Low-Temperature Structure of [Fe(ptz)₆](BF₄)₂ –Determination by Synchrotron-Radiation X-ray Powder Study–

Abstract

Temperature dependence of atomic coordinates is precisely determined for an iron (II) complex, [Fe(ptz) 6 ](BF 4 ) 2 (ptz = propyltetrazole), by means of synchrotron-radiation (SR) x-ray powder diffraction measurements. The spin state of the Fe 2+ ions is known to change from high-spin (HS; S = 2) to low-spin (LS; S = 0) with a decrease in temperature to below T c ≈130 K. We have found that the spin state transition accompanies a significant contraction of the Fe–N4 bond distance from ≈ 2.20 Å (HS) to ≈ 2.00 Å (LS).