Reversible structural change of host framework triggered by desorption and adsorption of guest benzene molecules in Fe(NCS)2(bpp)2·2(benzene) (bpp = 1,3-bis(4-pyridyl)propane)

Assembled iron complex Fe(NCS)2(bpp)2·2(benzene) (bpp = 1,3-bis(4-pyridyl)propane), enclathrating benzene molecules, has been synthesized and its host framework was 1D chain structure. By releasing benzene molecules, the host framework changed to 2D interpenetrated structure. The desorbed complex enclathrated benzene molecules again and the host framework returned to 1D structure. Although the spin state remained in the high spin upon the desorption and adsorption of the benzene molecules, 57Fe Mössbauer spectra revealed that the symmetry around iron atom changed depending on the sorption. The reversible structural change of host framework was tried to explain by two factors: the crystal stability by making up the interstitial space and the conformer stability in coordinated bridging ligand bpp.