Insight into non-covalent interactions in two triamine-based mononuclear iron(III) Schiff base complexes with special emphasis on the formation of Br⋯π halogen bonding

Two mononuclear iron(III) complexes, [FeL¹Cl]·CH₃CN (1) and [FeL²(N₃)] (2) {H₂L¹ = N,N′-bis(5-chlorosalicylidene)diethylenetriamine and H₂L² = N,N′-bis(5-bromosalicylidene)diethylenetriamine}, have been synthesized and characterized by X-ray crystallographic studies. In the solid state, there are strong hydrogen bonding interactions in both complexes due to the presence of the Fe(III)-coordinated amino group and anionic ligands, which are strong hydrogen bond donors and acceptors, respectively. These interactions have been studied by means of DFT and QTAIM calculations. Moreover, in the complex 2, the formation of halogen bonding interactions (Br⋯π) has been analyzed. The MEP analysis evidences the existence of a σ-hole at the bromine atom, and the concomitant Br⋯π interaction has been confirmed by QTAIM analysis.