概要 |
日 時 : 2005年12月8日 14:00-16:00
講演者 : Prof. Claude Lecomte 所 属 : LCM3B Universiti Henri Poincari Nancy I
講演要旨 Upon variation of external conditions (T, P, hν), some transition metals (3d4-3d7) in octahedral surrounding may undergo HS-LS reversible phase transition depending when the ligands force field at the metal center is of the order of magnitude of the electron pairing energy [1,2]. The talk will focuss on iron II complexes which undergo photo or thermoexcited transitions. The first part will give details on the mechanism of the phase transition by a carefull study of the crystallographic lattice changes:
- isostructural spin transitions [3,4] or incommensurate modulation of the photoexcited HS state [5] - domains formation: dynamics and orientation [3,6].
The second part of the talk will first compare the structural properties of phases 1 to 5 (figure below) and analyses for the first time the valence electron density of the HS and LS states of Fe(btr)2(NCS)2 H2O and Fe(Phen)2(NCS)2.
References [1] P. G殳lich, A. Hauser, H. Spiering, Angew. Chem. Int. Ed. Engl. 33, 2024 (1994) [2] P. G殳lich, Y. Garcia, T. Woike, Coord. Chem. Rev., 219-221, 839 (2001) [3] S. Pillet, J. Hubsch, C. Lecomte, Eur. Phys. J. B. 38, 541-552 (2004) [4] V. Legrand, C. Carbonera, S. Pillet, M. Souhassou, J.F. L師ard, P. Guionneau, C. Lecomte, J. Phys.: Conference Series 21, 73-80 (2005) [5] S. Pillet, C. Lecomte, C.F. Sheu, Y.C. Lin, I.J. Hsu, Y. Wang, J. Phys.: Conference Series 21, 221-226 (2005) [6] V. Legrand, S. Pillet, C. Lecomte, in preparation
-------------------------------------------------------------------------------------
日 時 : 2005年12月8日 14:00-16:00
講演者 : Prof. Philip Coppens 所 属 : State University of New York at Buffalo
講演要旨 Although ground-state structure determination is quite routine, the determination of transient species offers considerable challenges. To meet this challenge, time-resolved diffraction on a μsec time-scale has been implemented at the 15-ID Chem/Mat CARS beamline at the Advanced Photon Source.1 The analysis of 3 types of complexes has been completed so far: a) binuclear Pt and Rh complexes in which the metal-metal distance shortens by as much as 0.85(4) in [Rh2(dimen)4](PF6)2. b) Cu(I) dimethylphenanthroline photosensitizer dyes in which the molecular geometry is changed by metal to ligand charge transfer. c) the trinuclear Cu(I) complex [3,5-(CF3)2pyrazolateCu]3, in which reversible intermolecular Cu-Cu bond formation occurs (see fig.).2 The experiments are complemented by parallel theoretical calculations. A fast shutter of novel design has been developed and is now being applied in sub-microsecond studies. 3 The advantages and disadvantages of monochromatic vs. pink-beam Laue techniques will be discussed.
References [1] P. Coppens, I. I. Vorontsov, T. Graber, M. Gembicky and A. Yu. Kovalevsky, Acta Crystallogr. A 61, 162-172 (2005). [2] I. I. Vorontsov, A. Yu. Kovalevsky, Y.-S. Chen, T. Graber, M. Gembicky, I. V. Novozhilova, M. A. Omary, P. Coppens, Phys. Rev. Lett. 94, 193003/1-193003/4 (2005) [3] M. Gembicky, D. Oss, R. Fuchs, P. Coppens, J. Synchrotron Rad. 12, 665-669, (2005).
|