Electronic Structure of Transition-Metal Dicyanamides Me[N(CN)$_2$]$_2$ (Me = Mn, Fe, Co, Ni, Cu)

TL;DR

This study combines experimental spectroscopy and theoretical calculations to analyze the electronic structure and magnetic properties of transition-metal dicyanamides, revealing how metal 3d states and hybridization influence their electronic and magnetic behaviors.

Contribution

It provides a comprehensive analysis of the electronic structure of Me[N(CN)$_2$]$_2$ compounds using combined experimental and theoretical methods, highlighting the role of metal 3d states and hybridization.

Findings

Valence band top dominated by Me 3d bands

Hybridization between C 2p and N 2p states shapes valence band

Magnetic ordering depends on metal 3d shell occupation

Abstract

The electronic structure of Me[N(CN)$_2$]$_2$ (Me=Mn, Fe, Co, Ni, Cu) molecular magnets has been investigated using x-ray emission spectroscopy (XES) and x-ray photoelectron spectroscopy (XPS) as well as theoretical density-functional-based methods. Both theory and experiments show that the top of the valence band is dominated by Me 3d bands, while a strong hybridization between C 2p and N 2p states determines the valence band electronic structure away from the top. The 2p contributions from non-equivalent nitrogen sites have been identified using resonant inelastic x-ray scattering spectroscopy with the excitation energy tuned near the N 1s threshold. The binding energy of the Me 3d bands and the hybridization between N 2p and Me 3d states both increase in going across the row from Me = Mn to Me = Cu. Localization of the Cu 3d states also leads to weak screening of Cu 2p and 3s states, which accounts for shifts in the core 2p and 3s spectra of the transition metal atoms. Calculations indicate that the ground-state magnetic ordering, which varies across the series is largely dependent on the occupation of the metal 3d shell and that structural differences in the superexchange pathways for different compounds play a secondary role.