Structural and spectroscopical characterization of µ-oxo bridged Iron(III) bromide complexes of Pyclen ligands

[Display omitted] •Synthesis of iron(III) complexes of Pyclen ligands with different steric hinderance.•Structure determination by X-ray diffraction.•Analysis of the Fe-O-Fe unit vibrations by Raman spectroscopy.•Observation of the influence of coordination environment on the structure and vibrational spectra. Binuclear iron oxo-bridged complexes have found much interest since the early 80′s as synthetic models for relevant biological molecules, catalysts and magnetic probes. In this work, a series of iron(III)bromide-based oxo-bridged complexes of Pyclen ligands was prepared, with the aim of investigating the peculiar iron-oxygen bond features in different molecular environments. We observed the influence of the steric hindrance of the ligands employed in this study towards the formation of symmetrical and non-symmetrical µ-oxo complexes, and we confirmed this peculiar behaviour by single crystal X-ray diffraction and Raman spectroscopy. We report here structural and spectroscopical insight of three unprecedented oxo-iron complexes and their relative precursors, enlarging the existing database of these particular class of metal complexes.