Simple aromatic molecules may be precursors for polycyclic aromatic hydrocarbons in space, and some of the simplest ones are now detected in the earliest stages of star formation . Evidence of benzonitrile (C$_6$H$_5$--CN) in the interstellar medium  questions the presence of related aromatic nitriles and their ring-chain derivatives. In light of previous work  on phenylpropiolonitrile (C$_6$H$_5$--C$_3$N), we are investigating, by laboratory high-resolution studies, its ethynylbenzonitrile (HCC--C$_6$H$_4$--CN) derivatives where a --CN and a --CCH groups lie in ortho (2-ETB), meta (3-ETB) or para (4-ETB) positions.
The pure rotational spectrum of these compounds has been recorded at room temperature in the millimeter-wave domain using a chirped-pulse W-band (75--110 GHz) spectrometer.
To facilitate spectral assignments, quantum chemical calculations have been performed using density functional theory at the $\omega$B97X-D/cc-pVQZ level of theory (geometry optimization, harmonic frequencies).
We will report a description of the experimental set-up and of our assignment procedure.
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