Influence of Electron Correlation on the Electronic Structure and Magnetism of Transition-Metal Phthalocyanines

Abstract

There exists an extensive literature on the electronic structure of transition-metal phthalocyanines (TMPcs), either as single molecules or adsorbed on surfaces, where explicit intra-atomic Coulomb interactions of the strongly correlated orbitals are included in the form of a Hubbard U term. The choice of U is, to a large extent, based solely on previous values reported in the literature for similar systems. Here, we provide a systematic analysis of the influence of electron correlation on the electronic structure and magnetism of several TMPcs (MnPc, FePc, CoPc, NiPc, and CuPc). By comparing calculated results to valence-band photoelectron spectroscopy measurements, and by determining the Hubbard term from linear response, we show that the choice of U is not as straightforward and can be different for each different TMPc. This, in turn, highlights the importance of individually estimating the value of U for each system before performing any further analysis and shows how this value can influence the final results.

Magnetic configurations of open-shell molecules on metals: The case of CuPc and CoPc on silver

“…8(a), 8(d), and 8(e)]. These findings are in line with previous studies, which argued that the hybridization between the frontier orbital which is localized mostly on the central metal atom and the substrate plays a more dominant role for CoPc than CuPc [22,26,27,87,88]. The reason for this difference lies in the metal d-orbitals: in the case of CoPc, the Co-centered frontier orbital has d z 2 character, while for CuPc this is not the case for the frontier orbitals.…”

“…First, we focus on the CuPc-Ag system, for which several experimental surveys indicated interesting magnetic properties of the surface-adsorbed molecule [18,19,25,37,[87][88][89][90]. We find charge transfer of about one electron from the surface to the molecule.…”

“…The reason for this difference lies in the metal d-orbitals: in the case of CoPc, the Co-centered frontier orbital has d z 2 character, while for CuPc this is not the case for the frontier orbitals. The Co-centered d z 2 orbital is sticking out of the molecular plane towards the metallic surface and hence promotes a stronger interaction of the central metal with the surface for CoPc [22,26,27,87,88,98,99].…”

High temperature ferromagnetism in π-conjugated two-dimensional metal–organic frameworks

“…This set of ( U , J ) parameters for TM d orbitals have been tested extensively in MPc-based systems. 28,38–40 We have also tested a slightly different set of ( U , J ) parameters for MPc recently proposed by Brumboiu et al 41 and obtained results with quantitative similarity. Other details of the computational methods can be found in the ESI †…”

“…This unique feature of strong hybridization between the metal d orbitals and the π electrons of ligand in octaamino-MnPc also occurs in amino-free MnPc molecules, as has been demonstrated both experimentally and theoretically. 41,46–48 …”