With nearly three dozen observed neutral and anionic astromolecules, the cyano group (–CN) is the most commonly observed motif in space. One example of a cyano compound that has not been detected is cyanogen fluoride, FCN, which was sought by Hollis & Ulich in the 1970s. They looked for a single rotational transition of FCN unsuccessfully in four different sources: the star-forming regions W3(OH) and Orion A as well as NGC 2264 and Sgr B2(OH).

Cyanogen fluoride or fluorocyanide can be formed in the lab, but it easily polymerizes to cyanuric fluoride (C₃N₃F₃), which has a 6-membered ring structure of alternating C and N atoms with a F atom bonded to each C atom.

As shown in the table below, quantum chemical calculations indicate that the F-CN bond is strong, but it is weaker than the H-F bond. The drive toward equilibrium will thus favor HF (which was found in space in the late 1990s) and may explain the apparent absence of FCN. A possible place where FCN might still be found is a source where methyl fluoride (CH₃F) is present, which has a weaker C-F bond than FCN. However, CH₃F has not yet been detected.