Mossbauer,Crystallographic,and Density Functional Theoretical Investigation of the Electronic Structure of Bis-Ligated Low-Spin Iron(II) Phthalocyanines

摘要

We present the crystalstructure of pcFe94-methylpiperidine)_2 as a first exampele of a low-spin iron(II) phthalocyanine (pc) complex bis-axially coordiante dby aliphatic amines.It is shown tat electronic rather than steric effects are responsible for the elogation of the Fe-N(axia) bond in pcFeL_2 complexes.Using density functional theory,the electronic structures as well as Mossbauer isomer shifts and quadrupole splittings have been invstigated for a large number of pcFeL_2 and pcFeL~1L~2 complexes,in which the axial ligands have densities and electric field gradients at the iron ion were evaluated using a locally dense basis aproach with Wachters' all-electron basis set for the iron ion,the 6-311++G(2d) basis set for atoms directly bonded to the iron ion,the 6-31G(d) basis set for atoms two bonds away from the iron ion,and the 3-21G~* basis set for all other atoms.A good correlation betwe4en the theoretical and experimental isomer shifts and quadrupole splittings has been observed for all the complexes tested.It has also been shown that the for all the complexes tested.It has also been shown that the proposed model for the calculation of Mossbauer spectral parameters is adeuate for the evaluation f the axial ligand conformation in cases of conformational flexibility in pcFeL_2 complexes.