ELECTRON DENSITY DISTRIBUTION OF FE(PHEN)2(NCS)2 USING THE SYNCHRON RADIATION LIGHT SOURCE. C. C. Wang1, H. S. Sheu1,2, C. R. Lee1, J. J. Lee1, Y. Wang1, A. Darovsky3, R. Bolotovsky3, P. Coppens3, 1Department of Chemistry, National Taiwan University, Taipei, Taiwan, ROC, 2Synchrotron Radiation Research Center, Hsinchu, Taiwan, ROC, 3X3, National Synchrotron Light Source, BNL, Upton, New York, USA
Cis-bis(thiocyanato)bis(l,10-phenanthroline)-iron(II), Fe(phen)2(NCS)2 has certainly been one of the most well studied iron(II) spin-transition complexes. It undergoes an abrupt HSLS transition at 176K. However, the crystal structure does not undergo any phase transition at this temperature. The space group is Pbcn, cell parameters at 50K, a=13.242(2), b=9.884(1), c=17.123(6)Å, V=2241.17Å3. The structures of Fe(phen)2(NCS)2 were studied at three different temperatures (298, 140 and 50K), their structural parameters will be compared. Accurate diffraction data of this compound were collected on a 0.1 x0. 1 x0.08 mm using the synchrotron radiation light source (NSLS) with the wavelength 0.394Å at 50K, in order to investigate the electron density distribution of such complex at low spin state. Deformation density distribution according to the multipole model will be displayed. The strong covalent character of the ligand phen and NCS- are well illustrated. The d-orbital populations of Fe(II) at LS will be discussed. Parallel molecular orbital calculations on this molecule are also performed. A comparison between experimental and M.O. calculation will be given.