The Structural Parameter of Spin States of C 1 -Symmetric Four-Coordinate Cobalt Complexes: D 4

Abstract

Herein, we revealed the correlation between structure and spin-state for C1-symmetric four-coordinate cobalt complexes. A series of C1-symmetric four-coordinate cobalt complexes were synthesized and characterized with various steric, electronic, anions and chelation modes. X-ray diffraction studies revealed a structural distortion from square-planar to a distorted tetrahedral pyramidal geometry. Combining paramagnetic nuclear magnetic resonance (pNMR), magnetic measurement (SQUID), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT), the electronic structure with a cobalt(II) (SCo = 1/2 to 3/2) ion antiferromagnetically coupled to a radical anion ligand (SLigand = 1/2) was established. A new structural parameter D₄, was introduced as an improved parameter for quantitatively assessing the spin state in four-coordinate complexes.