Ab initio molecular and solid state studies of Fe$^{II}$ spin cross-over system [Fe(btz)$_2$(NCS)$_2$

TL;DR

This study uses ab initio density functional theory to analyze the electronic structure, vibrational spectra, and bonding characteristics of the Fe(II) spin crossover complex in both molecular and solid states.

Contribution

It provides detailed computational insights into the spin states, spectra, and electronic properties of [Fe(btz)$_2$(NCS)$_2$], advancing understanding of its spin crossover behavior.

Findings

Identification of high and low spin states and their electronic configurations.

Analysis of vibrational spectra for isolated molecules and crystalline solid.

Assessment of crystal field effects and Fe-N bonding contributions.

Abstract

Ab initio computations within the density functional theory are reported for the spin cross-over complex, [Fe(btz)$_{2}$(NCS)$_{2}$], where 3d$^6$ Fe$^{II}$ is characterized by High Spin (HS t$_{2g}^4$, e$_g^2$) and Low Spin (LS t$_{2g}^6$, e$_g^0$) states. Results of infra red and Raman spectra for the isolated molecule are complemented for the crystalline solid with a full account of the electronic band structure properties: the density of states assessing the crystal field effects and the chemical bonding assigning a specific role to the Fe-N interaction within the coordination sphere of Fe$^{II}$.