Researches on acetylenic compounds. Part XLI. The synthesis of diphenylpolyacetylenes

Abstract

The synthesis of a series of diphenylpoly-ynes Ph*[CiC];Ph is described, those with n = 3, 4, 6, and 8 having been isolated and crystallised. Their ultra-violet and infra-red spectra are described and discussed, and compared with those of the corresponding polyenes.THE diphenylpolyenes (11) are much more stable than the purely aliphatic polyenes.Consequently, having prepared a number of aliphatic conjugated polyacetylenes (Cook, Jones, and Whiting, J., 1952, 2883) which on the whole proved to be rather unstable, we turned to the synthesis of the presumably more stable diphenylpoly-ynes (I). Such a project appeared additionally attractive since it offered the possibility of comparisons with the well-known diphenylpolyenes, synthesised and studied by Kuhn and his collaborators (for summary see J., 1938, 605).Four new members of the series (I), where n = 3, 4, 6, and 8, have been obtained, and the general laws defining their spectrographic properties elucidated. After the completion of most of this work, independent syntheses of (I; n = 3 and 4) (Nakagawa et aZ., Chem.

Synthesis of extended polyynes: Toward carbyne

“…The TIPS endcapped octayne can be stored as a solid indefinitely under refrigeration without appreciable decomposition. When crystallized from ether/EtOH, Armitage reported that the phenyl endcapped octayne has been isolated as an unstable copper colored solid that tended to explode upon heating [103]. When crystallized from THF, however, the resulting rust-colored solid shows surprisingly enhanced stability, surviving years if kept under refrigeration [110].…”

Oligomers from sp-Hybridized Carbon: Cumulenes and Polyynes

“…8). The λ max value of diphenylhexatriyne (358 nm in EtOH) [97] is significantly higher energy than λ max of the corresponding sp 2 -hybridized framework diphenylhexatriene of 426 nm (in EtOH) [104]. Finally, λ max for the 1,6-diphenylcumulene lies at longer wavelength (445 nm in methylcyclohexane/pentane 2:1) than either the polyene or the polyyne [64].…”

Hydrogen‐Bond‐Assisted Helical Folding of Propeller‐Shaped Molecules: Effects of Extended π‐Conjugation on Chiral Selection, Conformational Stability, and Exciton Coupling

“…[22,46] The CD couplet of (S,S) 3 -4 is centered at λ = 292 nm (Figure 7), which is close to the λ max = 279 nm of the diphenylacetylene π-π* transition. [47,48] Exciton coupling here thus arises from two (phenylethynyl)phenyl chromophores that are brought into close proximity through O-H···O-H contacts ( Figure 2). The experimentally observed positive CD couplet (Figure 7) of (S,S) 3 -4 thus dictates a positive chirality (= clockwise torsional relationship) of two electric transition dipoles, each of which lies parallel to the long axis of the π-conjugation (Figure 9, a).…”