Magnetic properties of closo-carborane-based Co(II) single-ion complexes with O, S, Se, and Te bridging atoms

Abstract

We present a detailed computational analysis of a newly proposed family of Co(II) single-ion complexes with large magnetic anisotropy. Starting from previously proposed structures based on oxy- and thio-bridged 1,2-dicarba-closo-dodecaborane and 1,2-dicarba-closo-hexaborane, we explore the substitution of O and S bridging atoms by Se and Te atoms. Our calculations, based on CASSCF/NEVPT2 methods, show that these substitutions also lead to some large magnetic anisotropy complexes. Particularly, one of the proposed single-ion Se-bridged Co(II) chelated by 1,2-dicarba-closo-dodecaborane has a calculated anisotropy parameter D=-144 cm−1, and a single-ion Se-bridged Co(II) chelated by 1,2-dicarba-closo-hexaborane gives a calculated D=-133 cm−1. These large D values can be attributed in part to geometric distortion from Td symmetry at the Co(II) ion caused by the ligand structure, and in part to the electric effect of the Se atoms. Our results suggest that this strategy could be a feasible alternative to increase the magnetic anisotropy of single-ion transition metal complexes.