Studies on the configuration and structural stability of cyanides Fe(CN)ո (n=1-4)

Abstract

The structural properties and vibrational mode of Fe(CN)ո (n=1-4) species have been examined by using HF, B3LYP, B3P86, and B3PW91 methods at 6-311G basis set level. The Fe(CN)n (n=1-4) species exhibit two states. For FeCN and Fe(CN)₃ molecules, there are doublet (²Ʃ) and quartet (⁴Ʃ) states, while for Fe(CN)₂ and Fe(CN)₄ molecules, there are triplet (³Ʃ) and quintet (⁵Ʃ) states. The ground state of FeCN is the doublet (²Ʃ) state, both of which belong to C∞v point group. For Fe(CN)₂ species, the two states (³Ʃ and ⁵Ʃ states) have a V-type structure (C₂v point group) and a linear structure (D∞հ point group), while the ground state is the quintet (⁵Ʃ) state. In Fe(CN)₃ species, the doublet (²Ʃ) state (ground state) has a equilateral triangle structure belonging to D₃հ point group. But, the quartet (⁴Ʃ) state has an isosceles triangle structure. The Fe(CN)₄ species have a cubic (Td point group) structure in the triplet (³Ʃ) state and a square(D₄հ point group) structure in the quintet (⁵Ʃ) state.