A Theoretical Study of the Occupied and Unoccupied Electronic Structure of High- and Intermediate-Spin Transition Metal Phthalocyaninato (Pc) Complexes: VPc, CrPc, MnPc, and FePc

Abstract

The structural, electronic, and spectroscopic properties of high- and intermediate-spin transition metal phthalocyaninato complexes (MPc; M = V, Cr, Mn and Fe) have been theoretically investigated to look into the origin, symmetry and strength of the M–Pc bonding. DFT calculations coupled to the Ziegler’s extended transition state method and to an advanced charge density and bond order analysis allowed us to assess that the M–Pc bonding is dominated by σ interactions, with FePc having the strongest and most covalent M–Pc bond. According to experimental evidence, the lightest MPcs (VPc and CrPc) have a high-spin ground state (GS), while the MnPc and FePc GS spin is intermediate. Insights into the MPc unoccupied electronic structure have been gained by modelling M L2,3-edges X-ray absorption spectroscopy data from the literature through the exploitation of the current Density Functional Theory variant of the Restricted Open-Shell Configuration Interaction Singles (DFT/ROCIS) method. Besides the overall agreement between theory and experiment, the DFT/ROCIS results indicate that spectral features lying at the lowest excitation energies (EEs) are systematically generated by electronic states having the same GS spin multiplicity and involving M-based single electronic excitations; just as systematically, the L3-edge higher EE region of all the MPcs herein considered includes electronic states generated by metal-to-ligand-charge-transfer transitions involving the lowest-lying π* orbital (7eg) of the phthalocyaninato ligand.

Consistent characterization of the electronic ground state of iron(ii) phthalocyanine from valence and core–shell electron spectroscopy

“…As in the article of Carlotto et al 45 , our calculations show that the energy levels of the three different symmetries 3 E g , 3 B 2g and 3 A 2g are close to each other. However, we found differences in the sequence of states and obtained splittings.…”

“…In detail, in the Ref. 45 , the GS was found to be the 3 A 2g state separated to the 3 E g and 3 B 2g states by 0.05 and 0.06 eV respectively. In the present study the 3 E g is lower in energy by 0.14 and 0.37 eV than the 3 B 2g and 3 A 2g states, respectively.…”

Stabilization of high-spin Mn ions in tetra-pyrrolic configuration on copper

“…The multiplet structure at the Mn L 2,3 -edge reflects not only the metal ionization state, but also the local spin orbit configuration [48,49]. In particular, the spin configuration of the Mn 2+ ions in a coordinative environment with four nitrogen atoms can yield different total spin values depending on the particular molecule considered.…”

Impact of measurement error on maximum hybrid exponentially weighted moving average control chart

“…Study of electronic structure of molecular magnets (MM) has become a noticeable research trend owing to their interesting magneto-optical, electro-optical and photo-magnetic properties [1][2][3][4][5][6]. In an effort to interpreting the complete map of their electronic structure, a variety of experimental and theoretical methods are proposed [7][8][9][10].…”