Ligand field parameters and the ground state of Fe(II) phthalocyanine

TL;DR

This paper determines the ground state of Fe(II) phthalocyanine as an orbitally degenerate spin triplet through analysis of experimental data and ligand field parameters, confirming a strong-ligand-field regime.

Contribution

It provides a detailed analysis of ligand field parameters and conclusively identifies the ground state of Fe(II) phthalocyanine, using a novel diagram and correlation corrections.

Findings

Ground state is an orbitally degenerate spin triplet (^3E_g)

Ligand field parameters are quantified relative to Racah's C

System is in a strong-ligand-field regime

Abstract

A judicious analysis of previously published experimental data leads one to conclude that the ground state of iron(II) phthalocyanine is an orbitally degenerate spin triplet $a_{1g}^2 e_g^{\uparrow\downarrow\uparrow} b_{2g}^{\uparrow}$ ($^3E_g$). The ligand field parameters, in relation to Racah's $C$, are approximately as follows: $B_{20}/C=0.84$, $B_{40}/C=0.0074$. The uniqueness of this result is demonstrated by means of a special diagram in the $B_{20}/C-B_{40}/C$ plane (under additional conditions that $B_{44}/B_{40}=35/3$ and $B/C=0.227$). The system is in a strong-ligand-field regime, which enables the use of single-determinant techniques corrected for correlations within the 3d shell of Fe.