Magnetostructural correlation in isolated trinuclear iron(iii) oxo acetate complexes

Abstract

We elucidate the correlation between geometric structures and magnetic couplings in trinuclear iron(iii) oxo acetate complexes [Fe3O(OAc)6(Py)n]+ (n = 0, 1, 2, 3) when isolated and trapped as gaseous ions. Structural information arises from Infra Red-Multiple Photon Dissociation (IR-MPD) and Collision Induced Dissociation (CID) experiments in conjuction with Density Functional Theory (DFT) based calculations. We simulate the antiferromagnetic couplings between the FeIII (d5) centers by employing a Broken Symmetry approach within our DFT calculations, and we extract the associated antiferromagnetic coupling constants. Coordination of one, two or three axial pyridine ligands to the [Fe3O(OAc)6]+ subunit distorts the geometry of the triangular Fe3O core. The Fe-Ocentral bond lengths are enlarged or shortened depending on number of coordinated pyridine ligands. This significantly affects the antiferromagnetic coupling constants between the FeIII centers ranging from -62 cm-1 to -28 cm-1 in [Fe3O(OAc)6(Py)n]+ (n = 0, 1, 2, 3). A detailed analysis of the associated exchange couplings indicates a switching of magnetic ground states by pyridine coordination. The total spin ST in the ground states of [Fe3O(OAc)6(Py)n]+ raises from ST = 1/2 (n = 0) to 3/2 (n = 1) and 5/2 (n = 2). Coordination of the third pyridine ligand (n = 3) re-establishes a spin ground state of ST = 1/2. We thus identify a coordination controlled switching of magnetic ground states.

Application of continuous wave quantum cascade laser in combination with CIVP spectroscopy for investigation of large organic and organometallic ions

“…It is noteworthy that for the formation of complexes with tags cryogenic conditions in the ICR-cell are required. [66][67][68][69][70] The ions are trapped in the presence of a low background concentration of the neutral tag molecules, leading to a steady-state distribution between tagged and untagged species that is quite sensitive to the absorption of infrared photons. Arrival at the steady-state distribution, in the presence of resonant infrared radiation, or in its absence, takes only some seconds.…”

Advancing Inorganic Coordination Chemistry by Spectroscopy of Isolated Molecules: Methods and Applications

“…+ and its complexes with n-heterocylces. [41] Likewise, the elucidation of roll-over cyclometallation within Ru II Chemistry-A European Journal complexes, [42] and further related studies have benefitted from such CID studies and their corresponding interpretation. [43] Despite being able to routinely determine relative CID thresholds under such conditions it remains beneficial to search for calibration methods to transform these to absolute bond dissociation energies.…”

“…In such cases it is nevertheless gratifying to realize, that relative values of recorded fragmentation thresholds can still be useful for the interpretation of relative stabilities, for example of Au−Zn−Alkali Complexes, [40] or in magnetostructural correlations within Fe 3 O(ac) 6 + and its complexes with n‐heterocylces. [41] Likewise, the elucidation of roll‐over cyclometallation within Ru II complexes, [42] and further related studies have benefitted from such CID studies and their corresponding interpretation. [43] …”

“…Some further interesting cases of single colour IR‐PD investigations of oligonuclear TM complexes shall be noted in passing: the oxo centered Fe 3 O scaffold, when stabilized via six acetate anions in a C 3v symmetry, not only provides for interesting magnetostructrual correlations upon symmetry reduction by coordination of appropriate Lewis base ligands such as N heterocycles. [41] These coordinatively unsaturated Fe 3 O(OAc) 6 + complexes also manage to coordinate N 2 in “non‐classical” dinitrogen complexes that signify in vibrational blueshifts of the N 2 stretching modes. [118] The vibrational fingerprints of a tetranuclear cobalt carbonyl cluster within a cryo tandem ion trap revealed as convincing line narrowing by cryo cooling, ultimately enabled identification of CO coordination patterns.…”

Li4Ru2OCl10·10H2O: crystal structure, magnetic properties and bonding interactions in ruthenium-oxo complexes

“…Most oxo-di-metallic molecular clusters have been well studied for their catalytic properties and medicinal applications (Zimmermann et al, 2018;Arii et al, 2000;Kurtz, 1990;Engelmann et al, 2016). However, limited research has been conducted to understand their magnetic properties (Sessoli et al, 1993;Singh & Rajaraman, 2019;Lang et al, 2018;Barman et al, 2019). Although magneto-structural correlations largely differ from system to system, up-to-date studies reveal that the bridging bond angle is a crucial parameter in this context.…”