Finally: The X-ray crystal structure of the illusive unsubstituted iron(III) phthalocyanine μ-oxo(1) dimer. DFT-predicted Mössbauer quadrupole splitting and antiferromagnetic coupling constants for X-ray geometry

Abstract

The molecular structure of the unsubstituted iron(III) phthalocyanine [Formula: see text]-oxo(1) dimer ((PcFe)2O) was determined by single crystal X-ray diffraction. In agreement with the earlier speculations, the dimer has a bent (Fe-O-Fe angle is 152.4[Formula: see text]) structure. The interplay between the [Formula: see text]-[Formula: see text] interactions and steric hindrances caused by the isoindole units led to the observed staggering angle of [Formula: see text]24[Formula: see text] between two phthalocyanine ligands. The high-spin iron(III) centers are located significantly above the phthalocyanine N4 planes (0.57–0.58 Å). Several DFT exchange-correlation functionals were used to calculate the absolute value and sign of the Mössbauer quadrupole splitting and antiferromagnetic coupling constant for X-ray determined geometry of (PcFe)2O. It was demonstrated that the hybrid functionals provide the correct sign of the electric field gradient and the magnitude of the antiferromagnetic coupling constant compared to the pure functionals.