posted on 2022-06-07, 15:11authored byColin
P. Harmer, Saeed Kamali, Oleg I. Lebedev, Shannon J. Lee, Raquel A. Ribeiro, Paul C. Canfield, Kirill Kovnir
Systematic synthesis studies of the
formation of tetrahedral FeS-ethylenediamine
intercalates resulted in the synthesis of a new compound, [Fe9.4(2)S10][Fe(en)3]0.6(1)·en0.9(3). The composition and complex crystal structure were
determined based on a synergistic combination of elemental composition,
decomposition behavior, high-resolution synchrotron X-ray diffraction
and total scattering, 57Fe Mössbauer spectroscopy,
and electron diffraction. The structural model was derived based on
a systematic comparison to the previously reported structures [Fe8S10][Fe(en)3]1·en0.5 and tetragonal FeS. The new compound has flat Fe9.4S10 layers, analogous to those in superconducting binary
FeS. In the crystal structure of [Fe9.4S10][Fe(en)3]0.6·en0.9, the interlayer space
is occupied by [Fe(en)3]2+ complexes and neutral
ethylenediamine molecules in a ∼2:3 ratio. Interlayer species
are not randomly oriented but ordered as evidenced by superstructural
diffraction peaks in both high-resolution X-ray diffraction and electron
diffraction patterns. Magnetic studies reveal no superconducting transition
down to 2 K, indicating that the presence of minute amounts (∼6%)
of iron vacancies at the Fe-S layer in [Fe9.4S10][Fe(en)3]0.6·en0.9 is still
sufficient to shift the position of the Fermi level resulting in an
adjustment of the properties. Our work shows the importance of detailed
characterization of the crystal structure of intercalated compounds
to understand the origin of the observed properties and develop proper
structure–property relationships.