Correlation between molecular orbitals and doping dependence of the electrical conductivity in electron-doped Metal-Phthalocyanine compounds

TL;DR

This study investigates how the molecular orbital characteristics influence the doping-dependent electrical conductivity in various electron-doped metal-phthalocyanine compounds, revealing a correlation between orbital type and conductivity behavior.

Contribution

It demonstrates the link between molecular orbital nature and electrical conductivity trends across different MPc compounds, highlighting the role of orbital localization.

Findings

Conductivity shapes are similar for ligand-centered orbitals (ZnPc, CuPc, NiPc).

Different conductivity behavior observed when electrons occupy metal-centered orbitals (CoPc, FePc, MnPc).

Molecular orbital properties significantly influence macroscopic electronic properties.

Abstract

We have performed a comparative study of the electronic properties of six different electron-doped metal phthalocyanine (MPc) compounds (ZnPc, CuPc, NiPc, CoPc, FePc, and MnPc), in which the electron density is controlled by means of potassium intercalation. In spite of the complexity of these systems, we find that the nature of the underlying molecular orbitals produce observable effects in the doping dependence of the electrical conductivity of the materials. For all the MPc's in which the added electrons are expected to occupy orbitals centered on the ligands (ZnPc, CuPc, and NiPc), the doping dependence of the conductivity has an essentially identical shape. This shape is different from that observed in MPc materials in which electrons are also added to orbitals centered on the metal atom (CoPc, FePc, and MnPc). The observed relation between the macroscopic electronic properties of the MPc compounds and the properties of the molecular orbitals of the constituent molecules, clearly indicates the richness of the alkali-doped metal-phthalocyanines as a model class of compounds for the investigation of the electronic properties of molecular systems.