[FePAH]⁺complexes and [Fe_xPAH_y]⁺clusters in the interstellar medium: stability and spectroscopy

Abstract

Abstract. The relevance of organometallic complexes in the chemistry of the interstellar medium (ISM) was first suggested in the early 90s. This initial proposal has recently been re-considered in the light of new astronomical data, benefiting from pioneering experimental techniques and theoretical methods. In this article, a review of recent theoretical and experimental results obtained for PAHs coordinated to Fe atoms is presented, focusing on: -(i)-the IR spectra of [FePAH] + and [Fe(PAH)2] + complexes, found to be in line with the AIBs, with additional specific features in the far-IR range and -(ii)-the photoevaporation of [FexPAHy] + clusters as possible candidates for very small grains releasing PAHs in photodissociation regions. These results call for new astronomical data at high spatial resolution. Studies on larger clusters will require further experimental and theoretical developments.