The detection of the bicyclic aromatic hydrocarbon, 2-cyanoindene (C₉H₇CN), was reported in 2022 by Sita and co-workers in GOTHAM line survey data of TMC-1 collected with the 100m Green Bank Telescope. The work included calculating the structures and rotational constants of all seven cyanoindene isomers and measuring and analyzing the rotational spectra of five of the isomers: the other four isomers with measured spectra were not detected in the survey data.

2-Cyanoindene is a derivative of indene, which consists of an aromatic 6-membered ring and non-aromatic 5-membered ring. Indene was detected toward TMC-1 in 2021. As with many of the large number of detected cyano species, 2-cyanoindene may be formed by the addition of the CN radical at one of the doubly bonded carbon atoms in the 5-membered ring of indene (followed by the elimination of H), a mechanism first demonstrated by theory to operate in the formation of benzonitrile.