New molecular species at redshift z = 0.89

We present the first detections of CH₃SH, C₃H⁺, C₃N, HCOOH, CH₂CHCN, and H₂CN in an extragalactic source. Namely the spiral arm of a galaxy located at z = 0.89 on the line of sight to the radio-loud quasar PKS 1830-211. OCS, SO₂, and NH₂CN were also detected, raising the total number of molecular species identified in that early time galaxy to 54, not counting isotopologues. The detections were made in absorption against the SW quasar image, at 2 kpc from the galaxy centre, over the course of a Q band spectral line survey made with the Yebes 40 m telescope (rest-frame frequencies: 58.7-93.5 GHz). We derived the rotational temperatures and column densities of those species, which are found to be subthermally excited. The molecular abundances, and in particular the large abundances of C₃H⁺ and of several previously reported cations, are characteristic of diffuse or translucent clouds with enhanced UV radiation or strong shocks.