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SUMMARY:Broken Symmetry and Ordering Phenomena in Spin Crossover Solids
DTSTART:20141016T163000
DTEND:20141016T173000
DTSTAMP:20260405T191700Z
UID:4a87e7d9ec60a40a0ac9824951b42f93ecd938354d51a4638f4f3cec
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Grace Morgan\nSchool of Chemistry and Chemical Biology\, Un
 iversity College Dublin\, Ireland.\nSpontaneous symmetry breaking[1] gover
 ns many transitions in nature\, in condensed matter and in particle physic
 s. In the last decade it has also emerged as a structural feature in many 
 examples of two-step spin crossover (SCO) in FeII\,[2]\, FeIII[3] and CoII
 .[4] In correlated magnetic materials the underlying driving force for suc
 h structural phase transitions is often magnetic frustration\, such as the
  ferrimagnetic ordering observed in CsCoCl3\,[5] but despite the increasin
 g number of symmetry breaking events in SCO complexes the origin of the ph
 enomenon in these systems is not well understood. Here we present some new
  examples of symmetry breaking two-step SCO transitions in FeIII and in th
 e less well-studied MnIII ion\,[5]-[7] and examine the nature of the order
 ing in the intermediate phase. In particular we examine the nature and dir
 ection of the Jahn-Teller distortion in the S=2 state of the MnIII example
 s and how this affects the crystal packing. We also examine magneto- optic
 al phenomena at low temperature and and how these correlate with the broke
 n symmetry phase in some FeIII examples.\n[1] P. W. Anderson\, More is Dif
 ferent\, Science 1972\, 177\, 393-396.\n[2] N. Brefuel\, H. Watanabe\, L. 
 Toupet\, J. Come\, N. Matsumoto\, E. Collet\, K. Tanaka\, J. –P. Tuchagu
 es\, Concerted Spin Crossover and Symmetry Breaking Yield Three Thermally 
 and One Light-Induced Crystallographic Phases of a Molecular Material\, An
 gew. Chem. Int. Ed. Eng.\, 2009\, 48\, 9304-9307\n[3] M. Griffin\, S. Shak
 espeare\, H. J. Shepherd\, C. J. Harding\, J. –F. Létard\, C. Desplanc
 hes\, A. E. Goeta\, J. A. K. Howard\,A.K.Powell\,V.Mereacre\,Y.Garcia\,A.D
 .Naik\,H.Müller-Bunz\,G.G.Morgan\, SymmetryBreaking Spin State Transitio
 n in Iron(III)\, Angew. Chem. Int. Ed. Eng.\, 2011\, 50\, 896-900.\n[4] a)
  M. G. Cowan\, J. Olguín\, S. Narayanaswamy\, J. L. Tallon\, S. Brooker\
 , Reversible Switching of a Cobalt Complex by Thermal\, Pressure and Elect
 rochemical Stimuli: Abrupt\, Complete\, Hysteretic Spin Crossover\, J. Am.
  Chem. Soc.\, 2012\, 134\, 2892-2894.\n[5] A Manganese(III) Complex that E
 xhibits Spin Crossover Triggered by Geometric Tuning\, G. G. Morgan\, K. D
 . Murnaghan\, H. Müller-Bunz\, V. McKee and C. J. Harding\, Angew. Chem.
  Int. Ed.\, 2006\, 45\, 7172-7175.\n[6] Cooperative Spin Transition in a M
 ononuclear Manganese(III) Complex\, P. N. Martinho\, B. Gildea\, M. M. Har
 ris\, T. Lemma\, A. D. Naik\, H. Muller-Bunz\, T. E. Keyes\, Y. Garcia and
  G. G. Morgan\, Angew. Chem. Int. Ed.\, 2012\, 51\, 12597-12601.\n[7] Latt
 ice Effects on the Spin Crossover Profile of a Manganese(III) Cation\, K. 
 Pandurangan\, B. Gildea\, C. Murray\, C. J. Harding\, H. Müller-Bunz and
  G. G. Morgan\, Chem. Eur. J.\, 2012\, 18\, 2021-2029.
LOCATION:CH G1 495 https://plan.epfl.ch/?room==CH%20G1%20495
STATUS:CONFIRMED
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