Conformational change of [2.2]metaparacyclophane

Orientational disorder in [2.2]metaparacyclophane and in its charge-transfer complex with tetracyanoethylene: crystal structures and NMR studies in solution

“…At room temperature the rigidity of the molecule is evidenced by the non-equivalence of the H(15) and H(13) protons and the C(15) and C(13) C atoms. The high field shifts observed for the H(8) and H(15) aromatic protons are due to the ring-current effects of the opposite benzene ring extended over them (Akabori et al, 1969). The conformational mobility of the meta ring is detectable only at high temperature.…”

Condensed Benzenoid Cyclophanes

“…(CH,) 14 The [12](l,4)naphthalenophane 92 was prepared (as shown in Eq. 2 68 ) by an extension of a method developed by Allen and Van Allan 69 from the pentadienone 91.…”

“…14014 1 A photochromic crown ether incorporating anthracene has been synthesized by the same research group. Another recorded macrocyclic compound is [12](1.4)anthracenophane (154), which was prepared in a manner similar to that for compound 92 (see Eq. The incorporation of residues such as anthracene into a macrocycle offers many possibilities for controlled and reversible modification of the shape of the macrocycle.…”

Conformational Behavior of Rigid and Dancing (1,3)(1,4)Cyclophanes

“…The conformational energy barrier for the above process was estimated to be 92 kJ mor l .'.! In the conformational study of [2](l,3)cyclo- --8 [2H?,1O)antbracenopbane 7, the conformational barrier for 7a -~_ 7c (via7b) was found to be relatively lower (74 kJ mol"). Two kinds of non-bonding interaction are encoun-ter~in 7a (or 7c): thez-n repulsion between the (1,3)bridged ring and the adjacent terminal anthracene ring, and the steric interaction due to the H-B proton projecting into the adjacent terminal ring of the anthracene moiety.…”

“…Either factor would be unfavorable and could destabilize the conformational ground state in 7 compared with that in 4 and thus accounts for the lower energy barrier observed for 7a ;::: 7c, assuming that the relative stabilities of the transition states (4b and 7b) are not significantly affected due to their similar geometries. A model to allow studies and direct comparison _ of both these interactions in the same molecule would thus be the [2](l,3)cyclo [2](1 ,4)naphthalenophane 8.…”