Ferromagnetism in polynuclear systems based on non- linear [(Mn2MnIII)-Mn-II] building blocks

Abstract

The design of new polynuclear transition metal complexes showing large total spin values through parallel alignment of the spins is an important challenge due to the scarcity of bridging ligands that provide ferromagnetic coupling. Herein, we report two new complexes, a [(Mn4Mn2III)-Mn-II] system containing two non-linear [(Mn2MnIII)-Mn-II] units and a 1D chain system with [(Mn2MnIII)-Mn-II] units that are assembled through dicyanamide bridging ligands coordinated to one of the terminal Mn-II centers. In both cases, the main exchange interaction is between Mn-II center dot center dot center dot Mn-III, showing a relatively strong ferromagnetic coupling. Density functional theory calculations corroborate such ferromagnetic interactions and also provide one magnetostructural correlation, showing that larger Mn-II-O-Mn-III angles enhance the strength of the ferromagnetic coupling. Thus, the non-linear [(Mn2MnIII)-Mn-II] units present in these two complexes are specially suited because of their larger Mn-II-O-Mn-III angles compared to similar previously reported systems containing a linear [(Mn2MnIII)-Mn-II] unit.