Novel Fe4 cluster topology from a new hexadentate chelate: magnetic analysis by experimental, DFT, and magnetostructural correlation methods

Abstract

The new potentially hexadentate chelate N,N′-bis(2-pyridylmethyl)-N,N′-bis(2-hydroxyethyl)-ethylenediamine (bphnH₂) has been synthesized. It possesses a mixed diol/diamine/dipyridine nature and has proven the source of two new Fe^III/oxo complexes with unprecedented structures. [Fe₂O(bphnH)(bphnH₂)][Ce(NO₃)₆] (1) and [Fe₄O(bphn)₂(NO₃)₄](NO₃)₂ (2) contain pentadentate and hexadentate chelates, respectively. A three-pronged approach comprising fits of experimental magnetic susceptibility data, DFT computations and use of a magnetostructural correlation has been applied to analyse the variable-temperature magnetic properties of 2, the reliability of obtained pairwise J_ij exchange interactions, the occurrence and avoidance of overparameterization problems, and the quantitative determination of a very weak long-range interaction in a molecule also containing very strong and medium strength interactions.