changing mechanism. This work has laid the basis to construct systems for low-energy driven stimuli-responsive applications, hitherto a challenge to overcome.

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Section: Resultsmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

Arene Substitution Design for Controlled Conformational Changes of Dibenzocycloocta-1,5-dienes

Alam

et al. 2020

J. Am. Chem. Soc.

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“…Hamza [201] report on the synthesis of 5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene (THDC) and its two selectively deuterated isotopomers which were studied by resonance-enhanced two-photon ionization spectroscopy in a supersonic jet expansion. The results showed that about 90% of THDC in the gas phase exists in the twist-boat and the remaining 10% in chair conformation.…”

Section: Issuementioning

confidence: 99%

“…Good agreement between experimental results and theoretical results was reached. We look forward to studies comparing the findings of Hamza [201] to this article.…”

Section: Issuementioning

confidence: 99%

Interplay of thermochemistry and Structural Chemistry, the journal (volume 21, 2010) and the discipline

Ponikvar‐Svet

Liebman

2011

Struct Chem

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“…The thermal isomerization of DBCO between the twist-boat and chair isomers has been thoroughly investigated using DFT calculations, , X-ray crystallography, variable temperature NMR spectroscopy, and differential scanning calorimetry (DSC) . However, to the best of our knowledge, previous studies have yet to consider the influence of regiochemistry on the isomerization equilibrium.…”

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confidence: 99%

Tuning Epoxy Thermomechanics via Thermal Isomerization: A Route to Negative Coefficient of Thermal Expansion Materials

et al. 2021

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Fine control over the thermal expansion and contraction behavior of polymer materials is challenging. Most polymers have large coefficients of thermal expansion (CTEs), which preclude long performance lifetimes of composite materials. Herein, we report the design and synthesis of epoxy thermosets with low CTE values below their T g and large contraction behavior above T g by incorporating thermally contractile dibenzocyclooctane (DBCO) motifs within the thermoset network. This atypical thermomechanical behavior was rationalized in terms of a twist-boat to chair conformational equilibrium of the DBCO linkages. We anticipate these findings to be generally useful in the preparation of materials with designed CTE values.

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Gas-phase conformations and exciton couplings in 5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene

Cited by 6 publications

References 19 publications

Arene Substitution Design for Controlled Conformational Changes of Dibenzocycloocta-1,5-dienes

Arene Substitution Design for Controlled Conformational Changes of Dibenzocycloocta-1,5-dienes

Interplay of thermochemistry and Structural Chemistry, the journal (volume 21, 2010) and the discipline

Tuning Epoxy Thermomechanics via Thermal Isomerization: A Route to Negative Coefficient of Thermal Expansion Materials

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