The detection of the linear compound isocyanodiacetylene (HC4NC) was reported in 2020 by
Xue and coworkers and by
Cernicharo and coworkers toward
TMC-1. Cernicharo and coworkers sought
HC4NC toward the carbon-rich source
IRC +10216 as well but did not detect it there.
The first group used the 100m
Green Bank Telescope for their
observations, while the second group used the
Yebes 40m telescope.
Hyperfine lines of various rotational transistions
were resolved in both sets of observations.
Isocyanopolyyne compounds with the formula H–(C≡C)2n–N≡C are evidently
much rarer in space than cyanopolyyne H–(C≡C)2n–C≡N molecules. To date,
the only other isocyanopolyyne compound to be detected is
isocyanoacetylene (HC2NC). Both of
the groups that discovered HC4NC also sought HC6NC (isocyanotriacetylene) toward TMC-1
but did not find it. In 2013,
Vichietti & Haiduke published theoretical predictions
of the structures and dipole moments for isocyanopolyynes as large as HC16NC.