Double‐CO 3 2− Centered [Co II 5 ] Wheel and Modeling of Its Magnetic Properties

A high‐spin Co II cluster with a rare pentagonal molecular structure and formula [Co 5 (CO 3 ) 2 (bpp) 5 ]ClO 4 ( 1 ; Hbpp is 2,6‐bis(phenyliminomethyl)‐4‐methylphenolate) has been synthesized and characterized by single‐crystal X‐ray diffraction. This topology arises from fusing five [Co 2 (bpp)] moieties in a cyclic manner around two CO 3 2− central ligands, resulting in propeller‐like configuration. The irregular coordination of the carbonate ions to the metal centers results in a combination of coordination numbers (CNs) of the Co II ions of five and six. The bulk magnetization of this complicated magnetically exchanged system has been modeled successfully by employing a matrix diagonalization technique. For this, the combination of S =3/2 ions (CN=5) with ions exhibiting strong spin‐orbit coupling (CN=6) has been considered and a perturbative approach to handle the data in the whole studied range of temperatures (2–300 K) yielding parameters of g and D (for the five‐coordinate Co II ions), of A , κ , λ , and Δ (for the metals with spin‐orbit coupling) and of the exchange constants J . The agreement with results from DFT calculations, also presented here, is remarkable.