A quantum chemistry study of diethynylbenzene macrocycles: Structural and electronic properties

Computational Chemical Studies on Thermochemistry and Ring Strains in Cyclic [n]Metaphenyleneacetylenes, Butadiyne-Bridged [4n]Metacyclophynes, and Butadiyne-Bridged [4n]Paracyclophynes

“…The boat conformation of B-B[4 8 ]MC is more stable than the chair form by 1.7 kJ mol −1 , which is also reflected by a lower strain energy for this conformer (Table ). Zhao et al have reported a difference of 1.3 kJ mol −1 energy between the chair and boat forms of B-B[4 8 ]MC . In the case of B-B[4 9 ]MC, the chair conformation is more stable than the boat conformation by 1.6 kJ mol −1 .…”

Better big or strained? Deformations of shape persistent arylene butadiynylene macrocycles

“…According to theoretical calculations for a similar, though unsubstituted, hexameric phenylene-butadiynylene system, the most energetically favorable is the planar structure. 44 Being aware of the sterically insignificant volume of the OMe substituents in the macrocycle cavity, we believe that the folding into a chair conformation is caused by packing forces.…”

“…Theoretical calculations published by Zhao et al predicted that significant deviations from planarity can be observed for cyclic phenyl butadiynes higher than hexamers. 44 This should be true for macromolecules with no steric impedance within the cavity; hence, one of our goals was to discover how flexible these architectures could become when they are exposed to steric hindrance. Another, rather synthetic target, was to check if an introduction of spacious endo -annular substituents will shift as a result of shotgun synthesis towards larger macrocycles which appeared partially true.…”