A Mouml;ssbauer spectroscopic study of the sixhyphen;coordinate highhyphen;spin ferrous compound (mesohyphen;tetraphenylporphinato) bis(tetrahydrofuran) iron(II)

摘要

Mouml;ssbauer spectra of a polycrystalline form of the sixhyphen;coordinate highhyphen;spin ferrous compound (mesohyphen;tetraphenylporphinato)thinsp;bis(tetrahydrofuran)thinsp;ironthinsp;(II) have been recorded over a range of temperatures (4.2ndash;195 K) and magnetic fields (0ndash;6.0 T). Analysis of the spectra using a phenomenological model of the internal magnetic field and using anS=2 spin Hamiltonian, where applicable, yield the sign ofVzznegative, eegr;=0.4,D=6.0 cmminus;1,E/D=0.1, andAtilde;ast;/gast;Nthinsp;bgr;N=(minus;7.2, minus;7.2, and minus;24.3 T). These results suggest that the iron experiences an octahedral crystal field, trigonally distorted in the (1,thinsp;1,thinsp;1) direction, producing a prolate orbitaldz2as the ground state. Crystal field calculations confirm this interpretation by reproducing the spin Hamiltonian parameters listed above. The calculation predicts an orbital doublet 1667 cmminus;1above the ground state. Comparisons with deoxyheme proteins and their synthetic analogs suggest some common gross features of the orbital state and structurehyphen;related trends in the character of the ground quintet.