Probing the spin states of tetra‐coordinated iron(II) porphyrins by their vibrational and pre K‐edge x‐ray absorption spectra

Abstract

Tetra‐coordinated iron(II) porphyrins are observed in triplet (intermediate spin, IS) ground state with low‐lying quintet (high spin, HS) and singlet (low spin, LS) excited states. It is well known in the literature that the dFeprefix−N bond distances are dependent on the spin state such that the dFeprefix−N distances are larger for HS compared to the LS/IS states. This implies the existence of strong magneto‐structural correlations. Herein, the possibility to obtain the spin‐state information for a series of tetra‐coordinated square planar iron(II) porphyrin complexes have been explored by exploiting the magneto‐structural correlations obtained from first principle calculations. The spin‐state dependent nature of the chemical bonds and spin polarization on the N‐atoms play a crucial role in the vibrational dynamics of the central Fe‐atom. Theoretical nuclear resonance vibrational spectroscopy (NRVS) is adopted to investigate the vibrational dynamics and the Fe‐atom associated spectral peaks and their spin‐dependent features. We find that NRVS studies along with iron pre‐K‐edge x‐ray absorption analysis convincingly provide the information on the spin state, which could be utilized to identify the spin states without adopting any magnetic probes.

Unravelling the Highest Magnetic Anisotropy Among all the nd-Shells in [WCp2]0 Metallocene

“…The plane wave-based PBE + U calculations can provide comprehensive insights into the chemical bonding in various metal complexes. , The one-to-one correspondence between the electronic structures obtained from B3LYP/def2-TZVP and PBE + U methods has been depicted in Figure I­(b), II­(b), III­(b) and I­(c), II­(c), and III­(c). In the presence of a Cp ring, the overlap between the π electrons of the ligand ( p z in Figure ) and d xz , d yz orbitals of the metal facilitates the M–Cp bond formation (highlighted with blue background in the PDOS in Figure ).…”

Can Iron–Porphyrins Behave as Single-Molecule Magnets?

“…the triplet ( S = 1), quintet ( S = 2), and singlet ( S = 0) states, dictate the overall magnetochemical behavior of these complexes. The square planar iron­(II)–porphyrin as an isolated molecule exhibits a triplet ground state. − The addition of various ligands to the axial coordination sites of the metal center provides a route to manipulate the magneto-chemistry of the metalloporphyrin complexes. − The change in the ligand environment by such means triggers an alteration in the fundamental magnetic properties like the spin state of the complex, crystal field splitting, and so on. On the other hand, the strong chemisorption of the molecule on the substrate induces a set of modifications to the molecular structure that pave the path for manipulating the magnetic state of the molecule.…”