Observation of the C₇H radical was reported in 1997 by Guélin et al. in IRC+10216 using the and based upon the laboratory data of Travers et al. (see also McCarthy et al.). The detection does not appear to have been confirmed by subsequent study to date, though a search in TMC-1 by Bell et al. did not find the species.

The full name of the C₇H radical is 1,3,5-heptatriynylidyne, which indicates that there are three triple bonds. The figures below show the alternating short and long bond lengths (in Å) and how the bonding arises from the orbitals of the carbon atom.