Mössbauer effect study of the magnetic properties of <i>S</i>=1 ferrous tetraphenylporphyrin

Abstract

Mössbauer spectra of the polycrystalline form of the square planar compound α,β,γ,δ-tetraphenylporphinato–iron (II) have been observed at a variety of temperatures. Analysis of the resulting spectra yield a positive electric field gradient interaction with quadrupole splitting ΔE=1.51 mm/s (4.2 K) and 1.52 mm/s (300 K). At low temperature, an external magnetic field induces a negligible internal field along the symmetry axis of the molecule. In the transverse direction, it gives rise to a positive internal field with little temperature dependence up to 30 K. The data can be interpreted in terms of a crystal field model involving a low-lying 3A2g state which is split by spin–orbit coupling into a ground singlet and a doublet lying 80 cm−1 above it.