Conjugation in 1,4-diphenylbutadiyne and 1,2-diphenylacetylene: A combined experimental and theoretical study

We have performed a combined experimental and theoretical study of the molecular system of 1,4-diphenylbutadiyne and compared with previously reported 1,2-diphenylacetylene. 1,4-Diphenylbutadiyne exists as a half molecule in the asymmetric unit. Experimental charge density analysis of the molecule showed that the acetylenic linkers have triple bond character close to an ideal triple bond, in clear contrast to the situation 1,2-diphenylacetylene, where the charge density parameters resemble more closely those of a double bond due to extended conjugation. The influence of the reduced conjugation on the transport characteristics has been obtained using the Landauer’s formalism. Thus, 1,4-diphenylbutadiyne is found less conducting than 1,2-diphenylacetylene.